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You may copy it, give it away or % +% re-use it under the terms of the Project Gutenberg License included % +% with this eBook or online at www.gutenberg.org % +% % +% % +% Title: Matter, Ether, and Motion, Rev. ed., enl. % +% The Factors and Relations of Physical Science % +% % +% Author: Amos Emerson Dolbear % +% % +% Release Date: February 27, 2010 [EBook #31428] % +% Most recently updated: June 11, 2021 % +% % +% Language: English % +% % +% Character set encoding: UTF-8 % +% % +% *** START OF THIS PROJECT GUTENBERG EBOOK MATTER, ETHER, AND MOTION *** % +% % +% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % + +\def\ebook{31428} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%% %% +%% Packages and substitutions: %% +%% %% +%% book: Required. %% +%% inputenc: Standard DP encoding. Required. %% +%% %% +%% ifthen: Logical conditionals. Required. %% +%% %% +%% amsmath: AMS mathematics enhancements. 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You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Matter, Ether, and Motion, Rev. ed., enl. + The Factors and Relations of Physical Science + +Author: Amos Emerson Dolbear + +Release Date: February 27, 2010 [EBook #31428] +Most recently updated: June 11, 2021 + +Language: English + +Character set encoding: UTF-8 + +*** START OF THIS PROJECT GUTENBERG EBOOK MATTER, ETHER, AND MOTION *** +\end{PGtext} +\end{minipage} +\end{center} + +\clearpage + + +%%%% Credits and transcriber's note %%%% +\begin{center} +\begin{minipage}{\textwidth} +\begin{PGtext} +Produced by Andrew D. Hwang, Peter Vachuska, Chuck Greif +and the Online Distributed Proofreading Team at +http://www.pgdp.net +\end{PGtext} +\end{minipage} +\end{center} +\vfill + +\begin{minipage}{0.85\textwidth} +\small +\phantomsection +\pdfbookmark[0]{Transcriber's Note}{Transcriber's Note} +\subsection*{\centering\normalfont\scshape% +\normalsize\MakeLowercase{\TransNote}}% + +\raggedright +\TransNoteText +\end{minipage} + + +%%%%%%%%%%%%%%%%%%%%%%%%%%% FRONT MATTER %%%%%%%%%%%%%%%%%%%%%%%%%% + +\DPPageSep{001.png}{unnumbered}% +\clearpage +\null +\vfill +\begin{center} +\setlength{\fboxsep}{12pt} +\framebox{% +\begin{minipage}{3in}%[** Hard-coded width] +\begin{center} +\textgoth{By Professor A.~E. Dolbear} \\ +\tb[0.5in] +\end{center} + +\textit{\footnotesize MATTER, ETHER AND MOTION} +\smallskip + +\hspace*{\QUAD} +\begin{minipage}{\linewidth-2\QUAD} +\scriptsize +The Factors and Relations of Physical Science \\ +Enlarged Edition\quad Cloth\quad Illustrated\quad \$2.00 +\end{minipage} + +\medskip +\textit{\footnotesize THE TELEPHONE} +\smallskip + +\hspace*{\QUAD} +\begin{minipage}{\linewidth-2\QUAD} +\scriptsize +With directions for making a Speaking Telephone \\ +Illustrated\quad 50~cents +\end{minipage} + +\medskip +\textit{\footnotesize THE ART OF PROJECTING} +\smallskip + +\hspace*{\QUAD} +\begin{minipage}{\linewidth-2\QUAD} +\scriptsize +A Manual of Experimentation in Physics, Chemistry, +and Natural History, with the Porte Lumière +and Magic Lantern \\ +New Edition\quad Revised\quad Illustrated\quad \$2.00 +\end{minipage} + +\begin{center} +\tb[0.5in]\\ +\textgoth{\footnotesize Lee and Shepard Publishers Boston} +\end{center} +\end{minipage}} +\end{center} +\vfill + +\DPPageSep{002.png}{unnumbered}% i +% title page +\frontmatter +\pagestyle{empty} + +\setlength{\TmpLen}{0.125in}% + +\begin{center} +{\LARGE \scshape Matter, Ether, and Motion} \\[\Titleskip{4}] +{\itshape THE FACTORS AND RELATIONS \\[\Titleskip{1}] +OF\\[\Titleskip{1}] +PHYSICAL SCIENCE}\\[\Titleskip{4}] +{\scriptsize\upshape BY} \\[\Titleskip{1}] +{\scshape A.~E. DOLBEAR Ph.D.} +\medskip + +\tiny\upshape PROFESSOR OF PHYSICS TUFTS COLLEGE \\ +AUTHOR OF ``THE TELEPHONE'' ``THE ART OF PROJECTING'' ETC. + +\vspace*{4\TmpLen} +{\scriptsize\itshape REVISED EDITION, ENLARGED} +\vspace*{4\TmpLen} + +\small B\,O\,S\,T\,O\,N %[** PP: One-off gesperrt] + +LEE\quad AND\quad SHEPARD\quad PUBLISHERS +\smallskip + +\scriptsize 10 MILK STREET + +\small 1894 +\end{center} + +\DPPageSep{003.png}{unnumbered}% ii +% copyright page +\clearpage +\begin{center} +\scriptsize +\null\vfill +\scshape Copyright, 1892, 1894, by Lee and Shepard \\[\Titleskip{1}] +\itshape All Rights Reserved \\[\Titleskip{1}] +\scshape Matter, Ether, and Motion +\vfill +C.~J. Peters \& Son, \\ +Type-Setters and Electrotypers, \\ +145 High Street, Boston. +\end{center} + +\clearpage +\pagestyle{fancy} +\fancyfoot{} + +\stretchyspace + +\Preface{PREFACE TO THE SECOND EDITION} +\DPPageSep{004.png}{iii}% + +\First{The} issue of a new edition of this book gives me an +opportunity to make some needed corrections, and enlarge +it by the addition of three new chapters, which +I hope will make it more useful to such as have a taste +for fundamental physical problems. The first of these, +Properties of Matter as Modes of Motion, presents +the evidence that all the characteristic properties of +matter are due to energy embodied in various forms +of motion. The second, on The Implications of +Physical Phenomena, points out what assumptions +are made in explaining phenomena. It is the substance +of a series of articles published in the \textit{Psychical +Review} in 1892 and~1893. The third, on The Relations +between Physical and Psychical Phenomena, +was read as a paper before the Psychical Congress at +the World's Fair in August,~1893. + +Judging from some of the comments made about my +statements as to Modern Geometry on \Pageref{page}{57}, and +as to Vital Force, \Pageref{p.}{279}, I have thought it would be +useful to some to see corroboratory statements; and I +have therefore added, in an appendix, a few pages of +\DPPageSep{005.png}{iv}% +quotations from some of the most eminent mathematicians +and biologists on these subjects, and from them +one may judge whether or not my statements are +correct. + +As the work is a treatise on Physics, there is no +special reason for going beyond it; but if this presentation +of the subject is any approach to the truth, there +is an important conclusion to be drawn from it. If the +ether be the homogeneous and uniform medium it is +believed with reason to be, then, in the absence of +what we call matter, no physical change which we call +a phenomenon could possibly arise in it; for every such +phenomenon is a product, and in the absence of one of +the essential factors, viz., matter, it could not be. If +matter itself be a form of motion of the ether, the ether +must have existed prior to matter; also, if the atom be a +form of energy, then must energy have existed before +matter existed. Hence there must have been some +other agency radically different from any physical +energy we know, and independent of everything we +know, which was capable of producing orderly physical +phenomena, by acting upon the ether; for a homogeneous +medium could not originate it. Some philosophers +call this antecedent power The Unknowable; others call +it God. If energy \emph{as we know it} implies antecedent +energy as we do not know it, so, likewise, mind as we +know it implies antecedent mind under totally different +conditions from those in which we find it embodied. + +In whatever direction one pursues physical science, +\DPPageSep{006.png}{v}% +he is at last confronted with a physical phenomenon +with a superphysical antecedent where all physical +methods of investigation are impotent. Such considerations +raise the theistic hypothesis of creation to the +rank of such physical theories as the nebula theory +of the origin of the solar system, and the undulatory +theory of light. +\DPPageSep{007.png}{unnumbered}% vi +% [Blank Page] + + +\Preface{PREFACE} +\DPPageSep{008.png}{vii}% + +\First{Within} the past fifty years the advance in physical +knowledge has not only been rapid, but it has been +well-nigh revolutionary. Not that knowledge that was +felt to be well grounded before has been set aside,---for +it has not been,---but the fundamental principles +of natural philosophy that were applied by Sir Isaac +Newton and others to masses of visible magnitude +have been applied to molecules; and it has thus been +discovered that all kinds of phenomena are subject to +the same mechanical laws. It was thought before that +physics embraced several distinct provinces of knowledge +which were not necessarily related to each other, +such as mechanics, heat, electricity, etc. Such terms +as imponderable matter, latent heat, electric fluid, +forces of nature, and others in common use in text-books +and elsewhere, served to maintain the distinctions; +and even to-day some of these obsolete physical +agencies are to be met in books and places where one +would hope not to find them. As all physical phenomena +are reducible to the principles of mechanics, atoms +and molecules are subject to them as much as masses +\DPPageSep{009.png}{viii}% +of visible magnitude; and it has become apparent that +however different one phenomenon is from another, the +factors of both are the same,---matter, ether, and +motion; so that all the so-called forces of nature, +considered as objective things controlling phenomena, +are seen to have no existence; that all phenomena are +reducible to nothing more mysterious than a push or +a pull. + +Some say that science is simply classified knowledge. +To the author it is more than that, it is a consistent +body of knowledge; and a true explanation of any +phenomenon cannot be inconsistent with the best +established body of knowledge we have. If physical +factors are fundamental, then theorizers must square +their theories to them. + +The text-books have not kept pace with the advance +of knowledge; and there is a large body of persons +desirous of knowing more of natural philosophy, and +especially of its trend, who have neither time nor +opportunity to read and digest monographs on a thousand +topics. To meet the wants of such, this book has +been written. It undertakes to present in a systematic +way the mechanical principles that underlie the phenomena +in each of the different departments of the +science, in a readable form, and in an untechnical +manner. The aim has been to simplify and reduce +to mechanical conceptions wherever it was possible +to do so. + +One may often hear the question asked, What is +\DPPageSep{010.png}{ix}% +electricity? but a similar question as to the nature of +heat or light or chemism is just as pertinent, although +there chances now to be less popular interest in these +than in the former; not, however, because they are in +themselves better understood, or less interesting. + +It is hoped that some of those whose interests lie +along such special lines as chemistry, electricity, and +even biology, will find something helpful in the chapters +dealing with those subjects. + +In covering so much ground in so small a treatise, it +was necessary to select such facts as give prominence +to fundamental principles. Doubtless others might +have selected different materials, even with the same +end in view, for otherwise competent persons are +generally more familiar with certain details of a given +science than with others; and I have used what was +closest at hand. + +Aside from the topics usually treated upon in a book +of physics, the reader will find a chapter on Physical +Fields, which is unique, as it extends the principle of +sympathetic action---recognized in acoustics---to the +whole range of phenomena, including living things. + +The chapter on Life, in a treatise on physics, must +justify itself; while the one on Machines points out +their functions in a more complete way than has been +done before. + +Lastly, however large the physical universe may be, +and however exact such relations as we have established +may be, it is daily becoming more certain that +\DPPageSep{011.png}{x}% +even in the physical universe we have to do with a +factor,---the ether,---the properties of which we vainly +strive to interpret in terms of matter, the undiscovered +properties of which ought to warn every one against +the danger of strongly asserting what is possible and +what impossible in the nature of things. With the +electro-magnetic theory of light now just established, +and the vortex ring theory of matter still \textit{sub~judice}, +but with daily increasing evidence in its favor, one may +now be sure that matter itself is more wonderful than +any philosopher ever thought. Its possibilities may +have been vastly underrated. + +In the book called ``The Unseen Universe,'' it is +pointed out that possibly the ether may be the medium +through which mind and matter re-act. What fifteen +years ago was deemed \emph{possible}, is to-day deemed \emph{probable}, +and to-morrow may be demonstrated; and a perusal +of that book is recommended to persons who are +interested in questions of that kind. +\DPPageSep{012.png}{unnumbered}% +% table of contents + +\pagestyle{empty} +\tableofcontents +\phantomsection +\pdfbookmark[0]{Contents}{Contents}% + + +\iffalse + +CONTENTS + +CHAPTER PAGE + +I. MATTER AND ITS PROPERTIES 1 + +II. THE ETHER 26 + +III. MOTION 44 + +IV. ENERGY 59 + +V. GRAVITATION 83 + +VI. HEAT 99 + +VII. ETHER WAVES 134 + +VIII. ELECTRICITY 173 + +IX. CHEMISM 238 + +X. SOUND 256 + +XI. LIFE 277 + +XII. PHYSICAL FIELDS 298 + +XIII. ON MACHINES.--MECHANISM 312 + +XIV. PROPERTIES OF MATTER AS MODES OF MOTION 331 + +XV. IMPLICATIONS OF PHYSICAL PHENOMENA 354 + +XVI. RELATIONS OF PHYSICAL AND PSYCHICAL PHENOMENA 384 + +APPENDIX 397 + +INDEX 403 + +\fi + +%\DPPageSep{013.png}{1}% + +\mainmatter +\pagestyle{fancy} +\phantomsection +\pdfbookmark[-1]{Main Matter}{Main Matter} + +% MATTER, ETHER, AND MOTION + + +\Chapter{I}{Matter and Its Properties}{1} + +\First{All} kinds of phenomena that we can become conscious +of through any of our senses are traceable +directly or indirectly to what we call matter. The +sense of feeling implies contact with a body of some +kind; the sense of hearing depends upon movements +of the air, which is a body of matter having certain +properties; and the sense of sight, also due to vibratory +motion, implies that matter exists, however distant, +which has given rise to the vibratory motions that are +perceived as light. So of taste and smell, actual contact +of material particles endowed with particular +properties are the conditions for exciting these sense +perceptions. Some philosophers have added a sixth +sense to the five senses we have recognized for so long +a time---the sense of weight, as distinguished from the +sense of touch; and still others have thought to distinguish +a sense of temperature---relative perceptions of +heat and cold, from the sense of touch; and if these +truly represent distinct senses, they illustrate still +further the truth that it is through the reactions of +\DPPageSep{014.png}{2}% +matter upon the nervous organizations of living things +that all of our knowledge of things about us and of +the universe as a whole is obtained. + +It might seem to one as if our knowledge of matter +should be tolerably good, accurate, and complete, seeing +that it is thrust upon us everywhere, and affects us +for good or evil continuously from the dawn of sensation +till death; yet it may truly be said that the knowledge +of matter, its properties, and the wonderful complexity +of phenomena that are due to them, which we +possess to-day was wholly unknown to all mankind +until the time of Sir~Isaac Newton, whose discovery +of the law of gravitation was the first discovery of +a universal property of matter; and by far the larger +part of the knowledge we have, has been acquired in +this century and mostly within the last half of it. The +mass of mankind is, as it always has been, without +any knowledge at all and without any desire for it. +Whatever we have is due to the work of a small number +of persons in Western Europe and America. Probably +the large majority of mankind are quite unable +to understand phenomena and their significance, yet +among the brighter and more competent individuals in +every country there is an apathy and indifference to the +subject, due, of course, to the estimate they have of its +degree of importance; and this estimate is in a good +measure due to the philosophy of things in general +held by the individual thinkers. + +When Mr.\ Emerson was told by a Millenarian that +the world was coming to an end the next day, he +declared that he could get along without it, and so it +\DPPageSep{015.png}{3}% +probably has seemed to the majority of philosophers +that the material world was a condition of things to be +endured, rather than to be understood and utilized: +that they were in it but were not a part of it. + +Knowledge has, however, increased, and the wise +ones are growing wiser; and some of the modern questions +of philosophy and psychology are now so woven +in with physical details that a knowledge of matter and +its possibilities has become to them imperative. + +There have been many attempts to define matter, +such as, whatever occupies space, or whatever affects +our senses, and so on; and there is no brief definition +that has been generally adopted. In the ordinary +affairs of life one rarely needs to make such distinctions +as are necessary in philosophical and scientific affairs, +where accuracy and clearness are of the utmost importance. +There seems to be no way to define matter +except by means of some of its properties. If we say +that it is whatever occupies space, there is implied in +the statement that the term is properly applicable to +everything that exists in space; but so far as we know +there may be any number of things in illimitable space +that are not subject to any of the physical laws, such as +a piece of wood or an air particle are known to be controlled +by. If we say whatever affects our senses, we +again are going beyond our warrant; for electricity is +capable of affecting several of our senses,---sight, taste, +feeling,---and yet there is no good reason for thinking +electricity to be matter. + +There is one property of matter that may seem to +differentiate it from everything else, and hence, if +\DPPageSep{016.png}{4}% +\index{Matter, characteristic property}% +\index{Matter, its definition}% +adopted, will enable one to be precise about his use of +the term. One part of the law of universal gravitation +is---\emph{every particle of matter in the universe attracts every +other particle}. This makes gravitation a universal property +of matter. The astronomers have observed the +movements of exceedingly distant stars to be in accordance +with this law, and there are no exceptions to it +that have been discovered. + +If, then, one adopts as the definition of matter, \emph{whatever +possesses the property of gravitative attraction}, he +will have a definition that is in accordance with everything +we know, and with the added advantage that if +there be anything else in the universe that involves +observable phenomena he will not need to confuse it +with the phenomena of gravitative matter. This is the +sense in which that term is used throughout this book. +\TBskip + +Matter presents itself to our senses in a scale of +magnitude from particles in the neighborhood of the +hundred-thousandth part of an inch in diameter, and +requiring the highest powers of the microscope to see, +to such huge masses as that of the earth, eight thousand +miles in diameter, the planet Jupiter, nearly eighty +thousand miles, and the sun, eight hundred thousand +miles in diameter, while some of the more distant stars +are probably ten times larger than the sun. The large +masses, however, are but collections of smaller ones, +each particle bringing its own properties of whatever +kinds they may be; and it does not appear that new +qualities are developed by simply changing the distance +between bodies. So the properties of matter may be +\DPPageSep{017.png}{5}% +studied exhaustively without employing specimens +inconveniently large. + +The thin stratum of gold spread upon cheap jewelry +has all the characteristics and qualities of any specimen +of gold however large; and a small test tube of +hydrogen will exhibit all the kinds of phenomena that +any larger quantity would show. For such reasons the +study of the universe of matter can be carried on in +the laboratory. The universe may be in the crucible +one holds in the tongs; whatever difference there may +seem to be, it will really be one of bigness only. + +In treatises on physics one will generally find the +properties of matter arranged in two divisions, called +essential properties and non-essential ones. Of the +former are (1)~extension, or space occupying; (2)~inertia, +or passiveness under conditions of rest or motion; +(3)~impenetrability, or total and exclusive occupancy of +its own space; (4)~elasticity, or ability to recover its +form after distortion, this, however, varying in degree +in different bodies; (5)~attraction, of which there are +several varieties,---gravitation, acting at all distances; +chemism, acting at close distances and selective in its +operation, and apparently not existing at all between +some kinds of matter, as, for instance, between oxygen +and fluorine. Chemism is also capable of complete +neutralization, and is thus in marked contrast with +gravitative attraction, which is not affected in the slightest +degree discoverable by contiguity; and lastly, cohesion, +which is not apparent except bodies are in contact, +but is the agency that holds the particles of bodies together +so they form liquids and solids of any and all sorts. +\DPPageSep{018.png}{6}% + +The so-called non-essential properties are color, hardness, +malleability, ductility, and the like, which vary very +much in different substances. Among the metals silver +is white, copper is red, gold is yellow. Diamond is the +hardest substance known, while graphite is one of the +softest, though both are composed of the same ultimate +substance---carbon. Iron is malleable, and may be +forged into any shape. Gold may be hammered out into +leaves no more than one three-hundred-thousandth of +an inch thick, but zinc is wholly unmanageable in that +way. Platinum, one of the heaviest metals we have, +can be drawn out into a wire finer than a spider's web,---a +single grain may be drawn into a mile of wire; while +bismuth, also a metal, cannot be drawn at all. + +There are other conditions of matter that offer +opportunities for convenient grouping sometimes, such +as the solid, the liquid, and the gaseous: the solid +being the one where the parts strongly cohere; the +liquid, where the parts have but slight cohesion; and +the gaseous, where the individual particles do not +cohere at all, but, being elastic, bump against each +other and rebound continually. + +Farther on it will be shown how all substances may +assume either of these conditions, inasmuch as it is +temperature that determines whether a given substance +be a solid, a liquid, or a gas. + +Density signifies compactness of matter, or the relative +\index{Density}% +number of particles in a given unit volume. If compression +be applied to two cubic feet of common air until +it occupies but one cubic foot, there is twice as much +matter in that cubic foot as there was at the outset, and +\DPPageSep{019.png}{7}% +we express that fact by saying that the density is +doubled. If twice the amount of matter is in the unit +space, evidently the weight of the matter in that space +must be twice what it was at first. So one may measure +the density of matter by the weight of a unit +volume of it compared with the weight of the same +volume of some other substance taken as unity. Thus, +if a cubic foot of water weighs $62.5$~pounds, and a cubic +foot of rock weighs $155$~pounds, the density of the rock +is~$2\frac{1}{2}$, which means that it is $2\frac{1}{2}$~times heavier than +water, and that the amount of matter in the rock +is $2\frac{1}{2}$~times greater than that of the water. Such +determinations have been made of all the different +materials that could be found, and extensive tables +have thus been constructed; but it is seen that the +appeal is to gravitation, and presumes that every particle +obeys that law, and that degrees of compactness of +matter do not affect the law. Such comparative tables, +based upon gravitation measure, are frequently called +tables of \emph{Specific Gravity}, so that density and specific +\index{Gravity, specific}% +\index{Specific gravity}% +gravity mean substantially the same thing. The following +examples of the relative densities of bodies may be +of interest:--- +\begin{center} +\TableFont% +\begin{tabular} {ll<{\qquad} ll<{\qquad} ll} +Gold, & $19$ & Diamond, & $4$ & Alcohol, & $\Z.8$ \\ +Silver, & $10.5$ & Common Stone, & $2.5$ & Ether, & $1.1$ \\ +Copper, & $8.8$ & Wood, & $\Z.8$ & Water, & $1$ \\ +Iron, & $7.8$ & Sulphuric Acid, & $1.8$ & The Earth, & $5.6$ +\end{tabular} +\end{center} +Such numbers are to be understood as signifying that +if a given volume of water weighs one pound, an equal +volume of gold weighs nineteen pounds, an equal volume +of iron seven and eight-tenths pounds, and so on. +\DPPageSep{020.png}{8}% + +Sometimes, however, it is convenient to choose for a +standard of density some body, a small unit volume of +which is much lighter than water, such as air, or more +frequently hydrogen gas, a hundred cubic inches of which +weigh $2.2$~grains. In the metric system, a litre, which +is nearly two pints is the standard of volume; and a +litre of hydrogen weighs $.0896$~of a gram. + +In chemical work this is the common standard for +gases; while for solids and liquids a cubic centimetre of +water is taken, which weighs one gram. + +\Section{DIVISIBILITY OF MATTER.} +\index{Matter, divisibility of}% + +Particles of matter as small as the hundred-thousandth +of an inch may be seen with a good microscope +as the smallest visible thing, but there is no reason for +thinking that such a degree of fineness is any approach +to the ultimate fineness of the parts into which it is +possible to divide matter. For a long time philosophers +have considered whether or not there could, in +the nature of things, be an actual limit to the divisibility +of matter, so that the smallest fragment could +not be again divided into two or more parts by the +application of appropriate means, thus making matter +infinitely divisible, at any rate ideally. + +In Mr.\ Spencer's ``First Principles'' this subject is +considered at length, and the conclusion reached that it +is impossible to conceive the existence of real atoms---bodies +that cannot be divided into halves; nevertheless, +we shall see presently that it is possible to +conceive precisely that thing. It will be best here to +\DPPageSep{021.png}{9}% +note how far division has been carried and the means +employed to effect it. + +If a bit of phosphorus be put into a solution of gold, +the gold will be set free in such a finely divided state +that the particles remain suspended in the solution, +giving to it a blue, green, or ruby color, depending +upon the degree of fineness into which it has been +broken up. Faraday estimated that the particles of +gold in the ruby-colored liquid did not exceed the five-hundred +thousandth part of the volume of the liquid. +One-eighth of a grain of indigo dissolved in sulphuric +acid will give a distinctly blue color to two and a half +gallons of water, which would be about the millionth +part of a grain to a drop of the water. + +A grain of musk will keep a room scented for many +years. During the whole of the time it must be slowly +evaporating, giving out its particles to the currents of +air to be wafted presently out of doors; yet in all this +time the musk seems to lose but little in weight. + +The acute sense of smell of the dog is well known; +for he can detect the track of his master long after the +tracks have been made, which shows that some slight +characteristic matter is left at each footfall. + +A spider's web is sometimes so delicate that an +ounce of it would reach three thousand miles, or from +New York to London. No one would think it likely +that such a web would be made up of a single row of +atoms, like a string of beads; for it would not seem +probable that such a string could have such a degree +of cohesion as spiders' webs are known to possess. + +Chemists have concluded from their experience with +\DPPageSep{022.png}{10}% +matter in its various forms and conditions that it is +really reducible to ultimate particles which have never +broken up, no matter what conditions they have been +subject to; and these ultimate particles are called \emph{atoms}. +\index{Atoms}% +The term is not now understood to signify what is +implied in its derivation, as something that cannot be +divided, only something that has not yet been broken +up into smaller parts. Thus hydrogen, oxygen, iron, +silver, are reducible to such ultimate atoms; and there +are now known about seventy different kinds of +atoms, and these are often spoken of as the elements. +Though they are excessively minute when compared +with ordinary objects of sight, yet they have a real +magnitude which the physicist has measured in several +different ways. Most of these methods are complicated, +and, in order to be understood, require a pretty +thorough knowledge of molecular physics; but the following +one may probably serve to give one an idea of +the degree of smallness which atoms must have. + +When a soap-bubble is blown, the material of the +\index{Soap-bubbles}% +film slides down the sides, making the bubble thinnest +on top. When a certain degree of thinness has been +reached at the top, colors begin to appear in concentric +rings, and these colors appear to move towards the +equatorial regions, new rings being formed at the top +as fast as room is made for them by the displacement +of the earlier ones. These colors always appear in the +same order as they are in the rainbow, namely, beginning +with the red and ending with the violet, then +another set with the same order, until there have been +ten or more such sets of rainbow tints. They are +\DPPageSep{023.png}{11}% +explained as being due to what is called interference +in the light waves that fall upon the film. Light is +reflected more or less from every surface it reaches. +Some light is reflected from the first or outer surface +of the film; some goes through the film to the inner +surface, and is there reflected back to the outer surface, +and then takes the direction that the light has which +is reflected from the first surface, so that the light that +reaches the eye from a point on a bubble comes from +both outer and inner surfaces. That coming from the +inner surface has had to travel farther than that coming +from the outer surface by a distance of twice the +thickness of the film. As light consists of waves, if +one set of waves all of a length be made to move in the +same direction as another set having the same length, +their crests may coincide and produce a single higher +wave; or the crest of one may be behind the crest of +the other at any distance up to one-half the length of +the wave itself, in which case the crest of one will +coincide with the trough of the other, and the two +waves will cancel each other, and this process is called +interference. Now, in the case of the bubble, when the +thickness is such that the distance through the film +and back again is such as to equal half a wave length +of a given kind of light, that particular wave is extinguished; +and when one of the constituents of white +light is wanting, that which is left is seen as colored +light, and the color seen must depend upon the kind +of color that has been cancelled. Red light has the +longest wave length, about one forty-thousandth of an +inch, and violet, the shortest of the waves we see, about +\DPPageSep{024.png}{12}% +one sixty-thousandth of an inch; and when these colors +are seen upon the bubble we are assured that the +interferences are produced by thicknesses due to fractional +parts of such wave lengths. As the ray must go +through the thickness twice in order to fall behind one-half +of a wave, it follows that the thickness of the film +where the last set of colors appear can be no more than +one-fourth of the wave length of the shortest wave we +can see, that is, +\[ +\frac{1}{4} × \frac{1}{60,000} = \frac{1}{240,000} \text{ of an inch.} +\] +When a bubble has reached this degree of thinness, so +that no more colors are to be seen, a rather remarkable +physical effect may be noticed. The film becomes +almost jet black, with a jagged edge well defined +between it and the brighter colored rings where the +adjacent tint is purplish. The thickness of the film +has fallen suddenly off here to about one-fortieth of +the thickness it has where the tint is visible, and the +bubble breaks in a second or two after this black patch +appears; that is, when its thinness at any point becomes +as small as +\[ +\frac{1}{240,000} × \frac{1}{40} = \frac{1}{9,600000} \text{ of an inch.} +\] +As the bubble, however, does persist for a short time, +and the thin film has cohesion enough to enable it to +support the weight of the bubble, it seems highly probable, +but is not absolutely certain, that it must be more +than one molecule of water thick at the thinnest +place, which is, as shown, only about the one ten-millionth +\DPPageSep{025.png}{13}% +\index{Molecules, size of}% +of an inch thick. If one thinks it probable that +it be, say five molecules thick in order to have the +degree of cohesion it shows, then the size of such\DPnote{** [sic]} +molecule of water out of which the bubble is made +can be but the one-fifth of the above small fraction, +which gives about the one fifty-millionth part of an +inch as the diameter of a molecule of water. + +But a molecule is not the same thing as an atom: it +is made up of atoms, chemically combined, and is +defined generally as being the smallest fragment of a +compound body that can exist and possess the physical +characteristics that belong to such body. Thus, a drop +of water possesses all the characteristics of any larger +quantity of it, and a drop may be divided into smaller +and smaller globules, perhaps a million of them, each +one being visible with a good microscope; but if the +division be carried to a higher degree, as it can be by +various methods, chemical, electrical, and thermal, the +qualities of water disappear, and two different substances, +oxygen and hydrogen, are left, both gaseous +under all ordinary conditions, and neither of them exhibiting +any properties like water or from which any +of the properties of water might be inferred. It may +be well to remark here that this is only one illustration +out of multitudes that might be named throughout the +whole domain of physical science, that the properties +of things under common observation are not simply +the properties that belong to the elements out of +which the things are built up; such properties +being the result of collocation rather than inherent +qualities. +\DPPageSep{026.png}{14}% + +The molecule of water is then a compound thing, and +is made up of three atoms,---two of hydrogen and one +of oxygen,---and therefore the actual size of an atom +of hydrogen must be less than that represented by the +above small fraction of an inch. Evidently a thing +made up of three individual parts and two dissimilar +substances cannot be spherical, and it will be well to +bear this in mind in thinking of molecular forms. One +may imagine the atoms themselves to be spheres, or +cubes, or tetrahedra, or rings, or disks, or any other +forms he likes, for the purpose of getting some sort of +a mental picture of what a molecule might look like if +it could be seen with a microscope; and it is probable +that very many persons have hoped or thought that +the microscope would sometime be so far perfected as +to enable one to actually look upon the molecules of +matter and perhaps upon their individual atoms. Let +us therefore consider the problem of how much more +powerful a microscope must need to be than any we +possess to-day, in order that one should see a molecule! +We will assume atoms to be about the one fifty-millionth +of an inch in diameter, and that when combined +into molecules they are geometrically arranged +so that the diameter of a molecule made up of a large +number of atoms is proportional to the cube root of +the number of atoms, as is the case with larger bodies, +say a box of bullets. + +A molecule of water contains three atoms, a molecule +of alum about one hundred, while, according to +Mulder, a molecule of albumen contains nearly a +thousand atoms. Then, according to the assumption, +\DPPageSep{027.png}{15}% +the molecule of alum would have a diameter +equal to +\[ +\frac{\sqrt[3]{100}}{50,000000} = \frac{1}{10,776000} \text{ of an inch}, +\] +and that of albumen would be equal to +\index{Albumen, size of molecule}% +\[ +\frac{\sqrt[3]{1,000}}{50,000000} = \frac{1}{5,000000} \text{ of an inch.} +\] + +Now, the best microscopes made to-day will enable +\index{Microscope, magnifying powers}% +one to see as barely visible a point the one hundred-thousandth +of an inch, so that such a microscope would +need to be as much more powerful than it now is as +one hundred thousand is contained in five millions, that +is, fifty times, in order to see the albumen molecule, and +for the alum molecule as many times as one hundred +thousand is contained in ten million seven hundred +thousand, that is, one hundred and seven times. Now, +one who is familiar with the microscope would probably +admit that one might be made through improved +methods of making and working glass hereafter to be +discovered, two or three, or even ten times better than +the best we have now; but the idea of one being made +fifty or one hundred times more powerful than we have +to-day, I do not think would be allowed to have any +degree of probability. The case may be illustrated as +follows: Suppose in the days of the stage-coach +some one had imagined that by some improvement in +methods of travelling one might some day travel one +hundred times faster than the stage-coach could then +go. Twelve miles an hour was not an uncommon rate +then; but one hundred times that would be twelve +\DPPageSep{028.png}{16}% +hundred miles an hour, and that is sixteen times faster +than the best we can now do, and about twenty-five +times faster than express-trains now go. As a matter +of fact, we travel about three or four times faster than +the best stage-coaches did, and, on a spurt, may go six +or eight times faster. The powers of the microscope +have not been doubled within the last fifty years, and I +suppose more time and ingenuity have been given to +the problem of improving it than will ever be given +to it in the same interval again. + +There is another and still more serious reason why +there is no probability that any one will ever see a +molecule, even though the microscope had the magnifying +power sufficient to reveal it; namely, the motions +that molecules are known to have would absolutely +prevent one from being seen. A free molecule of +hydrogen has a velocity of motion at ordinary temperatures +of upwards of a mile in a second, and its direction +of motion is changed millions of times in a +second. A microscope magnifies the movements of an +object as much as it does the object itself. An object +in the field of a microscope that should have a movement +no greater than the hundredth of an inch in a +second could only be glimpsed, so there is no possibility +of one's being able ever to see a free gaseous +molecule. Supposing one should be seized and held in +the field, even then it is to be remembered that it is in +a state of vibration, changing its form constantly on +account of its temperature, so that its wriggling would +prevent any inspection. + +Lastly, there is every reason to believe that the +\DPPageSep{029.png}{17}% +molecules of all bodies are so perfectly transparent +that they can no more be seen than can the air, even +if there were no difficulty from their smallness and +their motions. + +If the atoms of a single element like hydrogen are +so minute, so restless, and so transparent that no one +can hope to see them so as to make out their forms +and what gives them their characteristic properties, +what shall be said of the case of seventy or more elements +similarly minute and restless and transparent, +yet each one easily identified in several ways, physical +and chemical? Does it seem in any way probable that +such differences in properties as are exhibited by gold, +carbon, iron, and oxygen can be due simply to differences +in size or shape of the atom? Presumably not; +and the constitution of matter has therefore always +been a mystery to philosophers, for if one is to attempt +to philosophize upon the subject in accordance with +such other knowledge as we have, one would need to +conclude that if the different kinds of matter, the elements +as we know them, were formed out of some +prior kind of substance, as bullets and marbles are +formed out of lead and clay, then there must be as +many different kinds of substances out of which the +different elementary atoms are formed as there are +different elements, which proposition does not seem to +have such a degree of probability that any one could +adopt it. If one sought for the explanation of the +different properties by assuming that all the different +kinds of elements were formed out of one and the +same fundamental substance, then it is equally difficult +\DPPageSep{030.png}{18}% +to understand how mere differences in size and shape +could give such profound differences in quality as the +elements possess. + +Then, again, it appears that the individual atoms of +\index{Atoms}% +each element are precisely alike. One atom of hydrogen +is precisely like every other atom, so far as we +have definite knowledge. Sir~John Herschel likened +them to manufactured articles on account of their +exact similarity. A machine may turn out buttons or +hooks or wheels or coins so exactly like one another +that no one can tell them apart. It is really appalling +to think of the immense numbers of atoms of every +one of these seventy elements. It is a simple matter +to calculate how many atoms there must be in say a +cubic inch. It requires no other process than the +application of the multiplication table. If the diameter +of one be the fifty-millionth of an inch, then fifty +\index{Molecules, size of}% +million in a row would reach an inch, and a cubic +inch would contain the number represented by the +cube of fifty millions, which is +\[ +125000,000000,000000,000000, +\] +($125$~followed by twenty-one ciphers) a number which +is more conveniently represented by $125 × 10^{21}$. The +utter impossibility of conceiving such a number will +be apparent if one would try to represent to himself +what the magnitude of only one million really is. Go +out on a clear but moonless night and the heavens +appear to be filled with stars. Count all that can be +\index{Stars, their number}% +seen in a certain portion of the sky, say one-tenth, as +nearly as can be estimated, and then determine the +\DPPageSep{031.png}{19}% +number in the sky that are in sight by multiplication. +It will be discovered that only about two thousand can +be seen in the whole sky. If one million stars were to +be thus visible, it would require five hundred firmaments +as large and as well filled as the one looked at +to contain them. With the largest telescopes less than +a hundred millions of stars are visible; but what shall +one say when he learns that beyond a peradventure +the number of atoms in a single cubic inch of matter +\index{Atoms}% +of any sort is more than a million of millions times +all the stars in all the heavens visible in the largest +telescope. + +If one fancies that kind of work he may compute +the number of atoms that make up the world. Of +course it will make the number much larger; but when +written out not so much longer as one might think, for +when it is multiplied a million times it will add but six +ciphers to it. Some mathematicians have been to the +pains to compute the number of atoms there are in the +visible universe, or, rather, the number that cannot be +exceeded; for if the number stated above fills a cubic +inch, if one knows the diameter of the visible universe, +the space it occupies can readily be known in cubic +miles and cubic inches, and if all this space was filled +with atoms one could know and write down their number. +Astronomers tell us that some stars are so distant +\index{Stars, their distance}% +that their light requires as long as five thousand +years to reach us, although the velocity of light is as +great as $186,000$ miles in a second, and this distance is +to be measured in every direction about us. If this be +our visible universe, then the maximum number of +\DPPageSep{032.png}{20}% +\index{Universe, atoms in}% +atoms in it are calculable, and are stated to be represented +by the figure 6 followed by ninety-one ciphers, +or, as it is usually written, +\[ +6 × 10^{91}. +\] + +If we return to microscopic dimensions, and compute +the number of atoms, there will be in the smallest +amount of matter that can be seen with the highest +powers of the microscope, the one hundred-thousandth +of an inch, it will be seen that five hundred atoms in +a row would just reach the distance; and the cube of +$500$ is $125,000,000$, that could be contained in a space +so small as to appear like a vanishing-point and the +structure or details be utterly invisible. We have read +of spirits that could dance upon the point of a needle, +but the point of a needle would be a huge platform +when compared with this last visible point with the +microscope; and the spirit that should dance upon it +might be a million times bigger than an atom of matter, +and not be in danger from vertigo. One may be +astonished at the amount of intelligence associated +with the minute brain structure of some of the smaller +forms of animal life---say the ants; but from the above +it will be seen that so far as such intelligence is associated +with atomic and molecular brain structure, the size +of the brain in the smallest ant, though measured in +thousandth of an inch, is sufficiently large to involve +billions of atoms, and the permutations possible are +almost unlimited. The same idea is applicable to the +brain of man, and seems to indicate that such differences +in quality of mind as we see are not so much due +\DPPageSep{033.png}{21}% +to the differences in amount of brain, measured in +cubic inches, as in atomic and molecular structure. + +The work of physicists and chemists, carried on for +many years, has convinced them that none of the processes +to which matter has been subjected has affected +its quantity in the slightest degree. A definite quantity +\index{Atoms, unalterable}% +of hydrogen, or, what is precisely the same thing, +a definite number of hydrogen atoms, may be subject +to any conditions of temperature, may be made to combine +with other elements successively, forming with +them solids or liquids or gases, and no atom is +destroyed nor its individual properties changed in any +degree. Neither has any phenomenon been discovered +indicating that new atoms of any kind are ever produced +by any physical or chemical changes yet known. +Time does not alter them. Elements that have been +imbedded in rocks from primeval times, reckoned by +millions of years, when liberated to-day and tested, +exhibit precisely the same characteristics as those +obtained from other sources and that have been subject +to many artificial conditions. Sometimes a meteorite +\index{Meteors}% +reaches the earth, a sample specimen from distant +space, having moved in some orbit about the sun for +millions of years. Thousands of such bodies are in +our possession, and they have been carefully analyzed, +but no element unfamiliar to the chemist has been +found among them; and the iron, the nickel, the carbon, +the hydrogen, and all the rest of the elements that +compose them, behave in every particular like those +found on the earth. + +So far as spectroscopic evidence goes, it testifies to +\DPPageSep{034.png}{22}% +the presence of the same elements in the sun and +planets and comets; and it is as certain as anything +physical can be, that the expert chemist here would be +an equally expert chemist in the planet Mars, if he +could find a way to cross the immense space that separates +that star from us. + +These facts and conclusions are frequently stated in +such a form as this, namely, that matter cannot be created +\index{Atoms, unalterable}% +or annihilated. All that can fairly be meant by +such language is that under all the conditions at present +known, the quantity of matter remains constant; +and this proposition has a high degree of importance +in social affairs as well as in philosophy. If matter +were liable to change in its quantity or quality by being +subject to various physical conditions, all industries +involving commercial interests would be in an unstable +state. If the ton of iron ore should turn out, when +smelted, only fifty per cent of iron instead of sixty +per cent, as now,---the rest being either annihilated or +transformed into lead or gold, or something else,---the +smelting company would soon go bankrupt, even if +gold were the product instead of iron, for if gold +were liable to be produced in that kind of a way, +its value would be next to nothing as a standard of +value. + +The old alchemists sought to transmute what they +called the baser elements into gold. It is safe to say, +if it were physically possible to do it and some one +should discover the art, and it were an economical process, +commercial disaster such as the world has never +known would follow its announcement. It would be as +\DPPageSep{035.png}{23}% +if the volcanoes of the world should suddenly begin to +eject gold in the place of lava. + +Stability of physical properties is as essential for +the stability of society as the regular recurrence +of day and night; and philosophy would be impossible +if fundamental data were not in every way immutable. + +These physical principles lead to some curious and +most interesting conclusions with regard to the great +difference there is between bodies of matter of any +and all kinds that are familiar to our senses and the +atoms out of which these larger bodies are composed. +In every case, where there is a difference in movement +between two of these larger bodies made up of atoms, +there is what we call friction, which invariably results +\index{Friction, its effects}% +in wearing away some of the material of both. It is +the result of mechanical friction, to tear away some of +the surface molecules of the two bodies. Bodies in use +much, and therefore most subject to friction, become +worn out. Our clothing is a familiar example; the journals +of machinery, the tires of wheels, the sharpening +of tools, the polishing of gems, the weathering of wood +and stone,---all show that attrition removes some of the +surface materials of such bodies, but there is nothing +to indicate that attrition among atoms or molecules ever +removes any of their material. It appears as if one +might affirm in the strongest way that the atoms of +matter never wear out, are not subject to such friction +and the consequent destruction as comes to all bodies +made up of them. The molecules of oxygen and nitrogen +that constitute the air about us have been bumping +\DPPageSep{036.png}{24}% +and brushing against each other millions of times a +second for millions of years probably, and would have +been worn out or reduced, as the rocks upon the seashore +have been beaten and ground into sand, if they had +been subject to friction. So one may be led to the +conclusion that whatever else may decay atoms do not, +but remain as types of permanency through all imaginable +changes---permanent bodies in form and in +all physical qualities, and permanent in time, capable, +apparently, of enduring through infinite time. Presenting +no evidences of growth or decay, they are in strong +contrast with such bodies of visible magnitude as our +senses directly perceive. Valleys are lifted up and +become mountain-tops; mountains wear away and are +washed into the ocean; the beds of the ocean sink and +rise; and the boundaries of continents may be worn and +washed away through the incessant beatings of waves +against their coasts. Wear and tear go on in all inanimate +nature unceasingly, so that it is only a question +of time when everything we see upon the earth will +have changed beyond identification. The sun is shrinking, +and must some time cease to shine. The stars, +too, are changing likewise, because they shine, and +their places in the firmament will be vacant. All living +things grow because of change, and decay because +of more rapid change, and there appears to be nothing +stable but atoms. If it could be shown that life itself +and the mind of man were in some way associated with +\index{Mind, a material habitat for}% +\index{Mind and matter}% +atoms of some sort, as inherent properties, the hopes +\index{Atoms, life associated with}% +and longings cherished by mankind for continuous existence +\index{Immortality}% +beyond the short term of three score years and +\DPPageSep{037.png}{25}% +ten would give way to convictions as strong as one +has in any physical phenomenon whatever; the evidence +would be demonstrative in the same sense as +it is for the existence of atoms and their physical +qualities. +%\DPPageSep{038.png}{26}% + + +\Chapter{II}{The Ether}{26} + +\index{Ether}% + +\First{An} incandescent electric lamp consists of a fine +thread of carbon fixed in a glass bulb from which the +air has been exhausted. When a proper current of +electricity is permitted to traverse the carbon filament, +it becomes white-hot and gives out light like any other +hot body. Other luminous bodies are in the air, and +one might infer that the light was transmitted from the +heated body to the eye by the material of the air itself. +The light in the vacuum shows that this is not necessarily +so, for the more perfect the vacuum is made the +more freely does the light from the filament reach the +glass bulb that encloses it. One is therefore led to +infer that matter is not the agent that transmits light. +The light of the sun reaches us after travelling through +ninety-three millions of miles of space in about eight +\index{Light, its velocity}% +minutes. There are the best of reasons for believing +that the atmosphere of the earth does not reach at +most more than two hundred miles upwards from the +\index{Atmosphere, height of}% +surface, and its density at the height of only one hundred +miles is such that there would be only about one +molecule to the cubic foot. + +It is not unlikely that there are free-roving molecules +in space, as there are meteors in all directions about +\index{Meteors}% +\DPPageSep{039.png}{27}% +\index{Light, its nature}% +us, varying in size from fractions of a grain to masses +weighing some tons, but the distance apart of these +bodies is so great on the average that they cannot be +considered as either help or hindrance to the passage of +the light of either sun or stars. It is known with certainty +that what we call the light from shining bodies +is a kind of wave motion. The phenomena of interference, +which can be brought about in several different +ways, and which was referred to in the first chapter +when speaking of the colors of soap-bubbles, show +this. It is possible to annihilate two rays of light by +making one of them to follow the other in a certain +way; and one cannot conceive that two particles of matter +of any sort could annihilate each other by simply +changing their positions, but this is precisely what +happens in light. + +Wave motions of all kinds can cancel similar wave +motions; for the wave consists of periodic movements, +a crest and a trough, and when the crest and +trough of one wave are superposed upon the trough +and crest of another similar one, the result is the +destruction of both waves. The lengths of these waves +have been measured by a great many persons in various +parts of the world, and they all concur that light +can only be explained by wave motions such as they +measure. + +If there be wave motions, evidently there must be +something moved. One cannot conceive of a wave +movement when there is nothing that can be moved; +so men have been compelled to believe that there is +some medium between the sun and the earth that is +\DPPageSep{040.png}{28}% +\index{Light, its velocity}% +\index{Stars, their distance}% +\index{Sun, its distance}% +\index{Universe, its size}% +capable of wave motion, and this medium they have +agreed to call \emph{the ether}. + +If one admits the existence of ether between the sun +and the earth as the agency for the transmission of +light, he will need to do much more than that. The +sun is but about ninety-three millions of miles distant, +but most of the planets are hundreds of millions and +some of them thousands of millions of miles from us, +and the light comes from them too; so the ether must +extend through the space occupied by the solar system, +the diameter of which is six thousand millions of miles, +and to cross this space light requires nine hours, +though going at the rate of one hundred and eighty-six +thousand miles per second. + +Then there are the stars beyond our solar system, +the nearest one so distant as to require three and a +half years for the light to get to us at the same rate; +and some of these are so remote that thousands of years +are needed for their light to arrive. That light we see +from them to-day left them before America was discovered, +before Jesus was born, before the pyramids +were built, and for all we should be able to see they +might have ceased to exist long ago, though their light +continues to shine. So the ether must extend to those +most distant stars we can see, and that, too, in every +direction. There is no exaggeration in the statement +that our visible universe is so great that light requires +ten thousand years to cross its diameter. There is no +reason, either, for setting that as a boundary to its +magnitude; but wherever light comes from to us, there +must this medium, the ether, be. +\DPPageSep{041.png}{29}% +\index{Medium, necessity for}% + +But there are other and just as good reasons for +thinking there must be some medium between bodies, +even when all atoms and molecules have been removed. +For instance, everybody knows that one magnet affects +another at a distance from it, and there is no kind of +substance known that will prevent such action when +interposed between them. + +If one of these magnets be placed in the most perfect +vacuum that can be made, it still acts as it would +in the air, only with still greater freedom. One cannot +believe that one body can thus act upon another body +without some kind of a medium between them. Is it +not absurd to think otherwise? One may, if there +appears to him to be a good reason, suppose that there +is a magnetic medium or ether different from that one +employed in the transmission of light; but there is a +similar need for imagining one for the effects produced +by electrified bodies upon other bodies in their neighborhood. +An electrified glass rod will attract a pith +ball or anything else just as well in a vacuum as out of +it; and it is certain that electrical attraction and magnetic +attraction are not identical, for an electrified body +will attract one kind of thing as well as another, while +a magnet is selective in its effects, and affects iron +chiefly. Hence, if each different effect in a vacuum +is to be attributed to some different kind of medium, +there would need to be an electric ether in addition +to the other two. + +Then there is gravitative attraction, which has before +been mentioned. If it is not rational to think that one +body can act upon another body not in contact with it +\DPPageSep{042.png}{30}% +\index{Newton, Sir Isaac}% +and without some medium between them, then one is +bound to admit that the gravitative effects observed, +say between the moon and the earth, the sun and the +earth, and in every other case, are due to the action of +some medium between them. Neither is it at all needful +to be able to explain \emph{how} the medium acts thus and +thus, or even to imagine how it might, in order to firmly +believe that there must be one. + +Here are four cases of apparent action at a distance +of one body upon another, requiring some sort of an +intermediate agency; and, unless there be some good +reason for thinking there are several such media occupying +the same space apparently, it is much more +philosophical to believe it likely that one medium +exists capable of transmitting effects of the different +kinds; and especially will this appear to be truer if it is +known, as it is known, that the magnetic and electric +effects are transmitted with the same velocity as is the +light. So that physicists to-day quite concur in the +belief that what was called at first the luminiferous +ether, on account of its function in transmitting light, +is the same medium that is concerned in the other phenomena +of magnetism, electricity, and gravitation. + +It is likewise true that there are some physicists who +hold rather lightly upon this belief, taking it as a convenient +working hypothesis, and who would seem to be +ready in a minute to surrender the idea, unless it had +been demonstrated in the same way as the existence of +matter and of motion has been. But this is not the +attitude of philosophic minds. + +Sir Isaac Newton deduced from the observed motions +\DPPageSep{043.png}{31}% +of the heavenly bodies the fact that they attract +each other according to the law now known as the law +of gravitation, but he says nothing about \emph{how} bodies can +affect each other. That is, in his ``Principia'' he does +\index{Principia}% +not attempt to explain gravitation. He explicitly does +say, however, that he has not employed hypotheses in +his work, yet we know from other of his writings that +the idea of a medium was constantly in his mind. His +``Principia'' closes thus:--- +\begin{Quote} +``And now we might add something concerning a +most subtle spirit which pervades and lies hid in all +\Pagelabel{31}% +gross bodies; by the force and action of which spirit +the particles of bodies mutually attract one another at +near distances and cohere if contiguous; and electric +bodies operate to greater distances as well repelling +as attracting the neighboring corpuscles, and light is +emitted, reflected, inflected, and heats bodies; and all +sensation is excited, and the members of animal bodies +move at the command of the will, namely, by the vibrations +of this spirit mutually propagated along the solid +filaments of the nerves from the outward organs of +sense to the brain, and from the brain to the muscles. +But these things cannot be explained in few words, nor +are we furnished with that sufficiency of experiments +which is required to an accurate determination and +demonstration of the laws by which this electric and +elastic spirit operates.'' +\end{Quote} + +This shows plainly enough that he believed that +some medium, different from matter, was essential for +a mechanical conception of the phenomena he alluded +to. In a letter to Bentley he states his philosophical +judgment upon the subject in still stronger terms, and +it shows, too, the sense in which he is to be understood +when he says: ``I frame no hypotheses''---% +\DPPageSep{044.png}{32}% +which has frequently been repeated to adventurous +hypothecators as the example of the model scientific +man. Hear him! +\begin{Quote} +``It is inconceivable that inanimate brute matter +should, without the mediation of something else which +is not material, operate upon and affect other matter +without mutual contact, as it must do if gravitation in +the sense of Epicurus be essential and inherent in it.~\ldots +That gravity should be innate, inherent, and essential +to matter so that one body can act upon another at +a distance through a vacuum, without the mediation of +anything else, by and through which their action and +force may be conveyed from one to another, is to me +so great an absurdity that I believe no man who has in +philosophical matters a competent faculty of thinking +can ever fall into it.'' +\end{Quote} + +Newton uses the word \emph{Spirit} in the sense of a substance +entirely different from matter (see \Pageref{page}{31}). +Evidently Newton was so strong a believer in the +medium that we call the ether, though he could not +\index{Ether}% +work out its mode of action, that he was ready to discount +the intelligence of any man who doubted it.\footnote + {In 1708 Newton wrote thus: ``Perhaps the whole frame of nature may be + nothing but various contextures of some certain etherial spirits or vapors, condensed, + as it were, by precipitation; and after condensation wrought into various + forms, at first by the immediate hand of the Creator, and ever after by the power + of nature.'' + + These with his other acute remarks concerning what we now call the ether + lead us to infer that his mechanical instincts were more to be trusted in this field + than his more labored efforts.} + +If our knowledge of the existence of the ether is +not so positive as it is for matter, but is inferential, it +will be readily understood that the knowledge we have +of its properties cannot be very exhaustive. Some +have imagined that it was only a finer grained kind of +\DPPageSep{045.png}{33}% +matter than that we know as the elements, and that it +must be made up of atoms, though almost infinitesimal +in size. Others think it cannot be granular at all, but +forms a continuous substance throughout space. By +``continuous'' is meant that there are no interstices in +it: that it is constituted like a jelly, only not made up +of distinct parts or atoms, so there can be no such thing +as separating one part from another, leaving a vacuous +cavity or rent between them. One of the reasons for +thinking this to be the case is, that if it were made up +of finer atoms or of atoms at all, such waves as those +of light could not be transmitted by it. Longitudinal +waves, like those of sound in air, can be transmitted +by atomic or molecular structures but not transverse +waves, that is, such as are at right angles to the direction +of propagation. Some of these light waves are as +short as the hundred-thousandth of an inch, and some +are as long as the one two-thousandth of an inch, and +perhaps longer. Yet all of them are transmitted with +the same velocity in any and every direction. From +the fact that light travels with the same velocity in +every direction, it is inferred that the ether is not only +homogeneous, but its properties are alike in every +direction. As light is transmitted in straight lines, it +seems to follow that there is no difference in its quality +in different parts of space. + +That wave motions travel with such high velocity in +it has been interpreted as proving it to have a high +degree of elasticity, while the fact that it offers no +appreciable resistance to the movements of bodies of +matter in it is supposed to indicate that its density is +very small. +\DPPageSep{046.png}{34}% +\index{Earth, velocity of, in space}% +\index{Friction, its effects}% + +There are some, however, who think that such terms +as elasticity and density are not appropriately applied +to the ether. These terms signify properties of atoms +\index{Ether}% +and molecules. If density signifies compactness of +atoms, then the word could not apply to something not +composed of atoms. In like manner, if elasticity +means ability to recover form after deformation, then it +is not applicable to substances that cannot be deformed, +and it is customary to speak of the ether as +being incompressible. Still, it is certain that stresses +may be set up in it in various ways, and that these +conditions may be propagated, in certain cases in +straight lines, in other cases in curved lines, so whether +the explanation be forthcoming or not, there is no +doubt about the facts. + +There is no evidence at all that the ether is subject +to gravitative action, or that it offers any resistance to +a body moving in it. That is to say, it gives no evidence +of friction. Here is the earth rotating upon its +axis, and the velocity of rotation at the equator is a +thousand miles an hour, and if there were an appreciable +amount of friction the earth must slowly be coming +to rest like a top spun in the air. Yet the astronomers +tell us that the length of the day has not changed so +much as the hundredth of a second within the last two +thousand years. Again the earth revolves in its orbit +about the sun at the average rate of nineteen miles a +second, and if the ether through which it moves offered +any resistance to the motion, the length of the year +would be changed, but no such change has happened +in historic times. Again, such bodies as comets move +\DPPageSep{047.png}{35}% +\index{Thomson, Sir Wm.}% +\index{Vortex rings in air}% +very much faster than the earth; some have been +known to have a velocity of three hundred miles per +second when near the sun, but the comets complete +their circuits and give no evidence of slackened speed +due to friction in space. + +If, then, the ether \emph{fills} all space, is not atomic in +structure, presents no friction to bodies moving through +it, and is not subject to the law of gravitation, it does +not seem proper to call it matter. One might speak of +it as a substance if he wants another word than its +specific name for it. As for myself, I make a sharp +distinction between the ether and matter, and feel +somewhat confused to hear one speak of the ether as +matter. + +Nearly thirty years ago Helmholtz investigated, in a +\index{Helmholtz}% +mathematical way, the properties of vortical motions, +and, among others, pointed out that if a vortical motion +was set up in a frictionless medium, the motion would +be permanent, and it could not be transformed. Sir +William Thomson at once imagined that if such +motions were set up in the ether, the persistence of +their form and the possibility of a variety of motions +would correspond very closely with the properties that +the atoms of matter are known to possess. Such vortical +motions as are here alluded to, all have seen, as +they are often formed by locomotives when about starting, +if the air be quiescent. Horizontal rings, three +or four feet in diameter, may be seen to rise wriggling +into the air sometimes to the height of several +hundred feet. They may be formed also by smokers +by a vigorous throat movement forcibly puffing the +\DPPageSep{048.png}{36}% +smoke from their mouths, and they can be made +% [Illustration: ] +\begin{figure}[hbtp] + \begin{center} + \fbox{\Graphic{0.9\linewidth}{048a}} + \end{center} + \Caption{1}{Diag.\ 1.} +\end{figure} +artificially by providing a box having a hole on one +side an inch or two in diameter and the side opposite +covered with a piece of cloth. A saucer containing +strong ammonia water and another with strong hydrochloric +acid may be set inside, and dense fumes will +fill the box. If the cloth be struck by the hand, a ring +will issue from the hole, and may go forward several +feet, and its behavior may be studied. Such as are +formed in the air under such conditions present so +many interesting phenomena that it is worth the while +here to allude to them for the sake of helping the +mind to a clearer idea of how some of the properties +exhibited by matter may be accounted for.\footnote + {The method of producing these vortex rings and their phenomena are fully + explained in ``The Art of Projecting.'' By Prof.\ A.~E. Dolbear. Illustrated\DPtypo{}{.} + \$2.00. Published by Lee and Shepard, Boston.} + +\DPPageSep{049.png}{37}% +\index{Vortex rings, properties of}% + +1. The ring once formed consists of a definite +amount of the gaseous material of the air in a state of +rotation, %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}[11]{r}{1.5in} + \Graphic{1.375in}{049a} + \Caption{2}{Diag.\ 2.} +\end{wrapfigure} +and in its movements afterwards retains the +same material. It is to be noted +that the ring is formed in the air, +the white fumes serving merely to +make the ring visible. The ring +moves forward in a straight line +in the direction it is started, just +as if it were a solid body. It may +move very fast too,---ten feet a +second or more, and reach the +distant side of the room, but it +always moves of its own motion in a direction perpendicular +to the plane of the ring. + +2. It possesses momentum, and will push against +the object it hits. + +3. If made to move rapidly adjacent to a surface +like a wall or table, it will move towards it as if it were +attracted by it, and generally will be broken up by +impact against it. + +4. A light body, like a feather or thread, will be +apparently pushed out of the way in front of it, and +drawn towards it if behind it---phenomena like attraction +and repulsion. + +5. If two such rings bump together at their edges, +each one will vibrate with well-marked nodes and loops, +showing that, as rings, they are elastic bodies, and that +their period of vibration depends upon the rate of the +rotation. + +6. If two such rings be moving in the same line, but +\DPPageSep{050.png}{38}% +the hindmost one swifter so as to overtake the other, +the foremost one enlarges its diameter while the hinder +one contracts until it can go through the former, when +each recovers its original dimensions. + +7. If two meet in the same line, going in opposite +directions, the smaller one goes through the larger and +may be brought to a standstill in the air for a short +time until the other has got some inches away, when it +starts on in the same direction as before. + +8. If two similar ones are formed at the same time, +side by side, at a distance of an inch or two, they always +collide at once as if they had a mutual attraction. The +result of the collision may be the destruction of one or +both, or--- + +9. Each one may break at the point of impact, and +the opposite ends may weld together, forming a single +ring which will move on as if it had been singly formed, +or--- + +10. Instead of breaking they may rebound from each +other, but always at right angles to the plane in which +they were moving at first; that is to say, if they were +moving in a horizontal plane before impact, they will +rebound from each other in a vertical plane. + +11. Three rings may in like manner be made to join +into one. + +12. The material of the ring may often be seen to +be in rotation about the ring, while the ring, as a whole, +does not rotate at all, a rotary wave. + +13. The parts of a ring may be in a state of vibration +in the ring without changing its circular form, +somewhat as if the ring were tubular and two bodies +\DPPageSep{051.png}{39}% +\index{Elasticity due to motion}% +should move up on opposite sides till they met and +rebounded to meet below, and so on. +\Pagelabel{39}% + +All these, and some other just as curious phenomena, +may be observed in vortex rings, and may fairly be said +to be due to the properties of the rings themselves. +For instance, the vibratory motions alluded to in the +fifth show that elasticity is a property of the ring, +and that the degree of elasticity does not depend upon +what the ring is made of, but upon the kind and +degree of motion that constitutes the ring. If such a +ring could be produced in material not subject to friction, +none of the motion could be dissipated, and we +should have a permanent structure, possessing several +properties such as definite dimensions, volume, elasticity, +attraction, and so on, all due to the shape and +motions involved. + +Imagine, then, that vortex rings were in some way +formed in the ether, constituted of ether. If the ether +be, as it is generally believed to be, frictionless, then +such a thing would persist indefinitely: it would have +just that quality of durability that atoms seem to possess. +It would possess physical attributes, form, magnitude, +density, energy, that is, it would not be inert. +It would be elastic, executing a definite number of +vibrations per second. This property of elasticity has +generally heretofore been assumed to be a peculiar +endowment of ordinary matter, and one was at liberty +to imagine some matter without it because not so made. +This view implies that elasticity is a necessary property +of vortex rings; for as the velocity of rotation is +reduced, so is the degree of elasticity, and if there was +\DPPageSep{052.png}{40}% +\index{Bonnenburger's apparatus}% +simply a ring without being in rotation, it would have +no elasticity at all, neither would it have any qualities +different from the medium it was imbedded in. + +That such a quality as elasticity may be due solely to +\Pagelabel{40}% +motion, and varying with it, one may assure himself +with that piece of apparatus to be found in most collections +in schools known as Bonnenburger's. It consists +of a disk of metal, mounted in gimbals so it can +be set spinning %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}{l}{1.5in} + \Graphic{1.375in}{052a} + \Caption{3}{Diag.\ 3.---\textsc{Bonnenburger's Apparatus.}} +\end{wrapfigure} +in any plane. If +this be set spinning in a vertical +plane it becomes tolerably rigid +in that plane, and cannot be moved +out of it but by the employment +of quite a degree of pressure. If +the framework be quickly struck +by the finger while thus spinning, +the wheel will begin to rock back +and forth like the prong of a +tuning-fork, and the more rapid +the rotation the higher the rate +of vibration. When the velocity +of rotation becomes slow the +vibratory motion may be as slow +as once a second, and, of course, when the ring is not +revolving it will not vibrate at all. Thus there is fairly +good physical reason for thinking that what we call +elasticity in the atoms of matter may be due simply +to the motion they possess, and \emph{how} that may be one +can understand if atoms be vortex rings. + +One may properly ask how one vortex ring can differ +from another so there could be so many as seventy or +\DPPageSep{053.png}{41}% +more different kinds of atoms. To this it may be said +that such rings may differ from each other not only in +size but in their rate of rotation: the ring may be a +thick one or a thin one, may rotate relatively fast or +slow, may contain a greater or less amount of the ether. +The word ``mass'' in physics is used to denote a quantity +of matter as measured by its resistance to pressure +tending to move it as a whole. Thus if a pressure of +one pound be applied to two different bodies for say +one second, and one of them was moved an inch and +the other but half an inch when otherwise they were +alike free to move, we would say that one had twice the +mass of the other---its resistance to being moved was +twice as great as the other. + +In the case of the Bonnenburger's rotating disk, the +resistance to the pressure tending to move it depends +upon the rate of rotation, and a thin and swift moving +disk would offer much greater resistance than a much +larger one with a slower speed. So one might infer +that the difference in what is called mass among the +atoms of matter might be due simply to the different +speeds with which the rings rotate, rather than in the +absolute volume of ether in the state of rotation. +There are other reasons than these for thinking that +motion is the chief characteristic of matter. Chemists +have discovered that both the chemical and physical +properties of all kinds of matter are functions of their +mass or relative atomic weights, and that they may be +arranged in a harmonic series. Harmonic relations +may imply either relations of position or of motion. +But the fundamental properties of matter do not change +\DPPageSep{054.png}{42}% +by changing its position, and one is therefore led to the +conclusion that one must look to the various kinds of +motion involved among atoms for the explanation of all +their properties and all their phenomena. + +There is another very important and peculiar property +possessed by vortex rings; viz., there cannot be +such a thing as half a ring or any fragment of one. +Break such a ring in two and there is not left the two +halves; not only is the ring broken, but each part at once +vanishes into the indistinguishable substance that composed +it, and all the properties that characterized it as a +ring have vanished with it. + +This greatly aids one to understand that matter may +not be infinitely divisible. Over and over again have +philosophers asserted that it was impossible to imagine +an atom of matter so small that it could not in imagination +be again broken into two or more parts. A vortex +ring, however, shows how the thing can be done. +If an atom be a ring, when it is disrupted it is at once +dissolved into ether, and that is the end of it. There +are no fragments of the ring. + +One, however, must not infer from the above treatment +that it represents knowledge of a demonstrated +kind, for it does not. It was remarked in the first +chapter that atoms are too minute to be seen and +studied as one would study an animalcule or a blood +corpuscle, and one's knowledge must be altogether +inferential concerning them; but what knowledge we do +have, and the inferences that may properly be drawn +from it, all tend to convince one that matter and the +ether are most intimately related to each other, and +\DPPageSep{055.png}{43}% +that some such theory as the vortex ring theory of +matter must be true. + +Now, it is either that theory or nothing. There is +no other one that has any degree of probability at all. +If what is presented herewith is not the precise truth +concerning a most difficult subject, it may have the +merit of helping one to conceive the possibilities there +may be of deducing qualities from motions, and rid him +of the idea that matter consists necessarily of some +created things that have no necessary relations to the +rest of the universe beyond the properties impressed +by fiat. In the latter case one could never hope to +understand them, because there could be no \emph{necessary} +reason for their being as they are, rather than some +other way, whereas, in the former case, the mechanical +relations can be understood, and there is left the possibility +that by and by, with more light and knowledge, +one may know the physical conditions under which +matter itself came into existence. +%\DPPageSep{056.png}{44}% + + +\Chapter{III}{Motion}{44} + +\First{Everybody} has so clear a conception of motion that +there would not seem to be any difficulty in defining it +absolutely, but philosophers and others from remote +times till now have been perplexed by its problems. +How can Achilles ever overtake the tortoise, though +he runs ten times faster? How can the top of a +cart-wheel move faster than the bottom? If the sun +cannot set above the horizon and cannot set below +it, how can he set at all? In the last chapter some +phenomena were alluded to which were attributed to +motions of different kinds, and one must needs have a +definite notion of what he is talking about in order that +his words shall convey to himself, as well as others, +the information he would impart. Rest and motion are +contrasted conditions of bodies, so if a body is at rest +we say it is without motion, and \textit{vice versa}. If two persons +sit side by side in a house they may be said to be +at rest, but if they sit side by side in a railroad car they +will be at rest relative to each other as they were +before, but may be in motion with reference to things +outside the car. If, as a vessel sails past the end of a +wharf, a person on board would talk with a person +standing upon the wharf, he will walk so as to keep +\DPPageSep{057.png}{45}% +opposite the man standing still, and the two will be +at rest in relation to each other, while one will be in +motion with reference to everything on board the vessel. +Thus it appears that rest and motion are relative +terms, and can only be understood to apply to the +relative continuous position of two bodies or objects. +Hence, if there were but one object in the universe there +could be no such thing as change of position, for that +implies another body with which position may be compared +at intervals. But such a single body might have +some internal motions by which there was a relative +change of position of its parts with reference to themselves. +For instance, a tuning-fork might be at rest as +a whole with reference to all other bodies, yet its prongs +might vibrate towards and away from each other, the +centre of mass or the centre of gravity of the fork itself +not moving in the slightest degree either with reference +to itself or anything outside itself. Again, a body might +spin like a top, and there would be no change of position +of the body as a whole with reference to any other +body, nor change of position of the parts with reference +to each other, yet there would be a change of position +of the parts with reference to all bodies outside itself. +Hence, a brief definition of motion is not so easy to +give. + +One might say that motion was the change of position +of a body with reference to other bodies, or the change +of position of the parts of a body with reference to each +other, or the change of position of the parts of a body +with reference to other bodies. But these would not cover +all possible cases. There need be no trouble, however, +\DPPageSep{058.png}{46}% +\index{Molecules, size of}% +\index{Motion, kinds of}% +in particular cases, because there will always be data at +hand to determine the character and direction of the +motion. + +One may study the geometry of positions and changing +positions of mathematical points, and attend only to +rates and direction of motion of all sorts, without considering +the motions of bodies of real magnitude possessing +physical properties like matter. The science +that has to do with such ideal conditions is called \emph{kinematics}. +\index{Kinematics}% +Whenever the motions of matter are considered, +the science is called \emph{kinetics}. Of course all +\index{Kinetics}% +phenomena involve the motions of matter. Although +one sees a great variety of motions, a few examples of +particular sorts may be helpful in analyzing them. + +1. The drifting of clouds, the flight of birds, of +arrows, of bullets, of meteors, the sailing of vessels, the +running of locomotives, are examples of one kind of +motion; namely, where the change of position is that +of the body as a whole with reference to other bodies +external to it. The cloud may drift with the air, but +with reference to the surface of the earth it moves. +Where a body thus moves straight on continuously with +reference to other bodies, whether the distance moved +be long or short, the motion is called \emph{translatory} or +\emph{free-path motion}. The latter term is most frequently +applied to the movements of the molecules of a gas. +In ordinary air the distance apart of the molecules is on +the average about the one two-hundred-and-fifty-thousandth +of an inch, but the molecules themselves being +only one fifty-millionth of an inch in diameter, it will +be seen that they have a space to move in about two +\DPPageSep{059.png}{47}% +\index{Vacuum}% +hundred times their own diameter before coming in +collision with another one; and after collision their +direction is only changed when they go on to another +collision, and we say that their free path is on an average +about the two-hundred-and-fifty-thousandth of an +inch. With some modern air-pumps it is possible to +reduce the amount of air in a space so that the average +free path of a remaining molecule will be a foot or more; +but neither the size of the moving body, nor the distance +hundred times their own diameter before coming in +collision with another one; and after collision their +direction is only changed when they go on to another +collision, and we say that their free path is on an average +about the two-hundred-and-fifty-thousandth of an +inch. With some modern air-pumps it is possible to +reduce the amount of air in a space so that the average +free path of a remaining molecule will be a foot or more; +but neither the size of the moving body, nor the distance +it moves, nor the velocity with which it moves, +makes any essential difference in the specific kind of +motion: so the movements of air particles among themselves, +of billiard-balls between impacts, of a bullet on +its way to the target, and of a planet or comet in its +orbit, are all examples of the same kind of motion, +namely, translational. + +2. The swaying of the branches of trees when +moved by the wind, the swinging of the pendulums +of clocks, the movement of the piston in a steam-engine, +of the prongs of tuning-forks, the reeds and +strings in musical instruments, are examples of a different +kind of motion, inasmuch as the changes of position +relate to the body itself rather than to external bodies. +The tuning-fork is the type of them all, and together +they are called \emph{vibratory} motions. Sometimes, when +the bodies that move thus are large and the motion conspicuous, +as, for example, in the pendulum of the clock, +and the steam-engine piston, the motion is spoken of +as \emph{oscillatory}. In such cases, as in the former one, it +should be borne in mind that mere differences in the +size of bodies, or of the rate of motion, does not in any +\DPPageSep{060.png}{48}% +\index{Motion, kinds of}% +manner change the character of the motion, so the +name that is applicable to one will be equally applicable +to all. If one calls the movement of a vibrating tuning-fork +\emph{vibratory}, the same term may be applied to an +atom if it goes through a like periodic change of form, +for that is the chief characteristic of vibratory motion; +and hereafter it will appear how needful it is to bear +this in mind, for what a given amount of motion will +do will be seen to depend altogether upon the kind of +motion. + +3. The spinning-top, the balance-wheels of engines, +the wheels of machines of all kinds, the turning of the +earth, and each member of the solar system upon its +axis, are examples of another sort, where the displacement +is not, as in the last, between parts of the same +body, but a change in the relative position of each part +of a body to what is outside itself. The pendulum of a +clock swings to and fro, but its point of suspension does +not move; whereas every part of a turning-wheel is +presented to opposite parts of space in the plane of its +revolution. This motion is called \emph{rotary}, and just as in +the other two cases, I wish to emphasize the fact that +the term is properly applicable to masses of matter of +all degrees of magnitude; so an atom may spin on its +axis as well as the earth or sun, and the phenomena it +will be competent to produce by such spinning will be +very different from that produced by its vibrations or +free-path motions. + +These three kinds are all of the primary ones: all +the others we see are made up of these or their compounds. +For instance, a compound of a free-path +\DPPageSep{061.png}{49}% +\index{Motion, kinds of}% +\index{Motion, molecular and atomic}% +motion with a vibratory motion will give a wave or +sinuous motion if the direction of the vibration be at +right angles to the free path. A combination of a free-path +with a rotary may give a spiral motion, as illustrated +by the movement of a screw when pushed and +turned into a piece of wood. + +In a sewing-machine may be seen all of these kinds +of motion and some other compounds more complex +than the ones spoken of, but one may readily analyze +them into the three primary ones. + +These forms of motion have been spoken of as if +they were peculiar to matter; but it ought not to be +inferred that motion is not attributable to the ether. +Indeed, we know that some sorts of motions are propagated +in the ether. For instance, what we call light +is an example. Its form is \emph{undulatory}; and, as we have +seen above, an undulatory motion is a compound of a +rectilinear and a vibratory. A spiral movement in the +ether is also known, and it is sometimes called rotary-polarized +light: its motion is like that of a screw, and +we know that such a motion is a compound of a rectilinear +and a rotary. Rotary motions in the ether are +also known as taking place in front of magnetic poles, +and are the results of the magnetism imparted to the +iron or other substance. I am not aware that any +simple rectilinear motion is known to occur in the +ether: there may be, and likely enough is, such. + +For convenience, motions that are large enough to +be visible are called \emph{mechanical motions}, while those +too minute to be seen are often called \emph{molecular} or +\emph{atomic}. Sometimes these molecular and atomic motions +\DPPageSep{062.png}{50}% +\index{Motion, velocity of}% +are spoken of as if they were mysterious, and not to be +understood in the same sense as the larger ones that +are visible to us; but it is difficult to justify any such +distinction, and difficult to imagine that any kind of a +motion a large piece of matter may have, a small particle +or atom cannot have, and \textit{vice versa}. It would +seem probable that whoever finds a difficulty in this +cannot have strong mechanical aptitudes, and is not +gifted with an adequate scientific imagination. + +A free body of any kind and of any magnitude may +have any kind of a motion whatever, and may move in +any direction and with different velocities, but the term +\index{Velocities}% +velocity is used in different senses when applied to different +kinds of motion. Thus the velocity of an atom +in its free path, of a musket-bullet, of sound-waves, is +measured in feet per second. The velocity of vibrating +bodies is indicated by the number of vibrations they +make per second. A tuning-fork making two hundred +and fifty-six vibrations in a second is said to have that +rate of vibration, whether the actual distance moved be +one distance or another, which, of course, will depend +upon the amplitude of each individual swing; while +rotational velocity is generally specified by giving the +number of rotations per second, or per minute, or some +other unit interval of time. A top may spin a hundred +times a second, a balance-wheel of a steam-engine turn +four times, while the earth makes one revolution in a +day of twenty-four hours. The range in velocities of +these different kinds that have been measured is very +great indeed. In free-path or translational motion, +there may be the snail's pace, perhaps less than an +\DPPageSep{063.png}{51}% +inch a minute, the pace of a man walking say three +miles an hour, which is at the rate of eighty-eight feet +per minute. A race-horse may trot a mile in two +minutes and ten seconds, which is forty feet per +second. A steam-locomotive may run seventy miles +an hour, which is nearly one hundred feet per second. +A rifle-bullet may go a thousand feet, and a cannon-ball +two thousand feet in a second. The earth in its orbital +motion goes seventeen miles per second; meteors come +to the earth, from space, sometimes having a velocity +of fifty or more miles per second, while comets may +reach the velocity of nearly four hundred miles in the +same time when near the sun. These are the velocities +of bodies of visible magnitude, but some of the motions +of molecules are fairly comparable with some of these. +Thus a molecule of common air is moving in its free +path about sixteen hundred feet per second, while a +molecule of hydrogen, which is much lighter, goes +more than six-thousand feet---upwards of a mile---in the +same time. As remarked before, the free path for air +molecules having but about the two-hundred-thousandth +part of an inch, it must change its direction an enormous +number of times in a second,---as many times as +one two-hundred-and-fifty-thousandth of an inch is contained +in sixteen hundred feet; +\[ +250,000 × 12 × 1,600 = 4800,000000. +\] +Four thousand eight hundred millions of times. How +one may assure himself that such a statement is not +fabulous will be pointed out farther on; so far one +needs only to trust the multiplication table. +\DPPageSep{064.png}{52}% + +For vibratory rates there are also enormous ranges: +there are the slow oscillatory movements of swinging +pendulums of various lengths, sometimes occupying +several seconds for the execution of one vibration; +piano-strings having a range from about forty per +second to four thousand; the chirrup of crickets about +three thousand. Short whistles and steel rods have +been made that will make as many as twenty thousand +vibrations per second,---a rate much higher than can be +\index{Vibrations per second}% +perceived by most persons, though occasionally abnormal +hearing in an individual enables him to hear sounds +to which ordinary ears are entirely deaf. When the +number of vibrations per second becomes so great that +they cannot be individually seen nor heard, one must +trust his judgment and the properties of matter in +determining whether there really are any still more +rapid. It has been found by experiment that the number +of vibrations a given body can make when it is +struck so as to produce a sound depends upon its shape, +its size, its density, and its degree of elasticity. If a +steel rod, having a given diameter and length, makes, +when struck, five hundred vibrations per second, another +similar one with but half the length will make twice as +many in the same time. If one were made of something +still more elastic than steel, and of the same size, +the vibratory rate would be higher still. + +A steel tuning-fork three inches long may make five +hundred vibrations per second; if it were only the one +fifty-millionth of an inch long it would make not less +than $30000,000000$ vibrations per second; and if it +were made of a substance like ether it would make as +\DPPageSep{065.png}{53}% +many as $1000,000000,000000$---a thousand million +of millions per second. As large as this number is, +and as improbable as it would seem to be, there is indubitable +evidence that the atoms of matter do actually +make such a number of vibrations per second. +\index{Vibrations per second}% +\Pagelabel{53}% + +If one knows the rate at which vibrations are propagated +in a medium and the wave length, one can readily +determine the number of vibrations the body is making +that sets up the waves. Thus, if the velocity of sound +in the air be $1100$~feet per second, and the length of +one wave be $1$~foot, then the body must be making +$\dfrac{1100}{1}=1100$ vibrations per second: that is, the velocity +divided by the wave length will give the number of +vibrations. + +The velocity of light is known to be $186000$ miles +per second; the wave lengths of light are also known with +great precision, and are all only small fractions of an +inch. If they were only one inch long, their number +would be the number of inches there are in $186000$ +miles, or $12 × 5,280 × 186000 = 11784,960000$ per +second. In reality they are only one forty-thousandth +or the one fifty-thousandth of that. +\[ +11784,960000 × 50000 = 589,248000,000000, +\] +nearly six hundred millions of millions per second. No +one can pretend to comprehend such a number; but in +proportion as he understands the process and the data +by which such a result is reached, will he have an abiding +confidence that it is legitimate and that it expresses +the actual truth. +\DPPageSep{066.png}{54}% + +Sometimes it is convenient to know the actual space +that is moved over by a vibrating body in terms +of free-path or translatory motion, that is, how far +would the body move in the same time if, instead of +vibrating, it went on in a straight line. If the prong +of a tuning-fork moves through the one-hundredth of +an inch each swing, and vibrates one hundred times in +a second, obviously its rate of motion measured that +way would be only one inch, which would be a relatively +slow motion when compared with many others. +If the same computation be applied to atoms, however, +whose rate of vibration is so enormously high, it leads +to some very respectable translational velocities. Thus, +\index{Velocities}% +suppose the amplitude of vibration of an atom of hydrogen +be as great as one-half its diameter, that is, one +hundred-millionth of an inch, if it vibrates five hundred +millions of millions of times per second, the actual +space moved through will be +\[ +\frac{500,000000,000000}{100,000000} + = 5,000000 \text{ inches} = 80 \text{ miles,} +\] +which is more than four times that of the earth in +its orbit. It does not appear probable, however, that +the amplitude of motion is anywhere near as much +as that assumed, at any rate for ordinary temperatures; +but if it be only the one-hundredth of that amplitude +the velocity exceeds that which can artificially be given +to any visible object, as it will then be nearly a mile a +second. + +Rotary speeds have wide ranges. The earth takes +twenty-four hours to make one revolution; the moon +about twenty-eight days, and the sun twenty-six, and +\DPPageSep{067.png}{55}% +\index{Earth, diameter of}% +some others of the planets perhaps much longer than +that. Some astronomers have concluded from their +observations of the planets Venus and Mercury, that +\index{Mercury}% +\index{Venus}% +their axial rotation corresponds with their time of revolution +about the sun, being $224$~days for Venus, and $88$ +for Mercury. Tops have been made to spin eight hundred +or a thousand times per second; and if molecules +ever rotate their rate has not been measured. The +velocity of rotation, when measured as a translation, +must evidently depend upon the diameter of the body +rotating. The diameter of the earth being nearly eight +thousand miles, a point on the equator moves twenty-five +thousand miles in twenty-four hours---something +over a thousand miles an hour, or about seventeen miles +a minute. A driving-wheel of a locomotive that is six +feet in diameter will advance nearly nineteen feet every +revolution. To have a speed of a mile a minute, which +is $88$~feet per second, it must turn round $\dfrac{88}{19}=4.6$~times +per second\DPtypo{}{.} A disk $4$~inches in diameter, spinning $800$ +revolutions per second, which was the speed given by +Foucault to one of his gyroscopes, would advance, if +allowed to roll, with the speed of $837$~feet per second---nearly +ten miles a minute. + +There are some facts, and inferences we draw from +them, with regard to motion and the geometry of space +that it may be well to mention here. When we speak +of the velocity of a body at a given time we mean by it +that its rate is such that if continued for the whole +interval of the unit of time, whether it be a second, or +a minute, an hour, or any other, the body will move +\DPPageSep{068.png}{56}% +\index{Sun, its distance}% +through the whole specified distance. A body will not +need to go a mile in a minute in order to have a velocity +of a mile a minute. It may not move ten feet, yet +may have that or any higher velocity. This is obvious +enough of course. Every one trusts arithmetical processes +to lead him to correct results in velocities and +\index{Velocities}% +time and all such familiar matters. One will say +frequently, ``It is six hours to New York'' instead of, +``It is two hundred miles to New York,'' and will not +be misunderstood. Some persons have computed how +long a time it would take to reach the sun if they were +to take an express-train running at the rate of fifty +miles an hour, without stopping for food or fuel; and +they find it comes out nearly two hundred years,---a +time of transit equivalent to five generations of men. +In like manner, presuming one knows the distance to +any remote point in space, the time required to get +there at a given velocity one would call a simple problem +in arithmetic, and it is. But there is an assumption +one has to make which is rarely considered: that is, +the properties of space and of time are the same everywhere, +and that the geometry of the space in which we +\index{Geometry}% +live is a geometry that holds everywhere and always: +that its propositions are absolutely and irrefragably true +always and everywhere. We assume, because we find +them practically true on a small scale, that they are +equally true on the largest scale. + +Within the past fifty years the great geometers have +made some very wonderful discoveries---one might say, +astounding discoveries; for they tell us that we do not +know that the sum of the interior angles of a plain +\DPPageSep{069.png}{57}% +triangle is equal to a hundred and eighty degrees, +that we do not know it within ten degrees if the +triangle be a very large one, such as is formed by +the spaces between remote stars and the sun; furthermore, +we are assured that, for all we know, and therefore +for all we can reason from, space itself may be +\Pagelabel{57}% +curved so that if one were to start in what we call a +straight line, in any direction, and travel in it on and on +he would find himself after a long time coming to his +starting-point from the opposite direction; that what +one would see if his sight were prolonged in any direction +would be the back of his own head much magnified. +Methods have been proposed for discovering if it be +true or not. Some folks have called this nonsense, and +have used descriptive adjectives to express their contempt +for it; but none of those who have spoken thus +of the new geometry are themselves mathematicians, +\index{Geometry}% +and one is therefore left with the fair inference that +they did not so well know of what they condemned as +did the mathematicians who reached the conclusion.\footnote + {See \hyperref[page:400]{Appendix}.} + +Now, we all of us trust such mathematical processes +as we can ourselves handle, even when they lead us to +magnitudes and distances too great for comprehension. +All that one needs to know is, that the process is a +legitimate one and is correctly worked out. This new +geometry I have alluded to has been worked at by the +best mathematicians of all the civilized nations, and +they agree in the conclusions. They certainly would +not do so if there were the slightest apparent reason +for rejecting them; for national jealousies are too +\DPPageSep{070.png}{58}% +strong, and a sense of the value of truth too great, to +allow any such notions to gain currency anywhere if +there were any possibilities of breaking them down. + +If the space we live in and the geometric relations +\index{Space}% +are only practically true upon a small scale; if we may +have a kind of space of four or more dimensions, whether +we now can conceive of it or not, then should one understand +that spaces and distances and velocities and all +computations formed upon them, though practically +true, for all of our experience must not be pushed up +into statements that shall embrace all things in the +heavens as well as on the earth. Perhaps even the +visible universe is not to be measured by our span, +much less things invisible in it and beyond it. +%\DPPageSep{071.png}{59}% + + +\Chapter{IV}{Energy}{59} + +\First{Whenever} a body of matter having any motion +strikes another body, it always imparts some of its +motion to it, and the second body moves. The ability +one body has to move another one is sometimes called +its energy, and the amount of energy received is proportional +to the amount of similar energy the first body +possesses. A body at rest can impart no motion to +another one, so it appears that the energy a body has +depends upon its own amount of motion. Neither can +a body impart to another one more motion than it possesses +itself, and rarely or never can it do so much as +that. Inasmuch as every kind of a phenomenon is the +\index{Phenomena, nature of}% +result of the transfer of some kind of motion from one +body to another, one may rightly infer that to understand +phenomena and their relations, one must need to +know, not only the kinds of motion that are transferred, +but must also know their quantitative relations, and he +must therefore have some units and standards for comparison. +This requires some measure for the amount +of matter involved, also some measure for the motion +it has. For the former it is customary to employ a +weight. A certain mass of matter called a pound is +adopted in England and America. Exact duplicates of +\DPPageSep{072.png}{60}% +\index{Falling bodies}% +\index{Falling bodies, energy of}% +\index{Weights, standards of}% +\index{Work, standard of}% +its standard weights are made and preserved by each +nation; so as weights become worn by usage, they +may be exactly replaced. Any unit space may be +adopted, as the foot, which is common. If a pound +has been raised a foot, a certain amount of work has +been done, which is called a \emph{foot-pound}, and it is important +\index{Foot-pound}% +to keep in mind just what it signifies. If ten +pounds be raised one foot, or if one pound be raised +ten feet, the same amount of work---ten foot-pounds---has +been done; and with this as a starting-point, it +will be easy to see how energy may be measured, for +the measure of it will be the amount of work, measured +in foot-pounds, it can do. It is found by experiment +that if a body be left free to fall in the air, it will fall +sixteen feet in a second, and its velocity at the end of +the second will be thirty-two feet. If a very elastic +ball weighing a pound should fall thus in the air upon +an elastic pavement, it would rebound nearly to the +height of sixteen feet. If it does not quite reach that +height, it is because the air retards it somewhat, and +some of its motion has been imparted to the pavement +upon which it falls. Adding those losses to the height +it did rise, and it would make the sixteen feet. Now, to +raise a pound sixteen feet required sixteen foot-pounds +of work; there must therefore have been sixteen foot-pounds +of energy at the instant of impact. Its velocity +was thirty-two feet per second. Hence a body weighing +one pound, having a velocity of thirty-two feet in a +second, is capable of doing sixteen foot-pounds of work. +It is found also that if the same body falls for two +seconds, it will fall sixty-four feet, and its velocity at +\DPPageSep{073.png}{61}% +the end of the second second will be sixty-four feet,---twice +as great as it was for the fall of one second; but +the pound weight in this case will rise under similar +\index{Weight}% +conditions to the height of sixty-four feet, which is four +times higher than for thirty-two feet per second; so it +is seen that in this case, when the velocity is doubled, +the power of doing work, measured in foot-pounds, has +been increased four times, and this is generally expressed +by saying that the energy of a body is proportional +to the square of its velocity. The particular +direction in which a body moves has not been found to +make any difference in this regard, so the statement is +a general one. If a mass weighing two pounds were +dropped, as in the first instance, it would rise no higher +than if it weighed but one; but two pounds raised sixteen +feet would give thirty-two foot-pounds, so the +work would be proportional to the weight as well as to +the square of the velocity. + +The amount of matter there is in, say, a pound weight +would be just the same in one place as in another; but +the attraction of the earth upon it depends upon where +it is. At the surface, where we measure it, it has a +certain value; but at the centre of the earth it would +weigh nothing. The farther it were removed from +the surface of the earth upwards, the less would its +weight be. At the height of a thousand miles it would +be but four-fifths of a pound; at a million miles it +would be but sixteen-millionths of a pound, or only +about the tenth of a grain. + +For that reason it has become necessary to find +some measure for matter that shall be independent of +\DPPageSep{074.png}{62}% +\index{Foot-pound}% +\index{Work, measure of}% +position, and this has been found by dividing the weight +of the body at a given place by the value of gravity at +that place, and calling the quotient the \emph{mass}; so if $w$~represents +the weight of a body at a given place, and +$g$~the value of gravity at the same place, that is, the +velocity that gravity will give to a body in one second +if left free to fall, then $\dfrac{w}{g} = m$, the mass. The distance +in feet that a body will fall in a second is equal +to the square of the velocity divided by twice the value +of gravity, or~$d$, the distance,~$= \dfrac{v^2}{2g}$; and as the weight +equals~$mg$, the product of the two is $mg × \dfrac{v^2}{2g} = \dfrac{mv^2}{2}$, +one-half the product of the mass into the square of the +velocity will give the energy of a body. But it is +generally more convenient to use the weight of the +body instead of its mass. As $m = \dfrac{w}{g}$, let it be substituted +for~$m$ in the expression of energy, and we shall +have $\dfrac{wv^2}{2g} = pd$ (pressure in pounds into distance in +feet), or foot-pounds, a very convenient expression to +keep in mind if one has any problems in motion and +energy for solution. + +An example will make plain the utility of this. A +body weighing ten pounds is moving with the velocity +of one hundred feet in a second; how much energy has it? +$\dfrac{wv^2}{2g} = \dfrac{10 × 100^2}{64} = 1562~\text{foot-pounds}$; that is, it has +energy enough to raise $1562$~pounds a foot high, or ten +pounds $156.2$~feet high. +\DPPageSep{075.png}{63}% + +This is applicable to all bodies, big and little, whose +weight and velocity of translation are given. + +When a person who weighs one hundred and fifty +pounds climbs a flight of stairs---say, to the height of +ten feet---he has done $150 × 10 = 1500$ foot-pounds of +work. Whether he has gone up fast or slow makes no +difference in the amount of work done; it will only +make a difference in the \emph{rate} of doing work. Now, a +horse-power is a rate of work, and is equal to $550$~foot-pounds +a second; and hence if the above individual +climbs the stairs at the rate of four feet a second, he +will be doing $4 × 150 = 600$ foot-pounds per second, +which is over a horse-power, and indicates the +probability that he would not climb so fast. If any +one thinks he can do it, it will be worth his while to +try it. + +Work can be measured on a horizontal as well as a +vertical plane. Suppose the horses on a horse-car pull +two hundred pounds, as indicated by a dynamometer, +and the car is moved five feet in a second: the pull +into the distance measures the work done; that is, +$pd = 200 × 5 = 1000$ foot-pounds, a little less than +two-horse power. These illustrations are given because +not every one has clear enough ideas concerning the +meaning of energy and work, much less the ability to +apply them to examples that may often come up. +When one sees the long trail of a meteor in the sky, +and remembers that its velocity may be as much as +twenty or more miles per second, he will now see that +it may have a good deal of energy, though its weight be +but a few grains. +\DPPageSep{076.png}{64}% +\index{Energy of translation}% +\index{Meteors}% +\index{Work, measure of}% + +The energy of a pound moving twenty miles a second +would equal +\[ +\frac{1 × (20 × 5280)^2}{64} = 174,240000 \text{ foot-pounds.} +\] +A grain is one seven-thousandth of a pound, and its +energy would therefore be but the one seven-thousandth +of that quantity. $\dfrac{174,240000}{7000} = 24891$, which is the +number of foot-pounds of work a meteor weighing one +grain, at that velocity, may have: enough to raise a +ton twelve feet high. + +As a matter of fact, the great friction it is subject to +in its path through the air heats it shortly to incandescence, +and it is presently dissipated. If it were not for +the air, therefore, even if we could subsist without it, +mankind would be in constant danger from the flying +missiles; for though they would weigh but a little, +their velocity would enable them to do destructive +work upon everything they struck. As there are some +millions that come into the atmosphere every day, no +one could be safe from them in any place. + +The energy of a workingman is measured in the +same way; namely, by the amount of work in foot-pounds +he can do. + +One of the most direct ways of knowing this for an +individual is to ascertain the amount of earth or stones +he can load into a cart, or the bricks he can carry up a +ladder to the mason. Suppose he throws fifteen shovelfuls +per minute, each one holding ten pounds, and each +one is raised four feet high: then in a minute he has done +\DPPageSep{077.png}{65}% +\index{Goose, work in flying}% +$15 × 10 × 4 = 600$ foot-pounds of work, or $10$~per second. +This is rather a small quantity, only the one fifty-fifth of +what a horse-power would do, and most men have been +found able to do forty or fifty foot-pounds per second; +still, there is a great difference in individuals in their +working ability. Climbing, in general, is hard work +because it is continuous lifting of one's self. One who +weighs one hundred and fifty pounds, and climbs one +hundred feet, has done $15000$ foot-pounds of work; and +if he has done it in a minute, he has spent nearly half a +horse-power, which is $33000$ foot-pounds a minute. + +Once more: a bird in flying has to do work; and one +may see how much is demanded of such birds as geese, +that make long voyages through the air in the fall and +spring,---sometimes for twelve hours or more continuously. +As work is measured by pressure into distance, +one may apply it thus. Geese are known to fly at the +rate of thirty miles per hour, which is forty-four feet per +second. In flying, of course, there has to be a push +forward by means of their wings, not only to advance, +but to maintain their elevation. Supposing that a large +bird flying at this rate should have to exert a push of +one pound continually: it would be expending then forty-four +foot-pounds per second, nearly one-twelfth of a horsepower; +and to maintain such a rate for twelve hours +would imply that it had a supply of energy to start with +of $44 × 60 × 60 × 12 = 1,900800$ foot-pounds for one +day's expenditure. This does not seem at all probable, +and one may therefore infer that the pressure exerted +when going at that rate is much less. If the pressure +were but one ounce instead of a pound, the rate of work +\DPPageSep{078.png}{66}% +\index{Energy of vibration}% +would be $\dfrac{44}{16} = 2.75$ foot-pounds per second, which is +much more likely; but this supposes the bird to have a +supply of energy of $\dfrac{1,900800}{2.75} = 700000$ foot-pounds. + +In the chapter on ``\hyperref[chap:chemism]{Chemism},'' the source of the +energy of animals will be more particularly treated. + +So far the energy involved in translatory or free-path---or, +as it is more often called, mechanical---energy +has been considered; but vibratory motions of matter involve +energy also, and the same expression is applicable +as in the first case,~$\dfrac{wv^2}{2g}$. Here the value of the~$v$, +or the velocity, has to be determined by analyzing the +motion itself. This is not simply the number of times +the body vibrates, but also the extent of each individual +vibration,---that is to say, the amplitude of vibration,---and +the product of these two factors will give the +value of~$v$ needed. So if $n$~be the number of times the +body vibrates a second, and $a$~be the amplitude of the individual +vibrations, the true velocity will be represented +by~$an$, and then the expression for the energy will be +\[ +\dfrac{wa^2 n^2}{2g}. +\] +For most bodies of visible magnitude the amplitude of +vibration is so small a quantity that for frequencies of +only a few hundred per second, the velocity, measured +as a translation, is small, and therefore the energy is +small, and there are few cases where it is very important +to take it into account. + +Suppose a vibrating body has an amplitude of the +\DPPageSep{079.png}{67}% +one-hundredth of an inch, and vibrates a hundred times +in a second: the total distance moved through in a +second would be but an inch, which would be the value +of~$v$, so the amount of energy it had would depend +more largely upon the weight of the body. On the +other hand, if a body is so small that its rate of vibration +is exceedingly high, as was shown in the case of +atoms on \Pageref{page}{53}, there might be a relatively large +amount of energy involved. In the case refered\DPnote{** [sic]} to, a +velocity of eighty miles a second was computed, on +\Pagelabel{67}% +the supposition that the amplitude of vibration was +equal to one-half the diameter of the atom; and what +amount of energy is possessed by a body weighing one +grain was computed. The amount in an atom with +that vibratory rate and amplitude would be calculated +by dividing the amount in the grain by the number of +atoms in a grain. Numerically it is a very, very small +quantity, and only becomes appreciable to any of our +senses when vast numbers of atoms act conjointly. + +There are some cases where energy is apparently +expended when there is no apparent motion, as is the +case when a man holds up a weight. If the weight be +\index{Muscular work}% +\index{Work, muscular}% +a heavy one, exhaustion will be the result as much as if +energy was spent in any other way. This muscular +work is called physiological work, and for a long time +it was not understood. It is now known, however, that +when a muscle is put in a state of tension, it is in longitudinal +vibration a great many times a second. This +may be perceived by putting the end of a finger into +the ear, pressing but gently, at the same time squeezing +with the rest of the hand as if grasping something +\DPPageSep{080.png}{68}% +\index{Energy of rotation}% +tightly; a low sound will be heard, made by perhaps +no more than thirty or forty vibrations per second. +The muscles in a state of tension produce this. When +one holds up a weight---say, a pail of water---the muscles +involved yield and contract rapidly, so the weight +is really raised in a vibratory way a short distance, but +a great many times in a second; and the heavier the +weight, the more the work done, and this too is measured +in the same way as other more visible kinds. +There is good reason for believing that a book resting +upon a table is supported by the vibratory motions +going on among the particles of the table, and therefore +energy is expended to do it, and that this is supplied +by the heat present in the body; that is, the +temperature of the table is a little different from what +it would be if it did not have any weight to support. + +Walking involves the expenditure of energy in the +same way. Each step requires the whole body to be +raised somewhat. Suppose it be only an inch. A +person weighing $150$~pounds would, for each step, do +$\dfrac{150}{12}$ foot-pounds~$= 12\frac{1}{2}$. If he takes two steps per +second, then each minute he does $2 × 12\frac{1}{2} × 60 = 1500$ +foot-pounds of work. Thus one can see how physiological +processes are measurable in terms of mechanical +units. + +The energy of a rotating body is more complicated +than translational energy, because a part of the body is +at rest,---the axis; and the velocity of movement at +any point away from that is proportional to its distance +from it. In the case of the balance-wheels of steam +\DPPageSep{081.png}{69}% +engines, where the most of the weight of the wheel is +in the rim, the velocity of the latter would be equal to +its circumference multiplied by the number of turns +per second or per minute. Thus if a fly-wheel, having +nearly the whole of its weight in the rim, weighs, say, a +ton ($2000$~lbs.), is six feet in diameter, and rotates four +times a second, its velocity will be $75.4$~feet per second, +and its energy will be $\dfrac{wv^2}{2g} = \dfrac{2000 × 75.4^2}{64} = 177661$ +foot-pounds, an amount of energy which is stored up, +\Pagelabel{69}% +and may be drawn upon to prevent fluctuations in +speed to which engines in workshops are liable. + +If a body having rectilinear motion be left to itself +in the air, it will speedily be brought to rest, for gravity +will bring it to the earth whether it be moving this way +or that. The air, too, will retard its motion, and would +ultimately bring it to rest if nothing else did, as it +would either of the other kinds of motion. If, however, +one could contrive to give to a body above the atmosphere +a sufficient velocity in a tangential direction, the +body would become a satellite, and revolve round the +\index{Satellite}% +earth. The curvature of the earth is about eight +\index{Earth, curvature}% +inches to the mile, and such a body would then need to +move a mile in a horizontal direction in the same time +it falls eight inches in order that it should continue to +go about the earth. As it takes about two-tenths of a +second to fall this distance, its velocity would need to be +five miles a second to prevent it from falling to the +earth; this velocity would carry it quite round the earth +in a little less than an hour and a half. + +Thus it is seen that, in order that matter should +\DPPageSep{082.png}{70}% +\index{Energy, factors of}% +\index{Motion, laws of}% +possess energy, it must have motion of some kind; +indeed, that energy has two factors, mass and motion. +When either of these is zero, there is no energy. This +is a consideration of great importance both in a scientific +sense and a philosophical one. One may often +hear it said and read it in carefully written books that +matter and energy are the two realities or physical +things in the universe, and energy is spoken of as if it +were an entity, or something that might exist though +there were no substance to move. If energy be a +product, and motion be one of the factors, then in the +absence of this there is no energy. This perhaps will +be seen still clearer after considering what are called +the laws of motion, which were first formulated by +Newton, and which, in conjunction with the law of +gravitation, were the fundamental principles that +enabled him to produce the ``Principia,'' which is what +\index{Principia}% +to-day we would call a treatise on mechanics. + +Of course, the science of mechanics is applicable to +motions of matter of any magnitude and in any place; +and Newton chose to follow out his newly discovered +principles into astronomy to the largest extent, and it +remained for later generations to employ the same principles +in other directions, largely molecular and atomic. + +The first law of motion is, that whether a body be in +a state of rest or of motion, it will remain in that state +of rest or motion until compelled by the action of some +other body upon it to change its state. This is sometimes +expressed by saying that all matter has \emph{inertia}, +\index{Inertia}% +\Pagelabel{70}% +or an inability to move or change its direction or velocity +if it has motion. This appears to be experimentally +\DPPageSep{083.png}{71}% +\index{Explosion products}% +true of all bodies whose magnitude and state +we can see. But it may very well be doubted if the +ordinary conception of the inertness of matter be true. +Many of the facts of chemistry indicate that matter in +its atomic form is not altogether so helpless as it has +been supposed to be. A stone may lie in the road for +an indefinite time and no one would suspect it possessed +any energy to do anything, and so of any other kind of +matter. Here is a piece of charcoal. Has it inertness in +any extreme sense of that word? Here is some sulphur +and some nitrate of potash; they, too, will lie as +quiescent as the coal and as long. Pulverize them and +mix them together, and we have powder the energy of +which would wreck a building. The products of the +explosion are gaseous mostly, and the carbon, the sulphur, +and the nitrate of potash have vanished as such, +and have entered suddenly into new combinations; +they have developed also a large amount of heat, while +at the beginning their temperature was that of other +bodies around them. This source of energy must have +been resident in the atoms; and if it is perceived that +for a body to have energy it is necessary for it to have +motion of some sort, it will be apparent that the +material itself must have possessed a large amount of +motion, even when it appeared to be at rest. If one +thinks that the law of inertia might still apply to atoms, +and that they cannot individually move except as they +are acted upon by other atoms, and even then only as +much as by the measure of the motion thus imparted, +he had better figure out to himself the energy of such +explosions per molecule, and see if anything initially +done will account for it. +\DPPageSep{084.png}{72}% +\index{Motion, antecedent of}% +\index{Top, sleep of}% +\index{Vortex rings, properties of}% + +When the mechanism of a clock is running, the +motion may be traced to a falling weight, and the work +done is measured by the product of the weights into +the distance it falls as the clock runs down; but in +the case of the powder, though the amount of energy +developed by the explosion is definite, it is not measured +by the work done in pulverizing and mixing and igniting +it. The case is much more nearly analogous to +that of a sleeping man. While asleep he would neither +move nor stop moving unless some other agency acted +upon him, any more than would a stone or other mass +of matter; and in that sense he would be inert, yet no +one would think of calling a sleeping man inert, except +in a very loose sense. + +Furthermore, there is an experimental analogy that +may help one to see a little deeper into this. Every +one knows what is meant by the ``sleep'' of a spinning +top. It appears to be absolutely at rest, and may not +even hum; but touch it, and the effect upon it will be +out of all proportion to the slightness of the touch. + +It has been observed as a property of vortex rings that +they have a tendency to move forward in the direction +of their axes, and when prevented from going forward +they press upon the body that arrests them. If they +be brought to rest, and then the barrier be removed, +\emph{they, of their own accord}, start on in the same direction +as if pushed from behind. Such a body cannot be +said to be inert without modifying the common meaning +of the word. + +This is not alluded to here as proving anything; but +inasmuch as the vortex-ring theory of matter has a good +\DPPageSep{085.png}{73}% +\index{Motion, laws of}% +probability in its favor, this property I have mentioned +helps one to understand how the atoms might be other +than inert, and yet large bodies of them together exhibit +that property with the rigorousness our observations +upon such bodies demonstrate. Suppose each +atom had the ability to move forward of its own impulse +when not acted on by any other atom. If there +were a million atoms joined together, no matter how, +provided they were promiscuously faced, they would +mutually neutralize each other's ability to move in any +direction, and the resultant of the whole would be that +passivity which we call inertness. + +We may by and by see that there may be still other +good reasons for thinking matter not to be so passive +as it has been often assumed to be. + +The second law of motion is, when two or more +bodies act upon a third body, the effect of each is the +same as if it alone acted, and the combined effect is +called the resultant; and the third law is, that action +and reaction are always equal and opposite in direction. +This third condition of action, or the relation of +motions in two bodies, is of a high degree of philosophical +importance, perhaps not more so than the others, +but of so much that it is worth while to attend to it +more particularly than to the second law. If a rope be +tied to the wall and one pulls upon it so as to make it +taut, the wall pulls back in the opposite direction as +much as the arm pulls forward. A spring-balance +attached to the wall would indicate the strength of the +pull, the pull of the arm representing the action, and +measured by the muscular vibration, as already described, +\DPPageSep{086.png}{74}% +and the pull of the wall representing the +reaction, and equal to the action in quantity and maintained +by molecular vibration. Imagine the action of +the arm to be steadily increasing in quantity: the +reaction of the wall would correspondingly increase +until the molecular tension could no longer be increased, +and either the rope would break, the hook be pulled out +from the wall, or the wall itself be broken away; but in +no case could the action exceed the reaction or \textit{vice +versa}. Now, if the amount of matter in the arm were a +constant quantity, as well as that of the rope, the hook, +and the wall, then it would follow that all the physical +changes noted in either the one or the other, so far as +energy is concerned, must be due to the motions involved +on either side. And if action and reaction be +equal, and the quantity of matter be uniform, then the +amount of motion involved must be equal on the two +sides. If a body in motion strikes another body, and +the second one is set in motion, the amount of motion in +the two will be just equal to the amount of motion +in the first. The amount of motion gained by one +body is just equal to that lost by the other, and there +has been simply an exchange of motions, one having +gained, the other lost; the one that gained being the +one that had less, and the one that lost having had +more, than the other one. In books of physics it is +customary to speak of the amount of motion a body has +as its \textit{momentum}; and it may be measured by multiplying +\index{Momentum}% +the mass of the body by its velocity, and oftentimes +one may read that in the physical exchanges that are +all the time happening in matter the momentum is +\DPPageSep{087.png}{75}% +conserved; that is to say, is neither increased nor +diminished. Seeing, therefore, that the amount of +matter is a constant quantity, and the momentum a +constant quantity, it follows that the amount of motion +is constant. Motion is conserved as well as matter. If +the amount of matter in the universe be constant, then, +according to this statement, the amount of motion must +be constant, and the amount of energy constant also. + +It is generally agreed that this statement concerning +energy is true, and one hears often about the law of +the conservation of energy. It seems to be less clearly +recognized that the third law of motion implies the conservation +of motion, provided matter is itself a constant +quantity. But there is another condition of things that +is as uniform as any other condition of things in +nature that has not been recognized as a law, and yet it +deserves to be perhaps as much or more than most +others, since, in our experience, it is never known to +vary; it is this: Wherever there is an interchange of +motions between two bodies, the transfer is always +from the one having more to the one having less. As +exchange of motions implies transfer of energy, it follows +that all transfers of energy of any given kind are +from bodies having more to those having less. + +Cause and effect are always determined by such a +\index{Cause and effect}% +disposition of things, though not every one has apparently +seen that questions involving what they please +to call causes and effects presume a kind of antecedent +and consequent that always work both ways at +the same time, for there is no such thing as an isolated +phenomenon. If everything takes place so and so +\DPPageSep{088.png}{76}% +because there is an exchange of motion going on, +then this thing that now moves faster than it did has +been acted upon by a body that had more motion in +this direction than the former one had, and it has +imparted some of its motion at the expense of its own +energy. If one inquires what caused the increased +velocity to this body, it may be said it was caused by +the impact with another body. In like manner one +may inquire what caused the slowing-up motions of the +second body, and the answer still must be, the same +impact with the first body. So, for every phenomenon +there is a corresponding and complementary phenomenon, +which it is just as appropriate to consider as a +cause as it is the first, and either element is just as +much a cause as the other, and in each and every case +all there is involved are exchanges in the amount and +kinds of motion in matter. + +There remains now the consideration of a topic +which those who have studied physical subjects only a +little must be more or less familiar with. The term +``potential energy'' has been much employed within the +last twenty years to express a certain condition of matter +that renders it a source of energy when no motion +is supposed to be involved: thus, where a weight is +raised, like that of a clock, or of a stone raised to the +roof of a house. By falling, either of them can be +made to do work; but so long as they remain raised +and are apparently quiescent, their stock of energy is +measured by their weight into their height, i.e., foot-pounds; +and this is said to be \textit{potential energy}. Examples +of this sort are numerous. The wound-up spring +\DPPageSep{089.png}{77}% +\index{Energy, factors of}% +of a clock or watch, a bent bow, compressed air or +steam, powder, nitro-glycerine, and the like explosives, +coal, wood, and other kinds of fuel, are all varieties of +so-called potential energy. Let it be remembered that +we have in natural phenomena matter and ether and +space and time and motion. If matter and ether be +substances, then the product of one into the other +would signify nothing; it would be physical nonsense. +So likewise would be the product of matter into space +or time; and yet if matter is to be possessed of energy, +and motion is \emph{not} one of the factors, then either space +or time must be, and no one can imagine how energy +can in any way depend upon time as a factor, and there +is no degree of probability that it is or can be so; and +hence, though we had no hint of how it might be, one +would need to avow his belief that in some way motion +was involved in every case where physical energy was +involved, for in any case where it had been hitherto +possible to trace it, it had been found to be present as +a factor in precisely the same relations as in all other +known cases, and hence he would avow a disbelief in +the existence of potential energy in any other than a +loose sense for a condition where the character of the +motion involved was obscure. This would imply that +all energy is kinetic, whether the character of the +motion was determined or not. This view is now held +by those who have taken the pains to think out the +necessary relations that are involved in this subject. + +In the last edition of the ``Encyclopædia Britannica,'' +Professor Tait, who contributed the article on ``Mechanics,'' +says, ``Now, it is impossible to conceive of a truly +\DPPageSep{090.png}{78}% +\index{Molecular fatigue}% +dormant form of energy whose magnitude should depend +in any way on the unit of time; and we are therefore +forced to the conclusion that potential energy, like +kinetic energy, depends in some unimagined way upon +motion;'' also, ``The conclusion which appears inevitable +is that whatever matter may be, the other reality +in the physical universe which is never found unassociated +with matter depends in all its widely varied forms +upon motion of matter;'' and in another place, ``Potential +energy must in some way depend upon motion.'' + +It was pointed out (on p.~67) that what was called +physiological work is now known to depend upon +the vibratory state of muscles in a state of tension. +Before that explanation was known, one might have +called such, potential energy, if it had not been for the +sense of fatigue felt by one who was doing such physiological +work that forbade him to assume that actual +energy was not employed to maintain such a stress; +and when it becomes evident, as it has, that one cannot +press upon a table, or pull upon a rope, or bring about +in any way a push or a strain upon matter, without +varying the temperature of the body, it is no longer +difficult to understand that all changes of that sort +upon matter result in atomic and molecular stresses, +for they are placed in abnormal positions as well as +stretched muscles, and their energy is spent in a similar +manner. There is a curious phenomenon exhibited +by all bodies that are made to do atomic and molecular +work for a considerable time. They become exhausted, +like living things, and require rest to recover their +properties. Thus, a tuning-fork, if kept artificially +\DPPageSep{091.png}{79}% +\index{Energy in the ether}% +vibrating for some time, will stop almost instantly +when the driving force is stopped, though at the outset +it would continue to vibrate for a minute or more when +left to itself. This is caused by what is called the +fatigue of elasticity: the body loses some degree of its +elasticity, and requires time to recover it. I have called +the phenomenon curious. Perhaps it is no more so +than any other phenomenon manifested by matter; but +it is so similar to what is so characteristic of living +things, that it almost excites one's sympathy. One +can have compassion for an overworked and exhausted +horse, but an overworked tuning-fork! The expression +would seem to be wholly inapplicable, but the fact is as +stated. The only difference between the cases is, one +has nerves, and becomes conscious of the exhaustion, +the other not. + +So far, both motion and energy have been considered +as related to matter, and matter as defined in the first +chapter, as distinguished from the ether, though immersed +in it, and can by no means be isolated from it; +but energy exists in the ether as well, as we are assured +by many phenomena. That light requires about eight +minutes to come to us from the sun has been proved in +numerous ways. When it gets to the earth it is found +to be able to impart energy to the matter it falls upon: +it may heat it and affect it in other ways that are +measurable, so energy gets to us from the sun, and is +eight minutes in transit in the ether. If we do not +call ether matter, and it has been shown that there are +good reasons for not doing so, then it follows that +energy exists outside of matter, and it is a proper line +\DPPageSep{092.png}{80}% +\index{Light, energy of}% +\index{Light, its nature}% +of inquiry to learn what shape the energy exists in, +and what mechanical conceptions are appropriate when +thinking about it. In matter one may isolate motions +of various sorts. A mass of matter, say, like a baseball, +may have translatory motion: it may vibrate or it +may spin. In each case one may contemplate the kind +of motion, and compute the energy involved in the +movement, and this is true for atoms as well as larger +masses; but when the substance is not made up of +discrete parts, but is absolutely homogeneous with no +interstices, and apparently incapable of changing either +its position or its form, as there is good reason for +thinking to be the case with the ether, it becomes +\index{Ether}% +much more difficult to picture to one's self just what is +happening when motion of any sort is involved. As +has already been said, we know that light consists of +waves, measurable quantities, and we know how much +energy reaches the earth from the sun and falls upon a +square mile or square foot. There have been several +estimates of this quantity, and it is found to be equal to +about one hundred and thirty foot-pounds per second for +each square foot section of sunshine. This signifies, of +course, that that is the amount of energy in a column +of ether one foot square and a hundred and eighty-six +thousand miles long, for that is the amount that arrives +per second. So one may calculate the amount of energy +there is in a cubic mile of sunlight to be about twelve +thousand foot-pounds, and also that the amount given +out by the sun in a second is about four millions of +foot-pounds, or nearly seven thousand horse-power for +each square foot of the sun's surface. All of this energy +\DPPageSep{093.png}{81}% +\index{Electro-magnets}% +\index{Magnetic waves}% +\index{Magnet, electro}% +is handed over to the ether, which distributes it in all +directions as undulatory movements which we call light. +Such wave motions do not exhibit anything like what +we call momentum as waves in water or air always do, +and they are therefore in striking contrast with waves +in matter. Moreover, being waves, having the amplitude +at right angles to the direction of propagation, +they must be compounded of two motions,---a rectilinear +and a vibratory one,---and not a simple one such +as a particle of matter may have. + +The ether is capable of being affected by other +motions of matter than simply the vibratory one of +atoms and molecules. + +Whenever an electro-magnet is made, it reacts upon +the ether in such a way as to affect other matter that +chances to be in the range of ether so affected. It +appears as if the ether were thrown into a state of +stress which it retains so long as the magnet retains its +property; and this condition extends to an indefinite +distance in all directions. If such an electro-magnet is +made and unmade by opening and closing an electric +current in its coils, there will be formed a set of electro-magnetic +waves in the ether which will travel outwards +from the magnet in a manner similar to light-waves, +only they will have an enormous wave length. If the +circuit be closed but once a second, the waves will be a +hundred and eighty-six thousand miles long; for a wave +in the ether travels in it with a velocity that depends +solely upon the property of the ether to transmit disturbances, +and not at all upon the source of the disturbance. +That such an electro-magnetic wave possesses +\DPPageSep{094.png}{82}% +\index{Gravitation}% +\index{Newton, Sir Isaac}% +energy, and can do work, one may satisfy himself by +observing the motions produced by them upon magnetic +needles within the affected space. + +In like manner an electrified body puts the ether into +a different kind of a stress from the magnet; and when +this is done periodically, as it may be by an induction +coil, and in other ways, electrostatic waves are set up, +and these too travel with the speed of light, and are +capable of affecting matter to a great distance, thus +showing that the ether may possess energy in an electro-static +form, as distinguished from the electro-magnetic +and light. There are some physicists who think these +last two to be identical, and the reasons for their +opinion will be given in a subsequent place. + +It only remains to point out that whatever the nature +of gravity may be, there can be very little doubt that +the ether is intimately concerned in it, as Sir Isaac +Newton supposed was the case. But if it is, and ether +is the agency by which one mass of matter is able to +affect another mass, then ether is in a state of stress +produced by the atoms of matter all the time, and +therefore in some way gravitative energy is lodged in it. +As the ether is so universal in its extension, one cannot +but see that it is a storehouse of an almost unlimited +amount of energy of many kinds; so that if every +particle of matter were instantly annihilated, there +would still be a universe filled with energy, though it +might not be serviceable, because lacking the conditions +for transformation into useful forms. This may +be said to be one of the functions of matter---the transformation +of the energy it gets from the ether. +%\DPPageSep{095.png}{83}% + + +\Chapter{V}{Gravitation}{83} + +\index{Attraction, gravitative}% +\index{Newton, Sir Isaac}% + +\First{That} all bodies will fall towards the earth if raised +above its surface and left unsupported everybody +knows and must always have known, for it is a fact +thrust into everybody's notice constantly and as long +as he lives. Also that bodies resting upon the earth +require energy to be spent in order to raise them +from it is equally well known. Thus all bodies act as +if they were attracted by the earth, and the weight of +a body is the measure of the attraction of the earth +upon it. + +One not unfrequently comes across statements by +authors implying that Newton was the discoverer of +this attraction which is called gravitation. This is a +mistake: not only was this idea common in Newton's +day, but the word itself was in extensive use. Kepler +had affirmed that the sun attracted the earth and the +planets, and Galileo had busied himself very much +with the study of attraction of the earth upon bodies. +The problem that Newton had before him was not +as to the existence of gravitative action, but what +was its law of operation and the limits of it, if it had +any limits. The familiar story of the fall of the apple +leading to the great discovery is generally believed to +\DPPageSep{096.png}{84}% +\index{Gravitation, law of}% +be mythical; at any rate, other facts well authenticated +do not accord with that story. When he was twenty-three +years old he undertook to apply the law as we +now have it, to the moon, using the size of the earth +and the moon's distance from it, as they were then +best known. The result satisfied him that his surmise +could not be the law, if the measure of the earth then +had was accurate. This was in 1666. In 1683 he +learned of some new measures recently made of the +magnitude of the earth, indicating it to be larger than +had been supposed. Then, with the new measures for +data, he made a new computation. It was then, when +he saw that the results were to prove his conjecture, +and he perceived the immense importance of the discovery, +that he handed over the unfinished work to an +amanuensis, because he was too much agitated to complete +it. If the discovery was made when he first +thought of putting the idea to the test, it is strange +that his emotional excitement should have been postponed +for seventeen years. Evidently it was at the +latter date when he thought he had made the discovery. +It was the \emph{law} of gravitation that Newton discovered, +and that it was universal. Every particle of matter +attracts every other particle; and the strength of this +attraction varies as the mass of each, and inversely as +the square of the distance between them. Thus, if at +the surface of the earth gravitation gives a weight of +one pound to a body, at the distance of ten radii of the +earth $= 40000$~miles, the weight would be $\dfrac{1}{10^2}$, one-hundredth +of a pound, and at the distance of the moon, +\DPPageSep{097.png}{85}% +\index{Attraction depends upon distance}% +or sixty radii of the earth, the body would weigh but +$\dfrac{1}{60^2}$=one thirty-six hundredth of a pound, and would +fall towards the earth in a second but $\dfrac{1}{3600}$ of the distance +it would fall at the surface of the earth, where it +is about sixteen feet. One thirty-six hundredth of sixteen +feet is about the one $\dfrac{1}{224}$ of a foot, which is +therefore the departure from a straight line the +body at the distance of the moon must make per +second to move round the earth. The mutual attraction +of these bodies at that distance is sufficient to produce +this amount of deflection, and hence accounts for +the rotation at that distance. When the same mathematical +relation is applied to the planets, comets, and +meteors that revolve about the sun, it is found to be +applicable to every one of them; and in the depths of +space in every direction are to be seen multitudes of +stars revolving about each other in similar manner, and +hence it is concluded that gravitation is a universal property, +and the law is applicable throughout the universe. + +There are other kinds of attraction that matter +exhibits, such as electric and magnetic, that follow a +part of the above law, but do not the other part. The +law regarding the distance is true for electrified bodies, +but the mass of the bodies does not enter as a controlling +condition. So it appears that the variability of +attraction with the distance is a geometrical condition, +and depends upon the property of space, and is not +peculiar to any physical phenomenon. Sound, light, +\DPPageSep{098.png}{86}% +heat, electricity, magnetism, as well as gravitation, +exhibit the property, as do circles and spheres. The +peculiar thing about gravitative attraction is that it +depends upon the masses of the attracting bodies, and +is not modified in the slightest degree by the interposition +of any substance of any magnitude between the +attracting particles or masses. In this particular it is +strikingly unlike magnetic attraction. If, for instance, +a piece of iron is brought between two magnets that at +a distance are attracting each other, the strength of +their action upon each other is decidedly less. The +strength of the attraction of the sun is just as great +upon a particle in the centre of the earth as for any +similar particle at an equal distance that is not +shielded. + +There have been numerous attempts in the past to +account for gravitation. It has been imagined that +space was full of particles swiftly moving in every direction +that produced a pressure upon all bodies by their +impact; that each body shielded other bodies in a measure, +and hence the pressure produced upon the adjacent +sides would be less than elsewhere, and, as a consequence, +each body would be pushed in the direction of +an adjacent body. But a push represents expended +energy, and this would imply that the moving particles +must be losing energy at the expense of their velocity; +and as no such particles are known, and if there were, +their velocity would have to be so much greater than +that of light, there is no degree of probability to be +allowed for the idea. The effect of vibrations upon +the ether has been a very common manner of attempting +\DPPageSep{099.png}{87}% +\index{Attraction of vibrating fork}% +to explain gravitation. It has been observed that if +light bodies are brought near to a vibrating body like a +tuning-fork, they are apparently attracted by it so long +as the vibratory motion continues; and the action is +explained by the rarefaction produced by the vibratory +motion, which reduces the pressure in the space about +the body, so when another body is brought near the +pressure is greater on the remote side than it is on +the side adjacent, and thus the body is pushed towards +the one vibrating. It is known that all the atoms of all +bodies are in a state of vibration at all temperatures; +and hence it was inferred that the pressure of the ether +must be reduced next to their surface, so that between +two atoms or molecules the pressure must be less than +external to them, and hence the pressure of the ether +will crowd them together. This idea has been worked +out by a large number of persons in different countries. +There are two fatal objections to this hypothesis: +First, it would make the attraction of gravitation +dependent upon their temperature, and there is no evidence +to show that temperature makes any difference; +and second, that the velocity of gravitative action is the +same as that of light. There is an abundance of astronomical +evidence, that if it has any velocity at all it +must vastly exceed that of light. If it were as much +as a million times greater, astronomical phenomena +would exhibit it plainly. + +Seeing that every particle of matter in the universe, +affects every other particle in a certain and definite +way, no matter what the distance between them, there +must be either the possibility that a body can act upon +\DPPageSep{100.png}{88}% +\index{Newton, Sir Isaac}% +another one at a distance without any medium between +them,---which is called action at a distance,---or there +\index{Action at a distance}% +must be a medium which is first affected by the bodies, +and which in turn reacts upon other bodies in it. +What Sir Isaac Newton thought of these contingencies +was cited in a former chapter (see \Pageref{p.}{31}). It +is now generally felt to be not only essential for consistent +mechanical thinking, but that in some way the +ether which is known to exist must have some essential +part in the phenomenon. It has been the subject +of curious speculation why Newton should so strongly +state his belief in the existence of a medium for the +propagation of physical conditions, and yet in his work +on light he should adopt the corpuscular theory---that +light consisted of emanations, which was a practical +denial of the hypothesis of the ether. The explanation +of the anomaly is probably in the fact, that he +could treat in his mathematical way the ideal corpuscles, +while he could not so treat the ether hypothesis of +waves. His work was developed with ideas he could +handle; and the outcome of it was that the science of +light was retarded by his misconceptions for a hundred +years, for every one now who knows anything about it +knows that Newton's hypothesis was a wrong one. +There are some persons who would curb the imaginations +of others in physical things by quoting Newton's +dictum, ``Hypotheses I do not touch,'' but they omit to +mention that Newton's work on optics was altogether +based upon a hypothesis that has wholly broken +down. Every one of the explanations he gave of +such phenomena is worthless, and no one gives attention +\DPPageSep{101.png}{89}% +\index{Neptune, discovery of}% +to them except for their historic relations to the +science. + +It has been thus in other lines. A symbolic representation +of things such as offers the possibility of +mathematical treatment has been seized and worked out +to great length, when the actual phenomena pretended +to be treated gave no countenance to the conceptions. +Such has been the case in electricity and magnetism and +heat. The mathematicians fought Ohm's, Faraday's, +and Joule's mechanical conceptions until death stopped +them. + +It is certainly true that all physical phenomena are +subject to strictly mathematical conditions, and mathematical +processes are unassailable in themselves. The +trouble arises from the data employed. Most phenomena +are so highly complex that one can never be +quite sure he is dealing with all the factors until +experiment proves it. So that experiment is rather a +criterion of mathematical conclusions and must lead +the way. Mathematics is a deductive science, yet the +\index{Mathematics}% +number of physical facts or phenomena that have been +discovered by its aid is so small that they may almost +be left out of the count. There is the discovery of the +planet Neptune, that has been spoken of as a triumph +of mathematical science, yet one of the most competent +mathematicians that ever lived---Professor Peirce of +Harvard---declared that it was only a lucky find, for the +computations would apply just as well to a planet $180°$~from +it. The conical refraction of light is another +one. Altogether they make but a small figure and +are unimportant. The law of gravitation was discovered +\DPPageSep{102.png}{90}% +\index{Gravitation}% +\index{Hypothesis, gravitation}% +\index{Kepler, the guesser}% +by trial, and although its importance is second +to none other yet discovered, it happens that it is one +of the very simplest and least complicated with other +laws we know of; but an explanation of how it can act +thus, or why it exists at all, or what its antecedents are +if it has any, these are questions that are matters for +the guessers, like Kepler, who kept guessing until he +guessed right, and so discovered what are known as his +laws. Meanwhile definite mechanical conceptions of +what the phenomena to be explained are like may be +helpful to those interested in them. + +Suppose two bodies, \textit{A} and \textit{B}, a certain distance apart, +and they so react upon each other that they tend to +mutually approach each other. Given a medium, ether, +can one imagine stresses set up by either body in the +ether that will be capable of affecting the other? + +Imagine a large space like a room occupied by glass +of uniform texture and properties throughout. If relieved +of gravitational property, the cohesion of all +its parts shows that every particle is in some sort of +stress, no matter what the origin of that may be. Now, +suppose there could suddenly be created somewhere +near the middle of the glass a bullet or a marble. It +would displace so much glass as would be equal to its +own volume, and the result of that would be that the +glass about it would be subject to a new stress, which +would be greatest, at the surface of contact of the +marble, and would be less as that surface is receded +from inversely proportional to the square of the distance +of the point of observation. If the glass be imagined to +be indefinitely great in magnitude, then the stress would +\DPPageSep{103.png}{91}% +extend in every direction through the whole extent of +it, and at any assignable point would still be in accordance +with the inverse law, diminishing outward. +Imagine now another similar marble to be created at +the distance of a foot from the first. Inasmuch as it +displaces so much glass it will set up a new stress in +the latter, and this stress must also be transmitted +throughout the whole mass as in the first instance. +Now, here will be two independent stresses overlapping; +and on account of the nature of the stress, it will be +greater between the marbles than it will be anywhere +else, because there the sum of the stresses will be at a +maximum. If one can now for the moment imagine +that the glass was of such constitution as to permit a +motion to the marbles, in any direction, when there was +a stress tending to move them, it would be obvious +that the marbles would separate from each other as the +medium, the glass, was under greater tension between +them than in any other direction.\footnote + {Such bodies might be said to have \emph{negative weight}.} +And if the glass +thus mobile was indefinite in extent and without friction, +the two marbles would continue to separate indefinitely. +The energy making them thus to move comes directly +from the medium, which in turn got it from the bodies +themselves when they were thrust into it, no matter +how. Such a phenomenon as separation in a manner +like the above is exactly opposite in character to that +of gravitation, but it points at once to a consideration +of the condition necessary to be similar. It was the +forcing of new material into space already occupied +with other material that developed the stress and led +to the above results. It will be necessary to find a way +\DPPageSep{104.png}{92}% +\index{Stress in glass}% +to develop a stress \emph{towards} a point instead of away +from it. + +Suppose, then, that instead of having a created something +imbedded in it, a cavity of equal volume to the +marble should be produced in its place. As part of the +material of the medium has been annihilated, there will +now be a less stress at its bounding surface than there +was when it was occupied with material, and the +direction of the stress will now be towards the cavity. +That is, the stress will be less there than anywhere +else in the glass; and this, too, if measured, will be found +distributed like the other, inversely as the square of the +distance from the origin. Let another similar cavity +be produced in the neighborhood of the first, and the +two stresses will overlap, and there will be less between +them than in any other direction. Let us imagine now +that the glass was mobile enough to permit the movement +of either of these cavities in any direction towards +which there was any pressure, and they would approach +each other because pushed by the stress in the glass +more towards each other than in any other direction. +If one of these cavities were larger than the other, one +would expect that the corresponding stress would be +greater, and so there would be a stress that for direction +and the resultant movement would correspond with +what is observed in the phenomena of gravitation. + +But such a conception as that of a vacuum as constituting +what we call the atoms of matter has no mechanical +validity at all. Atoms have not only volume, they +have mass, and that requires energy to displace. One +cannot imagine that the displacement of an absolute +\DPPageSep{105.png}{93}% +\index{Stress in ether}% +vacuum, if such a thing could be done, would require +any energy, for there would be no mass to move. + +Suppose, however,---instead of imagining, as was +done, the entire volume of the marble to be destroyed,---that +in some way the volume of the glass marble had +suddenly been reduced, no matter how, and that the +diminished volume was retained,---the material had been +condensed. This would bring about the same relative +condition of stress to the condensed portion, so that +there would be less adjacent to it than elsewhere, the +measure of it being the actual amount of condensation +represented in the body. What would be true of one +would be true of others,---an indefinite number,---and +no number of such stresses would in any manner interfere +with or neutralize that of others. At any point of +the space filled with such glass each such condensation +would have produced its effect at the outset, and if the +glass were practically limitless in extent this relationship +would be maintained so long as the reduced +volumes remained constant. + +So far has been considered a condition of things +somewhat analogous to gravitation; and to apply it one +needs to imagine the ether to be substituted for the +glass and the atoms of matter for the imagined condensation, +and also that the two, the ether and atom, +are capable of mutual reaction. + +There have been some physicists who have imagined +that the atoms of matter were condensations in the +ether, but I am not aware that any very satisfactory +reasons have been given for thinking so. That in itself +would be no reason for rejecting the idea in the +\DPPageSep{106.png}{94}% +\index{Attraction of disks}% +\index{Hypothesis, needful}% +absence of a better and more consistent one. For +scientific purposes a poor hypothesis is better than +none at all. + +A very large amount of scientific work has been +done by employing hypotheses that are now known to +be wrong. A working hypothesis is needful. If it be +wrong, one will by and by find it out and be able to +amend it, or replace it by a better. If it be right, it +will be vindicated, and will justify itself, and be generally +adopted. + +Until we know more definitely than is now known +what the constitution of matter really is, one can only +guess and try; and among the multitude of interested +workers in all civilized countries there will be some +who will guess right to the advantage of all. + +If, then, one adopts the vortex ring theory of matter, +\index{Vortex ring theory of matter}% +and endeavors to trace the mechanical conditions that +might obtain with such kind of atoms, he would be +led to inquire whether a vortex ring does or does not +exhibit any evidence of condensation in the material +that is in rotation; that is, does the material of the ring +occupy the same space while it is in rotation as it does +when not? + +There are several phenomena that seem to show that +it occupies less space. The reduction of pressure +in its neighborhood shows a rarefaction there, and the +mutual approach of such rings and of other light bodies +in their neighborhood indicates the same thing. If +one rotates a disk rapidly, any light bodies in front of +it will tend to approach it even from a distance of +several inches. If a dozen disks five or six inches in +\DPPageSep{107.png}{95}% +\index{Attraction of vortex rings}% +diameter are set loosely an inch apart upon a spindle a +foot long, so that they may be rotated fast, yet left free +to move longitudinally upon the spindle, they will all +crowd up close together as the pressure is less between +them than outside. If one can imagine the spindle to +be flexible and the ends brought opposite each other +while rotating, it will be seen that the ends would +exhibit an apparent attraction for each other, and, +if free to approach, would close up, thus making a +vortex ring with the sections of disks. If the axis +of the disks were shrinkable, the whole thing would +contract to a minimum size that would be determined +by the rapidity of the rotary movement, in +which case not only would it be plain why the ring form +was maintained, but why the diameter of the ring +as a whole should shrink. So long as it rotated it +would keep up a stress in the air about it. So far as +the experimental evidence goes, it appears that a vortex +ring in the air exhibits the phenomenon in question. +There is no doubt at all that two vortex rings in the +air attract each other, for they will mutually approach +if free to do so, and the explanation is plain that there is +reduced pressure between them; in other words, the +characteristic motion of the ring reduces the air +pressure about it, so that another body within that field +is pushed towards the place where the pressure is +least. The reduction of the pressure about any ring +must evidently depend upon the amount of material +embodied in it, and more especially the degree of +rotation which it has. A small, thin but rapidly +rotating ring might produce as great a rarefaction about +\DPPageSep{108.png}{96}% +it as a much larger one with less velocity, hence there +is something about it that corresponds to what is called +mass. It is not \emph{simply} an amount of material, but the +\emph{energy} the material has, which gives it its characteristic +properties. + +Analogy must not be mistaken for identity. There +is so great a difference between the properties of the +air and other gases and those of the ether that one +cannot affirm that what holds true of one must hold +true of the other; yet that is what is generally done by +such persons as those who try to show the properties +of the ether to be identical with those of matter. + +We know what conditions are necessary in order that +a ring should be formed in the air, and one of them is +that there must be gaseous friction. If that were not +the case a ring could not be formed. If the ether be +the frictionless medium it is generally supposed to be, +one would not know how to make a vortex ring in it. +On the other hand, the reason a ring in the air is so +soon destroyed is because of friction; and hence if one +were made in some unimagined way in the ether it +would continue to exist indefinitely, but how it could +act at all upon the ether surrounding it would be a +mechanical puzzle, and that is the present state of the +case. The puzzle is no greater with the conception of +a vortex ring than if the atom were made up in some +other way, and therefore that objection is not peculiar +to this hypothesis. It has been confessedly a puzzle +to see how the vibratory motions of atoms and molecules +could set up transverse waves in the ether if the +ether be without friction; nevertheless, they do set up +\DPPageSep{109.png}{97}% +such waves. A common objection to all attempts that +have been made to account for gravitation by means of +the motions of the atoms themselves is that it not +only requires a constant expenditure of energy, but that +the velocity of transmission must be so much greater +than that of light. Light is transverse vibratory movement. +A direct longitudinal wave may be much swifter +than the other. A pull upon a taut rope will travel +much faster in it than will a wave produced by a transverse +movement of the hand. + +It is not to be understood that what is presented here +is given as a proof that gravitation is but a simple +mechanical condition of things. It is probable that +every one who thinks about it believes that its explanation +is purely mechanical. Some perhaps are pessimistic, +and doubt that man will ever be able to understand +its mysteries, but pessimists are not discoverers. They +frequently so chill the air about them that more hopeful +ones, who are not persuaded that the end has yet +been reached, are sometimes deterred from venturing +into fields where they have to pass such self-constituted +gate-keepers. + +There are few physical problems of any generality +and complexity that are abruptly and completely solved +by one person. Tentative steps must be taken, and +much labor is oftentimes spent upon ideas that by and +by are proved to be worthless. A good deal of the +work done by Laplace upon the Nebula theory was +\index{Nebula theory}% +of that sort; yet all astronomers hold the Nebula theory +in some form: what the exact process was, if solely +mechanical, may be interesting, but not very important +from a philosophical standpoint. +\DPPageSep{110.png}{98}% + +So one may hold that gravitation is a mechanical +action, and in some way explainable on mechanical +principles, even if he does not see how at all. + +This chapter may help some to see not only what +the character of the problem is, but what factors are +present, and how somewhat similar phenomena may be +reproduced at will; but the radical distinction that +exists between the ether and matter must always be +kept in mind. +%\DPPageSep{111.png}{99}% + + +\Chapter{VI}{Heat}{99} + +\index{Heat, mechanical origin of}% + +\First{Heat} and cold are two words we apply to contrasted +sensations, either of which may imply comfort or discomfort; +and what is meant by either word in a given +case depends altogether upon what the sensation is +compared with. Thus, one would speak of a day when +the thermometer indicated one hundred degrees in the +shade as being a hot day, while if his cup of coffee had +the same temperature it would be called cold; so the +terms imply only roughly some departure from a +standard of comfort. To obtain more definite knowledge +of that physical condition which gives us the +sensation we call heat, it is necessary to attend to its +origin and its effects upon other bodies. + +\Section{I. MECHANICAL ORIGIN.} + +When a blacksmith hammers a small piece of iron, +like a nail, upon his anvil, it becomes too hot to hold, +and it even may be made to glow, red-hot, by the +repeated blows of the hammer. If a bullet be shot +against a target and be quickly picked up, it is found to +be hot; and in general the impact of any two bodies +always results in heating both of them. In the above +cases both the hammer and the target are heated, but +\DPPageSep{112.png}{100}% +on account of their size the degree of heat is not so +noticeable as it is with the smaller bodies. + +In like manner if the knuckles be rubbed briskly +upon one's sleeve, the sensation of heat becomes +unbearable in a very brief time. The friction of the +surfaces develops the heat, as may be learned by +taking a button or some similar object, and in the same +brisk manner rub it on the sleeve or other convenient +surface, and it will get too hot to be safely touched +against the skin. On a larger scale the brakes upon +railroad-cars exhibit the same quality when they have +been applied for a few seconds. The sparks that may +be seen flying from them in the dark is testimony to +the same thing; while the car-wheel boxes are often so +heated by the constant friction when the lubricating +oil is wanting, that the cotton waste takes fire, and +even locomotives may be delayed by their hot journals. +This source of heat is so common that instances may +be cited indefinitely. It is universally true that the +friction of one body moving in contact with another +heats them both, and the heat developed depends upon +the pressure and the velocity of the moving surfaces. +It is true not only for solids, but for liquids and gases +as well, and the friction of solids moving in either +liquids or gases. An extreme case of the latter kind is +illustrated by the shining trail of a meteor when it +enters the atmosphere. Its velocity is very great---twenty +or thirty miles a second---and the friction of the +air is so great on account of the high speed that it +renders the surface of the meteorite red-hot, and some +of its molecules are ground off as they would be if it +\DPPageSep{113.png}{101}% +were held against a swift turning emery-wheel that +scatters the sparks in the air. The luminous trail consists +of these heated particles. If the body is not large, +and most meteors are quite small, they may be entirely +ground to powder and dissipated before they can reach +the earth. Most meteors in this way rarely pass +through more than fifty or sixty miles of our atmosphere +before this happens. + +Another mechanical source of heat is compression. +Let a bullet be hard squeezed in a vise, or in any other +% [Illustration: ] +\begin{figure}[htb] + \begin{center} + \Graphic{4in}{113a} + \end{center} + \Caption{4}{Diag.\ 4.} +\end{figure} +way, and it is found that its heat is perceptibly increased. +Small differences of this sort may be easily detected +by the use of the thermopile and galvanometer. + +The rubbed button or pounded or squeezed bullet +placed upon the face of the thermopile shows the presence +of an amount of heat which the sense of heat +would %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}[11]{l}{.5in} +\null\hfill\Graphic{.25in}{114a}\hfill + \Caption{5}{Diag.\ 5.} +\end{wrapfigure} +never detect. Gases exhibit the heating effect +through pressure in a high degree. Before the invention +of friction matches, which are themselves good +\DPPageSep{114.png}{102}% +\index{Heat, chemical origin of}% +examples of the production of heat by friction, metallic +tubes, closed at one end with a tight-fitting plunger to +be worked by hand, were in common use for lighting +fires. A bit of punky wood was fixed to the +end of the plunger, and the latter was then +quickly driven to the bottom of the tube. The +air was compressed to so great an extent that +the heat developed became sufficient to ignite +the punk. The same heating effect of compression +may be shown by the thermopile and galvanometer +by compressing the air with an air-condenser, +and permitting the air thus condensed to +strike on its exit upon the face of the pile. + +Thus impact, or \emph{sudden} stopping of mechanical +motion, friction, or the \emph{gradual} stopping of mechanical +motion and condensation, or compelling molecules +to occupy less space, all of them of a purely +mechanical nature, result invariably in heating the +matter that is subject to the action. + +\Section{II. CHEMICAL ORIGIN.} + +The heat that results from the combustion of fuels +of all sorts is due to the chemical changes that take +place. When coal burns, its substance, carbon, is +entering into combination with the oxygen of the air, +and a new chemical product is formed called carbon +dioxide, which is a gas; and the change is accompanied +by the production of a large amount of heat, which we +utilize for our comfort or for the various arts that +depend upon heat as an agent. Wood, alcohol, the +various oils,---everything capable of burning, and which +\DPPageSep{115.png}{103}% +may be called fuels---are, in the process of burning, +\index{Fuels}% +undergoing what is called oxidation, in which new +chemical compounds are formed and which are nearly +all gaseous. Thus the products of the combustion of +\index{Combustion}% +wood, alcohol, coal-oil, etc., are always carbon dioxide +gas, and the vapor of water; and the heat developed is +proportionate to the amount of these produced. + +But combustion is not the only chemical source. If +sulphuric acid be mixed with water, the compound +becomes very hot although it is liquid. The two +substances enter into an intimate chemical combination. +A pint of each mixed together will not make a quart, +but will fall short of that volume a good deal when +they have cooled. This shows that condensation has +taken place; and, knowing that condensation produces +heat when brought about in other ways, one might have +suspected that chemical condensation would result in +a similar development of heat. + +Some substances when in a finely divided state, +though what we generally call solids, are capable of +entering into combination with each other at a very +rapid rate and then develop a great deal of heat. +Such a substance as gunpowder, a combination of carbon, +\index{Gunpowder}% +sulphur, and the nitrate of potash, when intimately +mixed, will combine with explosive violence, and great +heat results from it, as shown by the attending flash +and the scorching effects it produces upon some bodies +that do not happen to be destroyed by the explosion. +All chemical reactions whatever involve in some degree +temperature changes; and by so much one might be +led to suspect that there might not be so great a +\DPPageSep{116.png}{104}% +\index{Heat, electrical origin of}% +difference between the mechanical \DPtypo{souces}{sources} of heat at +first considered and the more obscure chemical ones as +one might think who attends only to the more prominent +features of the two. If one should adopt for +a basis of his philosophy that like causes produce like +effects, what shall he say when he sees the same effect +produced by pounding with a hammer, condensing a +gas, and burning a piece of wood? Either unlike causes +can produce similar effects, or fundamentally these +three processes are the same. We will attend to that +question more at length farther on. + + +\Section{III\@. ELECTRICAL ORIGIN.} + +As a chapter is to be given to electricity and its +phenomena, it will be sufficient here to point out that +wherever a current of electricity is flowing in a conductor, +there heat is invariably produced. The heat in +an electric arc is so great that all known substances are +either fused or volatilized in it. Gold, platinum, the +ruby, are easily reduced to the liquid form, and the +diamond slowly wastes away, being oxidized like a piece +of coal. Electric furnaces are now in use where the +most refractory substances, like clay, are reduced, and +the metal aluminum extracted from it. So long as it +cost so much to produce electricity as it did before the +dynamo was perfected, no one could afford to use it for +heating purposes. Now there will shortly be electric +heaters in houses, replacing stoves for cooking and +furnaces for warmth. The electrical current can be +brought on the wire where it is wanted, and the heat +developed from it to any degree desired. Electricity, +then, is another source of heat. +\DPPageSep{117.png}{105}% +\index{Energy in the ether}% +\index{Heat, radiational origin of}% + + +\Section{IV\@. RADIATIVE ORIGIN.} + +When one stands near a blazing fire the warmth felt +does not come from the heated air between the fire +and the person; for when one shields his face or hands +the warmth ceases to be felt, though the temperature +of the air might be the same in both cases. + +In like manner sunshine warms the earth, although +between the sun and the earth there is an enormous +space without air or other matter, through which the +sun's rays come producing warmth \emph{when they get here}. +This process of giving out rays to the ether independent +of matter, which is possessed by hot bodies, is called +radiation. It has been shown that all bodies are at all +times giving out such radiations; and oftentimes the +radiation itself is called radiant energy, sometimes it +is called light, and sometimes simply ether waves. +Here we do not attend to the origin of the waves, but +to the fact that when such waves fall upon matter they +result in heating it, and therefore radiation must be +looked upon as a fourth source of heat. + +I would again suggest the thought presented a page +or two back, as to the similarity or dissimilarity of each +of these four kinds of origins of heat,---mechanical, +chemical, electrical, radiant. They appear to be utterly +unlike each other, yet their effects upon matter are identical, +always thus and never different, so far as our experience +goes. Evidently there must be some factor +common to them all; and if this could be known for any +one of them, it would throw light upon all the rest. If +we take, for instance, the mechanical origin of heat, +\DPPageSep{118.png}{106}% +say, impact, which is one of the most obvious, and note +the factors present, it is plain there are but two; +namely, a mass of matter with a certain measurable +amount of motion of the translational variety. These +two embody the energy represented by the impact, and +of these the translational motion is destroyed when the +heat appears. The other factor, the mass of matter, +remains constant. The motion that was seen needs to +be accounted for; and as the heat that appears is the +result of that motion, it appears probable that in some +way the translational motion has been transformed into +some other kind of motion, not that it has been annihilated. + + +\Section{TEMPERATURE.} +\index{Temperature}% + +If a pint of boiling-hot water be mixed with a pint +of ice-cold water, the mixture will have all the heat +there was in the pint of hot water, but it would not +injure the hand thrust into it. The heat that was in +one pint has been distributed through two pints, and +hence each pint has one-half the heat that was in the +hot pint. A red-hot bar of iron will be cooled by being +thrust into a pail of water. The water will be heated, +and will have all the heat the bar lost; but as it is distributed +through so great a volume of water, the +amount of heat in a cubic inch of it will be but a small +proportion of the whole. + +The word ``temperature'' is used to denote the degree +of heat there may be in a unit volume of a substance, and +this is measured by means of thermometers in which +the property that heat possesses of expanding the volume +of bodies is made to indicate their degree of heat. The +\DPPageSep{119.png}{107}% +standard for this is an arbitrary one altogether. In the +common Fahrenheit thermometer there is a tube of glass +\index{Thermometer}% +with a bulb upon it filled with mercury. This, when put +into ice-water, acquires the same temperature, and the +mercury stands at a certain height in the tube, which is +marked. Then it is put into boiling-hot water, where +the mercury expands and reaches another height in the +tube, which is also marked. The space between the +two marks is divided into one hundred and eighty equal +parts, and the same scale of division is carried beyond +in both directions. A point thirty-two of these divisions +below the mark of the melting ice is called zero; +so between it and the boiling-point are two hundred +and twelve divisions, called degrees. The centigrade +thermometer is more generally used in scientific work. +In this the space between the freezing and boiling +points is divided into one hundred equal parts, called +also degrees. A centigrade degree is $\dfrac{9}{5}$~larger than a +Fahrenheit degree. The scales of either may be extended +indefinitely for the measurement of temperatures +departing from the more usual ones. For a lower +limit one cannot use the mercury below about forty +degrees below zero; for it freezes at that temperature, +and no longer follows the same law of contraction. As +alcohol does not freeze, thermometer tubes filled with +it are used to indicate such low temperature. In the +Arctic regions, and even in Siberia, the temperature +falls to fifty or sixty degrees below zero not infrequently +in winter, but temperatures have artificially been produced +as low as $400°$~below zero. +\DPPageSep{120.png}{108}% + +For the higher limits mercury thermometers can be +used for higher temperatures than alcohol, for the latter +boils and becomes vapor at~$174°$. The following table +of temperatures may be interesting:--- +\begin{center} +\TableFont% +\begin{tabular}{p{3in}@{\ }r}%[** PP: Hard-coded width] +Absolute zero \dotfill & $-460°$ \\ +Lowest degree artificially produced \dotfill & $-400°$ \\ +Lowest degree measured in Siberia \dotfill & $-72°$ \\ +Mercury freezes \dotfill & $-39°$ \\ +Water freezes \dotfill & $32°$ \\ +Blood in man \dotfill & $98.6°$ \\ +Temperature observed in India \dotfill & $140°$ \\ +Alcohol boils \dotfill & $174°$ \\ +Water boils \dotfill & $212°$ \\ +Lead melts \dotfill & $612°$ \\ +Mercury boils \dotfill & $650°$ \\ +Red heat visible in dark \dotfill & $1000°$ \\ +Silver melts \dotfill & $1873°$ \\ +Gold melts \dotfill & $2200°$ \\ +Iron melts \dotfill & $2700°$ \\ +Platinum melts \dotfill & $3600°$ \\ +\end{tabular} +\end{center} +\index{Temperature, table}% + +Gases, like liquids and solids, are increased in volume +by heat when permitted to expand. If not permitted, +the pressure upon the walls of the containing vessel is +increased; and it is found that this pressure is proportionate +to the temperature, and also that the pressure +diminishes about~$\dfrac{1}{273}$ for each centigrade degree of cooling, +starting at the freezing-point of water. If, therefore, +a gas could be cooled from that point $273°$~centigrade, +it would have no pressure, as it would have no +temperature. Such a degree has never yet been reached; +but all phenomena having any bearing upon the subject +\DPPageSep{121.png}{109}% +indicate that at~$-273°$ there is no heat: it is an +absolute zero. The molecules %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}{r}{0.5in} +\null\hfill\Graphic{0.25in}{121a} +\Caption{6}{Diag.\ 6.}% +\end{wrapfigure} +would have no translational +motion, otherwise they would produce +some pressure upon the walls of the vessel that +contained them. Air thermometers may be +\index{Thermometer, air}% +made with bulbs blown upon the end of a glass +tube. A small drop of water in the tube will +be pushed in or out as the temperature varies, +and is much more sensitive than ordinary thermometers; +but barometric pressure affects it +and renders it unfit for common use, but its indications +are proportionate to the absolute scale; +that is, the volume of the air at the melting-point +of water will be increased or diminished~$\dfrac{1}{273}$ +by every change of one degree in cooling or heating, +or~$\smash[t]{dfrac{1}{490}}$ if the degree be Fahrenheit. + + +\Section{MECHANICAL EQUIVALENT.} +\index{Heat, mechanical equivalent}% + +For a long time it was supposed that heat was a kind +of substance that ordinary matter could absorb and +emit. It was sometimes called caloric; and that word is +in common use to-day, but not in the sense it originally +had. Sometimes it was spoken of as one of the imponderables---a +substance without weight. Now there is +only one imponderable recognized, that is the ether. Sir +Humphry Davy and Count Rumford found they could +produce an indefinite amount of heat by the friction of +one body upon another; and that implied if heat was a +substance of any sort, that any piece of matter contained +an infinite amount of heat, else one could get +\DPPageSep{122.png}{110}% +out of a body what was not in it. These two men concluded +that heat was a kind of molecular motion, and +that what their experiments showed was that friction +only transformed the mechanical motion into molecular +motion, which was called heat. + +The old conceptions had got so thoroughly incorporated +into both the thoughts and the writings of others, +that they could not easily be dislodged, and men went +on as they had done. It was easier to do that than to +change notions and terms that were familiar for others +that were strange, even if true. A whole generation of +men had to be buried before any attention was paid to +what had been proved in the early part of the century. +Soon after 1840 it occurred to a number of persons in +different countries that if heat were but transformed +mechanical motion there should be some quantitative +relationship between them that might be discovered; +that is, a given amount of mechanical motion ought to +produce a definite amount of heat, and \textit{vice versa}. +This was worked out in the most complete and satisfactory +way by Joule of England. His method consisted +\index{Joule}% +in churning a definite amount of water and observing +the rise in temperature in it. The churn paddle was +driven by a known weight falling a known distance, and +therefore the work done in driving the paddles was +known in foot-pounds. In this way he found that $772$~pounds +falling one foot would heat a pound of water +one degree, and he called this number the mechanical +equivalent of heat. In like manner it is said that when +a pound of water loses one degree in temperature, it has +lost energy enough to raise $772$~pounds one foot high. +\DPPageSep{123.png}{111}% +This relationship renders it easy to determine the +amount of work a given amount of heat can do, and +also the temperature that will be acquired by a given +amount of water when a definite amount of work is +done upon it. But the scientific importance of this +new step is much greater than its practical utility. +Before that time men had thought there were such +things as \emph{forces}, independent of each other; and such an +idea as mutual convertibility had not dawned upon any +philosophic mind. Physical philosophers were so much +misled by their terminology and the accompanying +notions, that Joule's work, though demonstrative, made +no impression upon them for several years, and it was +refused a place in the transactions of their society for +seven years. The reason for this common hostility to +new knowledge is probably not far to seek. When one +has achieved distinction in his line of work, especially +in physical science, he is likely to possess his own philosophy +of things, in which not a small part of the data +is symbolic and is represented in mind only by a name; +and if this chances to suggest something mysterious, as, +for instance, an imponderable, the less is one likely to +attempt, or suffer others to attempt, to displace it by +definite mechanical conceptions. To change one's +fundamental conceptions necessitates a change in his +philosophy throughout,---a change that is not only difficult, +but highly \DPtypo{distaseful}{distasteful}; and one ought not to expect +a welcome to a man whose work necessitates such a +change. + +Within the present century the advance in all directions +has been such as to give definite mechanical +\DPPageSep{124.png}{112}% +\index{Thermodynamics}% +conceptions and relations where before only ghosts and +genii were supposed to do duty; and what can a man do +when his genii have been slain and he must now depend +upon~$mv^2$? To become acquainted with his new associate +is generally the last thing he sets himself about. +It was with Joule as it was with all the prophets and +discoverers. Joule, however, was young, and he lived +to attend the funeral of all his detractors. + +That heat and work are mutually convertible is now +called the first law of thermo-dynamics; and it has led +directly to a knowledge of the working-power there is +in fuels, and made the duty of steam-engines and other +sources of power beautifully simple. + +The amount of heat needed to raise the temperature +of a pound of water one degree Fahrenheit is called a +\emph{heat unit}. The amount of heat needed to raise the +\index{Heat unit}% +temperature of a kilogram of water one centigrade +degree is sometimes called a calorie, and this is a +unit in common use. It is found by careful experiment +that a pound of coal when burnt gives up $14500$ +\emph{heat units}, or would raise the temperature of $100$~pounds +of water~$145°$, or to any other equivalent. A +pound of hydrogen, in like manner, burning with oxygen, +will give $61000$ units, a pound of wood about +$7000$, and so on. Each different substance has its own +equivalent of such heat units. As each unit will do +$772$ foot-pounds of work, a pound of coal, when burnt, +will give $14500 × 772 = 11,194000$ foot-pounds of +work, and so on for any other. This equivalency is +independent of time or place. Whether the coal burns +fast or slow makes no difference. When wood is +\DPPageSep{125.png}{113}% +burned in the fire it develops its work-power fast; but +when it slowly rots it is undergoing the same process, +oxidation, and the same amount of heat is developed, +though at no time does the temperature appear to be +above that of surrounding things. The food we eat possesses +its mechanical equivalent, which is the maximum +amount of work it would enable one to do. If bread +and butter were used for the fuel of an engine, it would +develop about $21000$ heat units (or calories) per pound, +and this is equal to $772 × 21000 = 16,212000$ foot-pounds, +and it has the same value when used for food; +and thus one may know approximately the amount of +energy he is supplied with from day to day; also, he +may compare the amount of work he does, in lifting, +walking, or otherwise, in a day with the food equivalent +absorbed. Some of this is, of course, used to +maintain the temperature of the body, the circulation +of the blood, and so on---conditions that are tolerably +constant. + + +\Section{THE STEAM-ENGINE.} +\index{Steam-engine}% + +The steam-engine is a machine for utilizing the +heating-power of fuels, and, when complete, consists of +furnace, boiler, and engine. The furnace transforms +the energy of the fuel and air into heat units in the +boiler, and the engine transforms this into the work of +whatever sort it may be applied to. + +Evidently the efficiency of such an engine must depend +upon how large a proportion of the heat units it +utilizes compared with the heat units supplied to it. +Steam-engines permit the steam to escape into the air +\DPPageSep{126.png}{114}% +\index{Steam-engine, efficiency of}% +generally with a temperature higher than boiling water, +and that means a great waste of unused heat; for the +steam in the engine loses temperature proportionate to +the work done by it, and, as stated before, the steam +pressure is proportionate to its absolute temperature, +not its temperature as indicated by common thermometers. +And the absolute temperature on Fahrenheit scale +will \DPtypo{he}{be} found by adding~$460$ to the indicated temperature. +Suppose, then, an engine-boiler delivered steam +to the engine at $248° \text{ Fah.} = 708 \text{ absolute}$, and on exit +from the cylinder it was $212° \text{ Fah.} = 672 \text{ absolute}$, then +the proportionate amount of work done compared with +the whole supplied would be $\dfrac{708 - 672}{708} = \dfrac{36}{708}$, or only +about five per cent of the heating-power of the fuel. +Higher efficiency must be looked for chiefly by using +steam at higher temperature and, therefore, higher pressure, +which would increase the value of the numerator. + +The efficiency of engines is generally given in the +amount of coal required to maintain one horse-power +per hour. A horse-power for an hour is equal to +$33000 × 60 = 1,980000$ foot-pounds; and the coal required +varies from about two pounds in the best engines +to six or eight pounds, locomotive engines generally +being less efficient. As one pound of coal when burnt +has an equivalent of $11,194000$ foot-pounds of work, +two pounds will give $22,398000$ foot-pounds. When +that maintains a horse-power for an hour, or $1,980000$ +foot-pounds, the efficiency is $\dfrac{1,980000}{22,398000} = 8 \text{ per cent}$. +This appears very low; but it is to be remembered that +\DPPageSep{127.png}{115}% +\index{Heat, nature of}% +the coal is seldom anywhere near pure; that much heat +escapes by the flues without heating the water; that +much is lost by heating the engine, boiler, and the +pipes, etc., that does no good, and most of that that does +go through the engine escapes to the air without having +done any work; and it cannot be helped, for steam condenses +to water at~\DPtypo{$212$,°}{$212°$,} and is no longer able to do +steam service. In reality, such an efficiency is relatively +high. + + +\Section{AS TO THE NATURE OF HEAT.} + +It has been pointed out that it was concluded early +in the century that heat must be some kind of motion, +because its production depended solely upon antecedent +motion, and that later the quantitative relationship +between the two was accurately defined. The +\emph{nature} of heat was ascertained, but the particular kind +of motion that gave it its characteristics was not made +out; that is, whether the motion was one of free path +of the molecules,---a swinging to and fro in space,---or +a true vibratory motion, such as a change of form of +the molecules and atoms that made up the heated body, +or a rotation of them, or a combination of any or all of +these, was unknown. At first the conjecture prevailed +that it was an oscillatory motion of the molecules +among themselves even in a solid body; but after the +discovery of spectrum analysis it became apparent that +the atoms and molecules were in a state of true vibration, +and their temperature depended upon the amplitude +of that vibration. If one will remember that the +atoms of matter are certainly elastic, and are not solid, +\DPPageSep{128.png}{116}% +\index{Hydrogen vibrations}% +\index{Vibrations, gaseous}% +and will also picture to himself what mechanically +must happen when such a body is struck in any manner, +that it \emph{must} vibrate, for the same reason that any +visible elastic body must vibrate if struck, he will see +quite clearly the condition of things among elastic +atoms that collide with each other so many times per +second. + +That they do thus vibrate is proved by the spectrum +of substances in the gaseous state where between impacts +they have time to vibrate a great number of +times per second. At ordinary temperatures and density +a gaseous molecule of hydrogen, having a mean free +path of about the two-hundred-and-fifty-thousandth of +an inch, and moving at the rate of $6000$~feet per +second, will collide with its neighbors $17750$ millions +of times per second, but its spectrum shows that it +makes $450$~millions of millions of vibrations in the same +interval, so that in each interval between impacts it +would be able to make $\dfrac{450,000000,000000}{17750,000000} = 25352$, +more than twenty-five thousand vibrations. + +Now, imagine a number of bells suspended by cords +of equal length from the ceiling, but not so near as to +touch each other. Suppose each bell to have the same +musical pitch as every other one, and now let one of +the outer ones be pulled away from the rest and forcibly +swung back among them; presently every bell +among them would be set swinging by the impact of +others upon it, and each impact would cause each bell +to sound its own particular pitch, and the elasticity of +each individual one would maintain that vibration in +\DPPageSep{129.png}{117}% +some degree until the next impact, when it would be +strengthened, and one would hear along with the +bumping of the bells the sound due to the pitch of +the individual bells. Something very like this goes on +among the molecules of the gas. Their vibratory +movements we cannot hear, but with the spectroscope +they are detected and measured. Now, hot bodies cool +by radiation---the giving-off of just such waves in the +ether as we are describing,---and the fact that such cooling +molecules of a gas give out constant wave-lengths, +as is shown by their spectrum lines, is proof that the +vibrations that originate the waves +are not %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}{r}{1.25in} +\Graphic{1.25in}{129a} +\Caption{7}{Diag.\ 7.} +\end{wrapfigure} +free-path or oscillatory motions, +but true atomic ones, due to a +\emph{change in form}. How this can be is +easily seen by considering the change +in form made by any vibrating body, +say, a ring. Let the heavy lined ring +represent an elastic atom: if it be subjected to impact it +will assume an elliptical outline, and go through a series +of phases represented by the dotted lines. This change +of form, and uniform vibration, is a mechanical necessity, +and is independent of the size or particular form a +body may have. It is this kind of motion that embodies +the energy represented by the temperature of +an atom or a molecule, and the temperature varies with +the square of the amplitude of this motion; and two +bodies have the same temperature when their molecules +have the same vibratory energy. A single molecule in +free space would radiate all its heat away, and thus be +reduced to absolute zero, if it were not continually +\DPPageSep{130.png}{118}% +\index{Heat, nature of}% +receiving from other bodies an amount that depended +upon its nearness to them and their own amplitude of +similar motion. Hence the temperature of a body +depends upon the amplitude of vibration of its molecules, +and not upon any translatory or oscillatory or +rotatory motions. This is not saying that molecules +that are heated do not have other motions than the +vibratory ones constituting their temperature, but +when they do have others it is at the expense of the +vibratory, and therefore has reduced the temperature; +and such free-path motion as all gases have, and which +produces pressure upon the walls of vessels, is maintained +by the vibratory. It is not heat, but the result +of heat, in the same way as the translatory motion of +a bullet is not heat, but the result of heat. Most books +on heat do not make the distinction here made, but +combine the heat-motion of the molecules themselves +with the translatory motion they have, calling the sum +of them the heat of the gas. So long as one is concerned +only with the energy involved in the actions it +will make no difference; but if one analyzes the process +for the factors it is plain that there are two distinct +kinds of motion---one of them capable of setting +up waves in the ether, the other not, for it is not known +that any free-path or translatory movement of a body +ever disturbs the ether; and if distinctions of such +marked characters as these exist, and one of them involves +temperature and ether waves, and the other +does not, they ought not both to be called by the same +name. The peculiar character of the energy involved +in heat as distinguished from so-called mechanical +\DPPageSep{131.png}{119}% +\index{Heat of the sun, origin of}% +energy, is that the factor of motion is of the vibratory +sort, whereas the other is more or less translatory,---one +capable of easy transformation into ether waves, +the other incapable of such transformation, but each +of them easily transformed into the other by impact. +Equivalent velocities give the same amount of working +ability, or $\dfrac{W v^2}{2g} = \dfrac{W a^2 n^2}{2g} = P d$ (see \Pageref{p.}{69}). So it +can be understood how ordinary visible motion can be +transformed into heat, and \textit{vice versa}, as easily as one +can understand how the motion of the clapper of a bell +is transformed into sound. + + +\Section{ORIGIN OF THE SUN'S HEAT.} + +There has been much speculation as to the source of +the heat of the sun. Unless one assumes that it has +some miraculous or non-physical origin he is bound to +account for it, if at all, upon the assumption that physical +conditions and relations, such as we find at the +earth, hold good at the sun as elsewhere. + +At the beginning of this chapter the various sources +of heat were considered,---the mechanical, the chemical, +the electric, and the radiative. If these be tested as +to their sufficiency to account for the temperature of the +sun, one may reach a conclusion as to the probability +of any or all of them being concerned in it and their +relative importance. + +It will be convenient to consider them in the reverse +order, and first as to radiations. In order that a body +should become heated by radiations, there must first be +some body or bodies having as high or higher temperature +\DPPageSep{132.png}{120}% +to give rise to the radiations; and in this case, if +the sun's heat came from such a source, one would need +to look for the other bodies in the universe having such +high temperature. The millions of stars shining by +their own light would at first seem to furnish the proper +source; for the testimony of the spectroscope is that +they all are highly heated, and some astronomers think +some of them to be much hotter than the sun is. One +of the conditions under which radiant energy is distributed +in space is that its amount upon a given surface is +inversely as the square of the distance from the source; +and as every one of these bodies is at such an amazing +distance away, it is only with the most delicate instruments +that their radiant energy can be measured, and a +given surface upon the earth would receive as much as +the same surface upon the sun, and the earth would be +heated from the same source as much as the sun would +be. Practically it is found to be but a very small quantity, +and hence radiation from other bodies cannot +possibly account for the sun's heat. + +Second, as to electrical currents: it may be said at the +outset we have no direct knowledge that there are such +at the sun, and from other knowledge we have of its +constitution it would appear to be highly improbable +that there were or could be electric currents there. +Electric currents imply some generator and some conductor +for their transference; and from what is known +or may fairly be inferred that every substance we are +acquainted with as a conductor of electricity which is +present in the sun---and there are a good many of +them---iron being particularly abundant, yet they are +\DPPageSep{133.png}{121}% +all at such a high temperature as to be a far reach from +the conductibility we know anything about. There +may be, but it is by no means certain, something solid +in the sun, but the most of it is as gaseous as a bubble, +and gases do not conduct currents of electricity. + +Third, chemical action is known to be the antecedent +of vast quantities of heat. It may be recalled that a +pound of hydrogen, for instance, when allowed to combine +chemically with oxygen will give out $61000$ heat +units. The atmosphere of the sun appears to be made +up of elements mostly in an uncombined form, except +in the cooler, outlying parts; that is, the temperature is +so high that chemical combination is impossible except +in exposed places where radiation can allow cooling to +take place. It is tolerably certain that chemical combinations +are taking place there whenever it is possible, +and with such combination heat must be produced, if +physical laws are in operation there as they are at the +earth, but the amount of it going on, or possible, if the +whole body of the sun were to combine its elements in +this way, does not appear to begin to be equal to the +expenditure of heat actually taking place. + +There remains only the mechanical sources of impact, +friction, and condensation. There is good evidence +that there is a large body of meteors in the neighborhood +of the sun that must be falling upon its surface. +The sun's attraction can give a velocity of nearly four +hundred miles a second to any body reaching him from +distant space, and such a velocity would, on impact, +produce heat enough to reduce the whole body to a +gaseous state almost instantly. +\DPPageSep{134.png}{122}% +\index{Sun, its magnitude}% +\index{Sun, its heat}% +\index{Sun, its age}% + +Given the mass and velocity of a body, and one may +calculate how much energy it has, and how much heat +is the equivalent of the mechanical energy. Such a +computation shows that even if the earth were to fall +into the sun, it would be volatilized in a very brief time. +If the sun's surface were solid the impact would be +sufficient to effect it almost instantly. If the shell of the +sun were liquid it would be changed more slowly through +friction, but, in the end, the result would be the same. +It does not appear, however, that there is sufficient +material that finds its way to the sun to furnish but a +small proportion of the sun's heat, so neither impact +nor friction can be admitted as sufficient agencies. +There remains but one more, namely, compression. Is +there any evidence that condensation is taking place? +The body of the sun is $866000$ miles in diameter, and +is so far away that this immense magnitude occupies +but about half a degree of arc. If it were to shrink at +the rate of a mile in twenty years, it would account for +the present rate of expenditure, but such a shrinkage +could not be observed from the earth for several thousand +years, for nothing much less than a second of arc +can be observed with certainty, and a second of arc at +the sun's distance is equal to about $465$~miles, so it would +require $465 × 20 = 9300$ years to produce an observable +effect. + +Now, if the nebula theory be true, the sun once occupied +all the space between itself and the outer boundary +of the solar system and has shrunk to its present dimensions, +a process which, if heat alone were concerned, +would require about eighteen millions of years. It is +\DPPageSep{135.png}{123}% +\index{Heat, effects}% +not probable that heat alone has been concerned, so +it is probable that the sun is older than that, but the +shrinkage will account for the heat, and it appears as +the only probable conjecture. It will be understood +that the gravitative action is the occasion of the compression, +and that the approach is constant and as fast +as the generated heat can be radiated away. It has +been calculated that at the above rate of condensation +it may be reduced to one-half its present diameter with +its present radiation rate, in about five million years, +when its density will be about twice that of water. + +From such considerations it appears in a high degree +probable that the heat of the sun is due to condensation, +the condensation is due to gravitation, and thus +one is led back to a time when the substance of the +sun and all the planets was scattered through that +immense space, the diameter of which is not less than +six thousand millions of miles. How matter came to +be thus scattered is at present an enigma. It is important +to remark here, though, that until there was impact +among atoms, and molecules were formed, there evidently +could be no such condition as what we call heat, and +until these atoms and molecules vibrated there could +be no light, that is, ether waves. + + +\Section{EFFECTS OF HEAT.} + +Once in possession of a good, mechanical conception +of the action going on in a heated body, one can proceed +to trace out the various effects of heat in all +directions. Thus to take the familiar one of pressure +in a gas. A gas is simply a large number of individual +\DPPageSep{136.png}{124}% +\index{Molecules, number of, in universe}% +molecules moving about with great velocity and bumping +against each other and the sides of the containing +vessel. Each molecule, though small, has some momentum; +but the enormous number of them in, say, a cubic +inch, five hundred millions of millions of millions, and +their relatively high translatory velocities,---say fifteen +hundred feet per second, gives them momentum which, +when spent upon the side of the vessel, gives a pressure +equal to about fifteen pounds per square inch. If one +were to hold up a shield against which many balls were +thrown per second, he would need to brace himself to +withstand the pressure that would appear to be constant. + +If the gas be heated the molecules have increased +amplitude of vibration, and they rebound from each +other with greater velocity, and strike the side with +more momentum, and hence the pressure is greater. +As the pressure is proportional to the absolute temperature, +it is plain there could be no pressure if there +was no vibratory motion. If the density of the gas +be increased by adding more molecules per cubic inch, +there must a greater number of them strike upon the +sides of the vessel in a second, which will increase the +pressure, that is, the pressure varies as the density. + +When it is said that gases have a tendency to expand, +or that they exhibit a repulsive action, all that is signified +is this; as elastic bodies, the molecules rebound +after impact, and continue on in their direction, according +to the first law of motion, until otherwise obstructed. +When a ball rebounds from the side of the house it +has been thrown against, it is not because there is any +repulsion between the ball and the house. +\DPPageSep{137.png}{125}% +\index{Boiling-point pressure}% + + +\Section{EFFECT OF PRESSURE UPON BOILING AND FUSION.} + +When it is said that the boiling-point of water is~$212°$, +it is to be understood that the pressure of the air +upon the surface of the water is fifteen pounds per +square inch. At elevated places water boils at a much +lower temperature; and when in a tight vessel, like the +boilers of steam-engines, the pressure of the steam +affects its boiling-point in the opposite way, raising it. +Thus at twenty pounds steam pressure, the temperature +required to boil water is~$228°$, at sixty pounds it is~$291°$, +at ninety pounds~$319°$, and at the high pressures +employed in locomotives of one hundred and fifty pounds +or more to the square inch, the temperature of the +steam and water is $360°$~or more. As one goes down +into a mine the pressure of the air becomes greater, +and higher temperature is needed to boil water. The +explanation of this phenomenon is that the heated molecules +of the liquid are bumping against each other in +all directions, but the surface molecules can receive +such bumps only from below and on their sides. If +there were no molecules above to beat downwards, the +surface molecules would fly rapidly up into the free +space, which would be what we call a vacuum. This +escape of the surface molecules of a liquid into the +space above is called evaporation, and the higher the +temperature of the liquid the harder the bumps, and +the more will be flipped away from the liquid and +become free rovers, having a long, free path. When, +however, the gaseous particles are numerous and strike +back upon the surface, that is, when there is a gaseous +\DPPageSep{138.png}{126}% +\index{Earth, solidity of}% +pressure upon the surface, the surface molecules are +prevented from rising, that is to say, evaporation cannot +go on so fast, boiling is prevented until more energy is +given to the water, and that means a higher temperature. + +The melting-point of substances is likewise affected +by the pressure to which they are subject, and increasing +the pressure increases the temperature needed to +fuse them. Such small variations of pressure as only +a few pounds per square inch do not make much difference, +but pressure measured by tons per square inch +makes a great deal. The condition of the interior of +the earth appears to depend upon this as a most important +factor. As one goes beneath the surface of the +earth in mines and tunnels, it is observed that the temperature +rises about one degree for every fifty or sixty feet +of descent; and it was formerly inferred from this that at +the depth of a few miles a temperature would be reached +high enough to melt the most refractory bodies, and hence +the interior of the earth was probably in a fused state +while the crust was relatively thin. Such a view took +no account of the effect of pressure upon the state of +bodies. At the depth of a mile of water the pressure +must be equal to $62.5×5280=330000$ pounds per +square foot, and as rock is $2\frac{1}{2}$~times\DPnote{** PP: Slant fraction in original} the weight of +water, the pressure must be $825000$ pounds, or over +four hundred tons; and at five, ten, or a hundred miles, +it is obvious the pressure is correspondingly greater. +A body that at the surface of the earth would melt at any +assignable temperature would require a much higher +temperature to fuse when subjected to such enormous +\DPPageSep{139.png}{127}% +\index{Temperature, maximum}% +pressure. It appears that the pressure increases faster +than the observed temperature; and hence the earth +must be solid to the centre, instead of being liquid as +formerly supposed. This makes it appear that the +phenomena of volcanoes are only local, and do not indicate +\index{Volcanoes}% +any general melted condition of the earth. If a +body that would melt at a thousand degrees on the surface +of the earth be subject to such pressure that it is +not melted when its temperature is two thousand +degrees, then, if the pressure be suddenly removed +from it, the heat it has will instantly liquefy it. This +may be the condition at the base of volcanoes, where +shrinkage of the earth's crust in some direction may +relieve the pressure in some other direction; and a +large mass of heated material may become liquid, expanding +in volume, and overflow in any direction where +there is a vent, and this would be called a volcanic +eruption. + +\Section{MAXIMUM TEMPERATURE.} + +We have considered the condition called absolute +zero, wherein the molecules have no vibratory motion +whatever; and it has also been pointed out, and it is +generally agreed, that the temperature of a body varies +as the square of its amplitude of molecular vibration. + +It has often been assumed in treating of high temperatures, +such as that of the sun for instance, that +there is no limit to the temperature to which matter +can be raised. So some have estimated the temperature +of the sun to be several millions of degrees; but +a consideration of the factors involved will show such a +\DPPageSep{140.png}{128}% +conclusion to be impossible, for the dimensions and +form of a body set a limit to the amplitude it can have. +A tuning-fork cannot have its prongs vibrate beyond +the limit where its prongs touch each other, and a +vibrating ring cannot have an amplitude greater than +one-fourth its circumference; and this degree is only +possible to a mathematical circle having no thickness. +Make a ring of a piece of twine, and elongate any +diameter until the opposite sides touch, then move the +middle points through a similar distance, and it will be +seen that the limit will be equal to a quadrant of the +circle; but if the ring be a thick one, say made of rope, +it would be less than that, and how much less will +depend upon the relative thickness of the rope to the +diameter of the ring. If the thickness of the rope +were one-fourth the diameter of the ring, then the +amplitude could be but one-half the quadrant, and so +on. Now, the atoms of matter have a definite size, and +no one has ventured to suggest that they were variable +in size in any degree; and one may, therefore, compute +the greatest amplitude such a body could have, whether +it were a circle or a hollow sphere without thickness. +If the diameter be as before stated, one fifty-millionth +of an inch, calculation shows that the greatest amplitude +it could have would be about one sixty-four-millionth +of an inch. This, multiplied by the number of +vibrations it makes per second, will give the equivalent +velocity from which its energy can be calculated. On +\Pageref{page}{67}, it is shown that the velocity of a vibrating +atom, if the amplitude be one-half of the diameter, +will be about eighty miles a second. If the amplitude +\DPPageSep{141.png}{129}% +be equal in measure to the quadrant, as is here supposed, +this velocity would be not far from a hundred +miles per second, and the energy represented by that +velocity would be the utmost energy of heat, or highest +temperature that the body could have. The pressure +of gases enables one to determine the velocity of +the particles; and when this is known at a given temperature, +the temperature at any other velocity may be +computed. + +The statement that atoms and molecules can have a +maximum temperature must not be understood to imply +that the energy they can have is fixed at that limit, +because aside from their temperature energy, represented +by their vibratory motion, they can have any +assignable translatory velocity in addition. But it does +imply that ether waves, arising from temperature, +have a fixed limit for each element; and such radiant +energy from a given source cannot be transmitted beyond +a certain rate, because its amplitude has a limit, +so that whatever actual energy the sun as a whole may +have, it cannot lose that energy by radiation faster than +an assignable rate. + +This has an important bearing upon the question of +the age of the sun. Computations have been made of +the length of time the sun can have been giving out +its energy, on the assumption that the sun is a cooling +body, and that it was formerly much hotter than it is +now. If the above statements are correct, the probability +is that the sun is as hot now as it ever was, and +that its rate of loss of heat by radiation has not been +greatly different from what it is to-day; so, instead of +\DPPageSep{142.png}{130}% +being only fifteen or twenty millions of years old, it +may be very much more. + +As the temperature of a body represents its molecular +energy, and is measured by $\dfrac{mv^2}{2}$, it follows that if two +different kinds of molecules, such as hydrogen and +oxygen, have the same temperature, they will have the +same amount of energy; but the mass of an oxygen +molecule is sixteen times greater than the mass of a +hydrogen molecule. In an equal weight of the two +there will be sixteen times more molecules of hydrogen +than of oxygen, and therefore the hydrogen will have +sixteen times the energy of the oxygen at the same +temperature. To produce a rise of temperature of one +degree in a pound, or any given weight of hydrogen, +would require sixteen times as much heat as the same +weight of oxygen would need. This difference in +thermal capacity of different substances is called their +specific heat. In general, the lighter the molecules +\index{Specific heat}% +that make up a substance, the more numerous must +they be to make up a given mass, and the higher will +be its specific heat; i.e., the more heat must be expended +upon it to produce a given rise in its temperature. +The specific heat of water is chosen as a standard +and is unity, as it is found to require more heat to +raise a given weight of it one degree than any other +substance. One heat unit will raise the temperature +of a pound of it one degree; all other substances +require but a fraction of this. From what is said, it +appears that the specific heat of an element varies +inversely as its atomic weight. The specific heat of +\DPPageSep{143.png}{131}% +\index{Dissociations}% +a substance determines the temperature it will attain +when a definite quantity of heat is supplied to it. If +a pound of hydrogen and eight pounds of oxygen are +exploded together, and not allowed to expand in volume, +$51444$ heat units calories are produced. The $51444$ +heat units would be divided among nine pounds of +water vapor, that has a specific heat under such conditions +of~$.37$. The temperature attained would be +$\dfrac{51444}{9×.37}=15450°$. This temperature is much higher +than the limit of possible combination of the two +gases, which, at about~$3000°$, are unable to combine, so +such an action could not take place any faster than the +parts could cool down to the latter temperature. If +the mixture be allowed to expand, the temperature of~$3000°$ +may not be reached, and the action of the whole +is so rapid it is called an explosion. + +\Section{DISSOCIATION.} + +When compound molecules are broken up into their +elementary constituents in any manner, the process is +called dissociation. It may be effected by electrical +action, as when water is decomposed by it, or by chemical +action, as when wood is decomposed under water, +setting the carbon free; but heat is competent to effect +the same end. At the temperature of about~$3000°$ the +existence of water is impossible, as the elements cannot +stay united, and the reason is obvious. Whatever the +nature of the attraction that holds atoms together in +chemical compounds, if the elementary atoms are themselves +in brisk vibratory motion, as we know they are, +\DPPageSep{144.png}{132}% +\index{Matter, effect of temperature upon}% +they must be straining their bonds continually to separate; +and when the amplitude of such motion reaches a +certain maximum, the impacts are so violent as to make +the atoms rebound out of each other's neighborhood, +and thus prevent cohesion. The atoms then either +enter into new combinations with others, if possible, +and if not they remain as gaseous particles, and subject +to the laws of gases. + +If one starts with a piece of ice and applies heat it +melts, and we call the liquid water. Apply more heat +and the water becomes steam, in which the individual +molecules are no longer able to cohere, because of their +energetic motions; but each molecule remains intact, +having a long free path, for a cubic inch of water +becomes nearly a cubic foot of steam under ordinary +air pressure. If still more heat be applied, the molecules +become more and more unstable until they too +are broken up in the same way and for the same reason +that the solid and the liquid forms were. When it is +no longer possible for hydrogen and oxygen to combine, +it is still possible for the atoms of each to combine +with each other, hydrogen with hydrogen and oxygen +with oxygen, forming elementary molecules \textit{H H}, and +\textit{O O}; but if a still higher temperature be applied, even +this combination becomes impossible, and the atoms +themselves become free rovers and individually independent. +Thus it is seen that the different states +of matter depend altogether upon temperature. At +absolute zero there can be no such thing as a gas, for +the molecules would have no individual vibrations and +therefore no free paths. They would probably fall to +\DPPageSep{145.png}{133}% +the bottom of the vessel and remain quiescent. It is +also probable that both liquids and solids too would +cease to exist, not that matter would be annihilated, but +a solid, a liquid, and a gas are simply each a bundle of +physical properties that depend mostly upon temperature, +and those properties would probably disappear +with the disappearance of the conditions upon which +they depended. +%\DPPageSep{146.png}{134}% + + +\Chapter{VII}{Ether Waves}{134} + +\index{Ether waves}% +\index{Ether wave qualities}% +\index{Light, its nature}% + +It has already been stated in what has preceded this +that translational motions of matter are not competent +to originate ether waves, and that vibratory motions +of both atoms and molecules can originate them. A +consideration of the origin, transmission, and effects of +such ether waves constitutes the subject-matter of what +is called the science of light. The word ``light'' is +commonly used to signify that agency in nature which +is capable of affecting the eye and causes vision, or the +sensation of sight, and until within a very few years +has been supposed to be a peculiar kind of a wave +motion in the ether quite distinct from other waves +known to exist which were competent to produce heating +and chemical effects, so such waves as were known +from their effects were called heat waves, light waves, +and actinic or chemical waves, according as they heated +bodies, produced light, or brought about chemical reactions. +These three sorts of waves were supposed to +coexist generally, but were capable of being separated +from each other so there could be a beam of either +without the others. This is now known to be a mistaken +view, for what a given ether wave will do depends +upon what it falls on rather than on its own peculiarity. +The same waves that fall upon the eye and produce the +sensation of sight will heat other kinds of matter, and +\DPPageSep{147.png}{135}% +\index{Ether waves, their source}% +\index{Light, a sensation}% +if they fall upon a surface of molecules that are unstable, +that is, in which the atoms that make up the molecules +are not strongly cohesive, the molecules are +disrupted by the waves, and the atoms enter into new +combinations, and this process is called a chemical process; +and while it is true that some waves will not produce +vision, there are none that will not produce both +heating and chemical effects, so there is no such distinction +among ether waves as was supposed, and this +leads to another conclusion also; viz., if there is no +such distinction between waves, then there is no such +thing as light at all, unless we classify all rays as light, +whether they can produce sight or not, which is sometimes +done to save explanations, but it leads to the +anomaly that there is such a thing as dark light, which +is absurd. There will be no difficulty whatever if light +be defined as a sensation merely, and the waves competent +to produce the sensation be called visual waves. +Up to the present time, however, the old terminology +is quite generally adhered to in spite of the difficulty of +reconciling the old signification with the new knowledge. +There is no single word that signifies ether +waves in general, and independent of the effects that +may be produced in specific cases, and for that reason +this term has been adopted. The word ``light'' is +entirely inadequate, and likely to mislead one not well +versed in the phenomena. + +\Section{ORIGIN OF ETHER WAVES.} + +The source of ether waves of all degrees whatever +is the vibratory motions of atoms and molecules as distinguished +\DPPageSep{148.png}{136}% +\index{Elements}% +from their translatory, or free-path motions, +but their rates of vibration are determined by their +atomic weights. An atom of hydrogen, for instance, +has a different rate from oxygen, for the same reason +that two tuning-forks, though made precisely alike, +would have different rates if one were made of steel +and the other of aluminium. If they have different +rates, then the number of waves produced by them per +second will be different, and as all waves travel in the +ether with the same speed, namely, $186000$ miles per +second, the length of the waves produced by them +must be different. + +There are about seventy different elementary atoms, +each setting up its characteristic waves in the ether all +the time. It is to be remembered that all atoms and +molecules are always to be considered as hot bodies; +that is, bodies having some temperature, and mostly +a long way above absolute zero; and also that their +energy of this kind may be spent upon the ether. If +the waves from one molecule have more energy than +those given off by a second molecule upon which they +fall, the second one absorbs some of it so as to have its +own temperature raised until it is the same as the other; +that is, until the energy given off by them both is +equal. And this is universally true. Matter is continually +exchanging energy in this way, always tending to +bring about equality of temperature. But the number +of vibrations a body makes does not need to be the +same as that of another body in order to possess the +same amount of energy, for the energy depends upon +both mass and velocity. If the mass be small, the +\DPPageSep{149.png}{137}% +velocity must be greater, and \emph{vice versa}. And thus it +is that the seventy elements that make up the kinds of +matter we know are everywhere and at all times setting +up ether waves, each kind its particular rates, when not +otherwise interfered with. + +There is, however, a qualification that must be added +that has a high degree of scientific importance. Every +elementary substance is vibrating at several rates at the +same time, as do piano-strings, bells, and musical instruments +in general. Every particular rate of vibration +produces its own waves, and thus each atom and +molecule is continually producing, when not interfered +with, its own characteristic set of waves. This must +make the ether waves from the different kinds of matter +exceedingly complex, and disentangling them correspondingly +difficult; yet it has been done. + +When we look at luminous bodies, like the sun or +stars, or flames, or gas, they seem to differ from each +\index{Flames}% +other in brightness and sometimes in color, as is seen +in fireworks. A flame of alcohol has a bluish tint, a +little salt in it makes it yellow, some lithium makes it +red, and copper, green or bluish, while sunlight is white, +as is the electric light. If one looks through a common +prism at the landscape the edges of objects appear in +rainbow tints, and with the colors arranged in the same +order, while at the same time the shape of things is +more or less distorted. If a beam of sunlight be sent +directly through such a prism, a patch of colors may be +seen on the floor or wall, and this is called a solar +spectrum; and if this light of different tints has its +wave length measured, it appears that the red light has +\DPPageSep{150.png}{138}% +a wave length of about the one forty-thousandth of an +inch, and the violet light at the other extreme a wave +length of about the one sixty-thousandth of an inch, +while the intermediate tints range regularly from the +one to the other. There is in this spectrum that can +be seen an almost infinite number of wave lengths; +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{150a} + \end{center} + \Caption{8}{Diag.\ 8.---Visible Solar Spectrum.} + \index{Spectrum, solar}% +\end{figure} +there is no break among them apparently. The same +thing holds true of a spectrum produced by letting the +light from a lamp or candle go through the same prism: +\index{Prism}% +the tints, their order, and their wave lengths are found +to be the same. The prism then receives ether waves +of any or all wave lengths, and separates or disperses +them in the order of their wave lengths. In doing this +it deflects the longer waves less than it does the shorter +ones. The deflection of the waves from their original +course is called \emph{refraction}, and the separation from each +\index{Refraction}% +other so as to produce the spectrum is called \emph{dispersion}. +\index{Dispersion}% +A prism effects both at the same time, and thus enables +one to isolate at will any particular tint or part of the +spectrum; and if one takes a single narrow portion in +any such spectrum, he has a bundle of light rays of +uniform wave lengths, and he may then determine their +value. In this way the wave lengths of the different +colored parts of the spectrum of sunlight have been +found to be as follows:--- +\DPPageSep{151.png}{139}% +\begin{center} +\TableFont% +\begin{tabular}{ll<{\qquad\qquad}l} +Red, & about & $39000$ to the inch +\\ +Orange, & \PadTo{\text{about}}{\Ditto} & $41000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Yellow, & \PadTo{\text{about}}{\Ditto} & $44000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Green, & \PadTo{\text{about}}{\Ditto} & $47000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Blue, & \PadTo{\text{about}}{\Ditto} & $51000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Indigo, & \PadTo{\text{about}}{\Ditto} & $54000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Violet, & \PadTo{\text{about}}{\Ditto} & $57000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +\multicolumn{2}{l}{Extreme visible, about} & $60000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +\end{tabular} +\end{center} + +A spectroscope is an instrument composed of a prism +\index{Spectroscope}% +mounted between two tubes, one of them having an +adjustable slot for the light to be examined to pass +through on its way to the prism, the other being a short +telescope to magnify somewhat the image of the +spectrum that %[** PP: Width-dependent break] +%[Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{151a} + \end{center} + \Caption{9}{Diag.\ 9.---Spectroscope.} +\end{figure} +it may the better be seen. With this, +light from any source may be examined. Light made +up of all wave lengths that can be seen shows as +a complete spectrum, while any light made up of but +a part of these gives a corresponding incomplete +spectrum. The flame of an alcohol lamp, or a Bunsen +\DPPageSep{152.png}{140}% +\index{Spectrum analysis}% +gas-flame, gives but little brightness and not much to +produce a spectrum; but a little salt in the flame gives +to it a bright yellow tint, and shows in the spectroscope +a single narrow band of yellow light in the same place +as the yellow seen in sunlight, and therefore having the +same wave length. Such a beam made up of waves of +one wave length is called homogeneous light. This +sodium light has a wave length of about the one forty-four-thousandth +of an inch. With other more refined +methods, which cannot be described here, sodium is +found to have other wave lengths beyond both the red +and blue ends, and which cannot be detected by the +eye alone. Hydrogen, another element, gives a bright +red line and a blue line that are easily seen; and several +others may be detected with more delicate apparatus. +In this manner all the elements have been attentively +studied during the past thirty years, and many treatises +may be found that give full particulars of the processes +and results. The substance of knowledge obtained by +the study of the spectra of the elements may be briefly +stated to be,--- + +1st, Each element has its own vibratory rates at +a given temperature, and sets up corresponding ether +waves; some of these can be seen, and others require +more complicated apparatus to discover. + +2d, In order that the characteristic vibrations of any +atoms or molecules may take place, it is necessary that +they be allowed a free path to vibrate in; in other words, +they need be in the gaseous state. If they be crowded +together, as they are in solids and liquids, they have no +chance to vibrate without interference. A pailful of +\DPPageSep{153.png}{141}% +school-bells might make a jangling noise, but would give +no particular pitch or characteristic sound of any of the +bells, and only when not interfered with for a part of the +time at least could one give out its true sound. This +gaseous state is generally obtained by igniting in flames +or by the electric spark the substance to be examined. +In an electric arc all substances are volatilized, and may +be then studied with the spectroscope to great advantage. +Sometimes substances that remain in the gaseous +state at ordinary temperatures, such as hydrogen, oxygen, +chlorine, etc., are hermetically sealed in glass tubes, +after rarefication, in order to obtain long free paths, and +are lighted up by means of electric discharges through +them. + +3d, On account of the lack of vibratory freedom, the +molecules of solids and liquids give out vibrations of all +wave lengths, for every partial and incompleted movement +disturbs the ether; and there are all degrees of +these, but the energy of the shorter ones is rarely great +enough to affect the eye, and hence are not visible at +ordinary temperatures. If a body like a cannon-ball be +gradually heated in the dark, it will presently begin to +glow with a dim red tint. If looked at through the +spectroscope, only red light on the extreme red border +can be seen. As the temperature rises, additional +shorter waves appear, and the spectrum broadens to the +orange, then the yellow, and so on; the ones already +showing growing brighter meanwhile, until the ball is +in a bright glow, and a full continuous spectrum is produced. +As the ball cools, the reverse holds true; and +the violet waves are the first to disappear, then the blue, +\DPPageSep{154.png}{142}% +and lastly the red vanishes from sight. Still the ball is +much too hot to safely touch, and continues to cool by +giving off ether waves differing from the rest only in +being too long to affect the eye. They still are refracted +by the prism, and an invisible spectrum is produced, +and this spectrum has been traced out to ten +times the length of the visible spectrum. +%[Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{154a} + \end{center} + \Caption{10}{Diag.\ 10.---Complete Solar Spectrum.} +\end{figure} + +The sun, an electric arc, and other solid hot bodies, +\index{Spectrum, solar}% +give out similar long, invisible spectra. + +In like manner, where the body is white-hot, and giving +out the shortest waves the eye can see, there can still +be found, a long way beyond that limit, waves that can +do photographic work, which is but a kind of molecular +dissociation. + +4th, Where waves of a given length are made to pass +through a gas having similar vibratory rates, or capable +of producing waves of the same length, the molecules +of the latter will absorb such waves, and therefore stop +their progress, especially if they have more energy than +the waves the absorbing gas can give out. So if sunlight +containing the same yellow light as that of sodium +gas be made to pass through the latter, it will be stopped; +and if this be done where there is a spectrum of sunlight, +the yellow will be cut out from it, and there will be +but a black line instead. This is called gaseous absorption, +\index{Gaseous absorption}% +and is an illustration of what was said a little way +\DPPageSep{155.png}{143}% +\index{Sun, its structure}% +back about the exchange of energy always going on. +The absorbing power of a gas has a significance like its +radiations, and indicates its presence as well. + +The yellow light of sodium gas has a definite place +in the spectrum; and hence if one perceives those wave +lengths in a gaseous spectrum, he knows that sodium +must be present in a state of incandescence, giving rise +to the waves. But if the light from a white-hot cannon-ball +were to be sent through that same vapor, and afterwards +examined with a prism, the yellow light would be +absent, and the absence would still proclaim the existence +of sodium vapor. + +Hence, if an incandescent body gives a continuous +spectrum, it must be a solid or a liquid; the molecules +must be so compact that the individual vibrations are +prevented, and only irregular ones can be made. If a +discontinuous but bright line spectrum is shown, the +matter must be in a gaseous state, and the molecules +have free path. + +If a bright spectrum have black spaces or bands +across it, there is indicated a solid or liquid incandescent +body shining through gas that acts by absorption +upon it, and thus both the solid and gaseous conditions +are detected, as well as the nature of the substance in +the gaseous state. + +This knowledge has been applied to the discovery of +the substance and condition of the sun and other celestial +bodies, and it is concluded that the sun has a solid +or liquid surface as a shell to a gaseous interior, and +that the atmosphere of it consists of the various +elements that make up the body of the sun in so highly +\DPPageSep{156.png}{144}% +\index{Jupiter, temperature of}% +\index{Mars, atmosphere of}% +\index{Saturn, temperature of}% +heated a condition as to keep them in a vaporous or +gaseous state. The characteristic spectroscopic lines of +about forty elements have been found there. Some of +the elements have a very large number of spectroscopic +lines. Iron, for instance, has several hundred lines. +Hydrogen is particularly abundant. Perhaps the most +important discovery due to the spectroscope has been +this: that there are a very large number of gaseous +bodies, called nebulæ, in the heavens; some of these fill +immense spaces; they are in a condensing state, and +all of them are mostly made up of hydrogen. This +discovery gave an additional probability to the nebula +theory of the origin of the solar system, for it showed +that process in its various stages in more distant +parts of space: and in addition to that, it has led to +the surmise that in some way some of those we now +call elements are really compounds of more elementary +substances, probably hydrogen; but that is a speculation +merely, for there is no other than such spectroscopic +evidence that anything like transmutation of what we +call elements into others can take place. + +The spectroscopic examination of the other members +of the solar system has shown that Mars has an +atmosphere like ours, holding watery vapor in it; +that Jupiter is red-hot; that the temperature of Saturn +is probably much too high for any such living things +as exist on this earth---and in this way has answered +the question so interesting to most thoughtful persons +as to whether the planets are inhabited or not. Jupiter +certainly cannot be inhabited by any such beings as we +are, for the temperature would destroy all organic things. +\DPPageSep{157.png}{145}% +\index{Motion, kinds of}% +\index{Stars, their motions}% + +Velocities of translation can also be measured when +as high as two miles a second or more, by the displacement +of spectroscopic lines towards one or the other +end of the spectrum. If a star is approaching us, the +wave lengths are shortened a small quantity, and that +changes the position of a line towards the blue end, +while recession makes it longer and moves it towards +the red end, so it has been found that Sirius is receding +\index{Sirius}% +at the rate of nineteen miles per second; that Arcturus +\index{Arcturus}% +is coming towards us at the rate of sixty miles +per second. In like manner is shown that the sun, and +with him the whole solar system, is travelling in the +direction of the constellation Hercules at the probable +rate of about sixteen miles per second. + +Now, all this presupposes that the principles established +in the laboratory for substances there investigated +are applicable wherever such matter exists; +for instance, that the spectrum of sodium and of hydrogen +and iron, which depends upon temperature and +pressure, is as reliable if the light comes from a body +a million miles or a thousand million miles away as if it +came from only one mile or a foot distant. If it be +thus widely applicable, then do we have the best of +testimony that matter, its conditions, and its laws are +the same everywhere, and that the earth is a fair specimen +of the rest of the universe. + + +\Section{OTHER PHENOMENA OF ETHER WAVES.} + +Whenever a line of ether waves---which is generally +called a ray, whatever the wave length may be---falls +\DPPageSep{158.png}{146}% +upon matter, the ray may be either absorbed, transmitted, +or reflected. Neither of these results takes +place singly in any case. There is no known body, for +instance, that can wholly absorb all the rays that fall +upon it, nor wholly transmit or reflect them. If a body +should be able to absorb all the rays that fall upon it, +we should not be able to see it unless itself were a self-luminous +body, for we only see other than self-luminous +objects by means of the light reflected from them, +and such a body would reflect no light, and hence could +not be visible. + +Bodies which absorb most of the rays that fall upon +them we call black and opaque; that is, a body that +reflects but a small portion of the waves that are incident +upon it is a dark or black body, because we see +but little of it. If it reflected none at all, it would be +quite invisible. In like manner, a perfectly transparent +body would be one that would neither absorb nor +reflect any rays, and for that reason would be quite as +invisible as space itself. The air is perhaps as near an +approach to perfect transparency as anything that can be +\index{Transparency}% +named; yet if it reflected no rays at all, there would be +nothing of the diffused light that is now so plentiful on +the clearest day, but there would be only what would +come direct to us from the sun or other luminous body. +We call clear glass and water transparent because objects +can be plainly seen through them; and a sheet of hard +black rubber we call opaque, for nothing whatever can +be seen through it, nevertheless it has been shown +that waves longer than those that affect the eye, go +through such hard rubber as easily as the shorter ones +\DPPageSep{159.png}{147}% +we call light go through glass, hence transparency and +opacity are terms only relative to particular kinds of +waves. All kinds of matter reflect more or less of the +waves that fall upon it. This reflection is merely the +\index{Reflection}% +change in direction of the ray; but it always follows a +definite law, keeping to its original plane, and making +the angle of reflection equal to the incident angle. +The surfaces of most bodies are very rough, and the +rays are reflected in all directions, because the points +upon the surface face in so many ways. This will +be obvious to one who looks at the surface of paper or +of wood with a magnifying-glass. The smoother a surface +is made, the nearer will all the incident rays take +the same direction on reflection. Mirrors are thus +\index{Mirrors}% +made of smooth glass or metallic surfaces, and are +plane, convex, or concave; but whether they are made +with plane or curved surface, the rays reflected always +follow the above law. + + +\Section{REFRACTION.} +\index{Refraction}% + +So long as ether waves fall perpendicularly upon any +surface of any kind of matter, the rays go straight on +into it if they be not reflected or absorbed at the surface; +there is no change in the direction, but the velocity of +transmission is less in all kinds of matter than it is in +the ether. In glass it is only about two-thirds as fast, +and in water about three-fourths. When the ray meets +the surface at an angle, it is bent out of its course more +or less, depending upon the kind of material it falls +upon, and also the angle at which it meets it. This +change of direction, when entering a new medium, is +\DPPageSep{160.png}{148}% +called refraction, and this property is possessed by all +kinds of matter, solid as well as liquid and gas. The +refraction for a given angle of incidence is more for a +liquid than for a gas, more for a solid like glass than for +water or other liquids, and more for a diamond than for +any other known substance. The same rule that obtains +when the waves enter a medium, holds when it leaves +it; the direction it will now take will depend upon the +angle the rays make with that surface and the character +of the medium into which it enters. Thus, if a +ray meets a piece of plain glass at an angle, say, of~$45°$, +some of it will be reflected, making an angle of~$90°$ +with the incident ray, and some of it will be refracted +into it, making an angle with the original direction, and +continue on in a straight line until it meets the next +surface, when it will again assume its original direction: +but when the second surface is not parallel with the +first, as is the case with the prism, the direction may +depart still more from the original; and the shorter the +wave length, the more the deflection. It is this property +that is made use of in spectroscopes, microscopes, +and telescopes. A lens has one or both surfaces +curved, so as to be convex or concave, depending upon +the use it is to be put to,---a convex glass converging +the rays, and a concave one separating them,---and +almost any degree of either of these may be obtained +by proper curvature. + +Both microscopes and telescopes are so common, and +descriptions of them are to be found in so many places, +that they need not be described here. The inquiry is +often made, why still more powerful microscopes and +\DPPageSep{161.png}{149}% +\index{Microscope, magnifying powers}% +telescopes are not made so as to reveal the very smallest +and the most distant thing. The utility of a +microscope depends upon how plainly it is able to +make minute objects visible; and the more a given one +magnifies an object, the smaller the portion that can be +seen and the less light is available for the purpose, and +when the objects are so small as the few thousandths +of an inch, the light waves interfere with each other at +the edges, and produce colored fringes that cannot be +got rid of altogether, and very small objects become +indistinct for that reason. Microscope lenses are +marked as $1$~inch, $\dfrac{1}{2}$~inch, $\dfrac{1}{10}$~inch, and so on, meaning +by the fraction the approximate distance it must be +brought to the object in order that the latter may be +seen. The higher the power, the shorter this distance. +A one-tenth inch objective may magnify an object a +thousand diameters and perhaps more, so that a blood +corpuscle having a diameter of only one three-thousandth +of an inch may appear about three-tenths of an +inch in diameter, and the details of its coarser structure +may be very well seen; but if there be a minute +point upon it, still indistinct because it is minute, and +a still greater magnifying power required to see it, and a +$\dfrac{1}{20}$~objective be taken, the actual magnifying power +may be five thousand diameters. But now one is +approaching the dimensions of wave lengths themselves, +and the agent necessary for observing introduces +its own complications, producing distortions and +color fringes about the point to be studied, and no way +\DPPageSep{162.png}{150}% +has been found of obviating this. Objectives have +been made having a focal length of only the $\dfrac{1}{50}$~of an +inch and one having only the~$\dfrac{1}{75}$, but no work of any +importance has ever been done with them. The best +of the microscopic work has been done with lenses that +magnify no more than one thousand diameters. It is +said that the best microscopes will show an object that +is no more than about the one hundred-thousandth of +an inch in diameter, but it appears simply as a point or +a line, and no details of its structure can be seen. +Fine rulings upon glass have been made that are known +to have this degree of fineness, because the mechanism +that rules them can be gauged to that degree; but +many persons cannot see these in a microscope, though +others can. So within the limits of the visible not a +little depends upon the acuteness of vision, and there +is a great difference among individuals in this respect. +On account of the properties of the ether waves themselves +in their relations to each other, it does not +appear probable that much improvement is possible to +the microscope. This does not imply that we may not +know more of the minute structure of bodies than we +do now, for there are other sources of knowledge of +minute quantities than simply direct eyesight, which +are just as reliable, perhaps more so. A good chemical +balance will weigh to the millionth part of the load. +Whitworth showed that it was possible to measure to +the millionth of an inch by touch. The spectroscope +will indicate the millionth of a grain by the tint of the +\DPPageSep{163.png}{151}% +gas flame, and the color of a drop of water is appreciably +changed by the one three-millionth of a grain of +fuschine. Some substances, like essential oils, sulphuretted +hydrogen, and the odors of flowers, can be +perceived when the quantity is certainly less than the +fifty-millionth of a grain. + +Any day may bring tidings of new instrumentalities +that help in the solutions of the interesting questions +concerning molecular structure that are now quite out +of our reach. Let it be granted that the problems are +altogether physical ones, such as are justified by the +known mechanical relations of energy, and one may +wait with patience. Let one assume that some or any +of them are not mechanical, and he not only is in danger +of having to revise his judgment in some degree any +day, but he reasons against the significance of all the +knowledge we have of matter and its energy. + +The larger a lens is the more light can go through it: +a lens two feet in diameter will let four times as much +light through it as one only one foot in diameter. As +remote objects, like the distant stars, appear dim on +account of their great distance, it becomes needful to +concentrate the light from a much larger area than that +of the pupil of the eye. If the pupil be one-tenth of an +inch in diameter, a certain amount of light from a star +may enter it. A lens one inch in diameter would concentrate +at its focus $100$~times as much, and one a +foot in diameter, $14400$~times more; and hence the +object would appear so much brighter. Along with +this apparent brightening of the star, it is apparently +brought nearer and enlarged. There are limits to the +\DPPageSep{164.png}{152}% +size and useful magnifying power of telescopes as well +as to those of microscopes. The magnifying power +of telescopes depends very largely upon the eye-pieces +used, and the shorter their focal length the more do +they magnify. The large lens, called the objective, +serves mostly to collect a large amount of light. It is to +be kept in mind that the movements of bodies are magnified +as much as their apparent dimensions, and when +there are any movements of the body surveyed, or of +the instrument itself, distinct vision becomes correspondingly +difficult. + +With the telescope the chief trouble comes from +movements of the air, which are rarely of uniform quality +and motions. Not only its transparency, but its degrees +of density caused by heat and wind, are varying all the +time; and these seriously interfere with telescopic work. +If a magnifying power of say~$100$ be employed, these +disturbing causes are increased in proportion, and with a +power of~$1000$ nothing can be distinctly seen. Suppose, +however, the air be in best condition for observations, +and a power of~$1000$ be put upon the moon. As +the moon is about $240000$ miles away, this magnifying +power would have the effect of bringing it $1000$~times +nearer, or as it would appear to the eye if it were +but $240$~miles away. Now, an object $240$~miles away +can reveal no interesting details at all; anything much +less than half a mile square could not be distinguished +unless it were a very bright or very dark spot. Powers +as high as~$8000$ have been used; and such a one would +bring the surface of the moon as it would appear if it +were about thirty miles distant, which might show a +\DPPageSep{165.png}{153}% +city, a large town, a lake, and the difference between +field and woodland, yet nothing satisfactory was seen +for the reasons mentioned, so for most astronomical +work a magnifying power of only a few hundred is +used; seldom more than five hundred. When large +telescopes are set on elevated places like the Lick +Telescope on Mt.~Hamilton in California, some of the +troubles from disturbed air are obviated, and it is hoped +something more may be learned about our nearer astronomic +neighbors. But these large telescopes collect +so much more light that stars so distant as to be quite +invisible with smaller glasses become plainly visible +with them. With the unaided eye no more than $5000$ +or $6000$~stars can be seen in the whole heavens, with +an opera-glass as many as $100000$ become visible, while +the Lick telescope, with an object-glass three feet in +diameter, shows nearly $100,000000$. Each increase in +the size of the telescope adds to the number of visible +stars, and one cannot but wonder if their number be +infinite, or if there be a boundary to the universe of +matter. Though the visible boundary of our universe +has been greatly extended by the invention of the telescope, +nothing has been descried anywhere but matter +and motion: there has been nothing added to our knowledge +but the sense of bigness. Instead of only a few +thousand of hot and flaming stars, there are hundreds +of millions of them, made of the same kinds of matter, +having the same kinds of motions, controlled by the +same laws, and nothing animate in any of them more +than in a bowlder in the wall. Clifford said he wished +they were farther off. The problems of astronomy are +\DPPageSep{166.png}{154}% +\index{Space, navigation of}% +interesting studies in mechanics, but are not inviting to +those most interested in life and mind. Herschel and +Chalmers and Dick and Mitchell are dead. The +knowledge already gained has destroyed both their +arguments and hopes, and has left the inhabitants of +this earth the possessors of the universe, yet unable to +take possession. + +If there are inhabitants in Mars they are as unable to +traverse space as we are; and the possibility of our yet +being able to do that is not half so unlikely as it seemed +to be but a very few years ago, since it evidently requires +for accomplishment but a directed reaction against +the ether; and we already know how to produce the +reaction by electrical means; and every point in space +has the energy for transformation. + +It is generally agreed that the so-called attraction of +a magnet for its armature is really due to the pressure +of the ether upon the latter, and it may be as great as +two hundred pounds to the square inch. + +An electro-magnet without an armature is therefore +reacted upon by the ether to that degree. When this +reaction can in any way be neutralized at one pole and +not at the other, the ether reaction will push the magnet +backwards, and the navigation of space will at once +become mechanically possible. + + +\Section{THE RADIOMETER.} +\index{Radiometer}% + +It is a familiar enough fact that when sunshine falls +upon a surface the latter becomes heated. In general, +the darker the color of the surface the more rapidly %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}{r}{1.5in} + \Graphic{1.5in}{167a} + \Caption{12}{Diag.\ 12.---Radiometer.} +\end{wrapfigure} +does +the temperature rise; and some bodies, when thus exposed +\DPPageSep{167.png}{155}% +for some time, become unbearably hot. We are +able to say that the surface molecules of such a body +are in a brisk vibratory movement; that they have more +energy than other bodies with less temperature. If one +imagines the condition of things when the molecules of +the air impinge upon such a heated surface, he will understand +how they must bound away +from it with greater velocity than +they struck it with, and if with +greater velocity, then with greater +energy. As action and reaction are +equal, it must kick back upon the +surface as it leaves it, thus tending +to make the surface move in the +opposite direction; and a large number +of such impacts must give a resultant +backward pressure. If the +surface be a small one, the increased +pressure in the air in front will +travel round to the other side at +the rate of eleven hundred feet in a +second in ordinary air; so the pressure +will be equalized in a very short +interval of time. If the air be rarefied +in front of such surface to such a degree that the +free path of the molecule is many times greater than +its ordinary length, that pressure cannot get round +nearly so fast, and there will consequently be a constant +backward pressure, produced by the molecules that impinge +upon it and become heated by contact with it. +The pressure per square inch is very slight, as it is +\DPPageSep{168.png}{156}% +produced by a relatively small number of molecules; +but it may be made apparent by mounting some disks, +blackened on one side, upon a pivot in a glass bulb, +and, after exhausting a large part of the air, hermetically +sealing the bulb. Such a device is called a radiometer. +When put where sunshine, or the light from +the flame of a lamp or candle, or even the heat of the +hand, may fall upon it, the vanes begin to rotate, the +blackened side backing away from the source of the +energy. This movement was at first interpreted as +being due to the actual pressure produced by light +waves, but further investigation showed that idea to be +wrong. The movement comes from the transformation +of the motions of ether waves, first into heat, and +second into the translational mass motion observed. +The radiometer is, therefore, a machine for transforming +ether waves into visible mechanical motions. + + +\Section{PHOTOGRAPHY.} +\index{Photography}% + +It has already been explained how heat acts upon +molecules, increasing the amplitude of the vibrations of +the atoms that make them up, and, if carried to a sufficient +degree, is able to quite destroy the molecular structure +and enable the component atoms to enter into new +combinations. The degree needed for this depends upon +the kind of molecules. Some molecules are so stable +that only the very highest temperature we can produce +can break them up. Others are so feebly cohesive that +the least touch will cause them to go to pieces, and +sometimes with explosive violence, as is the case with +what are called fulminates, compounds of nitrogen with +\DPPageSep{169.png}{157}% +silver or with mercury; and sometimes the same result +is reached by ether waves, whose number per second is +such as to set one of the ingredients into sympathetic +vibration and thus decompose the compound, doing it +at a slower rate than the others. Nearly all complex +molecules are decomposable in this way, and the process +is going on all the time in nature where there are organic +things to act upon, but the process is usually +slow. + +When shingles are first laid they have a fresh surface +and new appearance, which is presently lost by +the exposure. Take a freshly planed piece of soft +pine or other white wood, and fasten to the surface a +piece of paper cut into any shape or design,---a circle, +a star, or the like,---and set the wood where the sun +can shine on it for a few days. When the design is +removed the figure will be plainly seen on the wood by +the difference in tint between its surface and that part +which the sun has shone upon. The latter is much +darker. This is an example of photographic action, +as is the color of fruit, etc.; for if a design is pasted +upon a green apple, which is red when ripe, the design +will protect the surface from the action of the light, +and will therefore appear upon the apple in a light tint. +Diagrams and letters may be fixed thus upon fruit of +any kind. Discolorations of all sorts, due to ether +waves or light, may properly be called photographic +action, both fading and darkening, as when the skin +becomes tanned. For practical purposes some compounds +of silver are generally employed, because they +are more sensitive to the action of visible waves than +\DPPageSep{170.png}{158}% +most other substances. They have the property of +being easily disorganized by waves whose length +ranges from about one forty-five-thousandth of an inch +to those in the neighborhood of the seventy-thousandth +of an inch, some of these being visible waves, the +others being too short for visibility. When a surface is +prepared with some one of the sensitive salts of silver,---generally +the iodide or the bromide,---and a picture +of an object produced by the lenses of the camera +is allowed to fall upon it, the decomposing action is +proportional to the amount of light and shade in the +different parts; and, when the plate thus exposed is +placed in certain chemical solutions called developers, +the decomposition is completed and the products dissolved +out, leaving a coating of pure silver, with a +thickness proportional to the chemical action that has +taken place. This gives, then, a correct likeness of +the picture that was in the camera. Formerly it took +a long time to produce such a picture, a person having +to sit still for half an hour or more. More and more +sensitive preparations were produced, until now a good +picture can be taken in less than the thousandth of a +second; and the practice of the art has become a great +industry. There are many preparations in common +use for taking such pictures, but nearly all of them +have silver for the chief constituent. It may be +remarked that silver compounds are remarkably unstable. +Silver is not easily oxydized\DPnote{** [sic]}, for it remains +untarnished for an indefinite time, as exemplified by +coins and jewelry. But there are plenty of other compounds +that may be used. Thus the common blue-print\DPnote{** Hyphenated across page, no other instances.} +\DPPageSep{171.png}{159}% +\index{Silver salts unstable}% +is a compound of iron. The salts of chromium +are also sensitive to such waves. + +It was remarked that the salts of silver are sensitive +to ether waves between quite a wide range in wave +lengths, but the longest of them is in about the middle +of the visible spectrum. They reach from there into +the region beyond the violet. Yellow and red waves +are incapable of affecting such a preparation, while the +waves that are the most efficient for it are the blue +ones. +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{171a} + \end{center} + \Caption{13}{Diag.\ 13.---Photographic Range for Silver Salts.} +\end{figure} + +Other substances have a different range, and a curious +chemical discovery has shown that silver molecules +may be loaded; that is, may have attached to them in +a temporary way some other kinds of molecules that +render them sensitive to waves of any length. If an +ordinary photographic plate has a solar spectrum +thrown upon it, there will be no indication of action +below the green; but, if aniline be added to the sensitive +coating and the plate be then exposed in the same +way, the action will now be seen to have gone on to a +distance below even the longest red wave that can be +seen. In this way photography has shown that the +spectrum of most incandescent bodies is much longer +than the visible part of it in both directions. It was +the observation that photographic action took place +\DPPageSep{172.png}{160}% +\index{Molecules, loaded}% +most strongly in the blue part of the solar spectrum, +and in the region beyond, that led to the belief that +light waves and chemical rays were, in some way, +unlike each other. From what has been said it will be +seen that the reason for the different action was due to +the character of the material used. When a molecule +is made bigger or heavier in any way, longer waves can +affect it more; and that is the significance of the so-called +loaded molecule. In reality, the whole molecule +is made more complex and bigger, and longer waves +can shake its atoms loose. + +It is to be hoped that all can understand that there +is nothing mysterious about photographic action; that +it is as simple in its mechanical principles as anything +can be. One may not be able at once to say in +any given case which atoms or which parts of a molecule +are loosened by the vibratory strains. In this one +it may be the nitrogen, in another it may be the silver, +and in still a third it may be oxygen; but in each case +the mode of action is the same, and it may be said to +be mechanical throughout. + + +\Section{VISION.} + +Our various senses differ much in their mode of +action, and require for excitation not only each its +proper stimulant, but degrees of remoteness from +actual contact to the most distant points. Thus the +sense of touch requires absolute contact of a body: so +also does taste,---the sugar or the salt must dissolve +upon the tongue. A distance of but the tenth of an +inch between the sugar and the tongue will be absolutely +\DPPageSep{173.png}{161}% +prohibitive to the consciousness of sweetness. +The sense of smell requires the actual contact of the +gaseous molecules upon the nasal membrane, but currents +of air and gaseous diffusion secure to us this condition, +so that the emanating body itself may be at +some distance, and yet we become conscious of the +bank of violets, the cup of coffee, or the chemical laboratory. +This sense, therefore, enlarges our field, so to +speak, and permits us to be conscious of bodies out of +our immediate reach. The sense of sound still farther +enlarges the space that can react upon us. But the +loudest sounds, such as the roar of cannon and thunder, +lose their intensity shortly, and can rarely be +heard beyond a few miles. If our endowment of +senses stopped with these, we should really be quite +\index{Senses}% +limited in our possible knowledge; for as we can know +only what comes into our experience, how small the +possibilities of existence would be to us! What we +could touch, taste, smell, and hear we could know something +about, though we were unconscious of any lacking +sense. We should need some apparatus that could +make us conscious of the most distant things as well +as those close at hand. We should need just what we +have got,---the sense of sight, that extends the field of +experience and of interest to us to the boundaries +of creation. The other senses give us information of +contiguous things, but sight brings the universe itself +to our consciousness. + +The sense of touch is diffused all over our bodies. +There is no such thing as an organ of touch. The +senses of taste and smell are restricted to localities and +\DPPageSep{174.png}{162}% +to organs that have other functions as well. Only sound +and sight have specific organs, having no other function +than to respond to sonorous and optical motions, and +thus they have a peculiar dignity in the physiological +mechanism; and precisely because the eye and ear have +these mechanical functions do they come into the domain +of physics. They are machines by which certain forms +of motion are transformed into others suitable for nerve +transmission to the seat of consciousness. + +It has often been pointed out that the structure of +the eye is like the camera of the photographer. In each +\index{Camera}% +there is a chamber~\textit{a}, having a lens in front, which has +a length %[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{174a} + \end{center} + \Caption{14}{Diag.\ 14.} +\end{figure} +of focus adapted to the distance between it and +the back of the chamber, so that the image of objects +external to it will be produced by it upon the back of +the chamber, where there is in each a sensitive coating +so affected by the light as to make an impress. In the +camera this action has been explained as chemical +reaction when molecular dissociation results, proportionate +to the amount of light that falls upon any part +of the surface exposed. + +In each there is an arrangement for altering the focal +distance of the lens. In the camera it is a ratchet-wheel +that moves the lens towards or away from the +back. In the eye there are muscles attached to the +\DPPageSep{175.png}{163}% +edge of the lens that by contracting make the pliable +lens less convex and so increase its focal length. For +the camera %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}[15]{r}{2.25in} + \Graphic{2.25in}{175a} + \Caption{15}{Diag.\ 15.---Photographic Camera.} +\end{wrapfigure} +there is +\index{Camera}% +an exchangeable diaphragm +having perforations +of various +sizes to admit more +or less light through +the lens. In the eye +there is a colored +muscular disk called +the iris, that contracts +or expands in +an automatic way so +as to expose more or +less of the lens to +the light. The functions +of the two devices are identical. + +The energy possessed by the ether waves that fall +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{175b} + \end{center} + \Caption{16}{Diag.\ 16.} +\end{figure} +upon the sensitive photographic plate is spent in doing +\DPPageSep{176.png}{164}% +\index{Vision, phenomena of}% +the molecular work of disintegration. In the eye all +the energy is stopped at the sensitive back coating +called the retina, and must of course be accounted for +in some physical way. In the camera all the energy of +the waves is spent in precisely the same kind of a way; +that is, there is no such distinction as what is called +color in it: and color photography---that is, the direct +picture of objects in their proper, natural tints, such +as we know they have, upon the sensitive plate---has +not been accomplished, for the probable reason that the +colors of the molecules that are the result of the decomposition +of the silver compound are either transparent +or blueish black. In the eye, the distinction between +wave lengths which we denominate color sensation is +very pronounced. + +The sensations are so much complicated with the +processes that induce them that it is not always easy to +keep in mind the purely physical side or the subjective +side while treating of them. + +The following are some of the more common phenomena +of vision which must be taken into account in forming +any judgment or theory of it. + +When a firebrand is swung round and round it +leaves an apparent luminous trail, the length of which +depends upon the rapidity of motion. This is called the +persistence of vision, and indicates that the sensation +does not cease instantly after the source has gone. If +the brand be swung round at the uniform rate of once +per second, the length of this luminous trail will be a +rough measure of the duration of the sensation after it +is once excited. Thus, if it appeared to be one-quarter +\DPPageSep{177.png}{165}% +of the circle, the sensation must last for one-fourth +a second. For impressions not very bright the sensation +lasts but about the tenth of a second. If, however, +the object looked at be very bright, like the sun, for an +instant, the sensation may last for many seconds; and, +in general, the older the person the longer does it last. + +Different colors also have different degrees of persistence. +\index{Colors}% +Violet, blue, and green soonest fade out, and red +is the last to vanish for most eyes. This signifies that +wave length has in someway to do with the persistence. +When a bright colored object, like a bit of red paper, +is put upon a sheet of white paper and steadily looked +at for a few seconds, and is then suddenly removed while +the eyes are kept fixed upon the same place, the image +of the red paper will still be seen, but it will appear with +a green tint, and will fade out in a few seconds. A +green piece of paper, or any green object looked at in +the same manner, will give an image in red. Blue ones +give yellow, and yellow blue; and these tints seen in +this way are called complementary to each other, as it is +found by combining such together they produce the +sensation of white light. Whiteness is therefore a compound +sensation. Formerly, it was thought that white +was only produced by the composition of all the colors +of the spectrum in the same proportions they exist in it; +but the same sensation of whiteness can be produced +by red, green, and violet, and by blue and yellow. This +is not to be understood as applying to pigments or +paints, but to light itself. + +If one looks at a strongly lighted object intently for +a few seconds, and then turns his eyes to a dimly +\DPPageSep{178.png}{166}% +\index{Vision, hallucinations of}% +\index{Vision, energy needed for}% +lighted drab surface, he will be able to see, sometimes +in a surprisingly realistic way, the same object against +the new background. If it be a person looked at, +the features may even appear in a startling way. +The size of the subjective figure will depend upon +the distance of the background, being larger the more +remote that is. Age and health have much to do +with the persistence of such sensations\DPtypo{}{.} Young and +vigorous persons seldom notice them until they +carefully look for them; while older ones, and especially +weakened ones, may be much troubled by +them. Some nervous systems react upon the eye itself, +and give rise to similar images there; and these subjective +images have not unfrequently been mistaken for +objective persons living or dead. The color a given +object appears to have is not unfrequently modified by +what colors the eye has been resting upon the instant +before, and hence two persons may look at once upon +the same picture and see it in very different tints. + +As ether waves are the source of the sensation, it is +obvious that a certain number of consecutive waves +must be necessary to affect the eye; that is to say, it is +not in the least probable that a single wave of any +length could produce a sensation. How many are +needed is not known, but one can determine somewhere +near what the number must be if he knows how +brief a time is sufficient to produce a sensation. It is +said that some flashes of lightning have been found to +occur in less than a millionth of a second, and those +may produce a very strong sensation. + +If there are five hundred million million vibrations per +\DPPageSep{179.png}{167}% +second, as we know there must be to give such a sensation, +in the millionth of a second there must be five +hundred millions; if the brightness were reduced ten +thousand times and it were still visible, there must +then have been not less than fifty thousand waves: and +this is equivalent to saying that the eye could perceive +light if it lasted no longer than the ten thousand +millionth part of a second, which is probably true. +But there is another condition; namely, the \emph{energy} +of the waves must be sufficient to effect a physical +change in the eye; and we know that the energy of +such ether waves varies with the square of their amplitude. +If, then, any wave whatever has not energy sufficient +to produce the necessary physical disturbance in +the eye, it could not produce vision. And this is the +most probable reason that we do not see in what we +now call darkness. It has been shown that all matter +at all temperatures is vibrating and setting up ether +waves, and also that in all liquids as well as solid +bodies there are vibrations due to their atomic and +molecular interference; and, theoretically, there must +be vibrations of all wave lengths at all times and in all +places, but at low temperatures the shorter waves, +though not absent, would have but small energy, and, +as the body becomes hot and the shorter ones acquire +more, it is done at the expense of the energy of the +longer ones, for the light given out by an incandescent +lamp increases faster than the supply of energy to produce +it. It therefore appears as a necessary conclusion +that the reason we cannot see in the dark is not so +much because the waves of proper wave length are +\DPPageSep{180.png}{168}% +\index{Vision of animals}% +\index{Vision, theory of}% +entirely absent, as that they have too little energy to +affect our eyes. Other animals, such as rats, mice, +owls, bats, and the like, can see where it appears to us +to be pitch dark. They must, therefore, have eyes +adapted for longer wave lengths than are ours, or else +the sensitiveness of their eyes exceeds ours. As +they see readily in the daylight, it is certain they are +adapted to such waves as our eyes are; and, if ours +were sufficiently sensitive, or had a greater range in +effective wave lengths, there would be no such condition +as darkness. That is the same as saying that +darkness is in us rather than being a condition external +to us. + + +\Section{THE THEORY OF VISION.} + +When it was discovered that the sensation of whiteness +could be produced by combining three different +colors,---red, green, and violet,---it was inferred that +there were probably three sets of nerves that were spread +as a fine net-work over the retina so that either of these +rays might fall at any point in the field of vision upon +it and so produce the sensation. At the same time, +when one or two of them were absent, the other nerve +ingredient would be present to be affected; and, furthermore, +each one of these three nerves was sensitive to +quite a wide range of wave lengths, and their overlappings +gave perception without any break from the +extreme red to the extreme violet. In this way color +perception could be explained. This view was adopted +as a working hypothesis; and there was no other proposed, +although there was no evidence whatever for the +\DPPageSep{181.png}{169}% +existence of three sets of nerves having different properties. +It has, however, lately been discovered that +the retina secretes a substance called purpurine, on +\index{Purpurine}% +account of its purple tint, which is very rapidly +bleached or decomposed by the action of light. That +is to say, it possesses photographic properties in a +marked degree. This discovery has led to the view that +vision may be altogether due to photographic action, +and the older view has been about abandoned. The +details of this theory have not yet been all worked out, +but the purport of it may be briefly stated. + +Given the purpurine spread over the retina: this +would be its sensitive coating corresponding to the silver +preparation upon the photographic plate. The +action of the light upon it being the same in character, +decomposes it into simpler molecular compounds. The +optic nerve is certainly spread over the retina, and the +purpurine is in its meshes, and any disturbance taking +place in this substance must correspondingly affect the +ends of the nerves imbedded in it. Given the disturbance +that can affect the optic nerves, and it is transmitted +at once to the base of the brain and there interpreted +as light sensation. The differences there might +be in the amount of disturbance would be the differences +that are called brightness or intensity. If molecules +are disintegrated, as in photographic action, there +must be a relatively large amount of free-path motion +resulting from the wave action in the eye, and the +amount of it proportional to the energy expended. +Such an effect would give a general sensation of light, +probably, also, effects of light and shade, so the forms of +\DPPageSep{182.png}{170}% +bodies would be readily enough seen. It would also +account for persistent effects; for, when molecules are +made to move fast or slow, they do not cease instantly +on the removal of the source of the motion, but they +continue to thus move until their energy has been +reduced to that of the surrounding medium. With +simple purpurine there appears to be no more possibility +of chromatic effects than there is in the common +silver preparation on the photographic plate. Suppose, +however, the purpurine to be not a simple kind of a +body, or made up of only a single kind of molecules, +but instead made up of as many as three different +kinds having as many different molecular weights, and, +therefore, capable of being reacted upon by three different +wave lengths. Call these three substances \textit{a},~\textit{b}, +and \textit{c}~purpurine. Let \textit{a}~be such as red waves can +decompose, \textit{b}~such as green ones can decompose, and \textit{c}~such +as only the short purple ones can break up or +shake up. If these are uniformly mixed together and +spread over the eye, then red waves would shake up +the red constituent, but would leave the others alone; +and the same would hold true of the others. If one +has been looking at red-light wave lengths, the \textit{a}~purpurine +would be used up, but the \textit{b} and~\textit{c} would still be +present unimpaired; and now, when white light is again +looked at, the \textit{b}~and~\textit{c} would be acted on strongly because +they are present in greater quantity. The resulting +sensation would be the compound of these two +reactions, which, as is well known, is a greenish tint. +In a like manner, each of the others when used up +would leave the same field fresh with the other constituents, +\DPPageSep{183.png}{171}% +\index{Color-blindness}% +\index{Retina, its functions}% +and so give the complementary tints; and in +this way chromatic effects of all sorts can be accounted +for. + +Some persons are color-blind; that is, they are +unable to distinguish some colors; and this defect is +usually for red rays. Such a color-blind person will be +unable to see the red end of the spectrum, and the +colors of it will appear to leave off in the yellow or +orange. The old explanation was that the red sensation +nerves were absent. The newer explanation is +that the \textit{a}~ingredient of the purpurine is wanting either +partially or altogether. + +Of course it is to be understood that the products of +decomposition by light in the eye are removed and +fresh material secreted in its place by the organ itself +in a manner similar to the removal of waste tissue and +its repair in any other part of the system. + +The function of the retina, then, would appear to be +the secretion of the sensitive substance needed for +vision, instead of itself being the sensitive substance. + +Such an explanation of vision makes the eye still +more like the photographic camera than appears in its +outward form and mechanical functions. And thus one +is able to trace the forms of motion that constitute the +heat and the temperature of a body through its resultant +ether waves to the molecular break-ups at the ends +of nerve fibres, whence the characteristic motions are +transmitted to the base of the brain, to be interpreted +thus or thus, according to position, number, and energy. +We begin with motion, we end with motion at the +seat of consciousness, and there we stop. It is vibratory +\DPPageSep{184.png}{172}% +in the hot body it starts from, it is undulatory +motion in the ether, it is oscillatory in the disrupted +molecules, and a longitudinal wave in the nerve. +Whether it is discharged from further service at the +base of the brain, or is stored up in some way as experience, +no one can say; but it is certain that a relatively +large amount of molecular energy finds its way constantly +to the brain, and some of it is re-employed as +reflex action, giving rise to voluntary and involuntary +\index{Reflex action}% +muscular and secretory processes, as when one winks, or +dodges a threatening motion before the will can act, or +laughs or weeps at sights and sounds. In either case +the result is the physical expression of a physical antecedent, +with an intermediate mental quality called +emotion. + +The eye may then be said to be a machine for the +transformation of ether waves into interpretable molecular +or atomic motions, and its function ceases at the +ends of the optic nerve. +%\DPPageSep{185.png}{173}% + + +\Chapter{VIII}{Electricity}{173} + +\First{The} industrial applications of electricity are now so +extensive and varied that every one is acquainted with +them in some measure, and yet fifteen years ago there +were millions of persons in the civilized nations who +had never seen an electrical phenomenon with the exception +of lightning. The apparently capricious behavior +of lightning, together with the attractions and repulsions +exhibited by electrified bodies, were phenomena +so different in character from any other, that it came +to be looked upon as a very mysterious force. Fifty +and more years ago it was classed with heat and light +as one of the imponderables. To-day even the question +is often asked, What \emph{is} electricity? with the +emphasis on the word ``is,'' as if one knowing enough +might describe it as he might describe a genii or an +object having specific qualities that might be isolated +from everything else. Some have thought it to be a +fluid, some two fluids, some vibratory molecular motion, +some a property of matter, some a motion in the ether, +some the ether itself; and, lastly, some have concluded +that we do not and never can know its nature. +Hence, to-day there is no generally received notion +concerning its nature. +\DPPageSep{186.png}{174}% +\index{Electricity, origin of}% +\index{Electricity, thermal}% +\index{Thermodynamics, electric}% + +Still, one may know a great deal about the agent +itself,---how it originates, what it will do, and its relations +to other phenomena,---and not concern himself at +all as to the nature of it. Heat and many of its laws +were well known before any one knew or even suspected +what its nature was. The law of gravitation +is known and applied on the scale of the universe without +demanding any explanation of the phenomena, and +it is equally true that our knowledge of electricity is +very extensive and accurate, and doubtless what we do +not know to-day we may know to-morrow. + + +\Section{ORIGIN OF ELECTRICITY.} + +It is here to be assumed as known, that various +instruments, such as electrometers and galvanometers, +are employed to detect the presence of electricity, and +descriptions of them will not be given. Attention will +be paid chiefly to the conditions that are present when +electricity is generated. + +\Section{1. THERMAL ORIGIN.} + +When two different metals, such for instance as copper +and iron, are touched together, they are found to be +electrified; that is, an electrometer shows the presence +of electricity. A piece of copper wire twisted to a +piece of iron wire always becomes thus affected, but +the effect is so slight that only delicate and sensitive +apparatus will detect it. Wires of any of the metals +under similar circumstances exhibit the same phenomenon, +but in different degrees. This electrification is +but transient; in a few seconds it has vanished. If the +\DPPageSep{187.png}{175}% +junction of the metals is heated by the fingers, or in +any other way, the electrical condition is maintained +indefinitely. If one will imagine such a compound wire +bent into a ring so the ends nearly touch each other, +it could be shown that the ends attract each other, the +attraction being but slight. Here we are not so much +concerned about the measure of what is taking place +as with its character. If the ends of the wires be +allowed to touch, and the twisted junction be kept warm, +a current of electricity will continue to circulate through +the ring; and, if the ends be connected to a galvanometer +of sufficient delicacy, the needle would be +continuously deflected, so long as the junction was +warmer than the outer ends of the wires; and the deflection +of the needle would be found to vary with the +difference in temperature between the inner and outer +junctions. Some metals, such as bismuth and antimony, +when fastened by solder, or in any other way, give much +stronger effects with a given temperature at their junction. +Such a combination is called a thermo-electric +pair. By joining a number of such together, so that +alternate ends may be heated at once, the electrical +effect is increased proportionally: two will give twice, +and ten ten times as much, and so on. When a number +of these are nicely compacted together and provided +with binding-screws, they are called thermo-electric +piles, and are of service in some investigations. It is +not necessary, however, to have two different metals in +contact to obtain the same kind of effects. If a piece +of soft iron or platinum wire be wound into a close coil +about a lead-pencil and the ends of it connected to a +\DPPageSep{188.png}{176}% +galvanometer, a current of electricity will traverse the +circuit when one end of the coil is heated in a flame. +If the other end be heated, the current will go in the +opposite direction. The twisting of the wire into +the coil produces a strain among the molecules that +changes the physical properties to a slight extent: the +density is altered. It therefore appears that in this +case, as in the cases with two different substances, we +have two \emph{physically} \DPtypo{diferent}{different} +bodies, though of +the same element. The +facts may be generalized +by saying that, %[** PP: Width-dependent break] +%[Illustration] +\index{Thermopile}% +\begin{wrapfigure}{l}{2.5in} + \Graphic{2.5in}{188a} + \Caption{17}{Diag.\ 17.---Thermopile.} +\end{wrapfigure} +whenever two differently +constituted bodies +are placed in contact +with each other, electricity +is generated, and +is maintained so long +as there is a difference +in temperature between +the junction and the external +ends. + +If one inquires for the +origin of such manifestation as the first case, when two +different metals are placed in contact, attention must +be directed to the actual molecular condition of the +two metals. Suppose them to have the same temperature,---as +they have different atomic weights their +vibratory rates cannot be the same,---and when the +surfaces are put in contact there must be a re-adjustment +\DPPageSep{189.png}{177}% +\index{Chemical origin of electricity}% +of their molecular motions, for each will interfere +with the other. This disturbance of molecular rates +is a disturbance in their relations of energy, and +furnishes the energy for the electrical phenomenon +that ensues. When equilibrium is restored, as it may +be shortly, there is no longer any electrical exhibit. + +When heat is applied so as to keep the junction continually +hotter than the other parts, the first effect is +continuous; for as each element has its own proper +vibratory molecular rate, which is increased by the +heat, the interference is kept up and an electrical current +results, which the heat is spent to produce and +maintain. One needs to have in mind what is signified +by heat as vibratory atomic, and molecular motion, in +order to clearly perceive what is expended in the +thermo-electric pile. The face of the pile, when it is +generating a current of electricity, does not acquire +that temperature it would acquire if it was prevented +from producing a current by having the wires detached. +Hence the amplitude of vibrations is lessened by the +electrical work done, and we may say that heat has +been converted into electricity, a thermal origin. + + +\Section{2. CHEMICAL ORIGIN.} + +When a piece of copper is dipped into a vessel of +water, and a wire leading from it is connected to a +proper electrometer, it is found to be electrified to a +certain degree. If a piece of zinc be substituted for +the copper, it too indicates a still greater degree; and +now let both be placed in the same water and connected +by a wire, and a current of electricity will flow through +\DPPageSep{190.png}{178}% +\index{Polarization of molecules}% +the wire, as in the case with the thermopile. This +current will be a transient one, or very slight, if the +water be pure; but if a little acid like sulphuric be +added to the water, the current may be relatively a +strong one. If, %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}[11]{l}{1in} + \Graphic{1in}{190a} + \Caption{18}{Diag.\ 18.\break Galvanic Cell.} +\end{wrapfigure} +instead of the zinc and copper, any +other two metals be taken, the results will differ from +the former only in degree. Zinc and copper, +or zinc and carbon, are generally employed, +because those have been found to +give better results than other available elements; +and such a combination of metals, +with some solution, acid or alkaline, which +is capable of \DPtypo{disolving}{dissolving} one or both of the +metals, is called a galvanic battery. A single +\index{Galvanic battery}% +jar with its proper elements is called a cell; and by +the addition of cells additional effects may be produced; +that is, with two cells twice, and with ten cells +ten times the effect. + +As with the thermo-pair, one may inquire what conditions +were known to be present that could furnish an +antecedent to the electrical current that results. This +is answered by pointing out, as in the other case, that +there are two substances differing in their physical qualities, +copper and water, or zinc and water, and molecular +rearrangement at their junction must necessarily +result. More than this. It is known that the zinc and +oxygen have a strong affinity for each other. The oxygen +is combined with hydrogen to form the water, and +in water the molecules are without any definite arrangement: +they face in all directions, and move about with +the greatest freedom, with but little, if any friction. +\DPPageSep{191.png}{179}% +When zinc is placed in it, the attraction of the zinc for +the oxygen part of the molecule must result in making +every water molecule in proximity to the zinc swing +round so as to present its oxygen side to it. This orientation +of the liquid molecules is called their polarization. +The attraction between the two is not quite +strong enough to disrupt the water molecule; but the +addition of sulphuric acid weakens the attraction between +the hydrogen and oxygen, and enables the oxygen +to seize a zinc atom, and both combine with the sulphuric +acid to form the sulphate of zinc. Here we +have chemical reactions such as always result in exchange +of energy; for the sulphate of zinc has less +molecular energy than the zinc, the water, and the +acid, in the same way that carbonic acid gas has less +energy than the carbon and oxygen gas that formed +it. There has been, then, a molecular change accompanied +by the development, first of heat and second +the generation of electricity; for if the electrical current +be not allowed to flow, the battery cell will itself +heat up more than it otherwise would do. There are +chemical, thermal, mechanical, and electrical phenomena +here, which may be perceived by carefully thinking +of the successive steps in the process. The distinctive +thing here is to bear in mind what the characteristic +antecedents of the electrical phenomena are. What are +the chemical, the thermal, the mechanical factors, except +special forms of exchangeable molecular motions? +So one may say that in a galvanic battery chemism or +heat has been transformed into electricity. Though +the mechanism of transformation is different, yet the +same factors appear as in the thermopile. +\DPPageSep{192.png}{180}% + + +\Section{3. MECHANICAL ORIGIN.} +\index{Electricity, mechanical origin}% + +When a piece of glass or of wax is rubbed with a +cloth or catskin, the two substances subject to the +friction become endowed with a new property which +they do not otherwise exhibit. If a glass disk be +mounted so as to %[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{192a} + \end{center} + \Caption{19}{Diag.\ 19.---Static Electrical Machine.} +\end{figure} +be rotated, and proper connections +made to it, as in the common Static Electrical machine, +a current of electricity may be maintained by maintaining +the friction, and all the electrical phenomena may +be produced that can be with electricity from any other +source. They are identical, but the source is the friction +of dissimilar substances. It will be recalled that +dissimilarity in substance was the condition in each of +the former cases; but in this, mechanical friction is the +\DPPageSep{193.png}{181}% +\index{Electricity, magnetic origin}% +\index{Stress, magnetic}% +second factor. In the chapter on heat it was pointed +out, and it is a familiar enough fact everywhere, that +heat is always the immediate result of friction. So in +this mechanical source, with apparatus so dissimilar in +all outward form to both thermopile and galvanic battery, +we still have precisely the same molecular conditions +that were operative in them to produce electricity,---two +dissimilar substances, and heat or a kind of motion +that results at once in heat. + + +\Section{4. MAGNETIC ORIGIN.} + +If a wire of any sort be placed across the pole of a +magnet, and held quiet there, no electrical effect will +be noted; but if the wire be moved toward or away from +the pole, it will become electrified, and if one end of it +be connected to an electrometer the movement of the +needle will indicate it. If the two ends of the wire be +connected to a galvanometer, whenever the wire is thus +moved in front of the magnet pole a current will flow +through the circuit, and the movement of the needle +this way or that will indicate the motion of approach or +recession. The strength of this current will vary with +the rapidity of the motion of translation of the wire +through the space in front of the magnet; and the wire +through which it goes becomes heated. This is the +same as saying that the mechanical motion of translation +of the wire is converted into heat in a manner as if +it had been subject to ordinary friction there; and as a +matter of fact, it is found to require more energy to +move the wire in such a space when the ends of the wire +are in contact, than it does when they are not. This +\DPPageSep{194.png}{182}% +\index{Electricity, electrical origin}% +shows that the material of the wire is subject to some +restraint under such conditions and in such positions, +and the degree of restraint depends upon the distance +it is from the magnet, as well as upon the strength of +the magnet itself. Hence the different parts of the +wire are in different physical states. And this is just +what is exhibited by the twisted wire in the case of +the thermal origin; and when motion is imparted to the +wire, the degrees of stress in it change, and a current of +electricity is the result. That such a stress is really +present in the wire can be proved in several ways, +which only need to be alluded to in this place. First, +the electrical resistance of a wire is greater when in +front of a magnet than elsewhere; and second, the +phenomenon known as Hall's, in which a current of +electricity going through a conductor is deflected from +its course in the neighborhood of a magnet. So we +have, in this magnetic origin, two bodies with different +physical constitutions and external motions impressed +upon them, which gives the electrical product +observed. + + +\Section{5. ELECTRICAL ORIGIN.} + +Imagine two wires parallel to each other and a foot +apart. If an electrical current from any source is made +to traverse one of them, a corresponding current will +be initiated in the other, but in the contrary direction. +In a like manner if a constant current be kept in one +of the wires, and the other one be moved towards and +away from the other, currents will be set up in it. +Their direction will depend upon whether the motion +\DPPageSep{195.png}{183}% +\index{Inductive action}% +\index{Stress, electrical}% +be approach or recession. The effect is the same +whether either or both move at the same time. The +effect is similar to the one described under the head of +Magnetic Origin, showing that in some way the space %[xref] +about a wire having a current of electricity in it is substantially +similar to that about a magnet. The process +is called electro-magnetic induction in both cases, and +the explanation is the same in this as in the other. It +will be well, however, to point out that there are steps +in this process that need attention for the sake of mechanical +clearness. + +Given say, an electro-magnet, through which a current +can be sent at will, and so be made magnetic, +and with the wire in front of it as before. There is +now no magnetism and no electricity in the wire. +Make the iron magnetic, and the current is at once induced +in the other. I say at once, but this does not +mean instantaneously. It takes a short time for the +effect of the magnet upon the ether to travel to the wire +and affect it. As no electricity escapes from the electro-magnetic +circuit, the electricity observed in the wire, +or second circuit, is generated in it, and the \emph{immediate} +antecedent of it was the stress in the ether which was +produced by the magnet. Hence an electrical current +can arise from a proper kind of stress in the ether, no +matter how that is produced, as one of the factors; the +other factor being motion of some sort, mechanical or +otherwise. The steps are, an electric current in a conductor, +an electro-magnetic effect of the current upon +the ether, the reaction of the ether upon the second conductor. +Let these steps be kept in mind always when +\DPPageSep{196.png}{184}% +thinking about inductive action, and there can then be +no confusion from trying to imagine how electricity +gets from one circuit to another when they are insulated +from each other. + + +\Section{6. PHYSIOLOGICAL ORIGIN.} + +There are certain kinds of fish that are capable of +giving powerful electrical shocks to men and animals. +They are provided with special organs for this purpose, +but they have not been the subject of much study for +several good reasons. First, they are only to be found +in a few localities, and are difficult to obtain; and second, +their electrical qualities cannot be studied except +when they are alive; and when they are living and +healthy their shocks can kill both men and animals, +and few are willing to incur the risk. Both mankind and +animals in general can give rise to electrical currents. +By grasping with the thumb and finger of both hands +the terminal wires from a delicate galvanometer, a current +is indicated,---a part often due to thermo-electric +action, and a part to physiological action,---and it will +vary with the tightness of the squeeze of contact and +the person experimenting, some developing much more +relatively than others. It also varies with the parts of +the body in contact with the wires. This physiological +effect is always extremely minute, and is not to be +mentioned beside the amount necessary to effect the +remarkable things said to be done by personal electricity, +such as moving chairs, tables, etc. I do not +think any one has been found whose physiological +electricity could do so much as raise a grain the tenth +of an inch. +\DPPageSep{197.png}{185}% + +The various processes continually going on in the +body, such as breathing, digestion, blood-circulation, +and muscular motions of all sorts, and under conditions +of different temperatures, different material, different +chemical reactions, are quite sufficient to account +for all that has been observed in this direction. + + +\Section{7. ATMOSPHERIC ORIGIN.} + +The origin of lightning, so far as details go, has +\index{Lightning}% +never been satisfactorily accounted for. It is obviously +not an affair that can be investigated in any very scientific +manner, for one can never control any of the conditions +when it arises. + +Some have thought it due to the condensation of +electrified vapor molecules condensing into drops of +water, the degree of electrification increasing with the +size of the drops. How the original electrification of +the molecules was produced is not explained by such. +There is no doubt but that a large amount of energy is +often involved in a stroke of lightning, judged by its +sudden destructive work. The immediate source of +this energy is the question\DPtypo{}{.} There is no doubt but +when a gas or a vapor is condensed into a liquid, a +notable amount of energy is liberated in motions of +some sort; for it requires energy to be spent upon water +to produce the vapor. This is given back when the +process is reversed. This energy has often been called +latent heat. If this process goes on faster than it can +be conducted away, it must either be transformed, or the +process must stop\DPtypo{}{.} We know, too, that heat motions +are most freely transformed into electrical by the phenomena +\DPPageSep{198.png}{186}% +\index{Electrical antecedents}% +\index{Terminology, electrical}% +of the thermopile and the galvanic battery, +and it is not improbable that this is the source of the +atmospheric electricity. It is certain that where it +originates there are two differently constituted kinds of +matter,---the air and the water; and it is equally certain +that there are some vigorous exchanges of motion, both +in the form of wind and heat, and these are the conditions +present in each of the cases where our knowledge +is most complete. + +One may then fairly conclude from the analysis of +all the known sources of electrical development, that +motion of some sort is the antecedent in every case. +This motion may be the sort called mechanical, or that +called molecular or atomic, as heat, but it is always a +factor; and the amount of electrical energy developed +in every case is equal to the \emph{immediate} mechanical, +chemical, or thermal energy which disappears when it +is produced. If one admits that the quantity of energy +in phenomena is constant, that the quantity of matter +is constant, there is but one variable factor, and that is +motion. If mechanical motion is transformable into +heat, and heat into electricity, and some known form of +motion is the invariable antecedent to the production +of electricity, it does not need a very profound logician +to say, \emph{so far}, the nature of electricity is known. + + +\Section{ELECTRICAL TERMINOLOGY.} + +Every particular science and art has some technical +terms to give precision and definiteness to its processes +and its laws, and the advances made in any science +depend very largely upon exact signification of its +\DPPageSep{199.png}{187}% +terms. The late rapid development of electrical science +is due in a large measure to terminology, adopted +about twenty-five years ago; for it enables a man not +only to know what he himself is talking about, but also +to understand others, and that was not the case before. +A system of units and names for them are matters of +the first importance. How these were derived need not +be stated here, but it is needful for every one now to understand +the significance of the more common of them. + +Imagine a wire in front of you with an electrical current +traversing it from left to right. If it travels in that +direction it is because the electrical pressure is less +towards the right than in the opposite direction, just as +water flowing through a pipe towards the right travels +thus because gravitative pressure is less in that direction +than in the other. Gravitative pressure is measured +in pounds, electrical pressure is measured in \emph{volts}. + +If the pressure at the left of the wire were increased +in any way, there would be an increased current of +electricity in the wire, just as there would be more water +go through the pipe if the head or gravitative pressure +were increased. The rate of water flow might be measured +as so many cubic inches or cubic feet per second. +The rate of electrical flow is measured in \emph{ampères}. + +If the water pipe were a large one, and the pressure +the same, more water would flow through it than if it +were a small pipe of the same length. In like manner +a thick wire will permit more electricity to flow through +it with a given electrical pressure than a thin one. The +water pipe is said to oppose friction to the movement +of water. +\DPPageSep{200.png}{188}% + +A conductor of electricity is said to offer resistance +to the flow of electricity. No name has been given to +any unit of frictional resistance, but electrical resistance +is measured in \emph{ohms}. + +A definite quantity of water flowing at a given rate +will be emptied from the pipe in a second or a minute. +So will a definite quantity of electricity go through +the wire in a second or a minute. The quantity of +water thus flowing would be measured as so many cubic +feet, or so many gallons; the quantity of electricity is +measured in \emph{coulombs}, a coulomb being an ampère per +second. Where the rate of flow of an electrical current +is given in ampères, the quantity will be found by +multiplying the ampères by the number of seconds the +flow has continued. Thus a ten ampère current in an +hour will have conveyed $10 × 60 × 60 = 36000$ coulombs. + +There are also measures of capacity. The cubic inch, +the cubic foot, the pint, quart, bushel, and so on, are +measures of volume or capacity: any of them may be +adopted as a unit, and when accuracy is required all are +reducible to the cubic inch as a standard. Thus in a +gallon there are $231$~cubic inches. + +In electricity the unit of capacity is called a \emph{farad}, +and it represents the capability of an electrical device +to receive and hold a definite amount of electricity +under the standard conditions of pressure. Thus, when +under a pressure of one volt it holds one coulomb, the +capacity of the apparatus is said to be one farad. +Actually a piece of apparatus of sufficient size to hold +that quantity has to be so enormously large that a much +smaller one was requisite for convenience, and consequently +\DPPageSep{201.png}{189}% +\index{Potential, electrical}% +the microfarad, or the one-millionth of the farad, +has been more generally adopted. + +As work may be got out of a flow of water, the +amount of work depending upon the pressure and the +rate of flow, so may work be got from an electric current, +the amount depending upon the pressure, volts, +and the current, ampères. The product of these factors, +volts into ampères, is called \emph{watts}; and the mechanical +value of one watt is such that $746$~is equal to +a horse-power, which, as before stated, is $550$~foot +pounds per second. The working power of a watt is +therefore $\dfrac{550}{746} = .735$ of a foot pound per second. + + +\Section{OHM'S LAW.} +\index{Ohm's law}% + +%[** PP: Putting upright variables in math mode] +This is simply that the current in an electric circuit +may be determined by dividing the electric pressure in +volts by the resistance in ohms. It is customary to use +symbols for each of these factors, $E$~or E.M.F. (electro-motive +force) for the pressure in volts, $R$~for the resistance +in ohms, and $C$~for the current in ampères, so Ohm's +Law when thus written reads $\dfrac{E}{R} = C$. Recurring to the +idea of a wire in front carrying a current of electricity +from the left to the right, and also the statement that +the electrical pressure is greatest at the left as the +cause of the current towards the right, it is well to +remark here that the electrical pressure at any particular +point in a circuit is sometimes spoken of as its +potential. If the potential at some other point in the +circuit be different from the first, the current will flow +\DPPageSep{202.png}{190}% +\index{Conductivity, electrical}% +from the higher towards the lower. The difference of +potentials may be measured in volts, and expressed as~$E$ +in Ohm's Law. + +There is a very wide difference among different substances +in their ability to transmit electricity. Some +transmit it freely, and are called good conductors; others +transmit it but slowly, and such are called poor conductors. +All solids, and liquids possess some degree of +conductivity; but some of them, such as glass, rubber, +and wax, are so poor in conductivity as to be called non-conductors. +The term non-conductor came into use +before the refined methods now in use for measuring +conductivity were known. It is now believed that +the only non-conductor of electricity is the ether. If +this be the case, then it appears that all the so-called +electrical phenomena in the ether are to be looked upon +rather as the results of electrified matter upon the +ether, than the presence of electricity in the ether, just +as radiations or ether waves are the results of actual +vibrations of atoms and molecules. Conduction, then, +is a general property of matter, and differs in degrees, +that difference depending upon both the kind of element +considered and its molecular combination. Thus, +copper is an excellent conductor; but if copper be +chemically combined with sulphur or with oxygen its +conductivity is greatly impaired. + +Conduction, too, implies contact, physical contact, +as in the case of heat; hence solids and liquids may +continuously conduct electricity, while gases can conduct +no faster than their individual molecules can move +in their free-path motions, and the rate of electrical +\DPPageSep{203.png}{191}% +\index{Ether, a non-conductor}% +loss is so slow from this source, that for telegraph lines +of hundreds of miles in length it is neglected as being +of no practical consequence. Neither is moist air +much better, and for the same reason. In all cases +where dampness appears to affect the working of electrical +apparatus, the loss is due to the moisture deposited +upon the surface of the apparatus, which thus +forms a thin conductive coating. A Leyden jar may +retain its charge for months if protected from a coating +of moisture, which, of course, it could not do if +either the air or the ether were conductors in any ordinary +sense of the word. + +The words conduction and conductivity represent the +property possessed by matter to become electrified by +mere contact with another body that is electrified; but +the terms do not have a very high scientific importance +now, for a much more convenient term is employed in +place, the term resistance, which is the reciprocal of +conductivity, that is, the greater the one the less the +other proportionally. The substance having the highest +degree of conductivity has the smallest degree of +resistance. Resistance is measured in ohms, and is of +two sorts; viz., specific and dimensional. Specific resistance +is that resistance which depends altogether +upon the nature of the particular element considered, +and may be determined for any element by measuring +the resistance of a cubic centimetre of it. + +Tables of conductivity and of resistance of wires +are common, and the following one gives the relative +values of a few of the elements for comparison. The +standard of conductivity being silver and reckoned as~$100$. +\DPPageSep{204.png}{192}% +\index{Conductivity, electrical}% +\index{Resistance, electrical}% +The standard of resistance being a column of +mercury $106$~centimetres long and one millimetre +square, which has a resistance of one ohm. The numbers +given are the resistances in ohms and fractions of +a wire $1$~metre long ($39.37$~inches) and one millimetre +($\frac{1}{\DPtypo{15.4}{25.4}}$~of an inch) in diameter. +\begin{center} +\TableFont% +\begin{tabular}{l<{\qquad}>{\qquad}r@{}l<{\qquad}>{\qquad}r@{}l} +\scriptsize\llap{SU}BSTANCE. & + \multicolumn{2}{c}{\scriptsize\llap{CONDU}CTI\rlap{VITY.}} & + \multicolumn{2}{c}{\scriptsize\llap{RE}SISTA\rlap{NCE.}} +\\ +Silver, & $100$& & &$.021$ +\\ +Copper, & $99.$&$9$ & &$.021$ +\\ +Gold, & $80.$& & &$.027$ +\\ +Aluminium, & $56.$& & &$.037$ +\\ +Zinc, & $30.$& & &$.072$ +\\ +Platinum & $18.$& & &$.116$ +\\ +Iron, & $17.$& & &$.125$ +\\ +Lead, & $8.$&$5$ & &$.252$ +\\ +German Silver,& $8.$& & &$.267$ +\\ +Hard Carbon, & $1.$& & $50$&$.00$ +\\ +Graphite & $0.$&$01$ & \multicolumn{2}{c}{Very variable.} +\\ +\end{tabular} +\end{center} + +The resistance of most liquids, and of such substances +as are used for insulating wires, is so very great +that they are given in units called megohms, each a +million ohms. The following represents the resistance +of a few bodies in such terms, the volume being one +cubic centimetre:--- +\begin{center} +\TableFont% +\begin{tabular}{l<{\qquad\qquad}r} +\qquad\scriptsize SUBSTANCE. & \scriptsize\llap{RESISTANCE} IN \rlap{MEGOHMS.} +\\ +Ice, & $284.$ +\\ +Water at freezing-point,& $150.$ +\\ +Mica, & $84.$ +\\ +Gutta Percha, & $450.$ +\\ +Hard Rubber, & $28,000.$ +\\ +Paraffine, & $34,000.$ +\\ +Glass, & $3,000,000.$ +\\ +Air, & Infinite. +\\ +\end{tabular} +\end{center} +\DPPageSep{205.png}{193}% +These must be read as so many millions of ohms. +Thus, ice\DPnote{** [sic], no verb} $284$ millions. Thus can be seen within what +wide limits this electrical property of matter ranges, +and also its significance as a factor in Ohm's Law, and +why some substances can be practically used as insulators +when in reality they possess a certain degree of +conductivity. Thus, glass is called an insulator. But +if there were a difference of potential or pressure on +opposite sides of a piece of glass one centimetre thick, +equal to $3,000000$ of millions of volts, there would be +a current of one ampère passing through for +\[ +\frac{3,000000,000000}{3,000000,000000} = 1 +\] +In no artificial way can we produce such a voltage as +that; but it is the opinion of some physicists that the +voltage of lightning may rise as high as some thousands +of millions. Under ordinary commercial voltages of +only a few thousands, the current would be insignificant. +Suppose it were $50,000$ volts, then +\[ +\frac{50,000}{3,000000,000000} = \frac{5}{300,000000} = \frac{1}{60,000000} +\] +of an ampère. + +Dimensional resistance is of more practical importance, +for by making a conductor larger its resistance +becomes less. When the cross section of a wire is doubled, +the resistance is reduced one-half. When the +diameter of it is doubled, it is reduced to one-fourth,---a +relation which may be stated as follows: The resistance +of a conductor varies inversely as its cross section, +or the square of its diameter if it be a wire; so by +making a relatively poor conductor large enough, it may +\DPPageSep{206.png}{194}% +\index{Electricity, activity}% +transfer as large a current as a much better specific +conductor of smaller dimensions. In the table it is +shown that the resistance of copper to that of iron is as +$.021$ to~$.125$, or that the latter is six times the former. +If, then, the section of the iron wire be made six +times larger, it will have the same degree of conductivity +as the copper. This means that one pound of +copper is worth nearly six pounds of iron for electrical +conduction; and whether the one or the other should +be employed in a given place depends chiefly upon the +relative costs. It is a commercial rather than an electrical +question. The resistance of all conductors varies +with their length. + +Temperature also affects the conductivity of nearly +all bodies. Some have their conductivity increased +by heat, as is the case with carbon; others have their +conductivity increased by cold. Thus, the conductivity +of copper at $100°$~below zero is increased nearly ten +times. + +An idea of the relative magnitude of the factor of +resistance in common electrical work may be gained by +knowing that a mile of ordinary electric arc-light wire +generally has a resistance of about two ohms; telegraph +and telephone wires five or six ohms, and often +more, per mile. If there be a current of ten ampères +going through a mile of wire that has a resistance of +one ohm, then Ohm's Law enables one to determine +what is the difference in pressure between the ends; +for $\dfrac{E}{R} = C$ and $E = RC = 1 × 10 = 10\text{ volts}$. So if any +two of these factors be known, the other may be computed. +\DPPageSep{207.png}{195}% +\index{Inductive action}% +The $E$~gives the available electrical pressure; +the $R$~gives the conditions under which it can work, +and the $C$~gives their resultant, the available current, +while the product of~$EC$ gives the activity, or rate at +which energy is expended in the circuit, while if this +product be divided by~$746$, the horse-power of the circuit +will be given. + +The further significance of Ohm's Law and its utility +will be given farther on, when considering the relation +of electrical energy to mechanical energy. + + +\Section{INDUCTION.} + +It has been pointed out that the term conduction +signifies the transferrence\DPnote{** [sic]} of electricity from one body +to another by contact,---contact in the sense that the +molecules of solids and liquids are in contact when they +cohere, and when their individual vibrations cannot take +place without mutual interference. It is found that +bodies become electrified by merely being in the presence +of another body that is electrified, without material +contact, and the more perfect the vacuum between +the bodies the more freely does this phenomenon take +place. As the electrified body that thus affects other +bodies in its neighborhood does not lose any of its own +electricity, does not share it with other bodies in any +degree, and as the other bodies lose their electrification +by simply being removed to a distance, and will recover +it again by being brought back, it follows that the +action is entirely distinct from the phenomenon of electrical +conduction. A similar body electrified by conduction +will retain its condition, and distance will make +\DPPageSep{208.png}{196}% +\index{Electrical field}% +\index{Fields, electrical}% +no difference. This kind of action is called \emph{electrical +induction}. To understand what changes take place, it +will be needful to attend particularly to the factors +present. Under the head of Electrical Origin of Electricity, %[xref] +it is pointed out that an electrical current may +be induced in a circuit adjacent to another circuit in +which a current is produced in any way; and here are +similar conditions and similar phenomena. Imagine an +electrified body freely suspended in the air. If a gold-leaf +electroscope is brought within a few feet of it, its +leaves will diverge; if brought nearer they will diverge +still more; recession will cause them to collapse. This +movement of the leaves can be produced indefinitely by +changing the distance of the electrometer from the +electrified body. It is important to note here that it +requires the expenditure of energy to move the gold +leaves, though the amount may be small. If it may be +done for an indefinite number of times, then the energy +spent may be indefinitely great; and that it is not +directly derived from the electrified body itself is certain; +for the latter loses by the process none of its electricity, +and cannot lose it except by conduction. Evidently +the body has in some way modified the physical +condition of the space about it so that another body +within that space is affected somewhat as it would be if +touched by an electrified body. But the property belongs +to the space itself, and cannot be extracted from it +so long as the electrified body remains in place. This +space about an electrified body within which other bodies +assume an electrical condition is called an \emph{electrical +field}. It may extend to an indefinite distance +\DPPageSep{209.png}{197}% +\index{Electrical stress}% +\index{Stress, electrical}% +from it, and its strength has been found to vary like +gravity, being inversely as the square of the distance. +This new physical condition into which the space has +been brought by the electrified body is known to be the +effect of the latter upon the ether, and is called its electrical +\emph{stress}. It is simply the reaction of the one upon +the other, and indicates that the molecules stand in +abnormal strained positions. A mechanical idea of +what it is like may be got by pressing the hand upon +the top of a table, and then producing a twisting strain +tending to turn the table round, but without moving it. +The whole table will be subject to a stress that will react +upon the hand, a condition which will, of course, be +retained by the table as long as such pressure is kept +upon it. For the hand substitute an electrified mass of +matter, and for the table the ether in any direction +about it, and one will have a fair conception of the +electrical field. Especially so, if he will add to it that +such twisting effect can be either right-handed or left-handed, +and so produce those distinctions known as positive +and negative, which run all through electrical +phenomena. + +A body brought into this distorted field of ether is +acted upon by the latter tending to twist its molecules +into new positions with reference to each other, which +is precisely the condition that brought about the original +stress, that is to say the electrical one, with this +difference, that if the original one was right-handed +the reaction of the ether would be left-handed, or +exactly opposite that of the inducing body. This is +simply because action and reaction are equal to each +other and \emph{opposite}. +\DPPageSep{210.png}{198}% +\index{Electrical waves}% + +One can now understand how it can be that bodies +can be electrified by induction without loss of electrification +by the inducing body. There are three steps in +the process. 1st,~The body electrified in any known +manner. 2d,~Its resultant stress in the ether. 3d,~The +reaction of the ether upon the second body, +inductively electrifying it. Electricity has not been +conducted by the ether, but a stress has been, and +the ether stress has electrified the second body. By +periodically electrifying and delectrifying a body, a +series of stresses will be produced about it which will +travel outwards as a succession of waves, the velocity +of which is the same as that of light, $186,000$ miles +per second, and the wave length of which will depend +upon the number of electrifications per second. Suppose +a sphere, like a cannon-ball in free space, to be +connected by wire, so that by pressing a Morse telegraph +key in connection with any source of electricity +it could be charged and discharged at will. If the key +was closed regularly once a second, the wave produced +would be $186,000$ miles long. If it could be +closed $186,000$ times per second, the wave would be +one mile long. And if it could be closed so often that +the wave length should be but the one fifty-thousandth +of an inch, there is every reason to believe that the +eye would perceive the waves as light; not so much +because the waves were produced by electrical means, +as that the eye is capable of perceiving ether waves of +that length, no matter how they may originate. + +The analogy between heat and electrical phenomena +in the ether is very close. The ether receives the +\DPPageSep{211.png}{199}% +energy from both sources and transforms it. The +ether is not a conductor of either heat or electricity: +it is neither heated nor electrified by them, but in each +case is simply a medium for the distribution of such +energy as gets into it according to its own laws, and +quite independent of its source. When heat gives up +its energy to ether it becomes ether waves or radiant +energy, and is no longer heat: it has been transformed. +When radiant energy falls upon other matter it is +again transformed into heat. In like manner, when +electricity gives up its energy to the ether, it becomes +radiant energy also, and when this falls upon other +matter it is again transformed into electricity. I have +been thus particular to enlarge upon induction, and +point out the factors present, in order to make it clear +how entirely distinct the electrical condition in matter +is from the electrical effect of it upon the ether. It is +from a failure to keep these distinctions in mind that +so many have been mystified by electrical phenomena, +and so many different theories have been propounded +as to its nature. + +In all our experience electricity originates in matter, +and whatever the particular character of the phenomenon +\emph{in matter}, it ought to have a different and distinct +name from the effect of such phenomenon upon the +ether. If such endowment of matter be called electricity, +then it is not proper to use the same word for +its stress, or wave effect, in the ether, and this for +precisely the same reason as is allowed to hold good in +heat phenomena. Formerly ether waves were called +heat, afterwards heat waves, now radiant energy, for it +is known that there is no heat in the ether. +\DPPageSep{212.png}{200}% + + +\Section{EFFECTS OF AN ELECTRICAL CURRENT---1. MAGNETISM.} + +If a wire through which a current of electricity is +passing be twisted into a loop or ring, it is found that +the loop acts in all ways like a magnet. Its sides have +polarity; and if it be so mounted as to be free to +assume any direction, it will move so its sides face the +north and south. If a piece of iron be placed in the +ring, the magnetic effect will be greatly strengthened. +Soft iron, however, loses its magnetic property as soon +as the current stops. A piece of steel will retain some +portion of the magnetic condition, and so is called a +permanent magnet. A given current of electricity +will make a much stronger magnet of a piece of soft +iron than it will of a piece of steel, and this is explained +by saying that the iron is more \emph{permeable} to +magnetism than steel is. Once in possession of a +magnet, one may proceed to study its physical properties +in many ways. That a magnet possesses poles; +that it can attract and hold to itself iron, steel, nickel, +cobalt, and affects other substances but slightly; that +it is attractive to unlike poles of other magnets, and +repulsive to similar poles,---and so on, are phenomena +so widely known that they need not be described here. +Only such phenomena will be considered as will be +helpful to an understanding of the constitution of a +magnet, and its relation to electricity and to the space +about it. + +The magnetism of a magnet seems to reside chiefly +near its ends, for these will sustain bits of iron, but +near the middle it will not; and when a small compass-% +\DPPageSep{213.png}{201}% +needle is moved around a bar magnet, it points towards +one end or the other, except when near the middle, +where it sets itself parallel. When such a bar magnet +has a sheet of paper laid upon it, and iron filings are +sprinkled upon the paper, the filings are arranged in +curious curved lines, starting from one pole and traceable +to the other, and quite around the magnet on both +sides. This %[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{3.5in}{213a} + \end{center} + \Caption{20}{Diag.\ 20.---Magnetic Lines.} +\end{figure} +arranging power of the magnet extends in +every direction about it, as one can satisfy himself by +trying the same experiment with the magnet turned on +different sides. If one will compare the direction of +these lines of filings with the positions of the needle, +he will see that the needle assumes the same direction +at any given place. Near the poles the lines all converge +to it, and opposite the middle the lines are parallel +with the magnet. If the magnet be of a U~or +horse-shoe form, the lines will be found still to extend +from one pole to the other, some straight, some curved +\DPPageSep{214.png}{202}% +\index{Fields, magnetic}% +outwards, but always forming a curve such as to touch +each pole of the magnet. While the filings are in the +position described, let the paper be gently tapped with +a pencil so as to jostle them slightly, and they will +begin to close up in such a way as always to shorten +themselves, and presently they will form a dense mass +between the poles, adhering to the latter as a solid +piece of iron would do. + +Such phenomena show that the magnet in some way +reacts upon the space about it, so that iron and other +magnets there are affected, just as an electrified body +affects the space about it, as has been described. This +space about a magnet within which such effects are +produced is called the \emph{Magnetic field}, which may be +\index{Magnetic field}% +said to be the stress in the ether produced by a +magnet. Like the electric stress, it extends to an +indefinite distance from the magnet, and travels with +the velocity of light; so if a magnet was charged and +discharged once a second, a wave motion would be set +up: the wave length would be $186,000$ miles long, and +if it could be charged and discharged so fast that the +waves were but the one fifty-thousandth of an inch in +length, it is very probable they would be perceived as +rays of light, and the magnet would be a luminous +body. Such waves are called electro-magnetic waves. +\index{Magnetic waves}% +At present the shortest waves of this sort, that can be +artificially produced, are several inches long, but it +seems highly probable that before long some way will +be discovered of making them of the required length +for vision. + +If a test-tube filled with iron filings be held near a +\DPPageSep{215.png}{203}% +delicate suspended magnetic needle it will be found to +give no indication of polarity, one part will act just +like any other part, and the magnet will be equally +attracted. Bring the test-tube against the poles of a +strong magnet for a few seconds, and then it will be +shown that the filings have become magnetic, and now +one end of the tube will attract one pole of the needle, +while the other end will repel the same end. Shake +up the filings well, and the polarity will be destroyed. + +Stir up iron filings with melted wax, and pour into a +paper mould, so as to form a stick the size of the finger, +or larger. If this be tested for magnetism, it will be +found without any; but magnetize it as if it were a +piece of steel, and it will be found to retain it, becoming +a permanent magnet. If a layer of iron be electrically +deposited upon a brass wire in a magnetic field, +the wire acts like a magnet. All these phenomena go +to show that what is called polarity or magnetism is +due to the \emph{positions of the molecules}, rather than upon +some sudden endowment which the molecules receive +and may lose. Imagine every molecule of iron to be +a magnet, having its poles or faces, then if in a mass +of them, such as makes up a piece of iron or steel, +all be made to face one way and keep such position, all +will act in conjunction to give polarity to the mass. +When some molecules face one way, and others adjacent +to them face the opposite way, they will but +neutralize each other, so the external evidence of +magnetism will be destroyed. How atoms may be +magnets and exhibit polarity may be imagined by considering +the phenomena of vortex rings again. In the +\DPPageSep{216.png}{204}% +ring all the motion on one side is towards the middle +of the ring inwards, on the other side all the motion is +outwards, so the properties of the two sides are opposite. +Each such ring must have its own \emph{field}, which +may extend to an indefinite distance from it, and may +be represented roughly by the diagram in which the +curved lines show the same features before described +as belonging to a magnetic field. When two or more +\index{Magnetic field}% +are facing the same way, and are in contact, these lines +cannot re-enter the ring except by going round the +second one; and when many are in line they must go +round them all, in which case the %[** PP: Width-dependent break] +%[Illustration] +\begin{figure}[hbt] + \begin{center} + \begin{minipage}[b]{1.25in} + \Graphic{1.25in}{216a} + \Caption{21}{Diag.\ 21.---Field of a Ring.} + \end{minipage} +% + \begin{minipage}[b]{1.5in} + \raisebox{12pt}{\Graphic{1.5in}{216b}} + \Caption{22}{Diag.\ 22.---Coinciding Fields.} + \end{minipage} +% + \begin{minipage}[b]{1.25in} + \Graphic{1.25in}{216c} + \Caption{23}{Diag.\ 23.---Opposing Fields.} + \end{minipage} + \end{center} +\end{figure} +direction of the lines +will be precisely those observed about a straight bar +magnet. +\Pagelabel{105} %[** PP: Label to p. 105 seems to point here] + +When they all face one way, as in diagram~22, the +resultant will be at~A, the sum of the outgoing movements, +and at~B, the sum of the ingoing ones, and +polarity at A and~B will be at a maximum. If they face +in different ways, each will tend to cancel the other, +and there will be no external field; as in diagram~23. +\DPPageSep{217.png}{205}% +\index{Ether pressure}% + +If two such atoms be brought face to face, each will +be blowing against the other; their fields overlap, and +the stress is increased between them, and they are +crowded away from each other,---a phenomenon called +repulsion. The opposite condition obtains when they +face the same way and are near together, with the +result that the stress is lessened between them, and +they are pushed together by it; and this is called +attraction. + +There has been growing the conviction for a long +time that the atoms of all substances are magnetic; but +\Pagelabel{205}% +when they combine into molecular groups they are +turned about so their magnetic fields neutralize each +other, and thus it happens that most molecular compounds +show no polarity. But every substance whatever +is attracted by a magnet, and will move up to it if +the magnet be a strong one. Brass, lead, stones, oats, +corn, and wood will all be affected alike by a strong +magnetic field, being pushed towards the magnet in the +same way as iron, though not in the same degree. The +pressure of iron against a magnet, due to the magnetic +field, may be as great as a thousand pounds per +square inch. + +When a piece of iron is brought near to a magnet, +and it becomes a magnet by induction instead of by +contact, it is to be understood that its molecules are +rotated into similar positions by the action of the +magnetic field upon it, not that magnetism has gone +from the magnet to the iron; and when it requires a +pull, and therefore work, to move a piece of iron away +from a magnet, it is against the ether the work is done. +\DPPageSep{218.png}{206}% + +It was stated at the outset that a loop of iron through +which an electric current is passing is a magnet, and +previous to that it was pointed out that an electric %[** PP: Width-dependent break] +%[Illustration] +\begin{wrapfigure}{l}{1.75in} + \Graphic{1.75in}{218a} + \Caption{24}{Diag.\ 24---Iron Filings about Electric Current.} +\end{wrapfigure} +current in a wire has a field +that extends indefinitely out +from it. If such a wire be +dipped in iron filings, they +form rings round it, showing +that the polarity is at right +angles to the wire. Now, if the wire with the iron +filings clinging about it be made into a loop, it will +be seen at once how the polarity of the different +segments is all in one direction inside the ring, and +opposite to that on the outside the ring, and the +structure will be a forcible reminder of a vortex ring. +If several similar turns be taken in the wire, and they +all be brought near together so as to form a helix, it +will also be seen that these conspire together to set a +boundary to the field on the inside, but allow indefinite +expansion to it outside; so if one should draw the lines +for it as iron filings would be arranged by it, he will +have the precise lines of a magnet, while the ring +structure will be, on a large scale, just +what was described on an atomic scale +as constituting a vortex ring magnet; +and the only thing lacking to complete +the analogy is the conception of a rotary +motion in the wire at right angles to its length. + +%[Illustration][** PP: Moved down to avoid LaTeX warning] +\begin{wrapfigure}{r}{1.25in} + \hfil\Graphic{1in}{218b}\hfil + \Caption{25}{Diag.\ 25.---Adjacent Turns.} +\end{wrapfigure}It has been found that when a current has been +started in a conductor, a torsional impulse is given to +the latter in such a sense that if one looks along it in +\DPPageSep{219.png}{207}% +the direction of the current the twist is in the direction +of the hands of a clock. So there is direct confirmatory +experiment showing that the nature of the motion in +an electric circuit is rotary in such a way that the +whole circuit may be considered as a vortex ring; and +as it is the matter of the conductor that is thus rotated, +it follows that electrical current motion is rotary, as +heat motion is vibratory. + +Allusion has been made to the opinion now current that +ether waves or light are electro-magnetic phenomena. +\index{Ether waves, their source}% +\index{Light waves}% +\index{Magnetic waves}% +How this can be may be understood by considering a +magnet of any form, with its surrounding field. If the +form of the magnet be changed, the shape of the field +will be correspondingly changed; and as this extends +out indefinitely into space, it follows that a succession +of changes of form would set up waves through the +whole of that space. Now, a magnet is an elastic body, +and if it be struck it will vibrate and produce a sound. +The vibration implies a change of form, and that in +turn a set of waves radiated into space. As the field is +an ether field, the waves will be ether waves. Now +assume that atoms are themselves elastic magnets, each +with a field indefinitely extended, and it follows that +the vibrations produced by impact, or in any other +manner, will set up corresponding waves in the ether, +the wave length depending upon the vibratory rate of +the atoms. Thus ordinary radiant energy, or light, +would consist of undulations in a magnetic field. + +Of course it will be perceived that vibrations of any +electro-magnetic body, large or small, would induce +similar waves, differing only in wave length, so there +\DPPageSep{220.png}{208}% +\index{Magnetic induction}% +would be in the ether wave lengths of all dimensions, +\Pagelabel{208}% +from the shortest possible to those millions of miles +long. It is now an important physical problem how to +produce such that shall be of the dimensions capable of +affecting the eye. + +\Subsection{Induction Coils.} +\index{Induction coils}% + +One or more loops of iron, through which a current +of electricity is flowing, is an electro magnet. When +iron is placed in the loop, it condenses the magnetic +field, and it may be made as much as thirty times +stronger than it would be without the iron. When a +magnetic field is produced inside a loop of wire, the +reverse effect %[** PP: Width-dependent break] +%[Illustration] +\begin{wrapfigure}{l}{1.75in} + \Graphic{1.75in}{220a} + \Caption{26}{Diag.\ 26.---Electro-Magnetic Induction.} +\end{wrapfigure} +happens, and a +current is generated in the +opposite direction. Suppose +a short rod of iron to have a +single turn of wire at each +end about it, one of them, +as~A, to be so connected to a source of electricity +that a current through it may be produced by closing a +key, the other one to be a closed circuit, as shown. If +a current be established through~A in one direction, a +current will be induced in~B, as indicated by the arrow. +There will be in the loop of the A~circuit a certain +electro-motive force,~$E$. A nearly equal electro-motive +force will be induced in loop~B. If there were two +loops at~B instead of one, the electro-motive force would +be twice that in~A, and for $n$~turns it would be $n$~times. +The current in~B will depend upon the resistance in its +circuit; that is, it will be $\dfrac{E}{R}=C$, according to Ohm's +\DPPageSep{221.png}{209}% +Law. The size of the wire in B~circuit will not make +any difference in the value of~$E$ in it. That value will +depend only upon the magnetism of the bar, and the +magnetism in the bar will be measured by the product +of the current into the number of turns of wire in +the circuit~A. And this product is called the \emph{ampère +turns}. The ampère turns will be nearly equal in the +\index{Ampère turns}% +two circuits. This process of obtaining electrical +currents in a second circuit by two transformations is +of great use in the electrical industries, and the device +is called an induction coil or transformer. The charging +circuit is called the primary, and the discharging +one the secondary. By making circuit~A of a small +number of turns of thick wire, so as to allow strong +currents in it, and having circuit~B consist of a great +number of turns, the electro-motive force may be +raised almost indefinitely. Suppose there be $100$~turns +in the \textit{A}~circuit,\DPnote{[** Italicized in orig, not sure why]} and a hundred thousand in the \textit{B}~circuit, +then for every volt in the A~circuit there may be +nearly a thousand volts in the B~circuit; and this is the +construction in those instruments known as induction +coils, with which so called jumping sparks are produced, +and represent sometimes a million or more volts. On +the other hand, it is sometimes desirable to change a +high electro-motive force to a lower one; and this may +be done by reversing the connections and making the +primary current go through a great number of turns, +and taking the induced current from the smaller number +of turns in the other circuit. Definite reduction in +either way may be effected by making the ratio of the +number of turns in the two circuits the reduction +\DPPageSep{222.png}{210}% +\index{Electro-magnets}% +\index{Welding, electric}% +wanted. That is to say, if there are $100$~volts in +the primary circuit, and only ten are wanted, make the +secondary of one-tenth the number of turns in the primary. +If a thousand volts are wanted, make the secondary +with ten times the number of turns in the primary. +It should be remembered, also, that two turns of wire in~B +have twice the resistance of one turn, and the current +induced will be reduced to one-half. If there be one +hundred turns, it will be reduced to one-hundredth and +so on. Hence, in the large induction coils for high electro-motive +forces, the current is necessarily a small one, +while in the transformers in which the reduction is to +lower values of~$E$ than are in the primary, the current +may be very great indeed. This is the case in Thompson's +Welding Apparatus. The secondary has but a +single turn of heavy copper, while the primary has many +thousands, and the current in the secondary may be +thousands of ampères. As the heating effect is proportional +to the square of the current, it is plain that +such large currents have enormous heating power. + +All such devices require either intermittent or alternating +currents to operate them, for there is no induced +current in any circuit when the inducing magnetism is +not changing. A constant magnetic field induces no +electrical changes. + + +\Subsection{The Electro Magnet.}\DPnote{** [sic] No hyphen} + +This is generally considered as consisting of a helix +of insulated wire about a piece of soft iron, and may be +either a straight bar, or crooked in any convenient form, +its function being to produce a magnetic field when a +\DPPageSep{223.png}{211}% +current circulates in the wire, and to lose it when the +current stops. This it does only partially, for all iron +when once it has been magnetized becomes more or less +permanently magnetic; hence there is only a difference +in degree between an electro magnet and a permanent +magnet. Until within a few years the electro magnet +had its most extensive field of usefulness in telegraphy. +It was combined with a piece of soft iron near its poles +called its armature, which was so mounted that the +magnetic field made it to move towards the magnet, and +a retractile spring pulled it away when the field was +absent. The movement of the armature was employed +to receive signals. In some cases the movement recorded +itself, and sometimes its prompt motion produced +a sound, a succession of these being arranged into a +telegraphic alphabet. + +If one has a good idea of a magnetic field and its +action upon a piece of iron in it, he will be able to +understand all the various combinations of forms and +functions of electro-magnetic devices, however much +they may apparently be disguised. Thus, the magnetic +telephone is an electro magnet with an armature +\index{Telephone}% +of such size and flexibility as to be capable of much +quicker movements than ordinary telegraph instrument +\index{Telegraph}% +armatures, the whole boxed so as to be convenient +to hold to the ear. A common telegraph sounder +acts in precisely the same way, though not so well, for +the armature is too heavy, and one cannot concentrate +its effects upon the ear on account of its form. An +electric bell also produces its ring by having a hammer +fixed to the armature, so as the latter moves in response +to the electric field it strikes the bell. +\DPPageSep{224.png}{212}% +\index{Motor, electric}% + +An electric motor, in the largest sense, consists of a +device for transforming electric into mechanical motions; +and the relation sustained between an electro +magnet, its field and an armature, is such as to do it +directly. A telegraph sounder is thus a simple motor, +for the armature moves visibly in response to the electric +current. If a wire be wound about the armature, +there is an induced current in it, as in an induction coil, +and for the same reason; and the movements of the +armature towards and away from the poles of the electro +magnet, called sometimes the field magnet, give +rise to currents in the armature coil. If a current +from another source is sent through the armature coil, +it gives polarity to the armature itself, and the reaction +between it and the poles of the field magnet is still +stronger, and the mechanical motions are still more +energetic. The armature thus wound with wire is obviously +an electro magnet itself, and when it is so +mounted as to be capable of rotating between the poles +of a fixed electro magnet, a continuous rotation may +be kept up. + +The current in the fixed magnet is steady, and therefore +maintains a steady magnetic field. The current +in the armature magnet is changed in direction by the +motion of the armature itself, and is effected by a device +called a commutator. The efficiency of such a +motor may be as high as $90$\%~or more. That is, for +every horse-power of electrical energy turned into it, it +will give back nine-tenths of a horse-power in actual +work. The small space they occupy for the working +capacity, when compared with a steam-engine for the +\DPPageSep{225.png}{213}% +\index{Efficiency of machines}% +same work, the small amount of attention they require, +and their freedom from the dirt inseparable from an +engine, commend the electric motor as a substitute +for the engine in most places where power is wanted +and an electric current can be had; for it is to be +remembered that fifty horse-power can travel through +a wire that can go through a gimlet-hole, while a steam-plant +for the same work would require a large boiler +and engine as well as a big chimney. + +When the armature of a motor is made to turn by +mechanical means, the shifting positions in the magnetic +field develop electric currents in its coils. Such +an armature cannot be turned as freely when the field +magnet has a current in it as it can when it has not, +and the energy spent in making it turn appears as a +current. The device is called a dynamo, which may be +\index{Dynamo}% +said to be a machine for transforming mechanical motion +into electrical motion. The steps are mechanical +motion, magnetic field, electrical current; while in the +motor they are simply the reverse,---electric current, +magnetic field, mechanical motion. + +The efficiency of a dynamo is very high indeed. It +can transform~$95$\% of the power applied to it into +electrical power, and in this particular it is one of the +most perfect machines in existence. There is absolutely +no room for any important improvement in the +dynamo as regards its efficiency. A good steam-engine +may transform ten to fifteen per cent of the energy +turned into it. A windmill may give fifty, a turbine +water-wheel ninety, but when a dynamo gives ninety-five, +it shows that the coming man has a margin of but +five per cent for improvement in its efficiency. +\DPPageSep{226.png}{214}% +\index{Energy. What determines transfer}% +\index{Fields, magnetic}% +\index{Lighting, electric}% +\index{Resistance, electrical}% + +Thus the magnetic field, which is simply the ether in +\index{Magnetic field}% +an abnormal condition of stress, is the common agency +between mechanical motions and electrical phenomena, +and transfers energy one way or the other. All that +determines whether it shall be one way or the other is +simply which side has the excess of energy; for energy +of a particular sort always goes from the body having +more to one having less. Which side has the excess +is determined solely by the mechanical conditions +present. + + +\Subsection{Electric Lighting.} + +An electric current always heats the conductor +through which it is passing. The amount of heat depends +upon the strength of the current, and varies as +the square of it. In a given circuit with a uniform current, +the current has the same value, and therefore the +same heating power, in every part of that circuit; but +the temperature to which a body will be raised by a +given current depends upon its own constitution, its +size and electrical resistance. Connect together three +wires of copper, iron, and platinum, each a foot long, +and of the same diameter, and make them a part of the +same circuit, so that the same current shall flow through +them. If the current be increased gradually, the iron +wire will grow appreciably warm, more current will +make it hot; platinum wire will be only warm; +while the copper wire will not have its temperature +much changed. Still more current will make the iron +red-hot, the platinum uncomfortably hot, and warm +appreciably the copper; and more current will fuse the +\DPPageSep{227.png}{215}% +\index{Electric lamps}% +iron, perhaps make the platinum red-hot, but the copper +may not yet be uncomfortably hot. This heating +effect in a given wire is found to be proportional to its +resistance: the iron wire having the greater resistance +is most heated, and the copper having least, is least +heated; hence to obtain a high temperature with a +given current, a conductor must be chosen that has a +relatively high resistance. Resistance, however, varies +with the cross section inversely, so a small wire must +be taken if the temperature of incandescence is to be +reached with a small current; and a current that will +raise half an inch of a wire to a white heat will raise a +mile, or any other length of the same wire, to the same +temperature; but the longer a wire is, the higher must +be the electro-motive force in order to get the same +current. For a given length of a wire the electrical +energy spent in it will be found by multiplying its resistance +by the square of the current,~\DPtypo{$RC,^2$}{$RC^2$,} which will +give the products in watts, of which $746$~equal a horsepower. +Metals are liable to fuse and become useless, +so that wires of carbon, made by heating organic fibres +in the absence of air, as in making charcoal, are substituted +for metals. They fuse only at extremely high +temperatures; and being enclosed in a vacuum in bulbs +of glass they cannot burn up as carbon does when exposed +to the air when red-hot. This is the electric incandescent +lamp. Most of them are so prepared that a +current of about three-fourths of an ampère is required +to properly light them, and this will be got when the difference +of potentials between the lamp terminals is kept +at a certain figure, so that lamps are specified by the +\DPPageSep{228.png}{216}% +number of volts they require, rather than the current; +thus there are $50$~volt lamps, $110$~volt lamps, and so on. +Now, such lamps take ordinarily about four watts for a +candle, so a twenty candle-power lamp requires eighty +watts, and that means $\dfrac{746}{80}=9.3$ such lamps to the +horse-power. Such lamps may last for a thousand or +more hours. If a stronger current be used, they shine +brighter, but their life is shortened. There is a process +of slow disintegration going on in these lamps +all the time. The surface molecules slowly evaporate +under the vigorous vibratory movements present, and +the carbon vapor thus formed sticks to the inside surface +of the bulbs, giving them the familiar blackened +appearance. + + +\Subsection{The Arc Light.} +\index{Arc light}% + +If an electro-motive force of forty or more volts be +maintained in a circuit, and the circuit be broken at +some place and the ends separated a small fraction of +an inch, the current does not cease, and is maintained +between the ends by what is termed an arc, where the +temperature is so very great that almost all substances +are reduced to vapor at once. All metals are fused and +dissipated there. Carbon does not fuse there, but is +slowly burnt up. The ends of the carbon reach a temperature +higher than can be reached in any other +known way, and the light they then give out is called +the arc light. The rate of expenditure of energy in +that small space where the brightness is, is generally +some less than a horse-power. The current employed +\DPPageSep{229.png}{217}% +\index{Mars, signalling to}% +is about nine and a half ampères, and the electro-motive +force about forty-five volts; hence $9.5 × 45 = 427.5$ +watts, and such a lamp may be equal to $800$~candles, +though they are generally rated as $2,000$ candle-power. + +By increasing the current the brightness increases, +and there is no especial limit to the amount of light +that may in this way be produced. With parabolic reflectors +the light may be concentrated into a powerful +beam. The inhabitants of Mars could see such a one, +and it could be used for signalling between the two +planets if the Martians had a similar one. + +Seeing that the temperature to which a given conductor +can be raised by a current is determinate, one +can arrange for heating on any scale. There is no +other reason than the relative cost of electric heating +compared with the ordinary method with fuels, why it +should not be in common use to-day. In most places +the dynamo for the production of the current would be +run by a steam-engine, requiring in its turn a furnace; +and it is cheaper to use the fuel direct for heating, than +to transform the energy so many times, each time with +some loss. A common furnace is much more economical +of energy than a steam-engine. But if ever electricity +is obtained directly from combustion in an economical +way, as there is some reason for thinking possible, +electrical heaters will displace stoves and the common +furnaces in the house. So the same current that +lights the house will serve for cooking and warmth. +\DPPageSep{230.png}{218}% +\index{Water decomposition}% + + +\Section{2. CHEMICAL EFFECTS.} +\index{Chemical effects}% + +When a current of electricity is passed through +conducting liquids capable of being decomposed, such +as acidulated water, and solutions containing more or +less of the metallic elements, decomposition of the solution +results, with the additional curious phenomenon +that one of the elements of the decomposed compound +appears at one terminal, and the other element at the +other. Thus, if water be the liquid, hydrogen appears +at one place and the oxygen at another. If the two terminals +of an electric circuit were on opposite sides of the +Atlantic Ocean, and a current were sent through the +circuit, hydrogen would appear on one side and oxygen +on the other. The oxygen is set free at that terminal +at which the current reaches the liquid. The direction +of the current being determined in the ordinary conventional +way. Bring the wire carrying the current over +and parallel to a suspended magnetic needle. If the +current be going from south to north, the north pole will +be deflected to the west. If the current be going from +north to south, the south pole will be deflected to the +west. Hence, if one looks along a wire in the direction +of the current, oxygen will be given off at the next +terminal if it dips in water. It may be convenient to +know that when a battery is employed as a generator of +electricity, hydrogen is set free at the terminal of the +battery from which the current flows, and oxygen at +the other end of that conductor. + +The decomposition of water may be taken as a type +\index{Decomposition of water}% +of electro-chemical work; hence, when the mechanical +\DPPageSep{231.png}{219}% +\index{Dissociations}% +\index{Polarization of molecules}% +conditions present where decomposition is going on are +understood, they may be applied to any other case. + +Under the head Chemical Origin of Electricity it %[xref] +was pointed out that the same factors which gave rise +to the current also arranged the molecules of the liquid +so that the oxygen sides of them all faced the same way, +towards the zinc, which of course necessitates that the +hydrogen sides should all face in the opposite direction. +The other terminal of the battery tends to bring about +a similar condition of things, so that between the terminals +the molecules are all polarized or brought into an +orderly arrangement. The direction of the electric +current in such an arranged body of molecules in the +liquid is from the zinc to the oxygen---oxygen, hydrogen, +oxygen, hydrogen, and so on to the last molecule +in the line, the hydrogen face of which is against the +other terminal. So far this represents molecular arrangement, +not molecular or atomic cohesion. There +is good reason for thinking that dissociation of atoms +in such molecules is going on all the time in some +degree, on account of their incessant and vigorous vibratory +motion. Such motion must tend to disrupt +the atoms so that at any given instant there would be a +relatively large number of atoms in the liquid already +free and quite indifferent as to whether they recombine +with the same or other atoms the next instant. If there +be another agency present, like an electrical current, +adding its energy tending to disruption, not only would +a larger amount of dissociation take place, but when at +one end of the line one element of the molecule, like +oxygen, enters into a new combination which is more +\DPPageSep{232.png}{220}% +stable under the conditions present, the remaining hydrogen +will combine with the oxygen of the adjacent +molecule when that molecule is broken up, and so on +along the whole line, leaving the hydrogen of the last +liquid molecule to be freed against the other plate of +the battery. This means that there is an exchange of +partners among all the molecules of the liquid that take +part in the current, else some of both oxygen and hydrogen +would be set free elsewhere than at the terminals, +which never happens. + +Now, all molecules are combinations of atoms in +definite proportions by weight, and it is therefore to be +expected when such decompositions as the above take +place the products will be found in the same proportions. +It is the necessary outcome of the operation. So for +every one part by weight of hydrogen set free, eight +parts of oxygen will be liberated; and for a like reason +twice the volume of hydrogen as of oxygen. + +If a current of electricity be led through any liquid +which it can decompose, and the material of the terminals +be some substance that neither of the constituents +of the molecule can combine with, both of the elements +will be set free. Platinum is such an element; and if +terminals be made of that, and dip into a tank of water, +the current polarizes the molecules precisely as in the +battery, and decomposition takes place in the same way,---oxygen +being set free at the in-going terminal, and +hydrogen at the out-going one. If the solution contains +molecules of metallic salts of copper, nickel, iron, silver, +gold, etc., the metallic side of the molecule faces in the +direction of the current, the same as the hydrogen in +\DPPageSep{233.png}{221}% +\index{Plating, electro}% +the former case; and as a consequence, the metal is deposited +upon the out-going terminal, whatever that may +be, and the other constituent of the molecule is set free +at the in-going terminal. For example, the sulphate of +copper is a compound of copper and sulphuric acid. +Where it is subject to decomposition by an electric +current, the copper is deposited at the one terminal, and +sulphuric acid at the other. If both the terminals be +made of platinum, one will be covered with copper, and +the other will be surrounded with the acid, and all the +copper in the solution may be taken out. If the in-going +terminal be itself of copper, the sulphuric acid +set free will itself dissolve off the copper as fast as the +acid is set free, and in this way the solution will be kept +saturated. The metal may be deposited on any other +metal. It is in this manner that electro-plating of all +sorts is done. Each different metal requires different +treatment from the others as to solution, electro-motive +force, current per square inch section, and so on for the +best results. To decompose water, as much as one and +a half volts are necessary to initiate it, but copper salts +require only a small fraction of one volt. The amount +of decomposition in a given time, say a second or an +hour, depends upon the current employed. A current +of one ampère will in an hour decompose only about +fifteen and four-tenths grains of water, liberating one +and seven-tenths grains of hydrogen. The weight of +other elements set free or deposited by an ampère per +hour is determined by multiplying the weight of hydrogen +set free by the electro-chemical equivalent of the +element, and this is either equal to its atomic weight, or +\DPPageSep{234.png}{222}% +\index{Lighting, electric}% +is one-half or one-third that. Thus, the electro-chemical +equivalent of gold is $\dfrac{196.6}{3} = 65.5$, of silver $\dfrac{108}{2} = +54$\DPtypo{}{,} of copper $\dfrac{63}{2} = 31.5$, of nickel $\dfrac{57}{2} = 28.5$, and so on. +So the amount of gold that will be deposited by an +ampère in an hour is $1.7 × 65 = 111.35$ grains; of silver +$1.7 × 54 = 91.8$ grains and so on. This shows a +definite relationship between electricity and chemical +reactions. + +It is to be kept in mind that when substances combine +there is always some transformation of energy, +and heat is either absorbed or given out. When +hydrogen and oxygen combine there is a large amount +given out, $61,200$ heat units for each pound of hydrogen. +When, therefore, water is decomposed so as to +set free one pound of hydrogen, the same amount of +energy must be spent to do it. The electrical energy +spent in a decomposing cell is, therefore, reducible to +the heating effect, and may be calculated as such. + + +\Section{3. LUMINOUS EFFECTS.} +\index{Luminous effects}% + +When an electric current passes from one conductor +to another through the air an electric arc is produced, +and great heat and light are developed there. An arc +is generally about an eighth of an inch long. By +having a higher electro-motive force one may be made +several inches long. The arc itself consists of the +incandescent molecules of the air in its path mixed +with some of the disintegrated particles of the carbon +of the terminal. When an arc is formed in a partial +\DPPageSep{235.png}{223}% +\index{Geissler's tubes}% +\index{Spark, electric}% +\index{Vacuum, a non-conductor}% +vacuum the character of the phenomenon is very much +changed. Instead of being concentrated into a narrow +space, it spreads out into an oval form, the size of +which depends upon the degree of exhaustion. The +terminals may be separated to a much greater distance; +the light becomes less intense, and shows as a kind of +glowing gaseous globe, and this may extend to the +walls of the glass vessel in which it is produced. + +If the vacuum be made very perfect, no current can +be got through it; for the ether is a perfect non-conductor. +Even the spark from an induction coil that +will jump several feet in the air will not jump a quarter +of an inch in a vacuum. The jumping ability of +an electric spark or current depends upon its electro-motive +force. A thousand volts will jump but +about the one-hundredth of an inch in common air, +and ten thousand volts only about one-tenth of an +inch. From such experiments it has been concluded +that a flash of lightning probably has an electric pressure +\index{Lightning}% +reckoned by hundreds of millions of volts, but +there is some doubt about the calculation for such +exceedingly high voltage. Glass tubes provided with +platinum terminals hermetically sealed, and from which +the air has been partially removed, when connected +with the high voltage terminals of an induction coil +exhibit phenomena that depend altogether upon the +degree of exhaustion in the tube. If the air pressure +%[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbtp] + \begin{center} + \Graphic{4in}{236a} + \end{center} + \Caption{27}{Diag.\ 27.---Crookes's Tube. Long Free Path.} +\end{figure} +\index{Crookes' tubes}% +be removed to about the one-hundredth of the normal +pressure, the discharge appears as a broad band of +purplish light between the terminals; if the reduction +be to the thousandth, the light fills the tube. Still +\DPPageSep{236.png}{224}% +further reduced, the discharge appears broken up into +striæ, or bright disks, their distance apart depending +upon the degree of exhaustion, and they measure +roughly the length of the free path of the gaseous +molecules. If the exhaustion is carried to a very high +degree, this free path may be made as long as the tube, +\index{Molecules, long free path}% +or longer. This means that a molecule may move +from one end of the tube to the other without coming +into collision with another one. + +When a molecule touches upon the electrified +terminal, it is impelled from it with great velocity, +quite like that exhibited in the radiometer, and probably +\DPPageSep{237.png}{225}% +\index{Heat by impact}% +for the same reason. It moves away from the +terminal in a straight line in obedience to the first +law of motion, and continues on till it strikes another +molecule, or the surface of the tube, and it shines as it +moves, on account of its vigorous internal vibrations; +for each gas gives its characteristic spectral lines when +thus made incandescent. Where they strike upon a +thin piece of platinum they may make it red-hot by +impact, and where they strike upon the +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{4in}{237a} + \end{center} + \Caption{28}{Diag.\ 28.---Crookes's Tube. Platinum made Red Hot by Impact.} +\end{figure} +walls of the +glass tube the latter is made luminous with a phosphorescent +glow, and may be made red-hot, and so +softened as to bring about a collapse of the tube. +These tubes are known as Crookes's Tubes, and their +phenomena are extremely interesting from the insight +they give into the behavior of matter under all sorts +of conditions. With a set of these tubes, the laws of +motion, kinetic energy, sound, heat, light, electricity, +and magnetism may be illustrated in a way unapproachable +\DPPageSep{238.png}{226}% +with any other simple and cheap apparatus. The +long free path, and inability to turn a corner when +projected from an electrified terminal, show the first +law of motion and inertia. The impact of the molecules +may make a wheel turn round,---an example of +energy as good as a windmill. The intermittent beats +upon the sides of the tube produce a sound, the pitch +of which is the same as that of the vibrations of the +induction coil. The heating of the tube and its contents +shows the transformation of free-path motion +into vibratory molecular motion. The luminousness +of the gas, and the phosphorescence of the tube, show +\index{Phosphorescence}% +the transformation of the electrical energy into the +vibratory molecular kind, at a rate capable of affecting +the eye. The phosphoresence\DPnote{** [sic]} itself showing the conditions +needed for producing it; the origination of the +motions in the tube showing the relation of electricity +to the other forms of motion developed; the deflection +of the stream of electrified molecules by a magnet +illustrating the effects of a magnetic field upon a +current of electricity. The fact that such streams of +molecules are projected from an electrified terminal +solely by impact there, is shown by their returning to +it when there is nothing in front of it to expend their +energy upon, as a ball returns to the earth when +thrown into the air, which is the case when but one +terminal is connected with the induction coil; and, +lastly, such a tube will be lighted up by being merely +in the neighborhood of an induction coil, or rather in +a varying electric field. They may be insulated and +several feet away from such induction coil or a Holtz +\DPPageSep{239.png}{227}% +or other similar machine and yet be internally lighted +every time a spark passes, which shows that the luminousness +seen in the tubes is not necessarily due to any +electrical current present, because in this case there +can be no electrical current. + + +\Section{THE NATURE OF ELECTRICITY.} + +There have been many theories proposed to account +for electrical phenomena, yet to-day there is no one +that is generally held, even as a provisional one, among +physicists. Some have even abandoned the hope of +mankind ever being able to reach a consistent theory of +it. The case has been the same in the history of heat, +of light, and of magnetism; yet text-books of to-day do +not hesitate to state what is the nature of each of these. +Electrical phenomena have greater variety, and the +apparent dual character oftentimes present has served +to give a perplexing degree of complexity to them. +The writer has thought that a summation of the principal +factors present in electrical phenomena might be +helpful to some in their endeavor to find some physical +explanation without having to assume something \textit{sui +generis}, which has no other necessity for being except +the very dubious one of accounting for a certain phenomenon. +Caloric, light corpuscles, and vital force +were such visionary creations; but further knowledge +has enabled science to dispense with all of them, leaving +nothing in their places but what was known to +exist before; namely, matter, ether, and their motions. +Such a steady course of reduction to these factors +leaves one with the fair presumption that it will likely +\DPPageSep{240.png}{228}% +fare the same way with any other agencies that have +been imagined to account for phenomena, though the +latter may, for the time being, seem not reducible to +simple mechanics. + +There are certain \textit{a~priori} reasons for thinking that +in electrical matters, as in all other physical agencies, +only matter, ether, and motion are concerned. No one +has ventured to identify ordinary matter and electricity, +which cuts down the possibility to one of the remaining +two. + +If it be admitted that matter is not altered in quantity +by any process to which it may be submitted, and +also that the amount of ether and energy in the universe +are constant, it follows that all the different phenomena +exhibited by matter are due to the different +kinds of motion it may have; for \emph{motion is the only +variable factor}. On such a premise one can fairly +maintain that no matter how obscure and puzzling a +phenomenon may be, its explanation lies altogether in +its characteristic motions, and, when they are fully +made out, there will be no more to learn about it. If +so much be granted, one has got on a long way towards +the final answer to the questions, What is the nature of +heat? what is the nature of light? what is the nature +of electricity? Two of these are settled, and no one +thinks of asking as to their nature. The nature of +heat was settled by Rumford and Davy, that it is a form +of motion in matter. The nature of light was settled +by Young and Fizeau, that it is a form of motion in +the ether. What remained to be done was simply to +discover the particular kind of motion in each case. +\DPPageSep{241.png}{229}% +\index{Electricity, origin of}% +Spectrum analysis and photography have since given +us the particulars. Electricity is on precisely the same +philosophical basis; and, in the absence of evidence of +the existence of some other physical factors than matter, +the ether, and motion, one would be entitled to the philosophical +opinion that \emph{electricity must be some form of +motion}. What the particular form is may be a subject +of investigation, but not the nature of it. + +It is my purpose to show, \emph{first}, that in every case +where electricity is produced motion of some sort is +antecedent to its production; \emph{second}, that in every +case the effect of electricity is to produce motion of +some sort, and that itself is annihilated in doing it in +precisely the same sense as motion of any other sort is +annihilated when it is transformed. + +1. \emph{As to its origin}. When the face of the thermopile +is heated and electricity is produced, we know that +vibratory molecular motion is the condition for its appearance. + +In a galvanic battery the molecular exchanges by +which zinc is dissolved and oxidized, and hydrogen is +set free, are well known, and also the heat equivalent +of such re-actions; and they are measured in heat units, +which in turn may be made the measure of the electricity +developed. + +When glass or wax or other substance becomes electrified +by friction, the word itself expresses the condition +necessary for producing it. Mechanical friction +is the antecedent. + +When a conductor is moved in a magnetic field and +becomes electrified, the effect depends absolutely upon +\DPPageSep{242.png}{230}% +\index{Electricity, mechanical origin}% +\index{Electricity, electrical origin}% +the motion. Stop that and all evidence of electricity +disappears. + +The same thing is true when electricity is developed +by so-called induction in a field produced by a neighboring +body that is electrified in any way. The continuous +production of it implies continuous motion of one or +the other body. + +In dynamos of every variety of form the mechanical +motion turned into them is the antecedent, and the +energy of the engine spent in turning the dynamo has +its full representation in the electric energy developed, +and when there is no motion there is no electricity. + +In the physiological development there are always +chemical, thermal, and mechanical motions, which are +spent to produce what electrical phenomena appear, +whether in mankind or in animals. + +In the air and in the earth there are changing temperatures, +condensations, etc., which signify molecular +motions. + +Some crystals, like tourmaline, become electric by +heating; some, like mica, become electric by splitting; +and so on. Every one implies that some kind of motion +has to be spent to develop the electrical condition, and +in each case the particular kind of motion that has +been spent to produce it has been \emph{spent}; that is, it has +been transformed in the same sense that the translatory +motion of a bullet has been transformed into vibratory +when it strikes the target. The electricity thus appears +as the representative of the kind of motion that +has been destroyed. + +Some have imagined that electricity was a kind of +\DPPageSep{243.png}{231}% +\index{Electrical effects}% +\index{Stress, electrical}% +dual matter, which was broken up by the various processes +described, or that some substance was transferred +from one place to another, so that there was +more than the normal amount in one place and less in +another. Even such conceptions do not get rid of the +idea of motion being the chief characteristic, for the +separations are the ideal embodiments of motion, and +in this case the measure of it; so nothing whatever is +gained, either in clearness or simplicity, by such invention. + +2. \emph{The effects of electricity} are to bring about mechanical +motions of some sort. + +The stress into which the ether is thrown by either +an electrified or magnetized body is a change of position +of adjacent parts with reference to each other, +and the fact that this stress travels with the velocity +of light shows that motion is the essence of it. The +re-action of the stress in the ether upon other matter +in it always results in the motion of the latter. If the +whole body can move, it will do so, and mechanical +motion is the immediate effect. If it cannot move as +a whole, its molecules are twisted into new positions, +so that motion, either molar or molecular, is the result. + +As the electric current in a conductor always heats +the latter in every part, one has but to reflect upon the +character of heat motions to perceive that some kind +of motion must be the antecedent of it. Consider a +short portion of wire through which a current of electricity +flows. It becomes warmer and now radiates +faster into space. It is losing motion by imparting it +to the ether. Trace back the ancestry of the ether +\DPPageSep{244.png}{232}% +\index{Electrical effects, reversible}% +\index{Physical processes, reversible}% +motion, and it appears as vibratory motions of the +molecules of the conductor, thence as electrical current, +thence as armature rotations of a dynamo, thence to +the engine movements, thence to the furnace and the +chemical re-actions going on there. There is no question +as to the nature of the factors in all of these but +one. Call the chemical re-actions \textit{A}, the engine \textit{B}, +the dynamo \textit{C}, the electricity \textit{D}, the heat \textit{E}, and the +ether waves \textit{F}. With the exception of \textit{D}, each one is +known to represent a certain kind of motion, molar or +molecular, and all in a consecutive series. Is it not +difficult to conceive that the step \textit{D} can be anything +different in character from the rest of the series, and, +whether understood or not, must represent some phase +of motion? To think otherwise is to think that motion +can have some other antecedent than motion. Whoever +sets himself in earnest to this problem will see +there is but one answer to it. + +So heat effects, light effects, chemical effects, as +well as the direct mechanical ones shown in Crookes's +Tubes, or otherwise, will lead to precisely the same +conclusion that \emph{electricity represents an intermediate +molecular kind of motion}, having definite motions +for its antecedent, and definite motions for its consequent, +and so must itself be some peculiar form of +motion, differing from the others as they differ among +themselves, and nothing beyond that. It may also be +remarked that every form of motion which is capable, +under definite mechanical conditions, of developing +electricity, electricity is itself capable of producing. +The processes are all reversible. If heat will produce +\DPPageSep{245.png}{233}% +electricity, electricity will produce heat. If chemical +re-actions produce electricity, electricity will produce +chemical re-actions, and so on of all the rest; so if they +be reducible to motions, so must electricity. + +Such considerations make logically certain what the +nature of electricity is; but they do not indicate what +the character of the motions is that gives it identity, +and distinguishes it so radically from other well-known +kinds of motion. In the chapter on ``Motion'' it is +pointed out that there are three fundamental kinds of +motions,---translatory, vibratory, and rotary,---and +that with these all the various complicated motions of +mechanical processes may be produced. It is also +pointed out that for convenience we call those motions +mechanical that are on a scale of visible magnitude, +but such as cannot be seen are called molecular and +atomic. It is plain, in this case, that the motions must +be on a molecular scale, for no motions are directly +perceived in electrical phenomena any more than in +heat phenomena; so there remains for consideration +what evidence there is for the motion being molecular +and therefore of matter, or of the ether. + +It appears that when certain kinds of work, such as +friction, are spent upon a mass of ordinary matter, electricity +is developed, and we say the body is electrified. +The body in this condition at once re-acts upon the +ether about it; and it has happened that some persons +have given most attention to this effect of the electrified +body, and the phenomena that may result from it, +and have called \emph{it} electricity; while others have given +more attention to the condition of the matter that +\DPPageSep{246.png}{234}% +\index{Electricity, dual}% +\index{Ether rotations}% +induced the ether stress, and they have called \emph{that} +electricity; while the greater number have hopelessly +confused the two, calling both by the same name, just +as formerly heat and ether waves were both called +heat. It is plain that a physical condition of things in +matter requiring a name ought not to be designated by +the same term as that physical condition in the ether +which is the result of the first. One is, therefore, +justified by the logical necessity of making a distinction, +in adopting the name electricity as applicable to +one and not the other, and also in calling the phenomenon +in matter by that name and denying its applicability +to any effect of it wherever it is plain there has +been a transformation. Thus it would be as illogical +to call ether waves set up by an electrified body electrical +waves, as it would be to call the swinging of a +pendulum that was actuated by electrical attractions +electrical vibrations. + +We are, therefore, now reduced to the sole consideration +as to the character of those molecular motions +which differentiate electricity from heat and free-path +motion; and here the apparent dual character, which +has been so puzzling, helps at once to an understanding +of it. + +For many years it has been merely a matter of convention +that a current of electricity is said to move in +a certain direction in a wire. It has often been noticed +that there is an apparent current in both directions +from any electrical source; and one has been called a +positive, the other a negative, one; yet the current, +reckoned either way from its source, is always the +\DPPageSep{247.png}{235}% +\index{Magnetic rotation}% +\index{Rotations in ether}% +same at a given point, and has not unfrequently been +considered as made up of two currents moving in +opposite directions. + +If one will take a limp rope a few feet long and tie +its ends together so as to form a ring, and, holding it +in his two hands, will begin to twist it in one direction, +he will see the twist start in opposite directions at his +hands, and each one can be traced quite round the ring, +neither interfering with the other; yet one is a right-handed +twist, the other a left-handed one; and one +might call one a positive and the other a negative current. +There will be as much twist in one part of the +rope as in any other, and the rate of rotation at the +hands will be the measure of the amount of motion, +and, consequently, of the energy that is in the circuit. +For a rope substitute a wire, and for the hands a +battery or a dynamo, and the analogy is complete, +except that no rotation is seen in the wire as a whole; +so, if there be rotations, they must be of molecules and +not of the mass. Molecular motions must, of course, +be inferential. It is so for heat. The waves called +ether waves imply vibrations of matter; and, if there +be any known rotary motions in the ether, they would +imply molecular rotations for the same reason. It is +conceded that in every electro-magnetic field the ether +is in a rotary motion, and in numerous books it is +pictured as a whirl both about a magnet and a wire +carrying an electric current. The rotation of an electric +arc in a magnetic field shows it, and the twist +given to a polarized ray of light in passing through it +also shows it; and it has been so interpreted for years. +\DPPageSep{248.png}{236}% +The twist given to a conductor through which a current +is flowing, which has been before alluded to, also +gives direct evidence of the same condition; so the +phenomena confirm the conjecture that the phenomenon +in matter which is called \emph{electricity is a phenomenon +of rotating molecules}, in the same sense as the +phenomenon called heat is a phenomenon of vibrating +molecules. + +If the atoms in molecules, and the molecules themselves, +were absolutely fixed in position so as to have +no individual freedom of motion, there could be neither +vibration nor rotation; but the vibrations tend continually +to separate them, and hence between impacts +there is freedom for rotary slip, if there be any tendency +to do so. In an electro-magnetic field the ether +stress re-acts upon molecules in it so as to rotate them +upon some axis tending to set them in certain position +with reference to it. This action will be stronger upon +an atom or molecule immediately adjacent to an electrified +molecule than to one more distant, and one may +therefore infer that the process called conduction, +where heat is the immediate effect of an electric current, +is really an induction effect, and depends directly +upon the ether rather than upon the direct mechanical +effect of one molecule upon another; for such mechanical +action would make the rotation of adjacent molecules +to be opposite in direction, whereas in an electric +current all are in one direction. There is, therefore, +impact and slip, impact and slip; each impact knocking +the molecule out of the position the induction had +set it in, and each arrest of the slip resulting in increasing +\DPPageSep{249.png}{237}% +the amplitude of vibration, and hence raising +the temperature of the conductor. Hence, the explanation +of the transformation of electrical energy +into heat energy. An electric current is, therefore, +not a simple phenomenon, but is considerably complicated, +involving motions of both molecules and the +ether; the molecular motion depending directly upon +the re-action of the ether stress produced by an adjacent +molecule rather than upon mechanical contact. +The electrical condition called static being itself a +compound of abnormal molecular position and stressed +ether, is the condition which, while being propagated +in a conductor, constitutes an electric current, propagated +in the ether, constitutes an ether wave. +%\DPPageSep{250.png}{238}% + + +\Chapter{IX}{Chemism}{238} + +\label{chap:chemism}% +\index{Chemism}% + +\First{The} atomic theory of matter was held in some form +by ancient philosophers, but the reasons they assigned +for their opinion were not such reasons as have led +men of the present day to adopt that theory to the exclusion +of all others. Modern chemical analysis enables +one to reduce compound substances to their elementary +forms, and out of those to build up numerous +other substances with entirely different qualities. +Each such elementary form can be isolated, its properties +can be studied, and by compounding them one can +at will produce thousands of substances, each with its +own distinctive qualities. Some of the more thoughtful +men of all ages have pondered upon the fundamental +questions of physical science, and they have guessed +how it might be: some guessed this way, some guessed +that, and none of them gave a sufficient reason. It +would be very remarkable if, among a multitude of +guessers, some did not guess nearer right than others; +but such lucky guessing hardly entitles one to the +honor of being the founder of a philosophy that had +to wait for later men and entirely different methods to +substantiate it. And this is the real state of the case +in nearly all departments of knowledge. Ask any chemist +\DPPageSep{251.png}{239}% +\index{Atoms, chemical properties}% +to-day why he holds the atomic theory of matter, and +he will reply that he can isolate the elements, and by no +process yet discovered can they be more finely divided; +that he can measure their individual magnitude and +weigh them, prove their existence in the sun and stars; +so that the weight of evidence is exceedingly great. +He will never think of assigning any such reasons as +the early philosophers gave for their teaching. Many +of the properties of bodies of visible magnitude depend +upon the number and arrangement of the molecules +that compose them, but the properties of atoms are +fundamental and not subject to change. All substances +are identified by means of their properties, and the +chemical properties of atoms are among the most important. +Not only do atoms combine together in groups +called molecules, consisting of two or more atoms, but +they combine in definite proportions by weight, and only +so; and these proportions are called the atomic weights +of the elements, and are known for all of them; so +that molecules are compounds of definite constituents, +definite weight, and possessing definite properties. For +instance, water is made up of hydrogen and oxygen, two +parts by weight of hydrogen and sixteen of oxygen; +and as to its properties, such as density, specific gravity, +conditions at different temperatures, etc., all are familiar +with. Most of these properties of bodies are called +physical, but by chemical properties is meant the +ability of atoms to enter into definite combinations +with other atoms, to form new compounds and develop +new properties. The chemist is concerned with such +atomic exchanges, called re-actions, and notes the conditions +\DPPageSep{252.png}{240}% +\index{Affinity, chemical}% +under which they take place, and some of the +new qualities that appear, such as its physical condition, +as to being a solid, a liquid, or a gas at certain +temperatures, its crystalline form, if it has any, its +behavior with polarized light, and so on. + +Underneath all chemical re-actions there lies the +question as to why atoms combine at all. At first it was +explained as due to an attractive force,---chemical attraction, +possessed by all atoms, but in different degrees +by different elements. When it became known that +this acted in definite selective ways, it was called chemical +affinity, but was still supposed to be a peculiar +force unrelated to other forces supposed to exist, such +as heat, light, electricity, and so on. In the progress of +knowledge, it became apparent that these latter phenomena +were so directly related to each other that they +were capable of being transformed one into the other, +and then the expression ``correlation of forces'' began +to be used. A further analysis showed them to differ +from each other chiefly in the character of the motion +involved in the phenomena; and so forces, as such, have +been banished from physical science, leaving not even +a single primal force; for as each one can be changed +at will into any of the others there is simply a closed +chain of phenomena, no one of which can be called an +elementary one more than any other. + +Chemical phenomena have been found to be a part of +the same grand division, and the term ``chemical affinity'' +has itself been in a measure supplanted by the +term ``chemism,'' which is now used to signify the +quality possessed by atoms to enter into definite combinations; +\DPPageSep{253.png}{241}% +\index{Chemism and heat}% +and its explanation is to be found by noting +the factors present when atomic and molecular exchanges +take place, and these have been found to be all +physical without exception. There is a large field +known as chemical physics with which one needs to be +acquainted in order to understand simple chemical +operations; namely, the effects of heat, light, and +electricity in bringing about chemical changes. + +When hydrogen combines with oxygen to form water +the process is called a chemical one; but, as has been +pointed out in the subject ``Heat,'' there is a definite +amount of heat given out by the combination of a definite +amount of the elements; and in like manner the +dissociation of the elements in water requires the expenditure +of energy proportionate to the amount decomposed. +This too is called a chemical process, but +the conditions for doing either are purely physical, depending +absolutely upon heat. The elements cannot +combine when heat cannot be given out, and cannot be +separated except by an equal expenditure. What is +true for this example is true in degree for all other +chemical re-actions; physical energy is involved in every +change and is the condition for the change. The first +law of thermo-dynamics states the quantitative relation +between heat and mechanical work; viz., that it is measurable +in foot pounds, and is equal to $772$ foot pounds +per pound degree, and this is called a heat unit. Now, +the chemical combination of a pound of hydrogen with +oxygen gives $61,000$ heat units, and is therefore at once +measureable in foot pounds, showing a direct relation +between chemical re-actions and heat or work. +\DPPageSep{254.png}{242}% + +It has also been discovered by experiment that in the +absence of heat chemical re-actions cannot go on, and +this has led chemists to the conclusion that at absolute +zero chemism does not exist. There is not only no +selective action, but no cohesion among atoms, and all +molecules would fall to pieces---that is, to atoms, quite +dissociated---at absolute zero. Instead of requiring +\index{Absolute zero}% +\Pagelabel{242}% +$61,000$ heat units to dissociate a pound of hydrogen +from water, it would not require any, for if the atoms +do not cohere, no work would need to be done in order +to separate them.\footnote + {See Appendix, \Pageref{p.}{400}.} %[** PP: Original reads p. 399] + +From this, then, it appears that chemism is determined +by heat, and does not exist in the absence of +temperature. When it is developed it manifests itself +in selective ways, and in the formation of definite compounds; +and it therefore is a proper subject of inquiry +as to how the temperature of atoms can give such selective +qualities to them. This requires a reconsideration +of the distinctive quality of heat itself. It has been +pointed out that this consists in the internal vibratory +motions of atoms and molecules, as distinguished from +translatory and rotary motions; that the evidence for +this comes, first, from the fact that a body of any size +possessing any degree of heat---that is, having a temperature +above absolute zero---is constantly exchanging +its energy with the ether, and that the rate of the exchange +depends upon the temperature; and, second, that +translatory motions of bodies in ether do not require +the expenditure of energy, or, in other words, that for +such motions the ether is frictionless. This is the +same as saying that, where the heat of a body is lost by +\DPPageSep{255.png}{243}% +\index{Atoms, vibrations of}% +radiation, it is the internal vibratory motion alone that +is lost, not its translatory velocity. Consider a body of +any magnitude whatever, having any temperature whatever, +and moving at any assignable velocity in space. +After an interval it will have lost some of its temperature +by radiation, and, if it moves long enough, it might +lose it all, reaching absolute zero; but its translatory +velocity will not therefore be reduced in any degree. +Hence, in considering the heat in a body, independent +of any other motions it may have, one has only to do +with its internal vibratory movements, and that the +temperature of a body, say an atom, is measured by +the amplitude of its vibration, and is proportional to the +square of that amplitude. + +If, therefore, chemism is directly related to heat, one +must attend to what must be going on in an atom, not +groups of them. + +To say that an atom vibrates is to say that it is +changing its form, and to explain how changing its form +can result in such selective properties as atoms exhibit +is to explain chemism by the mechanics of the motion +involved. Whether atoms have one form or another +will make no difference in this argument, which is that +the result is due to change of form, whatever that may +be; but, for making the subject mechanically clear, some +form may be adopted, and one can do no better than to +choose that form which now has most probability in its +favor judged by other phenomena; that is, the vortex-ring, +which has been treated under the head of ``The +Ether.'' + +When such a body vibrates in its simple way it +\DPPageSep{256.png}{244}% +\index{Attraction of vortex rings}% +elongates alternately on two axes at right angles to +each other; that is, the change in form is from a circle +to an ellipse, so as to assume first a horizontal, then a +vertical elliptical form, as shown in the cut. Such +%[Illustration: \textsc{Diag.~29.}] +\begin{wrapfigure}{l}{1.25in} + \Graphic{1.25in}{256a} + \Caption{29}{Diag.\ 29.} +\end{wrapfigure} +changes are due to the elasticity of +the ring, and are brought about in +such an atom by impact, by friction, +and by absorption of ether waves. +Whether produced in one way or +another, they represent absorbed energy +and exhibit it as heat, the temperature +of a given one depending upon the amplitude +given to it by a definite amount of energy however +applied. + +Such changing forms imply nodes and loops in the +vibrating body, positions of minimum and maximum +motions; and when the vibratory rate is the fundamental +one,---that is, the lowest rate the body can have,---there +will be four of each, the nodes being the positions of +minimum change of form. Such nodes may be seen in +vibrating bodies of all sorts,---strings, bells, rods, pipes, +and rings. The size of a body makes no difference in +this characteristic, and it therefore may be affirmed of +atoms as well as of any other magnitudes. + +%[Illustration: ] +\begin{wrapfigure}{r}{1.5in} + \Graphic{1.5in}{258a} + \Caption{30}{Diag.\ 30.} +\end{wrapfigure} +Let it be admitted that vibrating atoms can cohere +for any reason, it will be seen that an atom such as +represented could only have other atoms attached to it, +and be in a stable condition, when they were at the +nodes; and in this case four might be so attached and +no more, if they were approximately of the same size. +Such places in atoms might be called bonds: they would +\DPPageSep{257.png}{unnumbered}% +% [Illustration: ] +\begin{figure}[hp] + \begin{center} + \Graphic{3.75in}{257a} + \end{center} + \caption{Geometrical Forms of Snow Flakes.} +\index{Crystallization}% +\end{figure} +\DPPageSep{258.png}{245}% +be definite in number, position, and strength. If the +other attached atoms were themselves +vibrating, they +would each have their own +nodes; and if they were free +to turn into any position, one +might be sure that the nodes +of each would be in contact, +and that the loops of the vibratory +motions would be where +space to move in without interruption +was free. Such a combination +of atoms might be called a molecule. It would +consist of a definite number of atoms, each with its own +atomic weight; and if the strength of +the cohesion depended upon the vibratory +motion, it is easily seen that when +there was quiescence in that there +would be disruption or dissociation. +%[Illustrations] +\begin{figure}[hbt] + \begin{center} + \hfil + \begin{minipage}{1.25in} + \Graphic{1.25in}{258b} + \Caption{31}{Diag.\ 31.} + \end{minipage} + \hfil + \begin{minipage}{1.5in} + \Graphic{1.5in}{258c} + \Caption{32}{Diag.\ 32.} + \end{minipage} + \hfil + \end{center} +\end{figure} +Moreover, when there was such a nodal +bond it would be like a hinge, and two thus united +could swing upon it; while if three were thus united +and two were to swing upwards, +they would meet at a node on +each and stick together for the +same reason the other nodes did, +thus forming a symmetrical and +stable figure against which other +similar ones could be built up, +node against node indefinitely. A +hexagonal figure would result. If four were attached +to the primary nodes, and each was to swing up ninety +\DPPageSep{259.png}{246}% +\index{Chemical field}% +\index{Fields, chemical}% +\index{Fields, mechanical}% +degrees, there would be formed a sort of cubical box +without a lid; but at the top will be presented four +open nodes, upon which the four nodes of any other +similar one might be placed: and thus could a cubical +structure be built by addition of similar forms indefinitely. +Such symmetrical forms are called crystals. + +Of course all this presupposes that there is some +good mechanical reason for atomic cohesion, that is in +some way dependent upon temperature; and to make +this clear it is needful, first, to call to mind some phenomena +of a similar sort on a larger scale. + +It is well known that if a light body be brought near +a vibrating tuning-fork, the latter acts as if it attracted +it, for the light body will move towards the fork. The +same thing is true of other vibrating bodies, and the +explanation is that the vibratory motion reduces the +pressure about the body. Thus, suppose the hand to +move to and fro; as it moves forward the air in front +of it is somewhat condensed, while that behind it is +partially rarefied; when the hand returns the same +thing happens. The air follows up the hand because +the pressure is reduced next the hand, and if the hand +could swing back and forth, faster than the air could +return to it, there would be formed a perfect air vacuum; +and that means that the pressure would be +nothing at the hand and fifteen pounds per square +inch at a distance from it. Hence any body placed near +the hand would be subject to a pressure greater on its +remote side than on the side adjacent to the hand, and +would be pushed by it towards the hand. This would +be a phenomenon similar to attraction, the movement +\DPPageSep{260.png}{unnumbered}% +%[Illustration: ] +\begin{figure}[hp] + \begin{center} + \Graphic{\linewidth}{260a} + + \scriptsize CRYSTALLINE FORMS.\\[6pt] + \begin{minipage}{\linewidth} + The above figures illustrate very clearly the molecular arrangement in crystals of + various kinds. \textit{A}~represents a cross section of Brazilian Topaz, as shown in polarized + light. \textit{B}~is a hollow faced cube of salt, and \textit{C}~a similar hollow faced octahedron of + copper sulphide. They show that the cohesive strength is greater on the edges than + elsewhere. Some crystals, when being dissolved, leave a complete skeleton of themselves + the last to disappear. \textit{D}~is a skeleton crystal of silver from Scotland, where the + structure consists of a series of minute octahedral crystals adhering to each other in + such directions as would build up a single large octahedral crystal if filled out. + \end{minipage} + \end{center} +\end{figure} +\DPPageSep{261.png}{247}% +\index{Crystallization}% +\index{Vibrations, sympathetic}% +towards the vibrating body being due directly to the +pressure of the medium, while the difference in the +medium would itself be directly due to the vibratory +movement. The amount of such difference in pressure +is evidently determined by the degree of vibration. +Now, if one can imagine a similar condition of things +about an atom vibrating in the ether, he can understand +how its vibratory movements might reduce the ether +pressure adjacent to it in a way proportional to the +movement, and also how at the nodes such effect would +be at a minimum, and at the loops at a maximum, so +there would be produced what is called a field. As the +condition that produced it was one of mechanical +motion, one might call the field a mechanical field, for +mechanical effects of translatory motion result from it. + +When such an effect takes place among atoms one +might distinguish it as a \emph{chemical} field, for it would +bring about mutual cohesion among atoms, and the +nodes would determine the positions of stable combinations; +and a molecule so built up would require an +amount of energy spent upon it to break it up equivalent +to the energy spent, to produce the field, or, in +other words, equivalent to the heat in the atom. + +It is here to be noted that when atoms combine in +this way each one retains abundant space for its heat +movements, so its temperature may be varied within +considerable limits without interfering with molecular +stability. And, if the vibratory movements continue, +then each molecule will have its own field, which will +be the resultant of all the fields of the atoms that are +combined thus to make the molecule. The field of a +\DPPageSep{262.png}{248}% +\index{Growth}% +\index{Inductive action}% +molecule will then have a form which will depend +absolutely upon the number and arrangement of the +constituent atoms, and will extend to some distance in +space beyond the geometric boundary of the molecule +itself. + +The presence of such a chemical field must affect +other chemical fields in the neighboring space where +the fields overlap, hindering or facilitating the exchange +of atoms in other molecules, because lessening the +pressure holding them together. There are many +examples of this kind of action known. It is called +catalysis, which signifies the action of a given substance +\index{Catalysis}% +in bringing about chemical reactions without +itself being changed. For example, the binoxide of +manganese, when mixed with the chlorate of potash, +greatly facilitates its decomposition by heat, though +the binoxide is itself not decomposed. Pure zinc is +dissolved with difficulty by sulphuric acid; but a little +mercury or iron, or other so-called impurity, enables it +to be dissolved freely. Hydrogen and oxygen gases will +not combine when simply mixed; but a little spongy +platinum placed in the mixture will at once bring about +the combination, but will itself suffer no chemical +change. These gases will also slowly combine in the +presence of mercury when kept at the temperature of~$305°$. +In glass vessels without the mercury no combination +at that temperature occurs, but on raising the temperature +to~$448°$ it combines very slowly. In smelting +operations a flux has a similar function, and in some +cases the boundary line of such action can be observed. +Some re-actions take place at a different rate near the +\DPPageSep{263.png}{249}% +sides of the vessel that contains the solution than away +from it, and some mixtures of substances in solution +will separate from each other except within a short distance +from the surface. Such phenomena show that +the mere presence of some substances is sufficient to +profoundly affect chemical re-actions. The chemical +field of substances gives a consistent explanation of +catalysis. There is another class of phenomena well +known, but hitherto without any rational explanation; +viz., some supersaturated solutions seem unable to initiate +the process of crystallization, but the smallest crystal +of the substance starts it, and the whole body is +solidified in a few seconds. Here it is evident that the +crystal, taken as a nucleus, had a field that compelled +other and similar molecular groups to arrange themselves +in similar order. This is a phenomenon of such +importance as to warrant some attention here. When +two tuning-forks having the same pitch are separate +from each other a distance of several feet, and one of +them be made to produce a sound, the other one will be +made to sound likewise by the action of the sound +waves in the air upon it. The effect is called sympathetic +vibration. Other forks having different rates of +vibration will not be similarly affected, so the vibrations +in the air select out the particular fork having the same +rate as the one vibrating, and cause it to enter into a +similar state of vibration. So it appears with a magnet. +Any magnetic bodies in its field become magnetized +there; that is, they are brought into the same physical +state as the body that incited the field. Such physical +fields, then, are capable of compelling bodies in them +\DPPageSep{264.png}{250}% +\index{Fields, magnetic}% +\index{Magnetic field}% +\Pagelabel{252}% +to assume the same state of motion or similar position, +or both, as the body that produced the field, provided +the substance itself be constituted molecularly like the +first,---and this simply by being in proximity, not by +contact. It is a kind of induction, common through +the whole domain of physics. In the organic world of +living things the phenomenon of growth is manifested +by what are called cells, which are symmetrical groups +of molecules, as crystals are, only much more complex. +Growth consists in the formation of similar cells out of +suitable molecular constituents in the neighborhood. +Each different part of a plant or animal has a different +cell structure. If, therefore, it be conceded that each +cell has a field, which is the resultant of all the elements +that make it up, it will be seen how such field +must act upon other matter within it, compelling it to +assume a form similar to the cell that produces the +field; that is, to form a similar cell adjacent to itself. +Such formation is called growth; but the similarity in +form and function, when appearing among plants or +animals, has been considered as due to heredity, a term +that has a definite enough meaning, but which has not +been supposed to be due to mechanical necessity but +to some super-physical agency not amenable to purely +physical laws and conditions. It is possible to pursue +this much further and to show that cell structure itself +may be modified by molecular fields, and how stability +of form and function are possible with some and not +with others,---how what in natural history is called +variability, reversion, and other phenomena of the sort, +are explicable as due to the same factors that \DPtypo{organizes}{organize} +\DPPageSep{265.png}{251}% +atoms into molecules, and molecules into crystals. +Every one interested in the fundamental questions of +chemistry will be able to follow out in many ways the +mechanical conceptions here introduced, and compare +what he knows of chemical re-actions with them. It +will be especially helpful for one to draw upon paper +such ideal atomic rings with their edges touching, and +marking where the nodes must be. Such diagrams as +the one on \hyperref[fig:30]{p.~\pageref{fig:30}, fig.~30}, thus drawn, cut out, and the +parts bent up until they touch each other, will probably +surprise one at first to find how the nodes will be +brought adjacent to each other and therefore into a +stable position. + +So far it has been assumed that there will be in the +ether about a vibrating atom an effect comparable with +the effect produced in air about a tuning-fork or other +vibrating body that is producing sound waves. One +might be satisfied that there was such an action, even +though he were not able to explain it, provided there +were good reason for the assumption. The case is the +same as for a magnetic field within which magnetic +phenomena take place, though a magnetic field cannot +be isolated. It is the same for the existence of the +ether itself: it is inferential, but from a large body of +phenomena of different sorts, all corroborating the hypothesis; +so one is satisfied. When a magnet acts upon +a piece of iron not in contact with itself, we explain the +action by the magnetic field; and, if a body acts chemically +upon other bodies not in immediate contact, controlling +their motions and positions, as is the case, the +same kind of an assumption is to be entertained. If a +\DPPageSep{266.png}{252}% +\index{Heat, effects}% +reasonable explanation for the existence of the field +can be offered, all the better, though no one holds more +lightly upon a magnetic field because he cannot explain +it. In the chapter on magnetism it is remarked that +there is good reason to think that atoms of all kinds +are magnets. If that be the case, then every atom has +a field of its own, wherever it may be; and it would +seem likely that this magnetic field of atoms was the +underlying factor in the so-called chemical field; and it +is therefore well to analyze the phenomena, having that +magnetic field in mind. + +A single magnet of any form will have its field +under all conditions, and the \emph{shape of the field will be +determined by the form of the magnet}. If the magnet +were of sufficient size, there would be no difficulty in +locating it by its field, even though the magnet itself +could not be seen. A number of magnets arranged +promiscuously would so neutralize each other's fields +as to have no residual field, and in order to detect the +existence of magnetism it would be needful to get very +close to an individual magnet. When a steel magnet +is dissolved in an acid all evidence of the existence of +magnetism disappears, for the iron molecules are now +separated from each other and are scattered promiscuously +through the solution. Any disturbance whatever +that disarranges the magnetic arrangement of +molecules destroys the evidence of the magnetic field, +except at very short distances. When a piece of iron +is heated to redness it cannot be made magnetic in +the ordinary sense; for the vigor of the vibratory movement +continually knocks the molecules into new positions, +\DPPageSep{267.png}{253}% +and therefore changes their resultant fields, +leaving but a neutral effect upon outside bodies. + +As chemical re-actions take place in liquids or gases, +and only exceedingly slow in solids, it follows that in +them one has to deal with molecules in all positions,---that +is, an entirely disordered arrangement, and such as +would exhibit no evidence of magnetic field, even though +every atom was itself a strong magnet; and this condition +of neutrality would be constant so long as the +temperature kept up so much mechanical disturbance +as to prevent any systematic arrangement. Yet it is +to be borne in mind that the magnetic field of no one +has been \DPtypo{distroyed}{destroyed}: it is as strong, as far reaching, as +ever; but it is masked by overlying fields,---that is all. +Let any one of them suffer any change at all, and the +effect of it would be felt throughout the whole space +the field would occupy if there were no other one in +its neighborhood. + +Now, when the form of a magnet is changed, it +changes the form of the magnetic field---that is, the +distribution of the stress that constitutes the field; and, +when an atomic magnet vibrates, it is changing its +form; and as a result its field is changing at the same +rate. A multitude of such independent magnets, all +changing their forms and fields, would be sending out +waves into the ether; but they would be caused by and +measured by their heat motions, not by their magnetic +condition simply; and the effects of these waves at a +distance from their source would be practical uniformity +unless the waves were very long. For such short ones +as are produced by atomic and molecular vibrations +\DPPageSep{268.png}{254}% +there could be no ordinary indications of a magnetic +field such as are exhibited in the movements of bodies +of visible magnitude. Long waves of precisely the +same sort caused by motions of a slower rate might +make magnetic needles move. Thus, magnetic needles +upon the earth have been observed to move at the +same instant that solar disturbances have been witnessed +through a telescope, which indicates that the +waves were long ones, giving a magnet time to move +one way before it was impelled to move in some other +way. + +This condition of practical neutrality on account of +the rapidity of the change at a distance from the magnetic +body would not hold true in close proximity to +the body itself; for the changes in the field will not +only be actually greater there, but the fact that there +are nodes and loops necessitates changes in the stress +at the surface of the atom, and renders it possible for +the actual magnetism to assert itself and act upon +another very near to it which it cannot have in any +degree a little farther away, the actual distance being +comparable with the diameter of the atom itself. Hence, +atoms close by would have certain magnetic effects +upon each other in the nature of selective effects, on +account of the uniformity of the stress at the nodes, +and the number of nodes would determine the possible +number of cohesive attachments. So one may fairly +presume that the vibratory motions such as constitute +the heat motions of atoms are the physical conditions +that underlie chemical combinations and give to them +their quantitative character, their selective property, +\DPPageSep{269.png}{255}% +\index{Sound, origin of}% +and their symmetrical form into which they arrange +themselves. + +This gives a rational account of so-called chemical +attraction, and makes it clear how the laws of thermo-dynamics +are related to chemical re-actions. It reduces +the whole scheme to one of the mechanics of vibrating +magnets; and the evidence that atoms are such magnets +does not rest upon the necessity of the conception for +the hypothesis, but upon much confirmatory experiment +that has led physicists to the conclusion that +they are such, in a manner quite independent of what +phenomena might be deducible from matter with such +a constitution. In conclusion, it may be added that, +although the idea of ring-formed atoms has been +adhered to in this explanation, it is not to be understood +that the same explanation would not apply to +atoms constituted in any other manner; for all that is +implied in the above is that whatever their form and +substance they are magnets, and that they are so elastic +as to be capable of internal vibratory movements---that +is, of changing their forms in a periodic way; +and of this there appears to be no reasonable doubt. +When several such are combined together the resultant +motions and their effects become very complicated, and +therefore difficult to disentangle; but that would be no +reason for not holding a well-grounded conviction that +all chemical phenomena are truly physical, and referable +to fundamental mechanical laws, and are fully explained +when these mechanical conditions are pointed out. +%\DPPageSep{270.png}{256}% + + +\Chapter{X}{Sound}{256} + +\First{The} term ``sound'' has two very different sign\-i\-fi\-ca\-tions,---one +a physiological one referring to a sensation +in the organ of hearing, the other the physical cause of +the sensation. When one has the sensation of sound, +of course he usually infers that it was caused by some +external physical condition that has in some way impressed +itself upon his auditory apparatus; and, to one +who has thought but little about it, it is difficult to get +rid of the idea that sound is a something which exists, +whether it be heard or not. That is, there would still +be sound though there were no ears, that a tumbling +pile of books in a deserted house would make a racket +if no one did hear it. On the other hand, one may +call that sound which is capable of being heard; and +when those conditions are investigated it is found, in +all cases, to be some kind of a mechanical impulse, or +succession of impulses, generally in the air, which may +be traced from the ear to some body which is found to +be in a state of vibration. The latter is called a +sounding body, and the air is called a sound conductor; +but these conditions are not necessary for the +sensation of sound. One may not infrequently hear +what is called ringing in the ears, that has its origin +within the head, and, perhaps, in some cases independent +\DPPageSep{271.png}{257}% +\index{Pitch}% +of any of the auditory apparatus, like some +nerve disturbance even at the base of the brain itself. +Hence there is a distinction between hearing and the +cause of hearing, and the latter does not necessarily +imply anything external to the listener. One may be +deaf so that no conditions external or internal will +produce the sensation. As the sensation itself can +give no infallible testimony as to what causes it, it has +come about that the physical conditions which may be +heard as sound have been investigated, and the science +of sound, or acoustics, has been developed quite independent +of the sense of hearing, the latter being only +a convenient instrumentality in the investigation, not +an indispensable one. In this sense sound is the +science of the vibratory movements of elastic bodies, +and one may inquire first as to the origin of such +movements. When one body strikes upon another, +motion is imparted to the latter. If enough motion is +imparted, it may move visibly, and we then call such +motion mechanical. Though it does not visibly move, +yet energy has been spent upon it in some degree, and +must be represented by some degree of motion which +at first it did not have. If a pencil be struck upon the +table, one may be as sure that energy has been spent +upon it as if it had been struck with the fist, only +less in amount. + +When molecules are compressed together so as to +increase the density, and retained in such closer compactness, +heat is always the result; that is, the molecules +themselves have their amplitude of vibration +increased: but when molecules are compressed quickly, +\DPPageSep{272.png}{258}% +and the pressure be as quickly removed, the compressed +molecules at once rebound to their original +position with a velocity that depends upon the degree +of elasticity the body has, and, like a swinging pendulum, +do not stop at once when they have reached that +position, but go beyond a little, and thus oscillate back +and forth. Each molecule pushes against its neighbors, +and they upon theirs, and so on, the motion travelling +outwards from the point of disturbance in every direction, +with a velocity that is proportionate to the temperature; +that is, the vibratory rate of the molecules +themselves, which, as pointed out in the chapter on +heat, is exceedingly great. + +This particular kind of movement is called longitudinal; +that is, it is to and fro in the direction in +which the disturbance travels, and depends altogether +upon the properties of the body that is struck, and not in +any degree upon the initiating cause. When the table +is struck with the pencil the sound heard is different in +quality from that given out by a similar stroke upon +the window or a tumbler. It differs also in duration. +The latter may continue to be heard for some seconds, +while the former is brief. Every elastic body has some +particular vibratory rate, which depends upon its size +and shape as well as the material it is composed of. +A stretched string or wire, a board, a lath, a bridge, +a house, for examples, all have individual rates of +motion, into which they can be brought by some well-directed, +sudden push. When a strong wind shakes a +house, the shake is the vibratory rate of the building, +and may be as low as one or two per second. In +\DPPageSep{273.png}{259}% +general, as bodies are smaller their rate of vibration +increases, until it becomes greater than thirty or forty +per second, when the effect can be heard. Stones +have an individual pitch, or rate of vibration, so that +by selection one may get a set to represent the musical +scale when struck. Smooth bits of laths of different +lengths give out their pitch when dropped upon +a table; and, with a properly graded set, tunes may be +played by dropping them successively. The rate of +vibration, or pitch, of a table is relatively high---several +hundred per second; and a pencil knock distributed +over so large a body, and by it to the floor, reduces its +strength very fast. The tumbler has its motions +symmetrical, therefore of greater amplitude, and last +longer. A tuning-fork struck and held in the fingers +near the ear will be heard for a much longer time than +if the stem be held against the table, as any one may +satisfy himself by trying. In the latter case the +motions are conducted away freely, in the former case +not so freely. In the former case the sound appears +louder to the ear, because the air, in contact with the +vibrating table, receives vibratory motions from it as +well as directly from the fork; and so the air motions +are re-enforced, and the energy is dissipated so much +the more rapidly. + +The idea in all this is that, so far as sound consists +in vibratory motions, energy is involved, and is distributed +in accordance with mechanical laws; the size, +density, and elasticity of the sounding body being the +factors which determine the rate at which the distribution +can go on. +\DPPageSep{274.png}{260}% +\index{Sound, characteristics}% + +If the motion be properly mechanical, any agency +that can originate such motions can give rise to sound. +One might ask himself here if it be likely that any +kind of motion, or form of energy, cannot produce it. +If it be remembered that motion is the antecedent of +motion in all known cases, one will perceive that +sound might have a variety of antecedents, as it has. +To the mechanical ones alluded to might be added +all cases of percussion, impact, friction---indeed, the +whole range of mechanical motions. Any agency that +can change the form of a body can cause sound vibrations. + +That heat can directly produce sound is shown by +the roar of fire in furnaces; and tubes having a burning +gas-jet in them may give out a loud sound. In +these cases it is the body of air that is caused to +vibrate energetically\DPtypo{}{.} + +When a beam of light falls upon a body that can be +heated by it there is a re-action between the surface and +the air, in which the surface is pushed slightly backwards, +as indicated by the \DPtypo{radiometre}{radiometer}. If a beam is +allowed to fall intermittently upon such a surface, it +will be thrown into vibrations as if it had been struck, +and will give out a sound, the pitch of which depends +upon the number of interruptions per second. Such a +device is called a radiophone. + +A current of electricity sent through a conductor in +an interrupted manner makes the wire give out a sound. +The current heats the wire, expands it slightly, and +cools as suddenly when the current is stopped; so the +succession of currents results in sound. In like \DPtypo{manmer}{manner}, +\DPPageSep{275.png}{261}% +\index{Sound, range of}% +\index{Sound, velocity of}% +a current of electricity going through an electro-magnet +causes a click at the instant of making and +breaking the current. This is occasioned by the +change in position of all the molecules. A succession +of these may keep up a continuous hum. + +The electric spark itself always produces a snap of +brief duration, for short sparks from induction coils +and electric machines; but, when the spark is a long +one, like a flash of lightning, the sound may be prolonged +several seconds. Along the line of the flash +the air is greatly heated for a very brief time, and it +therefore rapidly expands. The quick cooling produces +a collapse of the heated column of air, with the consequent +noise. The duration of the thunder does not +signify that the lightning lasts such an appreciable +time, but that a part of it was a distance away, and that +time was taken for the sound to come from the more +distant place. + +That chemical action can give rise to sound is proved +by the explosion of gunpowder and other explosives, +solid and liquid. In these cases a large amount of gas +is suddenly formed, and at a high temperature; it displaces +the air quickly and forms a great wave. One +may often feel the wave of compression produced by +a cannon go by him, even at the distance of several +hundred feet from it. These examples show that heat, +light, electricity, magnetism, and chemism are directly +related to mechanical motions because competent to +produce them under appropriate conditions. If motion +be the antecedent of any given motion, and any of +these may be the immediate antecedent of mechanical +\DPPageSep{276.png}{262}% +motions such as sound, what shall be said as to the +nature of each of these physical agencies? + +\Section{CHARACTERISTICS OF SOUND.} + +As sounds may be produced by any of the physical +agencies, it does not matter, except for convenience, +what ones are adopted. Usually mechanical motions +are most convenient, and for musical purposes either +percussion, or currents of air. We speak of high +sounds and low sounds, and we find by experiment that +those called low are produced by fewer vibrations per +second than those called high. If sounds are considered +as vibratory movements, then it is evident there is +practically an infinite range of them; for there may be +any rate, from one a year or a thousand years all the +way to such vibrations as atoms make, measured by +millions of millions per second. There is no good reason +for drawing a boundary-line at one point rather +than at another, and saying that all vibratory movements +beyond this rate are not to be considered as +sound, yet it is convenient for some purposes to confine +the range to such as can be heard. + +When a succession of impulses follow each other at +such a rate as just to produce a continuous sensation of +sound, it is found to require from twenty to thirty per +second. It differs very much in individuals. In the +young it requires more, as the organ of hearing acts +more promptly than it does in the old. A less number +than these is heard as a tremble. From this as a minimum +one may go through a series, running from the +lowest sound produced by a piano---about forty per second---to +\DPPageSep{277.png}{263}% +\index{Echo}% +\index{Wave lengths of sound}% +the highest one of about $4,000$ per second. +Many insects make much higher sounds than this. +Such differences in the rate of vibration are called differences +in pitch; and, for musical purposes, a standard +of pitch has been adopted, making the middle~C of +the piano give from +%*[Illustration: ] +\begin{wrapfigure}{r}{1.25in} + \Graphic{1.25in}{277a} + \Caption{33}{Diag.\ 33.} +\end{wrapfigure} +$256$~to~$261$ vibrations. +The pitch of a sound may be +specified by giving its vibratory rate. +The pitch of men's voices ranges +from $100$~to~$150$ vibrations in conversation. Ordinary +whistling is produced by from $1,000$ to~$3,000$ or~$4,000$. +The squeak of bats is in the neighborhood of~$5,000$. +Beyond these figures it is difficult to hear anything,---not +because the vibratory motions are not produced, but +because they have too little energy to affect the ear. +Occasionally aurists find abnormally sensitive ears capable +of hearing sounds with a pitch as high as fifty or +sixty thousand, but ordinary persons have a limit in +the neighborhood of $20,000$; so it is customary to say +that the range of hearing of mankind is from thirty +per second to about $25,000$: but it should always be borne +in mind that the chief reason for not having a greater +range is in the difficulty of giving sufficient amplitude +to such very rapid changes. As the pitch rises the +amplitude decreases for a given amount of vibratory +energy. One might attribute the relatively low vibratory +rate of the maximum which the ear can perceive +to the lack of delicacy of the apparatus itself, which +would be true enough in an absolute sense; but the actual +sensitivity of the ear is really something wonderful, +for a piece of apparatus that is altogether mechanical +\DPPageSep{278.png}{264}% +in its mode of operation. It has been found that the +ear can hear such sounds as are produced by small +whistles at the distance of several hundred feet; and, if +the amplitude be computed,---assuming that it varies +inversely as the square of the distance---it is found to +be comparable with the diameter of a molecule, or less +than the ten-millionth of an inch. One who understands +the necessity for vibratory motions in elastic +matter will readily conclude that between the highest +number the ear can perceive, say $50,000$ per second, +and the lowest rate capable of affecting the eye ($400$ +millions of millions), there is an enormous gap; and man +has no organs for perceiving the intermediate ones. + +Experiments made in various ways have shown that +the velocity of sound waves in air is about eleven hundred +feet per second, and varies with the temperature, +being only $1,090$~feet at the freezing point of water, +increasing or diminishing about two feet per second for +each degree above or below that; and this is true for +sounds of all degrees of pitch. If it were not so, +music could not be heard at any distance from its +source. Suppose a tuning-fork makes one hundred +vibrations in a second. At the end of the second the +first wave would have got say eleven hundred feet +away, while the last wave would have just been completed; +or between the fork and the more distant wave +there would be a series, one hundred in all, reaching +eleven hundred feet. It follows that each wave would +be eleven feet long, or the velocity of transmission +divided by the number of vibrations. The wave length +of sounds can be measured in several ways, and of +\DPPageSep{279.png}{265}% +\index{Vibrations, sympathetic}% +\index{Vibrations, forced}% +course the product of the wave length into the number +of vibrations gives the velocity of sound in any conductor. +An idea of the actual wave length for common +sounds may be had thus: If the middle C of the piano +makes $261$ vibrations per second, and the velocity in +the air of the room be $1,140$ feet, $\dfrac{1140}{261} = 4.36\text{ feet}$, +as the length of the air wave, and for a man's voice it +will be about $\dfrac{1140}{125} = 9.1\text{ feet}$, while the highest note +on a piano will be $\dfrac{1140}{4000} = .285\text{ foot}$, or $3.4\text{ inches}$. In +water the velocity is four times greater than in air, in +wood about twelve times, and in steel about sixteen +times greater; and this will give a corresponding increase +in the wave length. This velocity of sound in +air is, roughly, about a mile in five seconds, or twelve +miles a minute; and at this rate nearly a day and a +half would be needed to go round the earth. + +Air waves, like water waves, are reflected when they +come against a more solid body. Such reflections of +air waves are called echoes. The mere fact of reflection +does not change the length of the wave, as the +pitch of a sound is not altered by having its direction +changed. The law of sound reflection is the same as +that for the reflection of energy in general; viz., the +angle of reflection is equal to the angle of incidence. +Neither does reflection change the velocity of sound +waves. + +The phenomena of echoes are familiar to every one, +for walls, houses, wood, and hills all echo sounds; and +one may roughly determine the distance to such an +\DPPageSep{280.png}{266}% +\index{Musical sounds}% +echoing surface. As one approaches such surface the +time between producing a sound and its return is +shortened, until, when about sixty feet from it, the two +so blend that the echo is no longer heard with distinctness. +The sound has then travelled $120$~feet. + +When sounds are produced at the ends of tubes the +walls of the tube prevent, by reflection, the scattering +of the waves, and the whole motion is kept in nearly +parallel lines, and with slight loss in strength; hence the +utility of speaking-tubes. If the tube be a short one, +and stopped at one end, a new phenomenon appears +for sounds having a wave length about four times the +length of the tube. The sound is much strengthened. +A tuning-fork making say $435$~vibrations per second will +have a wave length of about thirty-one inches. If it be +held while it is vibrating over a tube or vessel of any +sort, between seven and eight inches deep, the increase +in the strength of the sound will be very marked. The +motion in the air is so much swifter than the prongs of +the fork that, while one prong is beating downwards +and thus producing a condensation in the air, the wave +reaches the bottom of the tube; there it is reflected, and +gets to the top just as the prong of the fork has returned +to its normal position. As the fork continues +upward, forming a rarefaction, the rarefaction also +travels down the tube, and is reflected so as to get +back when the prong has returned to its normal position; +so for a complete vibration of the fork the air +wave has travelled four times the length of the tube. +It is possible in this way to make quite accurate measurements +of either the wave length of a sound, its +\DPPageSep{281.png}{267}% +\index{Musical ratios}% +\index{Noise}% +velocity, or the number of vibrations a sounding body +makes per second. This phenomenon is called resonance; +and it is the chief factor in wind musical instruments, +such as flutes, organ-pipes, and the like. +Resonance in general means the ability of a body to be +thrown into sound vibrations by sound waves, and there +are two well-marked cases that need to be considered. +When the stem of a vibrating tuning-fork is held upon +a table the sound in the air is much louder, for the +whole table is made to vibrate at the same rate as the +fork. The table will resound loudly to forks of any +pitch. Such vibrations as are different in pitch from +that belonging to the body itself are called \emph{forced} vibrations. +Resonance of this sort is the function of the +sounding-boards of pianos, the bodies of violins, guitars, +and other similar instruments. + +If two tuning-forks have the same pitch, and one of +them be made to sound, the other one will presently be +made to sound also, though it be several feet away from +the former one. The air waves act upon it like a +pusher upon one swinging; at each return a little more +energy is added, until the amplitude has become great +enough to make the sound audible. Such vibrations +are called \emph{sympathetic}, for they are only effective upon +bodies whose own rate of vibration is the same as that +of the sounding body. Raise the damper to the piano +and sing a sound of any particular note, then listen. +The same note will be heard prolonged by the piano. +The particular string which can give that pitch of sound +has been thrown into similar vibrations, and continues +to sound as it would if caused to in any other way. +\DPPageSep{282.png}{268}% + +The air as a body is too large to have a vibratory +rate of its own, and, consequently, all sounds in it are +properly called forced vibrations; but, when it is confined +in cavities, resonance becomes apparent, and +sympathetic vibrations may be so strong as to be deafening. +That is the case often in locomotive furnace-flues +when the door is opened. One may hear it a mile +or two. The resonance of large rooms sometimes +renders it very difficult to understand a speaker in +them. + +The prolonged sound of thunder has been often explained +as due in some measure to echo from the clouds, +but it is doubtful whether clouds do echo sounds. No +one ever hears the sounds of bells, whistles, or cannon, +or other strong sounds, coming from the clouds, as +would be the case if they reflected sounds appreciably. + +When a single key of a piano is struck, there is produced +what is called a musical sound. There is a definite +pitch that is maintained. Strike half a dozen +adjacent keys at once, and the effect is what is called +a noise, though each component by itself would give a +pleasing sound. A load of stones when tipped from +a cart makes a great racket; yet each stone, if struck +with a hammer, may give out a distinct musical sound. +Nearly every body has its own musical pitch; but, if a +number of bodies with different unrelated pitches are +listened to at once, the effect upon the ear is a discordant +one, and is called a noise. + +When, however, two or more musical sounds whose +pitches stand in a simple ratio to each other are heard +together, they blend so as to form a pleasing combinational +\DPPageSep{283.png}{269}% +\index{Musical instruments}% +sound. Thus, if one makes twice as many vibrations +per second as the other, the sound is a very +smooth musical one, and one is said to be the octave of +the other. If middle C of the piano makes $261$~vibrations, +the octave above will make~$522$, and the octave +below~$130.5$; and these may all be heard at once as a +musical sound. In music an octave is divided up into +eight parts called tones; and these are sung as \emph{do}, \emph{re}, +\emph{mi}, and so on. If a string be stretched between two +points and the distance measured, the sound it will +produce may be called \emph{do} of the scale. If the string +be now shortened by a bridge so as to produce the note +\emph{re}, and the length of the string be again measured, its +length will be found to be eight-ninths of the length +of the first, the note \emph{mi} will be four-fifths, \emph{fa} three-fourths, +\emph{sol} two-thirds, \emph{la} three-fifths, \emph{si} eight-fifteenths, +and the next \emph{do} one-half. As the number of vibrations +a stretched string will make is inversely as its length, +it follows that these fractions inverted will represent +the relative number of vibrations produced by each +member of the musical scale when compared with the +beginning or fundamental one. The following shows +the letters of the musical scale, with their ratios and +vibration numbers for the middle octave of the piano. + +\begin{center} +\TableFont% +\begin{tabular}{cccccccc} +C & D & E & F & G & A & B & C \\[1ex] +& $\dfrac{9}{8}$ & $\dfrac{5}{4}$ & $\dfrac{4}{3}$ & $\dfrac{3}{2}$ & $\dfrac{5}{3}$ & $\dfrac{15}{8}$ & $\dfrac{2}{1}$ \\[2ex] +261 & 293.62 & 326.25 & 348 & 391.5 & 435 & 489.37 & 522 +\end{tabular} +\end{center} + +The meaning of this is that $\dfrac{9}{8}×261 = 293.62$, and +so on, so that the notes of the musical scale stand in +\DPPageSep{284.png}{270}% +\index{Sound, vocal}% +\index{Voice}% +simple ratios to each other; and, if one has the vibration +rate of any one of them, he can compute any +others. Of course any octave above this one will have +simple multiples of these numbers for their vibration +numbers. + +But these numbers signify more than simply this: +they signify that, when a second one is sounding with +C, it will make the number of vibrations represented by +the numerator of the fraction; while C is making the +number indicated by the denominator. Thus, G makes +three vibrations while C makes two. The sounds are +concordant one-third of the time, and the effect is a +pleasing tone. On the other hand, D makes nine while +C makes eight, and the two are in accord but one-eighth +of the time; and the effect is displeasing, and is called +discordant. The smaller the ratio the more musical +and harmonious the sounds; and music is made up of a +succession of sounds standing in such relations to each +other, and, when different ratios are employed, it is only +for contrast, and return is quickly made to these ratios. +The ear will not long tolerate a departure from them. + +It has been stated that sympathetic vibrations would +cause a given body to vibrate. Press down gently a +base C on a piano, so as not to make it sound. Now +strike the C above it, holding down the key for a second +or two. On letting up the latter the sound of the +latter will continue to be heard, but coming from the +lower key, as can be learned by letting up the key, when +it will cease to be heard. If the G above the struck C +be now struck with the same low C held down, the +sound of the G will be heard from the base string, and +\DPPageSep{285.png}{271}% +so one may go up, finding eight or ten strings, each one +of which will make the low C string vibrate, giving out +the sound of the higher string. It is found that each +one of the strings able to do this has a vibration number +which is a simple multiple of the lowest one. The first +one is the octave, making twice the number; the second +one is the fifth of that octave, making three times the +number; and so on, to the upper limit of the piano. + +This means that a piano string is capable of vibrating +in a number of rates,---two, three, four, and so on, times +its own lowest rate, which is always called its pitch. +It is also found that this process is reversible; that is, +if each one of these keys in turn be held down and the +lowest one struck, they will each be set vibrating; and +this shows that the struck string vibrates itself in the +several different pitches represented by the multiples +of its fundamental rate. The sound of a piano string is +therefore a compound sound. In such a compound +sound the lowest one is called the fundamental, and the +others the over-tones, or harmonics. Some of these +harmonic sounds are likely to be stronger than others; +and some may even be so much more energetic than +the fundamental as to nearly drown the latter, so as to +make the pitch of the string to appear an octave or +more higher than it really is. The number and relative +strength of the harmonics in a compound sound make +the difference in the quality of sounds. In all such +instruments as pianos, violins, guitars, and the like +string instruments, the number and strength of the +over-tones depend in a large measure upon how and +where the strings are struck and made to sound. A +\DPPageSep{286.png}{272}% +\index{Ear}% +piano string plucked near its middle point gives a different +sound from what it will give if plucked near one +end, and different in each case if plucked by the fingernail +and by the finger. So the quality of sound can be +much modified by mechanically varying these factors. + +In other musical instruments the sounds are also +compound in a similar way, differing in the number and +strength of the higher harmonics. Some have the +even harmonics, as the second, fourth, sixth, and so on, +stronger; some have the odd ones---first, third, fifth, +etc.---stronger; some have few, and some many. A +flute has but one or two, a violin has twenty; and thus +the character of the sounds of musical instruments is +explained. + +As for the voice, the sound is produced by the vibrations +of what are called the vocal chords, which are +fixed at the junction of the trachea and æsophagus, and +through which all the air to and from the lungs has to +go. These chords are modified in tension by muscles +at will, and so change the pitch of the vibrations. The +cavities of the throat, the mouth, and nose act as resonators +for these sounds and seem to strengthen some +of the constituents, thus giving prominence to certain +ones to the exclusion of others. That the mouth acts +this way may be observed by pursing the lips as if to +produce the various sounds of ah, oo, o, snapping one +cheek with the finger. These sounds will result; +while, with a little trial, one may thus snap a tune +which may be heard through a room, merely altering +the size of the mouth cavity. The cavity of the nose +is as important as that of the mouth. When this cavity +\DPPageSep{287.png}{273}% +\index{Corti's fibres}% +\index{Fibres of Corti}% +is small and narrow, there is produced what is called +a nasal sound. When this is prominent, and is not the +result of a cold, as is sometimes the case, the trouble +is a physiological one, due to the bad shape of the +resonating cavities rather than to careless habits, as is +often assumed by some teachers of expression. Some +different pitch of the voice in ordinary speaking might +be adopted, and thus in some measure prevent the disagreeableness +of the nasal sounds, but no amount of +painstaking can altogether prevent it. That structure +and its acoustic effects are an inheritance in some parts +of the world, as are crooked noses, thick lips, black +eyes, and broad heads in other and different parts of +the world, and is no more to be legislated away than +are these other physiological peculiarities. Neither is +it a proper subject of ridicule, more than lameness or +defective vision. + +If the bell of a locomotive be rung while it is swiftly +approaching one, the pitch of the sound rises until the +engine has reached the observer. As it retreats the +pitch lowers, and the difference in pitch becomes +greater as the velocity of the engine is greater. The +explanation of the phenomenon is, that one judges of +the pitch of a sound by the number of vibrations that +reach the ear per second. Suppose an observer be +distant eleven hundred feet from a source of sound of +one hundred vibrations per second. If both observer +and source remained in place, one hundred vibrations +per second would reach the ear of the observer, and +there would be one hundred more on the way to his +ear. If the observer should continue to go that whole +\DPPageSep{288.png}{274}% +distance of eleven hundred feet to the source of the +sound in one second, he would not only receive all he +would by standing still, but in addition all that were +on the way to him,---two hundred vibrations in all,---or +just twice the number that would reach him if he +remained in place. Now, twice a given number of +vibrations represents a difference in pitch of an octave. +The sound he would hear would be an octave higher +than the sounding body was actually making. Any +less velocity than that supposed would make a corresponding +less difference in pitch, but such velocities as +railway trains have may make a difference in the pitch +of more than a musical tone. Of course, if the sounding +body and listener be separating, a less number of +vibrations will reach his ear, and the pitch will be correspondingly +lowered. One may roughly determine +the velocity of a train of cars by noting the change in +pitch of bell or whistle. Thus, if the difference be, +say a musical semitone,---one-sixteenth,---then the +speed of the train is one-sixteenth the velocity of sound +in air, one-sixteenth of $1,125$~feet, which gives seventy\DPtypo{-}{ }feet +per second, or forty-seven miles an hour. + +The ear is a complicated structure of tubes, muscles, +cartilages, bones, fibres, and nerves. The external +part, or conch, is of but little service in hearing in man, +for it cannot be directed, as can the ears of horses and +cattle. If it stands out from the head so as to have +some use as a collector, it is supposed to be in abnormal +position; but it is not much needed in any case. +The orifice of the ear is known as the tympanum, a +tube a little over an inch in depth and about a quarter +\DPPageSep{289.png}{275}% +\index{Life}% +of an inch in diameter. At the inner end it is covered +with a thin membrane called the drum of the ear. On +the inner side of this membrane, there is attached to +the middle of it a bone fixed to a kind of hinge, so that +any movement of the drum of the ear, in or out, makes +this bone to move in a similar way. Then follows a +network of bones and cartilages, and a set of fibres +known as Corti's, of different lengths, and whose function +has been supposed to be for sympathetic vibrations. +%[Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{3.5in}{289a} + \end{center} + \Caption{34}{Diag.\ 34.---The Ear.} +\end{figure} +There are in the neighborhood of $4,000$ of these +fibres, each one adapted to vibrate at a different pitch. +Then follow the nerve terminals and the acoustic +nerve itself, which goes to the base of the brain, where +its function as an acoustic instrument ends with the +delivery of its peculiar motions, interpreted by consciousness +as sound. + +It is easily seen that the whole structure is one +adapted to receive vibratory motions from the air, +within prescribed limits, and transmit them inwards +\DPPageSep{290.png}{276}% +\index{Life, definitions of}% +where they can be interpreted. The tube itself possesses +resonating properties like any other tube. The +membrane is shaken to and fro by sound vibrations, +and this movement is handed on to each distinct part +until the nerve itself is shaken. From beginning to +end, it is only the transfer of a particular kind of +motion,---what is called mechanical,---perhaps transforming +it from longitudinal to transverse vibrations. +That it is so extremely sensitive as to be affected appreciably +by motions so slight as the ten-millionth of an +inch is a marvel, and shows that mechanical motions of +translation, though on a scale of molecular magnitudes, +is able, through the proper avenue, to affect the mind +and develop consciousness, which experience enables +the individual to interpret by direct inference. + +Let one reflect upon the facts furnished in great +abundance by physical science,---that all the data which +comes to the mind through consciousness, and which +furnishes what is called experience, is simply motion +of some sort. Touch, producing pressure upon the +surface of the body, finds a suitable nerve to transmit +to the base of the brain that kind of a disturbance; +sight, another kind of disturbance to the optic nerve, +transmitted to the same place; hearing, still another +kind of motion given to another kind of nerve running +to the same headquarters. So, by means of motions +of various sorts man determines his place in the +universe, and learns how he may adjust himself to it. +%\DPPageSep{291.png}{277}% + + +\Chapter{XI}{Life}{277} + +\First{Any} scheme of physics which fails to present that +great body of physical phenomena exhibited by living +things, both vegetable and animal, must be incomplete. +Many of these phenomena have seemed to be so remote +from ordinary mechanical operations that, in the +absence of definite knowledge concerning them, their +origin, factors, and relations to subsequent phenomena, +it is not to be wondered at that they were long thought to +be due to some peculiar force residing in a living thing, +\index{Force, vital}% +\index{Vital force}% +\Pagelabel{277}% [** PP: Note to p. 277 clearly points here] +\Pagelabel{279}% +which was not to be attributed to the general endowments +of matter, but only to be found in certain organized +forms of matter, which organization it had itself +built up as a \emph{habitat}. It was conceived to exist apart +from any material organization as a kind of entity. +The difference between a living and a dead animal was +thought to be simply one of the presence or absence +of that entity called life. It was thought to be able to +effect changes in matter which the ordinary physical +and chemical forces could not possibly do; and many +of the chemical products of living things were supposed +to be formed only through its agency; and still +more than that: it was held to be capable of ``suspending +the action of chemical laws.'' That the stomach +\DPPageSep{292.png}{278}% +\index{Cell structure}% +\index{Protoplasm}% +itself was not digested by the gastric juice it secreted +was held to be proof of its control over chemical +operations. + +There have been many attempts to define life, but +the efforts have not been very successful. Thus Kant +defines it as ``an internal principle of action;'' Treviranus, +``the constant uniformity of phenomena under +diversity of external influences.'' Bichat, ``Life is the +sum of the functions by which death is resisted.'' +Duges calls life ``the special activity of organized +beings.'' De~Blainville's and Compte's definition runs +thus: ``Life is the twofold internal movement of composition +and decomposition, at once general and continuous;'' +and Spencer's is ``the continuous adjustment +of internal relations to external relations.'' It will be +observed that in all of these what is described is a +series of processes, or a body of functions belonging to +certain structures, rather than an entity,---a description +of what life does rather than what it is. + +Analogous difficulties were met in the attempts to +define other of the so-called physical forces. Thus +light was supposed to be a created something. The +corpuscular theory of it represented it as consisting +of particles of some sort that ordinary matter could +absorb and eject, and which, therefore, had an existence +independent of matter. The establishment of its +being but wave motion in the ether completely destroyed +the notion of its having an objective, independent +existence. + +Heat, too, was supposed to be a kind of imponderable +matter, and certain phenomena in ordinary matter +\DPPageSep{293.png}{279}% +\index{Molecular stability}% +depended upon its presence or absence; it, therefore, +was supposed to be an entity, and to have an independent +existence. Experiment showed it to be but a +particular kind of motion, so the idea that there was +any such thing as heat was abandoned. + +Electricity and magnetism were supposed to be +fluids; and some of the early terminology still survives +in popular speech to-day, as when one reads that the +electric fluid struck a tree or entered a house. Nevertheless, +nobody now believes that either of them is +a fluid, or has an existence independent of matter. + +The regular movements of the planets were thought +to require intelligent directive power to keep them in +their orbits; but now the gravitative property of matter +itself is held to be quite sufficient to account for all +the observed facts, and the extra material directive +force is held to be an entirely unnecessary assumption. + +The discovery of the conservation of energy, covering +every field that has been investigated, led to the +growing conviction that there are no special forces of +any kind needed to explain any phenomena. What +seemed probable forty years ago, to those who were +conversant with the facts,---that vital force as an entity +has no existence, and that all physiological phenomena +whatever can be accounted for without going beyond +the bounds of physical and chemical science,---has +to-day become the general conclusion of all students of +vital phenomena; and vital force as an entity has no +advocates in the present generation of biologists.\footnote + {See Appendix, \Pageref{p.}{400}.} +The +term has completely disappeared from the science, and +is only to be found in historical works; and every +\DPPageSep{294.png}{280}% +phenomenon which was once supposed to be due to it +is now shown to be due to the physical properties of a +particularly complex chemical substance known as protoplasm, +which is the substance out of which all living +things, animals and plants, are formed. This protoplasm +is entirely structureless, homogeneous, and as +undifferentiated as to parts as is a solution of starch, +or the albumen of an egg. Minute portions of this +elementary life-stuff possess all the distinctive fundamental +properties that are to be seen in the largest +and most complicated living structures. It has the +power of \emph{assimilation},---that is, of organizing dead food +into matter like itself,---and, consequently, what is +called growth. It possesses the ability to move---that +is, of visible, mechanical motion, which is technically +called \emph{contractility}; and it possesses \emph{sensitivity}---that +is, ability to respond to external conditions. + +It was formerly thought that the cell was the +physiological unit, a cell having walls differently constituted +from the substance enclosed, also a nucleus; +but as the microscope was improved, and anatomical +research continued, it became evident that the cell, +with its more or less complicated structure, was itself +built up by the structureless protoplasm. As before +stated, it is a highly complex substance, chemically +considered, made up of many atoms of carbon, hydrogen, +oxygen, and nitrogen, with a small number of +atoms of sulphur and phosphorus,---more than a thousand +of them in one molecule; and there appears to be +a great number of varieties of it. A small pellicle of +this substance, like a minute bit of jelly, without any +\DPPageSep{295.png}{281}% +\index{Growth of crystals}% +\index{Growth of lobster}% +\index{Matter, living}% +parts or organs, possesses its various attributes in equal +degree in every part. Any particular portion can lay +hold upon assimilable material, or digest it, or be used +as a means of locomotion; so that what are called +tissues of animals and plants are only the fundamental +properties of the protoplasm out of which they have +been built---thrown into prominence by a kind of division +of labor. The protoplasm organizes itself into +cells and tissues in the same sense as atoms organize +themselves into molecules, and molecules into crystals +of various sorts, having different properties, that depend +upon the kind of atoms, their number and +arrangement in the molecule. + +The greater the number of atoms in a molecule the +less stability does it have, and especially is this the case +with molecules containing nitrogen. Many of its compounds +are so unstable as to be liable to explosive +disruption. This fact makes it easy to understand how +there exists, in a mass of such molecules no larger than +the minute ones seen in the microscope, conditions for +internal motions in the nature of explosions. + +Let it be granted that atoms are in the neighborhood +of the fifty-millionth of an inch in diameter; then, +if a thousand of them are organized into a molecule, its +diameter would be about the five-millionth of an inch. +A speck of protoplasm, one ten-thousandth of an inch +in diameter, would require not less than five hundred +such molecules in a row to span it; and there would be +no less than one hundred and twenty-five millions of +such molecules in the small mass. Some of these molecules +would be less stable than others on account of +\DPPageSep{296.png}{282}% +\index{Food}% +the internal motions that all the time are present. +Physical disturbances, external to such a mass, such as +temperature, ether waves of light, and chemical re-actions +of any sort, and so on, can induce and add to the +disruption and other changes going on, and visible motions +might be expected to follow. + +That such external agencies can bring about visible +motions of microscopic particles has long been known. +A few small bits of camphor dropped upon the surface +of clean water in a saucer will begin to move about in +a remarkable way. They will spin round, and travel +from place to place, and dodge each other in a manner +strongly like living things. A little gamboge, which is +a reddish-yellow gum used as a pigment, if rubbed up +in water and looked at through a microscope, will be +seen to have its particles in constant motion like animalcules. +This is known as the Brownian movement, +and is caused by temperature changes between the +particles and the water. Such phenomena are rather +extreme cases of the re-action of external molecular conditions +upon a small mass of matter, resulting in mechanical +motions. In protoplasm there is added to +these same external ones others of the nature of molecular +explosions within the mass, and together they +give rise to a number of effects, in which the transformed +energy shows itself in redistributing the molecules, +absorbing additional material, and movements of +other sorts. + +Biological researches within the past few years have +added vastly to our knowledge of protoplasm and its +properties; and there is no longer any question that its +\DPPageSep{297.png}{unnumbered}% +%[Illustration: ] +\begin{figure}[hp] + \begin{center} + \Graphic{\linewidth}{297a} + \label{fig:frost} + \end{center} +\begin{minipage}{\linewidth} +\scriptsize% +The above picture is copied from a photograph. It represents the plume-like +forms assumed by water when crystallized in a basin. The similarity it presents +to vegetable forms is very striking. One may often see on frosty window-panes +fantastic imitations of organic things which forcibly suggest vitality. They are +too common to be considered coincidences. +\end{minipage} +\end{figure} +\DPPageSep{298.png}{283}% +\index{Muscles}% +qualities are the expression of the various movements, +chemical and physical, and belong to it simply as a +chemical substance. Chemists have synthetically +formed out of the various elements a vast number of +substances that were not long ago believed to be formed +only by living things; and there is but little reason to +doubt that, when they shall be able to form the substance +protoplasm, it will possess all the properties it is now +known to have, including what is called its life; and one +ought not to be surprised at its announcement any day. + +Some of the phenomena exhibited by bodies called +inorganic, such as minerals of many kinds, possess +properties that are very like those supposed to belong +solely to living things. A spider or a lobster will have +a new leg or claw grow to replace one lost in any way. +In like manner a crystal will replace a corner or side or +any defacement so as to complete its symmetry before +it will begin to grow elsewhere, and this in cases where +the crystal has been defaced or incomplete for millions +of years, as is found to be the case sometimes in geological +specimens. Such phenomena have led some of +the most thoughtful and best informed naturalists to +query whether the evidence we have does not lend +much support to the theory that \emph{matter itself is alive}, +and that the difference we observe in things is simply +one of degree rather than of kind. See \hyperref[fig:frost]{opposite page}. + +In the brief space of this chapter, only an outline of +the relations between vital and physical phenomena can +be given, and of these, only a few of the more prominent +ones. It will suffice to show that such phenomena +as assimilation and growth, movement and irritability, +\DPPageSep{299.png}{284}% +or sensitivity, have antecedents of physical energy in +the same sense as the movements of an electric motor +have physical antecedents in electric currents, dynamos, +steam-engine, and furnace. + +The food of an animal consists almost altogether in +highly complex molecular compounds. It may be said to +be matter stored with energy. A pound of bread may +have the mechanical equivalent of twelve thousand heat +units, and if burnt in an engine would be better for +heating purposes than a pound of coal. When this has +been digested, and has done its work in the body, the +excreted products are of course equal in weight to the +original pound, for no kind of a physical or chemical +process affects the quantity of matter in any degree; +but the products themselves represent much less complex +compounds, and the energy has been distributed +through the body, carrying on its various operations. +There is, first, that of ordinary movement, which can be +measured in foot-pounds, as work of any kind may be. +The blood in the arteries and veins has to depend upon +a kind of hydraulic apparatus to keep it in motion. +The temperature of the body demands a supply of heat +measurable in heat units to maintain it, while the +repair and waste going on through the whole body of +all animals implies a distribution of the material necessary +for the maintenance of the integrity of the tissues, +as well as a separation and removal of the used-up material; +that is, the material that has lost all its available +energy. The energy for doing all this of course comes +from the food, so the question is not as to its source +and quantity, but it is, How is this transformation of +\DPPageSep{300.png}{288}% +\index{Nerves, their functions}% +energy in the body effected? Is it direct, or is it indirect? +This is the same as asking as to the mechanism +in the body, by means of which energy supplied is transformed +to meet the various wants of the body. + +Roughly, there are five different kinds of motion to +trace the antecedents of in the body of any of the +higher animals. First, there is the common mechanical +motions of the bony framework, which transport the +body from one place to another, or change the position +of a part with respect to the rest, as when one moves +an arm. Second, there is the motion of a muscle, +wholly different in character from the first, for the +shape of the muscle changes by contracting in length +and increasing in diameter. The muscles are so attached +to the bones that the contractions of the one +cause the others to change their positions. The muscular +contractions of the heart, arteries, and veins keep +the blood circulating; and the same is true for the processes +of digestion, breathing, etc. + +Third, there is the motion constituting the temperature +of the body, which, as has been explained, is altogether +atomic and molecular in its nature, and is, +therefore, in strong contrast with the other two. + +Fourth, there is a kind of motion that is going on +throughout the body of the nature of transpiration, in +which solids, liquids, and gases are passing through the +various membranes without rupturing them. In the +lungs there is an exchange of gases, oxygen going one +way and carbonic acid gas going the other. In all the +mucous-membrane-lined cavities there is more or less +liquid oozing through the walls continuously, and there +\DPPageSep{301.png}{286}% +is no tissue so dense but protoplasmic masses do not +move into or out of apparently with ease. They go +through the walls of veins and arteries as if the latter +were porous bodies, though no visible pores have ever +been discovered in them. + +Fifth, there is the motion in the nerves, in the nature +of a longitudinal wave, and the velocity of which is in +the neighborhood of one hundred feet in a second, +which, though it is slow compared with sound waves or +light waves, is fast when compared with the other +motions of the body. He is a swift runner who can +run at the rate of thirty feet a second for any distance. + +The contraction of a muscle is to be measured in +fractions of an inch per second. The motion of heat, +measured as a rate of conduction, is exceedingly small +in the animal body,---probably not the hundredth of an +inch per second. The transpiration, or osmotic action, +is also a relatively slow movement, so that a velocity of +one hundred feet per second, which is upwards of a mile +a minute, is really rapid. + +How and why the bone moves we know: it is because +the muscle that is attached to it contracts; but how is +energy spent to make a muscle contract? As a matter +of fact, when a muscle contracts it evolves a considerable +quantity of carbonic acid gas and water; it also +becomes acid, all of which imply chemical actions, for +these are chemical products. Carbonic acid gas and +water are the chief products of the combustion of such +material as foods, for they are made of what are called +hydro-carbons (combinations of carbon, hydrogen, and +oxygen chiefly); and when these elements re-combine, +\DPPageSep{302.png}{287}% +\index{Nerves, their functions}% +forming water and carbonic acid, there is always a relatively +large but definite amount of energy given out +in the form of heat, and this effect is independent of +time or place; that is, the same amount is developed +whether the process goes on fast or slow, or whether it +takes place in a furnace, in the body, or by slow decomposition +called rotting. When it goes on faster than +the heat can be conducted or radiated away, the temperature +rises and we say the body is hot. When the heat +generated is at once employed to do work, as in a steam-engine, +the temperature of it is reduced proportional to +the work done. When this takes place in a contracting +muscle better results follow, for conduction and +radiation within a muscle can take place at only a slow +rate; so the temperature rises, and this explains the +sensation of warmth resulting from muscular exercise. +The increase in perspiration is also partly due to the +same re-action of decomposition, as water is one of the +products. When the muscle in contracting does additional +work, as in raising a weight, a corresponding +amount of decomposition takes place, and the heat is +but transient, as it is at once transformed into the +muscular motion, which is as much mechanical in its +nature as is the movement in a steam-engine. + +The muscle is quite like a spiral spring, which may +contract upon itself and do work by contracting. + +It is not the substance of the muscle itself that undergoes +the change of disintegration, evolving water, carbonic +acid, and other products; but there is evidence +that the muscle secretes a particular substance called +\emph{inogen}, the rapid decomposition of which causes the +\DPPageSep{303.png}{288}% +\index{Corn, life of}% +\index{Egg}% +contraction. As this substance can only be replaced at +a definite rate and in a definite amount, it is clear that +the work of a given muscle is limited by the physiological +processes that precede it. The rate of work of a +muscle is then determined by the rate at which inogen +can be secreted by the muscle, and work done beyond +that rate results in muscular exhaustion, which in its +early stages is called weariness, and requires repose for +fresh accumulation. Excessive draught upon the +muscles reduces their ability to secret inogen, and their +degeneration follows. + +Muscular contraction is satisfactorily accounted for +without assuming any vital force. It has a purely +physical origin, the structure itself acting as a kind of +mechanism for transforming the chemical energy supplied +in food into the mechanical forms of energy +represented by the various movements of the body, +external and internal, which have already been mentioned. + +That physical and chemical agencies bring about new +movements is of course well understood. Especially +clear is this for such nerve actions as accompany the +special sensations of sound, sight, touch, and the rest. +That the disturbance is properly described as a movement +is apparent when it is found that it has a rate of +progression, as before stated, of from one hundred to +three feet per second. Whether such movement be +similar to a sound wave in a rod or tube, or to an electric +disturbance, makes no difference so far as the transformation +and transference of energy are concerned. +For sound there is the antecedent of vibratory motions +\DPPageSep{304.png}{289}% +\index{Growth}% +in the air; for light, waves in the ether; for touch, +mechanical pressure; for taste, chemical solution; and +for smell, gaseous substances with definite constitutions +and rates of vibration. These represent the ordinary +stimulants to action of such nerves, and so are commonly +understood to be the source of disturbance; but +every one of these so-called special nerves may be +excited to action by other agencies than the common +or normal ones, and the effect is the same. Thus, the +optic nerve may be stimulated by pressure, by cutting, +pricking, thumping, and electricity, and the effect is the +sensation of light; and, in the absence of other sources +of information as to the origin of the sensation, no one +could tell which of these was the originating one. +Every one of them, however, represents some form of +energy spent upon the nerve. What is important to +note about it is this,---the nerve transmits an impulse +it receives, quite indifferent as to its source, and is +interpreted as a definite sensation, quite independent +of its origin. The latter is only an inference, and is, +therefore, liable to be \DPtypo{eroneous}{erroneous}. + +But there are several other kinds of nerves, each +with some different function from the rest. Thus there +are nerves running to muscles, causing them to contract, +called motor, or efferent, nerves; secretory nerves, +to glands that cause secretions; vascular nerves, that +cause contraction or dilatation of the walls of blood-vessels;\DPnote{** Only instance,} +inhibitory nerves, that affect other nerves so +as to moderate or entirely stop their action; reflex, or +afferent, nerves, which convey disturbances to the brain +or other nerve centres, but which cause no sensation; +\DPPageSep{305.png}{290}% +and still others known to exist, but the special functions +of which are unknown. + +To describe the action of any nerve is to describe +the transmission of energy in greater or less amount, +and transmission in all cases requires time. This does +not mean that the energy which does the special work +of moving muscles or the chemical transformations of +foods into tissues is transmitted by the nerves, but +that the transformations of energy already present in +each place where the work is to be done are controlled +by nervous energy in the same way as a local galvanic +circuit is controlled by a relay, or the explosion in a +mine is determined by an electric spark. The energy +available for all the purposes of an animal, including +man, exists in the material of the body. The activity +of protoplasm in the various cells transforms the various +food stuffs into the proper substances needed. The +energy is already present; it is only differently distributed +by protoplasm; and nervous action determines +what changes, if any, shall go on at a given place. + +Temperature determines whether any of the physiological +process shall go on or not. Plants and animals +of a low order, such as snakes, frogs, and fishes, may be +frozen without injury. Some of the minuter forms of +life can withstand arctic winters, for there is an abundance +of insect life in those regions. On the other +hand, a temperature of~$140°$ is destructive to the life of +everything except the seeds and spores of a few microscopic +beings. Some of these have been known to +survive a temperature of~$200°$, continued for an hour +or more; but nothing has been found that can withstand +\DPPageSep{306.png}{291}% +\index{Matter, living}% +\index{Toepler-Holtz electrical machine}% +the boiling temperature of~$212°$. The retarding +influence of cold upon vital processes can be understood +by considering that special chemical compounds require +special temperatures to form; and, if energy has to be +supplied to maintain the proper temperature, so much +the less will be at disposal for other processes. If life +processes were other than physical, it might be expected +that they would not be quite so rigidly conditioned by +physical surroundings. + +There is a distinction between a living plant or animal +and the seed or spore or egg out of which they +grow. Both are commonly spoken of as living things, +but the processes that constitute life in the one are not +present in the other in any degree; thus, for example, +growing corn and the grain of corn from which the +plant started. The grain of corn may be kept in a +suitable dry place for several years without any apparent +change, unless it be some loss in weight due to +evaporation from it. How long it may exist thus and +still be able to grow if planted is not known. Grains +of wheat found with Egyptian mummies buried three +thousand years ago have been said to grow, but there +is much doubt about it, and botanists do not credit +the story. A few years' keeping in moister climates +destroys their ability to grow, and farmers always +choose seed corn from last year's growth, which is an +indication that there is a process of slow deterioration +going on that ends after no long time in utter inability +to grow under any conditions. This ability to remain +for several years in a nearly stable condition is a property +of the seed that does not belong to the plant; for, +\DPPageSep{307.png}{292}% +when growth has once really begun, it must keep on +growing or die: arrest is impossible, which seems to +show that life is a process rather than a condition, and +the grain of corn is simply a combination of materials +where, under suitable conditions, life may begin. + +The constitution of corn is well known; that is, the +elements out of which it is built up, and the proportionate +parts of each. Like other kinds of food, it has +carbon, hydrogen, oxygen, nitrogen, for the chief constituents, +and in addition a little sulphur, phosphorus, +iron, potassium, and a trace of some others. These, +when organized as they are in a grain of corn, form a +very complex body indeed. There are not only molecular +groups of many sorts, but these are segregated +into families, so that bodies of one constitution are all +in one locality, and bodies of other constitutions in +other separate localities, but definitely arranged so as +to be available when the life process begins. Once +formed, it appears to be as inert as a crystal of any +sort, and no change happens to it until such physical +conditions as heat and moisture are provided. These +it absorbs and transforms; a sprout appears, then a +root, each with different functions, one for absorbing +ether waves, the other for absorbing water. The +energy of ether waves is utilized in digesting carbonic +acid and building up the structure, and the +growth is simply the addition of materials gathered +in this way and elaborated into similar protoplasmic +form and structure. Growth implies transformation +of one substance into the material of another, and is +effected by means of energy from external sources. +\DPPageSep{308.png}{293}% +\index{Atoms, life associated with}% +\index{Foster, Dr.\ Michael, quoted}% +The energy of a stalk of corn may be found by using +it as fuel and finding its heat units per pound. It has +about the same value as wood. The corn itself has +somewhat higher value, which shows it to have a more +complex molecular structure, and is correspondingly +less stable. + +In like manner an egg, say that of a hen, possesses a +degree of stability that does not belong to it after it +has begun to grow. It may be kept with some care +for a few months and retain its ability to develop into +a chick; yet it ultimately wholly loses its possibility, +which shows that slow changes of the nature of disintegration +are going on that cannot be arrested. The +physical condition necessary to initiate the growth of +the egg is simply one of temperature. One hundred +and four degrees continued for three weeks completes +the process. When one reflects upon the nature of +heat,---that it is but vibratory motion,---he can at once +see that energy has been supplied to a complex mass +of matter and it has been chemically transformed. +There are new chemical products and new properties +produced; and however wonderful the completed product +may be, the factors at work to produce it have been +absolutely physical from beginning to end. After +growth has once begun the process must continue, at +the peril of quick degeneration on stopping; so that an +egg, like the grain of corn, seems to be a material +structure where life may begin, rather than a living +thing itself. Such a distinction has not, however, +been made in the literature of the development of living +things. It has, perhaps, only a philosophical importance; +\DPPageSep{309.png}{294}% +but, if there are any who would still hold that +life is a something \textit{sui generis}, that may be considered +apart from some material structure and not as a transformation +process, it will be well for such to inquire +what can become of such life as a grain of corn or an +egg has when either of them is cooked, or when either +of them is left for months or years and they rot. At +first it is in the grain of corn or egg. If it be an entity +of any sort it must be somewhere else after leaving +either the one or the other. On the other supposition +the question does not arise at all, for it is plain that +disintegration destroys the molecular arrangement, and +with the destruction of that the properties of such +organizations of matter must go also; for the properties +of a mass of matter are, by general agreement, the +result of the arrangements of the matter. Woody fibre +and starch are of precisely the same chemical composition, +but the properties of the two are far from being +identical. + +What, then, is the distinction between what is called +living and dead matter? One is able to transform +energy for its maintenance, and the other seems to be +wholly inert; yet, if analyzed, both may be reduced to +precisely the same amount of elements. + +An analogy may make the distinction plainer. A +maker of physical instruments may make what is called +a Toepler-Holtz electrical machine. It is composed of +wood and glass and brass and tinsel and tin foil, and +possibly of other materials. Each one of these is got +at a different place from the rest, and all are assembled +in the shop of the maker. The individual parts are +\DPPageSep{310.png}{295}% +\index{Fields, physical}% +\index{Fields, thermal}% +\index{Physical fields}% +shaped in particular ways, and these are at last fixed in +their appropriate places. The machine is done; but it +has never generated an electric spark, and one could +discover no electricity about it. Indeed, there is none, +any more than when the material was unshapen and +lying upon his bench. If the proper kind of energy is +spent upon it, however, it at once becomes electrified, +and electrical energy may now be got from it in indefinite +quantity, dependent wholly upon the proper turning +of the crank. If that be turned the wrong way, or +if it be stopped, the electricity soon quite disappears. +Now, it is the function of such a machine to transform +mechanical energy into electrical, and it does this so +long as energy is furnished for transformation and the +integrity of the machine is maintained. If one weighs +the machine before it has been worked, and also while +it is electrified, he will find no difference. If the brass +buttons get off or displaced, if the belt gets broken or +the glass cracked, the machine will weigh just as much +as it did when they were in place; but the property of +the machine to transform energy will be destroyed, and +it may be as useless for the purpose as a coffee-mill +would be. One might speak of the whole machine as +an organism,---its wood and glass and brass as its molecular +composition, its function depending upon each +of these being in its appropriate place, and nothing +more. It can only exercise that function when energy +of the proper sort is turned into it. If its molecular +composition is deranged in any of a dozen different +ways, no one is surprised that it no longer responds to +the turning of the crank. If the complete and perfect +\DPPageSep{311.png}{296}% +machine be called living, then the one with its +parts disarranged so it can no longer perform its functions +might be called a dead machine. + +The egg may be likened to the machine. So long as +its molecular arrangement is intact, so long it is competent +to transform the heat supplied to it and exhibit +new properties. When the molecular arrangement is +interfered with, whether from within or without, its +function as transformer ceases, and we call it dead. + +It may be said, and often has been, that every living +thing has an ancestry of living things; and in human +experience it is true. It is sometimes said that one +cannot get out of a mass of matter what is not in it, +which, in this case, might imply that matter itself is +alive, as suggested a few pages back, though I have +never heard any one so conclude. If one would apply +this dictum, let him settle with himself before turning +a new electrical machine whether the electricity he is +to get from it is or is not in the machine, and how, if it +be in the machine, he can get an infinite amount from +it by simply turning the crank. He may reach the conclusion +that what can be got out of a mass of matter +depends upon its composition and structure. + +In conclusion, one perhaps can do no better than to +quote the words of Dr.\ Michael Foster, Professor of +Physiology, University of Cambridge, England, as to +the properties of protoplasm. ``The more these molecular +problems of physiology are studied, the stronger +becomes the conviction that the consideration of what +we call structure and composition must, in harmony +with the modern teachings of physics, be approached +\DPPageSep{312.png}{297}% +\index{Electrical field}% +\index{Fields, electrical}% +under the dominant conception of modes of motion. +The physicists have been led to consider the qualities +of things as expressions of internal movements; even +more imperative does it seem to us that the biologist +should regard the qualities of protoplasm (including +structure and composition) as in like manner the expressions +of internal movements. He may speak of +protoplasm as a complex substance, but he must strive +to realize that what he means by that is a complex +whirl, an intricate dance, of which what he calls chemical +composition, histological structure, and gross configuration +are, so to speak, the figures; to him the +renewal of protoplasm is but the continuance of the +dance, its functions and actions the transferences of +the figures\ldots. It seems to us necessary, for a satisfactory +study of the problems, to keep clearly before +the mind the conception that the phenomena in question +are the result, not of properties of kinds of matter, +but of kinds of motion.'' + +If such be the case, it is clear that the solution of +every ultimate question in biology is to be found only +in physics, for it is the province of physics to discover +the antecedents as well as the consequents of all modes +of motion. +%\DPPageSep{313.png}{298}% + + +\Chapter{XII}{Physical Fields}{298} + +\Section{I.---THE THERMAL FIELD} + +\First{When} a mass of matter of any kind possesses +energy of such a kind as to be able to impart some or +all of it to the medium about it, whether that medium +be the air or the ether, which transmits or distributes +it outwards with a velocity which depends solely upon +the ability of the medium to transmit energy, and not +upon the source of it, the energy so distributed is +called radiant energy. + +The term was first applied to the energy radiated by +a hot or luminous body, from which the heat was said +to be radiated away, the motions of the molecules of +the hot body being transformed into wave motions in +the ether. The wave motion thus set up is known to +be competent to set other masses of matter upon +which it falls into vibratory molecular motions, similar +to those that originated the waves. In other words, +they are capable of heating other matter. The space +within which such effects can be produced will evidently +be limited only by the distance to which the +wave motion is transmitted, and this in turn depends +upon the special medium concerned---in this case the +ether---and the uniformity of its distribution. As has +\DPPageSep{314.png}{299}% +\index{Inductive action}% +been already pointed out, the ether transmits such +wave motions in straight lines, and to an indefinite +distance,---so great at least as to require not less than +five thousand years to cross the space accessible to our +observations. As such waves of all wave lengths +travel with equal velocities, and as all known bodies +of matter are continually radiating waves of many +wave lengths, it follows that in reality every molecule +of matter sets the whole visible and invisible physical +universe in a tremor. The magnitude of this effect is +not now under consideration. + +The space external to a body within which the body +can act in this physical way upon other bodies, so as to +bring them into a condition similar to its own, is called +its \emph{field}. The heat or thermal field of a mass of +matter of any size and of any temperature must, +therefore, be as extensive as the universe, unless the +ether absorbs the energy to some extent and becomes +itself heated. At present there is no evidence that +such an effect is produced. Some astronomers have +inferred that absorption takes place, else the whole +surface of the sky would be bright with the multitude +of stars that occupy it. On the other hand, if absorption +did take place in a manner at all comparable +with gaseous absorption, it would be selective in some +degree, and the more distant stars would have a color +different from those closer to us; and the colors of all +stars would depend upon their distance from us. If +such a condition had been observed, it would be conclusive +evidence of absorption in the ether, but it has +not been observed. +\DPPageSep{315.png}{300}% +\index{Earth, a magnet}% +\index{Electrical waves}% +\index{Magnetic field}% +\index{Waves, electric}% + +Furthermore, the perception of light implies a definite +though a small amount of energy; and, as the +energy of ether waves from a given point upon a +surface varies inversely as the square of the distance +from the point, it follows that there must be some +distance from it where the energy upon the retina +must be too slight to affect it; and hence the inability +of the eye to perceive the light could not be +used as an argument against the existence of the waves +altogether. At the rate of $186,000$ miles per second +light travels $5,800000,000000$ (nearly six millions of +millions of miles) a year, and in five thousand years, +which is the distance of some of the more remote +stars, $29000,000000,000000$ (twenty-nine thousand +millions of millions) of miles. This, therefore, is the +known length of the radius of the thermal or light +field of a heated or luminous body; and, as such heat-producing +waves are radiated in every direction about +the body, the sphere having such a radius represents +the space within which any or every atom of matter +can affect other atoms to heat them. + + +\Section{II.---THE ELECTRICAL FIELD.} + +The phenomenon called electrical induction, by +which one body becomes electrified by simply being +in proximity to another body which is electrified, is +another illustration of both a \emph{field} and its property, +depending altogether upon its origin. But an electric +field differs in a marked way from a thermal field. + +Imagine a sphere---say a cannon-ball---to be electrified, +and be isolated a long way from any other body. +\DPPageSep{316.png}{301}% +Its effect upon the ether about it would be equal in +every direction. Practically, it would be distributed as +the thermal field would be; and, if the strength of the +field should be measured in any way, it would be found +to vary inversely as the square of the distance from +the body that produced the field. When such an electrified +body is adjacent to other bodies, as is necessarily +the case with every electrified body upon the +earth, the strength of the field at a given point is +found to depend upon the size, the nearness, and the +quality of the adjacent body. Suppose the adjacent +body were a similar cannon-ball, and its distance from +the former one foot. Then the strength of the field +would be found to be greatest between them, and to be +very weak in the space equidistant and on the opposite +side. One may get a mechanical idea of the condition +of things by imagining straight lines drawn from the +electrified body when out in space as if they were rays +of light, evenly distributed in space. When, as in the +second case, another ball is near to it, these rays crowd +around the second one and apparently are absorbed by +it; and these may now be represented by the same +lines, starting at the same places as before, but sweeping +in curves to the second, with only here and there +one to escape into the unoccupied space. The nearer +the two are together the more closely are these lines +crowded together in the space between; and, as the +number of these lines in a given area represent the +strength of the electric field, it is plain the field is +strongest where the lines are most crowded. On the +other hand, if the second ball had been made of glass, +\DPPageSep{317.png}{302}% +\index{Chemical field}% +\index{Fields, chemical}% +the field would have been changed but little, for glass +is a substance having but little absorptive power for +electric rays; that is, it is not much affected by an +electric field. When such an electrified ball is suspended +in an ordinary large room, these lines, representing +the field, are distributed about the room in a +manner that depends altogether upon the kind of +material there is in the room. The metallic objects, +such as a stove, a steam-radiator, a gas-pipe, and the +like, will divide the field between them, not equally, +for the nearer ones will have the most, and other parts +of the space in the room will have but a trace of it. +The great distinction between the electrical and the +thermal field will be apparent when one reflects upon +what the latter would be for the same cannon-ball made +hot and suspended, in the same manner, in the room. +The rays go straight in every direction, and are not +deflected by proximity to other bodies. The one is +uniform in every direction about it; the other is warped +by the presence of other bodies. + +An electric field, which is merely the ether in a +condition of stress, electrifies the bodies upon which it +acts; that is to say, it produces in them a condition +similar to that of the body that produced the field. It +does not heat them: it electrifies them. The process +is ordinarily called induction. If one would follow +mentally the mechanical conditions and changes that +take place when this process of induction takes place, +let him imagine the two cannon-balls suspended in +a room a few feet apart, and one of them to be +suddenly electrified artificially in any kind of a way, +\DPPageSep{318.png}{303}% +\index{Crystallization}% +as by connecting it to a charged electrical machine for +an instant. The re-action upon the ether will at once +begin. The stress into which it will be thrown will be +propagated outwards as a wave, with the velocity of +light, and equally in every direction about it too, until +the advancing wave reaches the second ball, when the +absorption so reduces the stress that other parts of +the field can move towards it, thus distorting it; for +at the outset every part of the wave moved in a radial +line. This must be the case unless the field acted +intelligently instead of mechanically, and knew where +it was to go beforehand. Of course no one would +suppose that, but the remark is made to emphasize +the necessity for the mechanical steps in order to have +clear ideas of what has happened. The whole would +happen in so small a fraction of a second that it would +be exceedingly difficult to measure it, but the rate at +which a thing is done does not necessarily modify the +way of doing it. + +\Section{III.----THE MAGNETIC FIELD.} % + +The distribution of iron filings about a magnet gives +one a very definite mechanical conception of the shape +and properties of a magnetic field. It has before been +remarked that the shape of the field depended upon +the form of the magnet, and when this was altered the +field changed its form. That it too represents a condition +of the ether seems unquestionable. That it is produced +by the arrangement of the molecules of the magnet +is also certain; but that presumes that the atoms +themselves are magnets, each having its own field. +\DPPageSep{319.png}{304}% +\index{Mechanical field}% +When these atoms are either in disorder or so arranged +as to mutually cancel each other's field, there is no field +observable. When they are made to all face one way, +their individual fields will conspire to produce a resultant +field, which will be strong in proportion to the +number of such individual fields that make it up. The +nature of this magnetic field is probably a kind of +whirl or spiral movement in the ether between the +two poles of the magnet; but, as two similar adjacent +whirls or lines are mutually repulsive, they spread out +into space indefinitely, and are almost always curved. +The earth as a great magnet has such a field, the lines +reaching from the north polar regions upwards and +southwards, re-entering the earth by similar downward +sweeps in the south polar regions. How far away +from the earth some of them may extend no one +knows, but there seems to be no reason why they +should not extend as far as any ray of light. There is +good reason for thinking that the other members of the +solar system are magnets, especially as iron and nickel +are so abundant in the sun and in the meteorites that +reach us from space. If that be the case, they are all +moving in each other's magnetic fields. As the movement +of a conductor in a magnetic field produces an +electric current in the conductor, and as what are known +as earth currents, apparently due to some extra terrestrial +source, are well known, their origin is accounted +for. But, when there is iron in a magnetic field, the latter +acts upon it so as to compel it to produce a field of +its own. In other words, it makes a magnet of the iron. +The process is called magnetic induction. Like the +\DPPageSep{320.png}{305}% +other cases, it is a two-step process. There is, first, the +magnet with its molecular arrangement; second, the +action of the magnet upon the surrounding ether; and, +third, the re-action of the ether upon the second body, +making it a magnet. The heat field heats a body, the +electric field electrifies a body, the magnet field magnetizes +a body; and each of these fields may exist separately +or simultaneously, and each do its own characteristic +work, quite independent of either of the +others: so the same body may become magnetized, electrified, +and heated at the same time by the same medium, +acted upon by three different sources. The magnetic +field is more selective in its action than either of +the other two. A heat field will heat any kind of matter +in it if it be solid or liquid; an electric field will +electrify all bodies to some degree, but solid conducting +bodies to the highest degree; while the magnetic field +magnetizes only iron, nickel, and cobalt appreciably, +and the two latter but to a very small extent. The +point of chief importance here is the function of the +field itself to produce, in a certain kind of elementary +solid matter, a molecular disposition and arrangement +similar to that of the body which produced the field. + +\Section{IV.--THE CHEMICAL FIELD.} % + +The phenomena attendant upon the combination of +atoms into molecules, and molecules in cohering together +to form larger masses, make it certain that each +atom has a peculiar field, which, for a name, may be +called its chemical field, within which it acts upon the +\DPPageSep{321.png}{306}% +\index{Attraction, gravitative}% +\index{Gravitation}% +ether about it, and which extends to a distance from it +many times the diameter of any atom or molecule. + +Chemists have concluded that there is really no distinction +between what has been called chemical attraction +and cohesive attraction; such, for instance, as enables +a drop of water to adhere to a surface, or glue to +hold wood surfaces together. + +Crystals are built up of similar cohering molecules +arranged in a definite order. And these molecules exist +as independent bodies while in the solution before +being crystallized, and consequently each molecule must +have some degree of attraction for others; and this is +about the same as saying that there is an ether stress +about each one that depends upon its temperature, for +crystallization cannot take place in a solution above a +definite temperature. But one of the best evidences of +a chemical field of the sort is found in the fact that a +solution of a given crystallizable salt has its process +easily initiated by putting in a small crystal of the same +kind of a substance. Moreover, the mere presence of +certain kinds of molecules among others is sufficient to +bring about chemical changes which otherwise would +not occur; while the catalytic body, as it is called, is not +changed. This is the case with starch, which is converted +into sugar by the mere presence of sulphuric +acid, which undergoes no change. This is apparently +inexplicable, unless it is admitted that molecules of all +sorts have fields which, in one degree or another, control +chemical combinations. This has been treated of +at some length in the chapter on chemism. Its signification +here is to point out again that the field of similar +\DPPageSep{322.png}{307}% +\index{Growth}% +molecules is of such a sort as to compel within it an arrangement +of atoms into similar molecules, and molecules +into similar positions, as exhibited by crystals of +any sort. It is, therefore, another example of the property +of a physical field to bring about in a mass of matter +within it the same kind of physical phenomena as +that which induced the field. + +\Section{V.--THE MECHANICAL FIELD.} % + +A sounding body sets up air waves that travel outwards +radially from it in every direction to an indefinite +distance. Such periodic waves are capable of making +other bodies vibrate at the same rate as the original +body. When the second body has the same specific +rate, absorption takes place, the amplitude of vibration +increases, and the case is known as one of sympathetic +vibration. When the specific rate is different from +that of the recurring waves, there is more or less interference, +and this case is called forced vibration. In all +cases, however, the second body is made to vibrate by +the sound waves that fall upon it, whether the medium +be the air or any other substance, solid or liquid. And +the space within which such effects are produced is the +field of the first or sounding body. If one considers +simply the air as the medium of the field, it will be +perceived that sound waves travel in every direction in +it, and to distances unlimited except by the presence of +the air itself. Of course, the farther the distribution +goes on the less energy there will be to any cubic inch +or any other dimension, and there must be some limit +\DPPageSep{323.png}{308}% +\index{Thought transference}% +where the energy is too small to affect the organs of +hearing; but such a limit ought not to be considered +the actual limit of sound vibrations or the field of the +sounding body. There is no reason for doubting that +every sound vibration of every kind and degree is distributed +throughout the whole earth and its atmosphere, +and more than that: as the impact of molecules in +sound vibrations results in heating them to a higher +temperature, increased radiation into space follows, and +the consequent energy in this form must affect in some +degree every particle of matter in the universe upon +which it falls. It is plain how far-reaching almost every +act and movement of every kind must be. + +A sound vibration, being a to-and-fro movement of a +mass of matter, may easily be great enough to be seen, +as in the case of a tuning-fork or a piano string; and, +therefore, it is treated as being mechanical as distinguished +from molecular: but even where the sound +vibration is too slight to be seen as an actual displacement, +it can give to another body a large amount of +visible motion, as when a suspended marble is held +against a sounding tuning-fork, or as when a paper +windmill is held over a sounding Chladni plate. + +The motion of a sounding body being mechanical, +the field it produces may be called the mechanical field, +because the effect of it upon other bodies is similar in +kind to that which produced the field. There are, therefore, +five well-defined modes of physical action,---heat, +electricity, magnetism, chemism, and sound,---which, in +the past, have often been called physical forces, each +one of which affects the medium about it, producing +\DPPageSep{324.png}{309}% +\index{Hair-cloth loom}% +\index{Machines}% +either a stress or a motion, or both---conditions that +travel outwards into space indefinitely, and constitute as +many different physical fields. They may all co-exist in +the same space without interference, and each one produces +upon other bodies of matter within it the same +physical condition of motion, position, or arrangement as +that which initiated the field itself. So the established +relation deserves to be called a law better than many +relations that are called laws, but are such only within +rather narrow limits (as, for instance, the law of Charles +and \DPtypo{Boyles}{Boyle's} Law), inasmuch as this law of physical fields +is as universal as gravitation. + +What is called gravitation might be included in this +list, for every particle of matter attracts every other +particle near or far; so every atom has a gravitative +field as extensive as the universe, and there is no more +interference between it and the other fields than there +is between any of them. The chief distinction between +the gravitation field and all of the others is that +they are all artificially\DPtypo{,}{} variable while gravitation is not +known to be, though some phenomena indicate the +possibility of it. + +It follows, from the foregoing, that every object large +or small is continually affecting the space about it in +several different ways,---through its temperature, electric +and magnetic conditions, as well as by its various +movements; and it also follows that the shape of a body +as well as its molecular arrangement determines whether +the field shall be symmetrical or otherwise. A crystal +certainly has a symmetrical field, but it cannot be +turned over in the hand without affecting in some degree +everything outside of it. +\DPPageSep{325.png}{310}% + +If it be true for certain collocations of matter that +external form and molecular arrangement determine +the existence of its field, it is difficult to imagine why +it should not hold true for all cases,---a cell structure +for instance, in which case the organization of a similar +cell in adjoining space where the proper material for +construction exists would only be in accordance with +the physical properties of fields in general; and the +phenomenon of growth would be as definitely understood +as the growth of a crystal. This is not demonstrative; +but it is in accordance with everything else we +know, and is what would be predicted by one who knew +the properties of physical fields, though he had no +knowledge of cell growths. + +To take one step more, yet not to go beyond the domain +of physics: It is as certain as any physical fact +can be that every movement of an individual---change +of attitude, gesture, or expression of countenance---must +produce a corresponding change in his field, and +tend to bring about in others similar movements; and, +even if such phenomena are not observed in every one, +it is no more of an argument against the existence of +the operative conditions than is the failure to perceive +through the sense of feeling the sound vibrations produced +by a speaker's voice, when it is certain the whole +body is in a state of tremor; and the effect of sympathetic +speech is more largely physical than has been supposed. +Strong emotions, or the physical semblance of +them by skilful actors, re-act in the same physical way. +This is not saying there may not be other factors, but +the purely physical ones are present and act in the way +\DPPageSep{326.png}{311}% +\index{Motion, transformations of}% +described. The term ``sympathetic action'' was applied +to physical phenomena when it was discovered to be a +mode of action quite analogous to mental phenomena +between individuals in which similar mental states are +induced. + +Lastly, so far as mental action depends upon brain +structure, any changes in the latter must produce corresponding +changes in the brain field, and there must +be a brain field if there be any truth in the foregoing; +the conclusion is inevitable. Other similar structures +must be affected in some degree by them, and whether +such induced changes be able to induce similar brain +changes with the accompanying mental phenomena or +not must evidently depend upon the possibility of +synchronous action. + +This is not to be understood as asserting that such +thought transference as is implied in the foregoing actually +occurs. All that is asserted is that the physical +conditions necessary for such transference actually +exist, and one who was acquainted with the properties +of physical fields would certainly predict the possibility +of thought transference in certain cases. +%\DPPageSep{327.png}{312}% + + +\Chapter{XIII}{On Machines.---Mechanism}{312} + +\index{Push and pull}% + +The common notion of a machine is that it is an implement +designed for doing this or that: as, for instance, +a loom is a machine for weaving cloth or carpets; a +steam-engine is a machine for driving machinery; a +water-wheel, for utilizing the power of water; and so on. +Some of these structures, built for specific purposes, are +highly complex, and many of their parts stand in curious +relation to each other, and altogether they may be able +to produce results that seem but little short of intelligent +action. Looms weave out beautiful fabrics with +artistic designs in colors, when furnished with only the +bare threads. The hair-cloth loom draws with iron fingers +a single hair from a large bundle of hairs. If it +fails to grasp one, another and another attempt is made +until one is seized, and meanwhile the rest of the machinery +waits. If it seizes more than one, as sometimes +happens, it drops both and tries again, the rest of the +apparatus waiting as before, exhibiting a kind of deliberativeness +and consciousness of what it is about that +one hardly looks for through any combination of wheels, +ratchets, levers, and the like, such as make up a complex +machine. Every one knows that by far the larger +number of things in common use which were formerly +\DPPageSep{328.png}{313}% +made by hand tools are now made by machinery more +rapidly and oftentimes more perfect than they could be +made by hand. The parts of clocks and watches are +so made; papers are printed, folded, and directed at +the rate of ten thousand in an hour by one machine; +grass is mown, grain is cut, threshed, and winnowed by +one machine as fast as it can be driven through the +field; shoes, toys, and beautiful pictures are thus made +by the million, and there is no department of human +effort but is dependent upon mechanism of some kind. +In many cases the entire work is thus done automatically, +as when pins and needles are made from the wire, +sharpened, polished, counted, arranged in papers, and +folded ready for the market. There is no field independent +of such aids. Even music is absolutely dependent +upon it, and all that is called sentiment and feeling +in it are resolvable into degrees and directions of movements +for the production of sounds; and there are no +movements of muscles but may be duplicated by automatic +mechanism. If the effects produced by mechanism +to-day are not the effects wanted, it only shows +that the mechanism has not been perfected, not that it +cannot be done. + +If one considers the almost infinite number of processes +needed for the maintenance, conveniences, comforts, +and tastes of what is called civilized life, it might +seem as if an almost unlimited number of physical conditions +would be necessary; but let such an one recall +the fact that all kinds of motions are reducible to not +more than three fundamental kinds,---translatory, vibratory, +and rotary,---and he will be prepared to trace +\DPPageSep{329.png}{314}% +\index{Lever}% +\index{Pulley}% +the most complicated movements to these elementary +forms. + +In the chapter on motion, only the kinds of motion +were considered; but here it is proposed to point out +the conditions under which motion is transferred from +one place to another, and how these elementary forms +are transformed into each other. For convenience, the +term ``mechanical motion'' will be employed for all having +visible magnitude, but simply on the ground of visibility, +not because there is any other distinction between +such motions and those of a molecular or atomic kind. + +When one pushes against a paper-weight on the table +and it moves in consequence, no one is surprised, for +the movement is expected. If the weight were free to +move and it did not move, no matter how strong the +push, one would have reason to be surprised, because +such a phenomenon is not in accordance with the +experience of mankind. If one billiard-ball in contact +with another one received a push in direction toward +the latter, the latter would be moved in the same direction, +and the motion of the second one would be explained +by saying it was due to the push of the first +upon it. Suppose there were ten or a hundred such +balls in a line. If the end one was pushed towards the +rest of them, they would all move, the farthest one as +much as the first, as the movement imparted by push +to the first would be handed on step by step to the last. +If the balls were glued together at their points of contact, +that would make no difference in this transfer of +motion by contact; and, if there were a thousand or a million, +or any other number, there would be no difference. +\DPPageSep{330.png}{315}% +\index{Work, measure of}% +Neither would there be any difference if the separate +balls were no bigger than molecules. A rod of wood +or metal is entirely made up of a great number of cohering +particles, and, when a push is applied to one end, +every particle is pushed as much as the end particles. +If there was a row of thin rubber balls and the end one +was thus pushed, the side would be flattened somewhat, +and the opposite side in contact with the next adjacent +ball would push against its neighbor and each be flattened, +and so on, till the last one was reached, which +would be pressed on one side but not on the other, and +would, therefore, be like a single ball pressed upon one +side. The intermediate balls would act as transferrers of +pressure from one end to the other. The rubber balls +so flattened by pressure will recover their form when +the pressure is removed, and the same may be said of +a rod of any material, the difference in this particular +being only one of degree. The same process takes +place when one pulls upon a rod. It is to be remembered, +however, that in either case the transmission of +the pull is not instantaneous for any distance, however +short. Time is requisite, and hence there is a rate of +propagation of such motion in all bodies, which depends +upon the degree of elasticity and the density of the +material; and this rate cannot be exceeded, no matter +how great the initial push or pull. This rate is about +sixteen thousand feet per second for steel and the most +elastic woods, and is about eleven hundred feet per +second for air. If one inquires what the condition is +that initiates motion in any given body, it will be found +to be a push or a pull, and either of them may be measured +\DPPageSep{331.png}{316}% +in pounds. The chief distinction between a push +and a pull lies in the relative position of the moving +power and the body being moved by it. In the push, +the body being moved leads in the line of movement; +in the pull, the moving power leads. When a locomotive +goes ahead of the train, it pulls; if the train goes +ahead, it pushes. A stiff rod or bar may be used for +either a push or a pull, but a rope can be used only for +a pull, for when pressure is applied to it longitudinally +it bends at right angles to the direction of the pressure, +and so fails to act in the right direction. A rod can +transmit a push or pull only in the direction of its +length, while a rope may rest on a pulley and the pull +may act upon any other body in the same plane the +pulley turns in. If a pressure of ten pounds be applied +as a push at one end of a rod or bar, the whole of that +pressure may be transmitted to the other end. The +same may be said of the pull either with a rod or rope, +but neither rod nor rope can possibly transmit and give +up at the one end more than is applied at the other. +For this reason, a rope hanging over a pulley will hold +equal weights on its two ends. If a ten-pound weight +be tied to one end, the pull transmitted will be ten +pounds, which may be balanced by a pull either by +weight or in any other way on the other leg of the rope. +The function of a pulley is to change the direction of +the pull: it does not alter its amount. + +\Section{MECHANICAL MACHINES.} + +In the older treatises on natural philosophy, there +were described several machines which were called the +\DPPageSep{332.png}{317}% +mechanical powers, because their principles were embodied +in mechanical devices for transmitting pressure +or pulls. The \emph{lever} stood first among them. It consists +of a stiff rod or bar resting upon a point of support +for it called a fulcrum, and this fulcrum may be +placed anywhere between the ends of the bar. The +advantage or disadvantage of this machine depends +upon how near the fulcrum is to the body to be moved. +A stiff rod four feet long supported at its middle would +be balanced if it were of uniform dimensions. If a +weight of ten pounds was hung at one end, an equal +weight or pull would be needed at the other end to +balance it. If one weight fell one foot, it would do ten +foot-pounds of work in raising the other ten pounds +one foot. In any case the work done, measured in +foot-pounds, will be the same at both ends of the bar or +lever. + +The lever changes the direction of motion or the +amount of pressure, but does not change the amount +of work measured in foot-pounds. + +The simple \emph{pulley} is a device for changing the direction +of a pull, as seen in the apparatus for raising merchandise +to higher levels in buildings; but by far the +most extensive use of it is in the transfer of a continuous +pull from one place to another through the agency +of belts of leather or other pliable material. + +This combination of pulley and belt is adaptable to +many places and purposes, as well as permitting great +ranges in speeds of rotation by simply making the diameters +of the pulleys proportional to the differences in +rotation wanted. It is the chief agency in machine-% +\DPPageSep{333.png}{318}% +\index{Transformations of motion}% +shops, factories, etc., for distributing the power to the +various machines. By crossing the belt the second +pulley can be made to turn in the opposite direction. + +In all the ways in which it is serviceable, it is plain +that it cannot deliver more of a push or a pull than is +given to it any more than can a lever. There is no +gain of energy or work by its use, but always some loss, +because friction uses up some of the working-power in +other than useful ways. The \emph{wedge}, the \emph{inclined plane}, +and the \emph{screw} are but simple devices for utilizing push +or pull; but there are other means also employed for the +same purpose; for instance, the pressure of the air or +other gas, and steam. Windmills are made to turn by +the pressure of the wind upon the inclined blades, and, +by forcing air into pipes, an increased pressure may be +transmitted for long distances and then used. The +reason this method of using air is not in more general +use is that when the air is compressed it heats. The +heat it loses soon if conveyed in pipes very far, and as a +consequence its pressure is very much reduced, so it is +not an economical thing to do. Water-wheels utilize +the pressure of water, and the amount of work it can do +is definite and easily calculated. If at a waterfall a +hundred pounds of water falls ten feet, then it can do +$100 \times 10 = 1,000$ foot-pounds of work; that is, it can +raise $1,000$ pounds a foot high, and so on for any other +amount. A perfect water-wheel that did not let slip +by any water without its doing its work would give up +practically $1,000$ foot-pounds. Really, the best water-wheels +give but about ninety per cent of \DPtypo{the-working-power}{the working-power} +of the water. So-called water-motors are but properly +\DPPageSep{334.png}{319}% +constructed wheels enclosed in the pipe through +which water is made to flow with considerable pressure. +In the cases of air, steam, and water power there is the +condition we call a push, which may be measured in +pounds; and a push measured in pounds multiplied by +the distance in feet through which it is maintained is +the measure of work. + +In each of the cases, the air, or steam, or water, +as it moves on and does its work, gives up the motion +it has; and the substance itself, being no longer of use, +is allowed to escape as a waste product. Such bodies +have been sometimes called \emph{prime-movers}. + +So far has been considered only the apparatus in +common use for transferring motion of one body to +other bodies, but frequently it is important to have the +\emph{form} of the motion changed from the kind it may +chance to have at the outset to one better adapted to +the special end desired. + +In a sewing-machine, for instance, the particular +movement of the needle must be vibratory. The +treadle has a similar movement, but not rapid enough; +so there is arranged between them a series of movable +parts, which not only \emph{transfers} a certain amount of +motion, but the latter is \emph{transformed} into appropriate +forms. The vibratory motion of the treadle is transformed +into the rotary motion of the balance-wheel, +this into swifter rotation of the pulley by means of a +belt; then by lever and cam the needle receives its +proper kind of motion, the shuttle a similar one at +right angles to that of the needle, and the other moving +parts such forms of motion, and rates of motion, as +\DPPageSep{335.png}{320}% +are needful for their special kinds of work. In a steam-engine +the constant pressure of the steam is made to +act upon the alternate sides of a piston, giving it a +vibratory motion, which must be transformed for most +purposes into rotary; and this is effected by means of a +crank, which is, therefore, a device for transforming vibratory +motion into rotary, or \textit{vice versa}. When the +driving-wheels of a locomotive are made to rotate, their +adherence to the track carries the whole structure forward; +that is, the rotary motion is transformed into +translatory. In the stationary engine the rotary motion +of the balance-wheel is transferred to a pulley by a +belt, and the shafting transfers this through its whole +length to other pulleys. If the reader will follow back +to its antecedents any particular motion he may think +of, he will see that the function of each movable part of +a machine of any sort is to transfer push or pull, or +transform one kind of motion into another kind. However +complex a machine may be, it does no more. + +It is to be noted that \emph{what} a given thing will or may +do depends altogether upon what kind or form of +motion it has, not upon how much motion or energy +it has. For instance, a bullet might spin on some axis +on the table before one, and have great rotary velocity +and energy, yet be perfectly harmless; whereas, if it +had the same amount of energy with the motion translatory, +it might be destructive to anything it struck. + +\Section{MOLECULAR MACHINES.} + +If one of the functions of a machine be to transform +the kind of motion it is supplied with into some other +\DPPageSep{336.png}{321}% +kind of motion,---translatory into rotary or vibratory, +any one into either of the others,---one may be prepared +to follow mechanical processes from masses of +visible magnitude into molecular magnitudes, and thus +note the antecedents of the new phenomena that +appear. + +When a gas is condensed by pressure the individual +molecules have less free space to move in, and they +consequently collide with each other more frequently. +Being elastic, their average amplitude of vibration is +increased proportionally, and a greater number of them +will strike with greater velocity upon the walls of the +containing vessel per second than before. Thus the +temperature and the pressure of the gas are increased. +We say that mechanical energy has been converted +into heat energy, or sometimes simply into heat, +though what has really happened has been the transformation +of external translational motion into internal +vibratory motion, which the elasticity and mobility +of the molecules permit. When by friction or percussion +a body is heated, the same thing precisely +has happened: translatory motion has been transformed +into vibratory, through the agency of the +molecules, which have, therefore, acted as machines for +transformation. + +In like manner the reverse transformation may take +place in several ways. When the increased vibratory +motion of the molecules produces an increased pressure +upon the movable head of a piston in an engine, the +piston as a whole may move and do work. Also, when +the molecules strike harder upon one side of a surface +\DPPageSep{337.png}{322}% +than upon the other side, the surface moves toward +the side of less pressure, as with the radiometer; so +that both engine and radiometer are machines for +\index{Machines}% +transforming vibratory molecular motions into translatory +mechanical motion. + +When the temperature of steam is raised to about +$5,000°$~F., the amplitude of vibration is so great that the +atoms can no longer cohere in the molecules, and they +become separated into the gases hydrogen and oxygen; +and again vibratory motion is transformed into translatory, +which in gases is called free-path. + +Heat is also largely derived from the chemical properties +of coal, wood, oils, gas, and other substances +called fuel. As the heat is derived from some antecedent +condition which is not heat, it follows that the +stove or furnace is a machine for transforming into +heat motions those motions which constitute and are +the measure of chemism. + +When heat is applied in any way to the face of a +thermo-pile, electricity may appear which may be made +to do work in many ways. The vibratory motion disappears +as such,---that is, it is annihilated,---while an +electric current appears as its substitute. The thermo-pile +is, therefore, a machine for the transformation of +heat into electric current. If heat be a kind of molecular +motion, then an electric current must be some +other kind of motion! + +When the armature of a dynamo is turned and an +electrical current is developed, the latter is the representative +of the mechanical movement of the armature. +It takes more power to make it move at a given +\DPPageSep{338.png}{323}% +speed when it is producing a current than when it is +not. The current represents the difference. It is mechanical +motion that goes into the dynamo, and an +electrical current comes out of it; and hence a dynamo +is a machine for the transformation of mechanical into +electrical motion. One is visible, the other molecular, +as is the case when friction develops heat. + +An ordinary static electrical machine possesses a +similar function. + +On the other hand, a galvanic battery transforms +chemical into electrical motions; and, in every case +where electricity is developed, there is some sort of +apparatus which receives one kind of motion for transformation. +That one kind of machine will transform +mechanical motion, a second heat, a third chemical, all +into the same kind of a product, helps one to see that +the antecedents, which at first seem to be so unlike, +are really but varieties of the same condition, namely, +motion, which, when transformed by suitable machines, +might be expected to appear as a similar product of +each. + +An electrical current always heats the conductor +through which it passes. It is, therefore, an antecedent +for the production of heat in the same sense as mechanical +motion is an antecedent in condensation, percussion, +and friction; and the conductor is the agency for +the transformation into the vibratory molecular form. + +So far as the production of light by electricity is concerned, +whether by the incandescent or the arc system, +the function of the current is to raise the temperature +of the conductor to the proper degree for luminousness. +\DPPageSep{339.png}{324}% +The light comes from the hot molecules, not from the +electricity; but here, as in the simpler case of heating +the conductor, the conductor itself, whether it be a filament +of carbon or the tips of the carbon rods, acts as a +transformer of electrical into heat motions, and thence +to ether waves. + +Ether waves may be transformed in two different +ways. First, by falling on molecules of matter; the +latter absorb them, and are heated in consequence, +which is the converse of the production of ether waves +by heated molecules. Second, by their own interferences +plane, elliptical, and spiral waves may be produced, +which resultant waves are capable of affecting matter +in different ways. One of these consequences is of so +much theoretic importance it will be well to allude +to it. + +Given a flexible section of a spiral ether wave, no +matter what its origin. If its ends were to come together, +there is good reason for thinking they would +close and weld together, forming a ring, which would +then be practically a vortex ring. The ends of vortex +rings formed in the air will do thus, so if the atoms of +matter are really vortex rings, as has been supposed, +the above suggests how they may originate, or how +matter is created. + +All the different kinds of phenomena which are generally +attributed to different forces one may readily +trace to these antecedents; namely, matter, ether, and +motion of various forms. The condition necessary for +a new phenomenon to appear is that the present forms +of motion in either matter or ether needs to be transformed. +\DPPageSep{340.png}{325}% +Atoms and molecules, as well as large masses +of them, which we call bodies of visible magnitude, act +as machines for the transferrence and the transformation +of motion; and one might define a machine as a \emph{collocation +of matter having for its function the transferrence or +the transformation of motion, or both}. An atom and a +molecule, then, are as much machines as a steam-engine +or a dynamo; and every molecule in the universe, +whether near or remote, is constantly receiving and +transforming energy through its individual motions. +What the particular phenomenon will be in a given +case depends upon the form of the motion received by +the mechanism and the new form which the latter has +made it to assume. As before remarked, what a given +mass of matter will do depends upon the kind of motion +it has. + +So far nothing has been said about the relation of +these mechanical principles to living things,---animals +and plants; but it will be obvious to every thinking +person that unless, when matter assumes the forms exhibited +by such living things, it surrenders its mechanical +properties and relations, then such transformations +must be going on constantly in all living things. Mechanical +motions, chemical re-actions, heat, and so on, +ought to be expected from such complex machines as +animals. Foods, as fuel, air, and water, are physical +factors which imply metamorphosis; and the forms into +which the factors will be changed depend upon the +special mechanism provided. Hence, an animal is a +complex machine for the transformation of motions of +various sorts, the sum of them being what are called +the phenomena of life. +\DPPageSep{341.png}{326}% +\index{Solar system}% + +The foregoing analysis shows that what have heretofore +been considered as forces in nature are non-existent;\DPnote{** Only instance.} +that all phenomena in the different fields of +physics are simply and plainly mechanical; and that +an application of the laws of motion, as presented by +Sir Isaac Newton, supplemented by the laws of ether +action, is sufficient to account for all kinds of phenomena: +and therefore the supposition of particular forces +of any kind is entirely unnecessary. What have been +called forces are but various forms of motion, of matter, +or of the ether, each embodying energy; the particular +phenomenon a given body may produce depending +upon its size and the particular quality of motions it +chances to have. Granting this, one may at once perceive +that expressions implying higher and lower forms +of force are misleading. No one is higher in dignity or +importance than any other one. Let one ask the question, +Which is higher, vibratory or translatory motion? +and he will see the absurdity of the language. + +If one will bear these principles in mind, they will be +helpful in unravelling phenomena which otherwise may +appear to be very puzzling. For instance, one may frequently +come across the statement that one cannot get +out of a machine what is not in it or put into it. Is it +so? Coal is put into the furnace, and heat comes out. +Mechanical motion is put into a dynamo, and electricity +comes out. A current of electricity is turned into an +arc lamp, and light comes out. The character of the +product thus depends upon the form of the machine +and its relation to some antecedent factor. The physical +\DPPageSep{342.png}{327}% +\index{Physical universe a machine}% +knowledge we have enables us in most cases to +trace and understand the metamorphosis. In some +cases the molecular changes are not so completely +known in detail, yet the quantitative relations between +what goes in and what comes out of the machine are so +definite that one is warranted in asserting that no other +factors are present than the one considered. In one +sense the product of any machine is like its antecedent, +if both be but kinds of motion, or forms of energy as +some prefer to say; but if one assumes that these +various forms of energy differ in any way from forms +of motion, or that they have distinct individualities, +then one can get out of a machine what he does not put +into it. What seem to be more unlike than the mechanical +movements of a steam-engine and the electricity +of the dynamo? One is simplicity itself; the +nature of the other, its product, has been the despair of +philosophers for generations. The subject is of fundamental +importance chiefly because some philosophers +have evolved their schemes without duly considering +these obvious relations. + +However much a given phenomenon may differ in +character from its known antecedents, no good reason +can be assigned for thinking that, when properly analyzed, +it would be found resolvable into other factors +than matter, ether, and motion. Furthermore, there is +no evidence that any one of the physical forms of +motion is or was necessarily prior to any other. As +there is no hierarchy among them, no one of them can +be called primal. A linear arrangement does not +\DPPageSep{343.png}{328}% +\index{Matter, as modes of motion}% +properly represent their mutual relations. They are +more like a closed ring of interrelations thus:--- +%[Illustration: ] +\begin{center} + \Graphic{2.5in}{343a} + \Figlabel{35} + + {\scriptsize Diag.\ 35.---Forms of Energy.} +\end{center} + +The visible universe may be considered as a vast +machine, within which motions are being exchanged +by contact and by radiation. It is not the absolute +amount of energy a body may have which determines +whether it shall give or receive, but it is the degree +it has of a given kind of energy. Thus it is the temperature +of a body that determines for it whether it +shall gain or lose heat in the presence of other bodies. +The whole tendency is towards equalization of conditions, +and for this reason some philosophers think they +foresee the end of this act in the drama of the solar +system. The possibility of the variety of phenomena +that gives interest to existence depends upon the fact +that at present matter is in an unstable condition, and, +when uniformity of condition is reached, there will be +an end to changing phenomena. Astronomers have +figured out that in five or ten millions of years the sun +\DPPageSep{344.png}{329}% +\index{Cohesion, in solids and liquids}% +\index{Matter, states of}% +will have radiated away so much of his energy that the +earth will no longer be habitable. Perhaps so; but it +is certain that the whole solar system is drifting in space +somewhere at the rate of seven hundred millions of +miles a year, and in one million of years it may reach a +region in space where the present rate of loss might be +greatly reduced. In that time it will have travelled +three times the distance to the nearest of the fixed +stars. It could hardly be where its expenditure would +be greater than now. If it should drift into one of the +great hydrogen regions such as are numerous in the +heavens, not only would the supply of energy be renewed +indefinitely, but the earth would become uninhabitable +in an hour. At any rate, there is no guarantee +in nature for permanent stability, supposing that stability +should be attained; for simple mechanical impact +between the sun and any of the millions of stars would +not only annihilate the earth as such, but would so +reduce to a nebulous mass the matter that now composes +the solar system that the whole process of world +formation would have to be gone through with again. +The sudden blazing out of stars here and there in the +heavens shows that similar physical processes are taking +place elsewhere in the universe. Such an end is +quite as probable as the refrigerating one referred to; +for there is implied in the latter not only that the present +conditions in the solar system will continue, but +that the environment of the solar system will remain +for so many millions of years what it is. The matter +is not alluded to here on account of its humanitarian +\DPPageSep{345.png}{330}% +\index{Cohesion, destroyed}% +\index{Gas, motion in}% +interest, but to point out that in either case the results +will be due to purely physical conditions. What mankind +would contemplate as a dreadful catastrophe would +be but the interaction of huge machines, where energy +was transformed on a grand scale, and no particle of +matter omitted for an instant to conform to the three +laws of motion. +%\DPPageSep{346.png}{331}% + + +\Chapter{XIV}{Properties of Matter as Modes of Motion}{331} + +\index{Gas, free path in}% +\index{Gas, pressure in}% + +In the first chapter of the book only the most +obvious qualities of matter are considered, such as +magnitude, density, inertia, and so on, the properties +which are exhibited by masses of matter of visible +magnitude and form, from which the common notions +concerning its nature and possibilities have been derived. +If one stops his inquiries concerning the properties +of matter with these, and imagines that they are +the ultimate properties, and may rightly be assumed +and asserted of the individual atoms, he will be greatly +in error; for it is not difficult to show that nearly +every property of masses cannot be true of atoms, and +that nearly if not quite all material properties of what +we call matter, are derived from antecedent conditions, +and are resolvable into them or into mere relations +which are not inherent, and may be absent. It is, +then, worth the while to study the real significance +of some of the physical terms in common use, in +order the better to eliminate from the mind unessential +qualities when thinking of the inherent qualities +of matter. + +During the past ten years laboratory facilities for +physical investigations have greatly aided inquirers, +\DPPageSep{347.png}{332}% +\index{Heat, effects}% +and added much to real knowledge in this field. Some +of this knowledge is of such a character as will presently +make it needful for every one to reconstruct +his notions and explanations of physical phenomena, +in order to prevent hopeless confusion in his own +thinking. + +\Section{THE STATES OF MATTER.} + +Under the conditions of ordinary observations matter +is found in the solid, liquid, and gaseous states; +the solid state being that in which the molecules +cohere so strongly as not to be easily separated from +each other nor from the relative positions they have +assumed with reference to other molecules. Thus, a +piece of granite, as the type of a solid, may have its +molecules cohering to each other in certain positions, +so strongly as to require a ton's weight to pull apart +a section of one square inch. + +The granite is made up of small crystals of quartz, +mica, and feldspar, each having a definite chemical +composition. The individual crystals retain their relative +places for an indefinite time, and the atoms of the +individual molecules retain their relative positions for +a like indefinitely long time, else the crystalline structure +would be lost, for crystalline structure implies +definite atomic arrangement as well as molecular +arrangement. So in solids the adjacent molecules +are in what are called stable positions, and are not +easily separated. + +In a liquid there is little cohesion among the molecules, +and no stable arrangement at all. The individual +molecules move among each other without +\DPPageSep{348.png}{333}% +\index{Absolute zero}% +\index{Charles, Law of}% +\index{Chemism and heat}% +\index{Chemical reactions depend on temperature}% +\index{Gas, pressure in}% +\index{Gas, destroyed}% +\index{Matter, effect of temperature upon}% +apparent friction, and the slightest force acting upon +them makes them to turn on any axis; and there is +good reason for thinking that in a liquid like water, +the individual molecules are continuously rolling and +tossing about with perfect freedom to move in every +direction. The phenomena of diffusion exemplifies +this. There is also good reason for thinking that the +individual atoms in the water are continuously changing +partners at a rapid rate, so if there were some +means for identifying the atoms of hydrogen and oxygen +in a given molecule, they might be seen presently +all separated and forming temporary constituents of +other molecules a relatively long remove from the first +position where they were observed. When the water +is frozen, that is has become a crystalline solid, this +freedom of atomic change and molecular rotations is +no longer recognized as a property. Molecular cohesion +is now exhibited where before there was none. +There are also new qualities called crystalline, hardness, +density, and so on, which before this change did +not belong to it. The new qualities which seem to +have been developed are produced by lowering the temperature +of the water, that is, reducing the amount +of kinetic energy the molecules had; and by again +imparting a like amount to the ice \emph{both crystallization +and cohesion are destroyed}. + +A gas is a body of molecules in which the individuals +are free to move in every direction unconstrained by +any degree of cohesion, and where they are in frequent +collisions, bounding away in new directions through +distances usually many times the diameter of the molecules +\DPPageSep{349.png}{334}% +themselves. Thus, in air the ordinary average +distance between impacts is nearly two hundred times +the diameter of the individual particles which, as before +stated, is in the neighborhood of one fifty-millionth of +an inch. Their continuous bumping against each other +and the walls of the containing vessel, produces what +is called the gaseous pressure. Increasing the temperature +of the gas increases the velocity of movement +in the free path, and, consequently, the momentum and +the pressure. It has been customary to say that heat +increases the elasticity of a gas, that a gas occupies +the whole space which encloses it, that a gas has a +tendency to indefinite expansion, and that the properties +of a gas are due to repulsive force among the +molecules. In a loose sense such expressions may be +allowed, but they are not to be understood as correctly +specifying the qualities of the gaseous matter. It is +not repulsion that makes a ball move which has been +struck by a bat, but impact; and that it should continue +to move on until it strikes another body, follows +from the first law of motion, as true for a molecule of +a gas as for a baseball. The direction the ball takes +depends upon where it is hit, as well as upon how hard +it is hit; the velocity it has depends upon how hard it +is hit, and there is nothing peculiar to a gaseous particle +requiring the affirmation of different properties. + +Some years ago improved methods of making a +vacuum were adopted, by which one could reduce the +amount of gas in a tube to even the hundred millionth +of its ordinary amount, so that a particle might have a +relatively long free path measurable in feet instead of +\DPPageSep{350.png}{335}% +\index{Diamond, hardness of}% +\index{Hardness not atomic property}% +hundred thousandths of an inch, and the phenomena +of such rarefied gases were so new and surprising that +it was at first conjectured that a new state of matter +had been discovered, and it was called the fourth or +ultra gaseous state to distinguish it from the others; +but it was soon perceived that it was still only rarefied +gas, and that no new qualities had been developed, and +the same phenomena witnessed in the rarefied gas were +present in the denser, only disguised by the greater +number of molecules which took part. So what was +called for a short time the fourth state has been +practically abandoned. + +The three states already considered are known to +depend upon temperature. Thus, if ice or iron or +many other solids be heated they become liquid; if +heated still more they become gaseous. Some solids, +like wood, when heated do not assume the liquid intermediate +form, but are at once converted into a gas; +but different substances have different temperatures at +which they change from one form to the other. Thus, +water becomes a solid at $32°$~Fah., and a gas at $212°$~Fah. +Iron becomes fluid at~$2,800°$ and gaseous at~$6,000°$. So +far, then, it appears one might as properly speak of +iron as a liquid or a gas, as of water as either, if they +both may exist in the three conditions, and no temperature +is specified. We do not do that, because when +speaking thus ordinary temperatures are implied, but +seldom or never thought of. If one had been brought +up in the sun it is probable he would never have seen +a solid, and if at the moon, he would know of neither +liquid nor gas. +\DPPageSep{351.png}{336}% +\index{Color, nature of}% + +But the pressure of a gas is caused by the impact of +its molecules, and is proportionate to the temperature. +The law of Charles states what has been found to be +true within the limits of experiment; namely, that the +volume of a gas is proportionate to its absolute temperature; +that is, temperature measured from an absolute +zero, in which case, it is plainly to be seen, at +absolute zero the \emph{gaseous} volume would be nothing. +It does not imply that the matter of the gas would be +annihilated, but that the matter no longer existed in +its gaseous form; the individual molecules would no +longer have any free path motion, but would fall to +the floor of the containing vessel, and thus remain +quiescent, like so much dust. \emph{At absolute zero there +would be no gas.} + +Again, in the chapter on Chemism it is shown how +chemical reactions are determined by temperature, and +cannot take place in the absence of heat. The late +experiments of Pictet and Dewar show that as temperature +is lowered chemical reactions become weaker +and weaker, until some of the elements that have very +strong affinities at ordinary temperatures, and so combine +with energy, are incapable of combining, and +appear inert at such low temperatures as can now +be artificially made without great difficulty. Their +experiments confirm the conclusions given on \Pageref{page}{242}; +namely, that at absolute zero chemical affinity +does not exist. Molecules would not only fall apart, +but their individual atoms would no longer exhibit +any cohesive quality; and this, it will be perceived, +would render the existence of such a thing as either +\DPPageSep{352.png}{337}% +\index{Impenetrability}% +a liquid or a solid quite impossible, for each requires +chemical action for both molecular formations and +cohesion in any degree. Every kind of a structure +would crumble to atoms in a literal sense. Book, +tower, mountain, ocean, as well as every living organism, +would completely disintegrate, and lose every characteristic +property which had belonged to it. Hence, +such qualities of matter as would be absolutely emptied +out of it by simply reducing its temperature, cannot +be considered as essential qualities. Yet when the +atoms were thus deprived of what seems to us as all +their useful qualities, there is reason for thinking they +would still have definite form, mass, gravitation, magnetic +and electric qualities which, however, by themselves +could not make the mass of matter we call the +earth a habitable place, nor give to life a material +habitat as it now has. + +It is then plainly evident that what we call solids, +liquids, and gases, with all the laws that belong to each +of them, are simply the relations of heat energy to +groups of atoms, not the properties or laws that may +be asserted of the atoms as such, and do not need to +be considered by one who is inquiring for the essential +endowments of matter. + +There remains, therefore, an examination of the +other so called qualities to see if, perchance, they +too may not, in a similar manner, be resolvable into +energy relations, which, in turn, may be absent. +\DPPageSep{353.png}{338}% +\index{Elasticity}% +\index{Elasticity due to motion}% + +\Section{MOLECULAR AND ATOMIC QUALITIES.} +\Subsection{(HARDNESS.)} + +Substances vary greatly in what is called hardness, +and this properly serves, in many cases, to distinguish +one mineral from another. The mineralogist employs +a scale of ten, differing in degree from talc which is +the softest, to diamond which is the hardest, and with +these all other minerals are compared. But the mineralogist +tells us that this scale does not represent hardness +in any proportional way, because diamond is as +much as ten times harder than the ruby which stands +next to it in the scale; also that some diamonds are so +much harder than others, that no means has yet been +discovered for grinding and polishing them. + +The diamond, however, is crystallized carbon, yet carbon +exists in another crystalline form called graphite, +or plumbago, which is soft, and may be whittled with +a knife, while coke, charcoal, and lampblack are forms +of precisely the same element, and these vary through +the whole range in hardness. What, then, does hardness +mean? Evidently it signifies the resistance +offered to the separation of molecules from each other. +It is the measure of their cohesion, and could have no +existence in a single molecule of carbon. Furthermore, +as has been pointed out, as molecular structure +can have no existence at absolute zero for lack of +energy needed for maintaining cohesion, \emph{hardness cannot +be a property of atoms at all}. +\DPPageSep{354.png}{339}% + +\Subsection{COLOR.} + +Color, either simple or compound, is exhibited by all +masses of matter---for white is but a mixture of wave +lengths, and no object is so black as to be invisible. +Gold is yellow, copper red, lead is bluish. The petals +of flowers, the feathers of birds, the gorgeous dyes of +the chemist, seem to impress us with an assurance that +color is a real quality of some kinds of matter, and can +be affirmed of it without any qualifications. Bodies +become visible either by their own luminousness as +when they are hot or phosphorescent, or by the light +reflected by them from some other source, as is most +commonly the case. When sunlight falls upon a rose +it is to be remembered that the sunlight is what we +call white light; it is made up of all wave lengths which +we can see. The rose petals absorb some of these +waves,---the blue, the green, and the yellow, but not +the red; these are rejected by the surface, and they +therefore are reflected away, and testify to the selective +power of the petals, \emph{not their color}, as can be found +by holding the same rose in yellow or blue light, when +it will appear black, that is, will absorb all offered to it +and reflect little or none. Again, when a body is self-luminous, +as, for example, a piece of burning sodium +which gives out a yellow light, it is to be kept in mind +that the yellow rays are produced by certain vibratory +rates which the atoms are compelled for the time +being to make, but which the atoms will not make +except on compulsion, that is, the high temperature +which the heat energy gives to it, and therefore does +\DPPageSep{355.png}{340}% +not represent what can be called the color of the body---only +an artificial state of vibration. Lastly, if all +substances whatever were at absolute zero in temperature, +they would be setting up no ether waves of any +length, and could not effect any organ of vision, and, +consequently, would not only show no color, but would +be absolutely invisible. \emph{Hence color cannot be affirmed +of atoms.} + +\Subsection{IMPENETRABILITY.} + +It has seemed to nearly every one who has given +thought to the subject that what is called impenetrability +must be a fundamental property of matter; +that it was axiomatic, if anything could be, that two +masses of matter could not occupy the same space +at the same time. This has been believed to be +true, not because it was demonstrable, but because +it seemed to be reasonable. Maxwell, however, calls +it a vulgar opinion. He further takes the pains to +say, If hydrogen and oxygen combine to form water, +we have no experimental evidence that the molecule +of oxygen is not in the very same place with the two +molecules of hydrogen.\footnote + {See Art. Atom.\quad Encyc. Brit., 9th ed.} + +When it is possible to make one, a mechanical model +is often of great assistance in helping one to conceive +of conditions which are more or less difficult to describe +in mere words; and a mechanical model that +embodies this possibility of the coexistence of two +atoms in precisely the same space may easily be made. +Roll up a length of wire into a loose helix or spiral of +any convenient length---say two feet long. Cut it in +\DPPageSep{356.png}{341}% +\index{Hertz waves}% +\index{Magnetic waves}% +\index{Tesla ether waves}% +two parts of equal length, and bend the ends of each +round until they touch, and fasten them thus, so as to +have two rings made of spirals of wire. Each one may +be taken as representing an atom of matter somewhat +similar to a vortex ring, which has been assumed as +\index{Vortex ring model}% +the probable form of the atoms of matter. Each has +form, size, and various other qualities, but if one of +them be pressed down upon the other it will be found +they will make room for each other, so that \emph{as rings +they both occupy precisely the same space}. This is not +given here as anything more than as, possibly, a +helpful suggestion as to how a seemingly impossible +condition may be true. Evidently in this case the +difficulty lies in the assumption that an atom of matter +is a hard, impenetrable, geometrical solid, and, as Maxwell +says, there is no proof that such is the fact. +\emph{Impenetrability is an unwarrantable assumption.} + +\Subsection{ELASTICITY.} + +Elasticity has been assumed to be a fundamental +property of atoms, and so not derivable from physical +conditions underlying it; but Lord Kelvin has shown +good reason for thinking that elasticity is a derived +quality, for it is possible to construct models which +exhibit the phenomenon in a high degree while they +are in motion, and not at all while they are at rest. A +number of gyroscopic disks set whirling on a circular +axis, shows this in a remarkable way, and suggests on +inspection, that something like such an arrangement +may be the complete explanation of the quality as +exhibited by atoms. A vortex ring may be considered +\DPPageSep{357.png}{342}% +\index{Inertia}% +\index{Mass}% +as a large number of revolving disks on a circular +\Pagelabel{342}% [** PP: Best guess at page anchor] +axis, which will give to the ring not only rigidity, but +stability of form, any departure from which will be +resisted by the mechanical structure, and it will return +to its original form after the deforming stress has +ceased, with a rate depending upon the rate of rotation +of the constituent +%[Illustration: ] +\begin{wrapfigure}[15]{l}{1.375in} + \Graphic{1.375in}{357a} + \Caption{36}{Diag.\ 36.} +\end{wrapfigure} +parts of the ring. On \Pageref{page}{40} +reference is made to the behavior of a rotating disk, +and how it simulates this property of elasticity. The +common gyroscope may be cited as exhibiting it in a +\index{Gyroscope}% +manner that depends upon the +way in which the disk is mechanically +mounted. + +An ordinary whirling disk can +be freely moved only in its plane +of rotation, or planes parallel to +that. Any attempt to change +the angle of the axis is mechanically +resisted. This may be understood +by reference to diagram +where $a$~$b$ is a disk capable of +rotation on axis $c$~$d$. While rotating, +it can move freely in the +plane $a$~$b$, but any attempt to tip +the axis in any direction will be +resisted by it. Imagine, then, a large number of similar +disks, mounted on a circular axis, as in diagram~36, +each one rotating. It is plain that any attempt to tip +the ring in one direction or the other, or to change +the form of the ring itself, supposing it to be flexible, +will necessarily change the plane of some of the revolving +\DPPageSep{358.png}{343}% +disks, and will be resisted as a whole, for the +same reason that one of its parts will do the same. It +will be seen that if all these disks be rotating in the +same direction the movements will be like those of a +vortex ring. If additional disks could be inserted +upon the axis, so as to form a continuous body quite +round the circular axis, it would constitute a ring; +and if the proper rotation were set up, it would possess +all the qualities of a vortex ring, and elasticity +would be a prominent quality, as stated on \Pageref{page}{39}. It +is no longer necessary, if it ever was, to assume elasticity +as a fiat quality, imposed upon atoms which +might have existed without it; \emph{for the laws of motion, +acting in a properly constructed mechanism, are quite +sufficient to produce it}. + +\Subsection{MAGNETISM.} + +On \Pageref{page}{205} the statement is made that magnetic +phenomena have led to the belief that all atoms of +all kinds of matter are magnetic, and are only obscured +in ordinary matter by the molecular arrangements +which tend to neutralize the magnetic fields of the +individual atoms. Attention is again invited to the +diagrams on \Pageref{page}{105}, with the accompanying description, +in order to freshly bring to mind how vortex +motion necessarily produces what is called polarity---the +two sides of the ring have different qualities. +On one side the movements are all inwards, on the +other outwards, and from these the phenomena of +apparent attraction and repulsion necessarily follow. +But beyond this, once\DPnote{** PP: Missing "we"?} assume that individual atoms +\DPPageSep{359.png}{344}% +\index{Gravitation}% +are magnets by virtue of their constitution, and that +every magnet has a magnetic field infinite in extent, +within which it can affect other atoms, one can see +at once that every atom in creation has a magnetic +hold upon every other atom, because every one is +in the magnetic field of every other one. This effect +is not necessarily one of attraction or repulsion tending +to move one mass towards or away from another; +but, on the other hand, it tends to rotate each on an +axis so both shall face the same way. So long as +there is no change in position or in \emph{form} of such a +magnet, the magnetic field will be uniform; but if the +form be changed in any way the whole field has to +change in conformity with it, as described on \Pageref{page}{252}, +and such vibrations as constitute the heat of an atom +are really the change in form of the atom, and this, +therefore, changes necessarily the whole magnetic +field of the vibrating body. These changes in the +field, which originate in this way, are what are called +ether waves. When the waves are produced slowly, +by an alternating dynamo current, or more swiftly by +some of the methods so ingeniously devised by Hertz +and Tesla, they are called electro-magnetic waves. +When produced so swiftly as to have a wave length +only the one thirty-thousandth of an inch, they have +been called heat waves; and when the waves are so +short as to be capable of affecting the retina of the +eye, they are called light waves, though there is no +distinction between any of them except in their length. +The vibrations of the atomic magnet are rapid because +it is small; the waves it produces are changes in +\DPPageSep{360.png}{345}% +\index{Gravity follows from structure}% +its magnetic field in the ether, so one may trace +back in this manner the phenomena of light, of heat, +and electricity, to the mechanical structure of atoms; +and it is mechanically intelligible too, and, like the +preceding accounts of properties, it appears \emph{that magnetic +and electric qualities are due to the peculiar kinds +of motion embodied in the atoms}, and cannot be considered +as particular endowments of a something called +matter, which it might have been without. + +\Subsection{INERTIA.} + +The inertness of matter has been touched upon on +\Pageref{page}{70}, and here may be added the consideration of +what interpretation could be put upon such phenomena +as are exhibited by such a device as is represented by +diagram 36, supposing it were enclosed in a box so one +could not see the mechanism? The box enclosing it +would exhibit a new quality of the nature of inertia, +by virtue of the motions within it, which it would lose +as the friction diminished the rate of motion, and +when this stopped altogether the property would no +longer be present. \emph{Hence, inertia, too, must be looked +upon as probably due to motion.} + +\Subsection{MASS.} + +Mass, as a property of matter, is generally defined +as the amount of matter considered, and is measured +by what is called acceleration, that is, the velocity +it acquires in a second when acted on by a constant +force or push. Amount of matter is a very indefinite +expression, but is often convenient, and seldom misleading +\DPPageSep{361.png}{346}% +\index{Atoms, as vortex rings}% +when one is considering a given weight of a +substance. + +One may speak of a pound of iron or of hydrogen +as a mass of iron or of hydrogen, meaning a definite +weight made up of a very large number of molecules +of one or the other element; but if one will think of +the atoms of these, and endeavor to form an idea of +what can be the physical meaning of mass, when applied +to one of them, he will at once see that the term +carries with it no conception whatever of the physical +difference between atoms of different kinds. An +atom of iron is said to contain fifty-six times the mass +of an atom of hydrogen, while an atom of gold has +a hundred and ninety-six times the mass of the hydrogen +atom, and all the elements differ in mass in the +ratio of their atomic weights. Can any one suppose +for an instant, that an atom of gold is a hundred and +ninety-six times larger than an atom of hydrogen? +There is some evidence that atoms differ somewhat +in magnitude from each other, but none of any such +difference as is represented by their atomic weights. +Furthermore, this would imply that atoms were blocks +of some primeval stuff of uniform quality, and that +atoms of a given element were but uniform volumes +of it; and it hardly needs to be said that such a view +is negatived by all we know, for the properties of the +various elements do not vary simply with their weights, +as would be the case if they were thus constituted. +Hence, mass as applied to atoms cannot be thus conceived. +It is possible to form a conception of the +physical meaning of mass as applied to atoms or +\DPPageSep{362.png}{347}% +molecules, by recalling the phenomenon of rigidity +in position, which is the outcome of rotations, as described +on pages \Pageref{}{40}~and~\Pageref{}{342}, for the amount of effort +needed to move such a rotating body depends not +simply upon the amount of rotating material, but its +velocity of rotation; so a small amount of material +with a high speed may offer as great a resistance to +movement from its position as another much larger +amount of material with corresponding slower rate, +but otherwise the two would necessarily have great +differences in their other properties; thus their rates +of vibration would be very different, because their +degrees of elasticity would be different. + +One may then assume that such differences between +\emph{the atoms of the elements as are called their masses, +are due to the relative rates of rotation}. This, of +course, on the fundamental assumption that the atoms +themselves are vortex rings such as we have argued as +being highly probable. + +\Subsection{GRAVITY.} + +There now remains to be considered one more +general property of atoms and all combinations of +them; namely, their gravitative property. If one be +content to say that not enough is known about it +to warrant even a tentative opinion, and, therefore, +refuses to draw any inferences from what is known +as to what gravitative property is, or is like, one +need to have no quarrel with such an one; but if, +on the other hand, one is interested in fundamental +questions, and thinks that whatever be the truth +\DPPageSep{363.png}{348}% +\index{Hertz waves}% +\index{Materialists}% +about gravitation or any other unsolved problem, when +it is known, it will be seen to be in harmony with +every other physical truth, and will, therefore, be a +consistent part of the body of physical knowledge +which we now possess, such an one will perceive that +with the banishment of the old notions concerning the +structure of matter, with its endowments of sundry +properties which might have been otherwise, or that +the matter we know might have had entirely different +properties, must also go the notion of quality endowments +in any such sense as was formerly held. He +will also have good reason for holding it altogether +probable, that if the other properties of matter are +reducible to modes of motion, so the last one in +the list will be found to be reducible to the same +factor. If the others have been interpreted thus, one +after another yielding as molecular phenomena became +better understood, he will conclude that if the problem +of gravitation has not been solved, as the others +have been, it is not because it is insoluble in itself, but +because it is inherently more difficult, or has not received +the degree of attention that has been given to +other problems since conservation has been discovered +and forms a part of every discussion. + +One thing seems certain, if the vortex-ring theory +of matter be true, or anything like it, then gravity +must follow from the structure; for in the absence of +any evidence of the existence of gravitation in the +ether, no one is at liberty to postulate it there for +the sake of finding it in the atoms. It must be looked +for as due to the particular kind of motion that constitutes +\DPPageSep{364.png}{349}% +\index{Ether phenomena not explained}% +the atom, and is constant because that motion +is constant. + +In the chapter on gravitation is given a mechanical +conception of gravitative conditions which, whatever +may be its inadequacy, is consistent with other physical +knowledge. Faraday, as is well known, made +several efforts to discover some relation between +gravitation and electricity, but only negative results +were reached. He was not discouraged by his lack +of success, and had planned still other experiments, +which he was not able to finish. He always worked +on some hypothesis almost always radically different +from the hypotheses of his scientific contemporaries, +and time has vindicated his rather than theirs; and +that there must be some physical relation between +the two classes of phenomena was one of his, and so +it seems to-day; for if gravity be due to the form of +motion in the atom, and if an electric current in a +circuit represents a real vortex ring, having the conductor +for its core, then it seems likely there is some +gravitative effect between such current and the earth; +but it may be so slight with a single circuit as to not +be detectable with present means, and the mutual gravitative +effects between two such circuits would be +obscured by their electro-magnetic effects. + +Lastly, if the atom itself be a vortex ring, as +explained in the chapter on the ether, it follows that +in the absence of such form of motion there would +be no atom---no matter, though the substance out of +which the ring was constituted would exist, but without +any of the characteristics that we assign to matter +\DPPageSep{365.png}{350}% +\index{Laws not compulsory}% +\index{Miracles possible}% +\index{Phenomena, unexplained}% +in any of its forms. If one chooses to call a common +smoke-ring \emph{alpha}, evidently when the ring is dissipated +there is no more ring, there is no alpha, it has been +annihilated as a ring; and in like manner, one may +understand that what constitutes an atom is not so +much the substance it is composed of as the motion +involved in it. Such \emph{an atom is a particular form of +motion of the ether in the ether}, in the same sense +as what is called light is a form of motion of the +ether in the ether. One is an undulation, the other +a vortex. One we call an ether wave, the other we +call matter: both involve energy, and both have properties. +Thus, one after another of the properties of +matter are found to be resolvable into ether motions, +ether being the primal substance, and matter only one +of its manifestations. + +Such a conception of matter as is here presented, +resolving as it does all its physical properties, even +itself, into modes of motion of the ether in the ether, +is not simply a new conception of matter, it is rather +a revolution in fundamental conceptions, and if trustworthy, +necessitates an abandonment of nearly every +notion concerning them which men have entertained +when thinking and discoursing upon the subject. +The mystery of phenomena is not lessened but made +greater by the discovery that everything which affects +our senses in every degree is finally resolvable into a +substance having physical properties so utterly unlike +the properties of what we call matter, that it is a misuse +of terms to call it matter. + +No one in the past has been able to forecast its +\DPPageSep{366.png}{351}% +\index{Electricity, origin of}% +properties. The necessity for such a medium has not +been felt by many philosophers, and though there has +been some expectation on the part of a few, any new +\index{of}% +step has been a source of surprise. For instance, when +Hertz succeeded in producing electro-magnetic waves +in the ether only two or three feet long, it was heralded +as being a demonstration of the existence of the +ether, implying that all the phenomena of induction +and electro-magnetic waves developed by machines +vibrating up to four thousand per second in telephonic +apparatus, could have some other interpretation. The +point here emphasized is that the properties of the +ether and their relations to such physical phenomena +as have been the subjects of research are so little +known, that no one has yet ventured to embody them +in an all embracing philosophy, so as to deduce apparent +phenomena from them. + +The significance of this will be apparent when one +recalls the various attempts of materialistic philosophers +to explain all sorts of phenomena as due to +matter and its properties. Some of them have been +ignorant of the existence of the ether; others have +grouped matter and ether together and called both +matter, and considered both as subject to the same +laws as are found to hold true for matter as defined +in this book. When it is apparent that such physical +views are radically unsound, that one cannot reason +from our perceptual matter to imperceptual ether,---for +it is true that there are no known nerves that +respond directly to ether action,---it will also be apparent +that any scheme of things that ignores this knowledge +\DPPageSep{367.png}{352}% +or fails to make proper distinctions here cannot +be entitled to respectful consideration. Indeed, such +physical materialism is less rational than ever, for it +ignores much knowledge now in our possession which +is as certain as any we possess, and it ignores the +trend of all the physical knowledge we have; for it +cannot be denied that the advance in knowledge which +has been so marked during the past half century has +been in the discovery of the simplicity of relations, +rather than towards ultimate explanation. It may +truly be said that, in a philosophical sense, nothing +has been explained. Familiarity with constant phenomenal +relations induces in us expectations of certain +happenings, and presently they seem obvious. +The car moves because the engine pulls it; the engine +moves because the steam pushes it; the steam +pushes because the heat pushes it; and the heat +pushes because---it is the nature of heat to do work. +In that way, every physical phenomenon runs at last +into an inexplicable, into an ether question; and the +necessity for it follows from nothing we know or can +assume. No one may assume for an instant that the +possibilities of ether phenomena are limited by such +interactions as have hitherto found expression in treatises +on physics. Indeed, there is already a body of +evidence which cannot safely be ignored, that physical +phenomena sometimes take place when all the ordinary +physical antecedents are absent, when bodies move +without touch or electric or magnetic agencies,---movements +which are orderly, and more or less subject to +volition. In addition to this is still other evidence of +\DPPageSep{368.png}{353}% +\index{Postulates of Physical Science}% +\Pagelabel{356}% +competent critical observers that the subject-matter +of thought is directly transferable from one mind to +another. Such things are now well vouched for, and +those who have not chanced to be a witness have no +\textit{a~priori} right from physics or philosophy to deny such +statements. Such facts do not in any way invalidate +physical laws, nor make it needful to modify present +statements concerning energy. Physical laws are not +compulsory; they \emph{rule} nothing; they are but statements +of our more or less uniform experience. If +these things be true, they are of more importance to +philosophy than the whole body of physical knowledge +we now have, and of vast importance to humanity; +for it gives to religion corroborative testimony of the +real existence of possibilities for which it has always +contended. The antecedent improbabilities of such +occurrences as have been called miracles, which were +very great because they were plainly incompatible +with the commonly held theory of matter and its +forces, have been removed, and their antecedent probabilities +greatly strengthened by this new knowledge; +and religion will soon be able to be aggressive with +a new weapon. +%\DPPageSep{369.png}{354}% + + +\Chapter{XV}{Implications of Physical Phenomena}{354} + +\index{Fable, La Fontaine's}% + +A physical phenomenon is a phenomenon which +involves energy. Every change of condition in matter +is brought about by the action of energy upon it in one +way or another. It may be gravitative energy or heat +or light or electric or any other; but every physical +change has a physical antecedent as well as a physical +consequent, and the explanation of any given phenomenon +consists in pointing out the precise antecedents that +brought it about. There is a common saying that like +causes produce like effects, but this is far from being +true in the popular sense. If it were true the development +of science would not be the difficult and painfully +slow process it has proved to be. Electricity may be +produced by turning a crank, by dissolving a metal, by +twisting a wire, by splitting a crystal, and in others +ways. The product is the same, but the antecedents +are so different that no one can tell by examining the +product how it was produced. If it became important +to know what caused the electrical phenomenon, it +would not be sufficient to know that electricity could +be produced in these different ways; one would need +to know the specific apparatus employed. The more +\DPPageSep{370.png}{355}% +complicated the phenomenon the more difficulty there +is in unravelling it. + +So far as experiment and experience have led us, the +antecedents of every physical phenomenon are themselves +physical, and more than that, all reactions are +quantitative, that is, the product is proportional to the +antecedent, and this is sometimes embodied in what is +called the doctrine of the Conservation of Energy +which every one knows about. + +The exchange relations between the different forms +of energy,---mechanical, thermal, chemical, electrical, +etc., which are so well-known, being quantitative, are +therefore mathematical. They have therefore become +a corporate part of the body of knowledge, and are no +longer subject to any questions as to their validity +under any circumstances whatever. One who should +challenge them would no more be deserving of attention +than if he should offer to prove he could square a +circle. + +The fundamental postulates of physical science are +binding upon the one who understands them, for the +same reason that the multiplication table is. There +are no contingencies and no possibilities of hedging. +If any one of them could be overthrown the whole +body of science would go with it. This is said because +there are not a few who appear to think that +what is called physical science may not be so certain +as its advocates think, and that there may be factors +which have not yet been reckoned with that may quite +transform the whole scheme. Science is a consistent +body of relations, not simply a classified body of facts. +\DPPageSep{371.png}{356}% +\index{Blavatsky, Madam, pretensions of}% +\index{Guppy, Mrs.}% +\index{Power, needed for rapid movement in air}% +These relations have been discovered by experiment, +not by deduction. + +Some of them are the following:--- + + 1. Physical changes affect only the condition of +matter, not its quantity. One cannot create or annihilate +it, nor can one element be changed into +another. + + 2. Every atom is continually exchanging energy +with every other atom, the rate of the exchange depending +upon their difference in temperature. + + 3. The different forms of energy are transformable +into each other, but the quantity of energy is not +altered by the transformation. + + 4. Complex organic molecules differ from simpler +inorganic molecules in possessing more energy. The +differences in this respect are definite, may be measured +in foot-pounds, and are practically enormous. + +5. Every physical change has a physical antecedent, +is therefore mechanical, and is conditioned by the laws +of energy. + +These principles are the outcome of modern investigation, +the evidence for them is overwhelming, and +a working knowledge of them needs to be a part of +the mental equipment of every investigator, especially +of the one who takes it as his province to explain +phenomena. + +Science is strong here if it is anywhere; and any +description of any event, any explanation of a genuine +phenomenon that practically ignores these, cannot be +true, and can have no claim to consideration. + +Before any explanation is needed there is always the +\DPPageSep{372.png}{357}% +\index{Sound, origin of}% +\index{Spiritualistic theory}% +\index{Spirit disembodied}% +advisibility of ascertaining that the alleged event really +happened, and whatever is not professedly miraculous +must not be in discordance with the bast knowledge +we have. + +With the above principles in hand one is prepared to +fairly judge as to whether a given statement is credible +or not. It is not necessary, as some seem to suppose, +that one should be able to explain a phenomenon if he +rejects the explanation of another one, or to assert with +emphasis whether a thing is possible, probable, or +impossible. + +In La Fontaine's fable the philosophers were at the +theatre witnessing a play in which Ph{\oe}bus rose in the +air and disappeared overhead. They undertook to explain +the phenomenon. One says Ph{\oe}bus has an +occult quality which carries him up. Another says +he is composed of certain numbers that make him +move upward. Another says Ph{\oe}bus has a longing +for the top of the theatre, and is not easy till he gets +there. Still another says Ph{\oe}bus has not a natural +tendency to fly, but he prefers flying to leaving the +top of the theatre empty. Lastly, a more modern +philosopher thinks that Ph{\oe}bus goes up because he +is pulled up by a weight that goes down behind the +scenes. The last is an explanation. From a physical +standpoint the others are not simply inadequate explanations, +they are absolute nonsense. They make +the antecedents of a phenomenon involving energy, +factors that have no more relation to energy than has +moonshine to metaphysics. Yet there has been a large +number of men in all ages, men able in many ways +\DPPageSep{373.png}{358}% +too, who have ventured to explain phenomena in such +a \emph{non-sequitur} way, and who have spurned the mechanical +philosopher and his explanations. + +In that class of phenomena called spiritualistic there +is a large body of reputed physical phenomena, vouched +for by large numbers of witnesses, such as the movements +of furniture, chairs, tables, books, pianos, etc., +the playing upon musical instruments, guitars, accordions, +pianos, the appearance of lights, of faces, of +full forms clothed, of conversations with materialized +spirits, and so on, in great variety. + +I suppose no one doubts that to move a body of any +magnitude requires the expenditure of energy, and to +do a definite amount of work requires always the same +amount of energy, yet I suspect there are many persons +who give credence to statements of occurrences +which practically deny the above proposition, thinking +it to be probable that spiritual agencies may have +control of powers that mankind knows nothing about. +This may be true enough, but the question is not as to +what this or that agency can do, but whether if spirits +do a certain kind of work it takes less energy than if a +man should do the same thing. + +Whenever a weight or a resistance and a velocity +are given, it is always possible to compute the energy +spent to produce or maintain it. Let us study a case +or two. In olden times it was related that one of the +prophets was carried through the air by the hair of his +head from Babylon to Jerusalem. In later times it +was said that Mrs.\ Guppy was similarly transported +from Edinburgh to London. The distance is about $400$ +\DPPageSep{374.png}{359}% +\index{Séances, phenomena at}% +miles, and if I remember rightly she made the transit +through the air in less than one hour. This makes the +velocity to be about seven miles a minute or $600$ feet +per second, which is three times faster than the highest +tornado velocity. The resistance offered by the air +to the movement of bodies in it is very well known. +Pressure in hurricanes has been observed as high as $90$ +pounds per square foot, and as the pressure increases +with the square of the velocity, it follows that at $600$ +feet per second the pressure per square foot would be +about $800$ pounds; and if the exposed surface of Mrs.\ +Guppy was no more than six square feet, the total air +pressure must have been not less than $4,800$ pounds. +Now, the energy of this is found by multiplying the +pressure by the velocity per second. +\[ +4,800 \times 600 = 2,880,000\text{ foot-pounds,} +\] +and as a horse-power is equal to $550$ foot-pounds per +second, it follows that it took not less than +\[ +\dfrac{2,880,000}{550} = 5,236\text{ horse-power} +\] +to move Mrs.\ Guppy in that way at that rate. + +It was reported when Madam Blavatsky was living +that she was in the habit of receiving letters from +distant correspondents, brought to her by some occult +agency and dropped upon her table. These letters +were said to have been written only a few minutes +before by persons living in the most distant parts of +the earth. + +It takes but a little figuring to discover the amount +of energy necessary to do a work of this kind. Thus, +\DPPageSep{375.png}{360}% +\index{Light, a sensation}% +let the distance be $10,000$ miles, the time ten minutes. +The pressure per square foot due to such a velocity in +the air will be $17,000,000$ pounds, or $118,000$ pounds +per square inch. Assume but one square inch as the +area exposed to such a pressure, then the energy +needed to transport it with the speed of $16.6$ miles +per second, will be +\[ +\dfrac{118,000 \times 5,280 \times 16.6}{550.} = 18,000,000\text{ horse-power.} +\] + +Unless such packages were protected by occult +agencies also, they would be burned up before they +had gone the first mile of their journey. + +The popular idea is that at death the spirit leaves +the body, but that it may, and often does, remain +in the locality, and is frequently in the presence of +its friends, unperceived by them, though occasionally +they may be seen and communed with through the +agency of certain preternaturally gifted persons called +mediums. + +This proposition has so many physical data, and involves +so many physical implications, it will be worth +the while to look squarely at some of them. + +1. A spirit is supposed to be a conscious entity dissociated +from matter, having ability to move at will and +to be more or less interested in what is going on in the +world, and capable of giving information on matters +remote from observation or the knowledge of men. +Suppose then such an entity, a disembodied spirit, +without a corporeal body, but anxious to be in the +neighborhood of its former friends. Seeing that it +\DPPageSep{376.png}{361}% +\index{Light, its nature}% +now has, according to this view, no longer a hold upon +matter, it has ceased to be in any way affected by +gravity and inertia, for these are attributes of matter. +Now the earth has a variety of motions in space; it +turns on its axis, so that a point on the equator is +moving at the rate of a thousand miles an hour. It revolves +about the sun at the rate of nearly seventy thousand +miles an hour, and with the sun and the rest of +the bodies that make up the solar system it is drifting +in space at the speed of sixty thousand miles an hour +or more, so that the actual line drawn in space by any +point upon the earth is a highly complex curve drawn +at the rate of upwards of a hundred and twenty-five +thousand miles in an hour. Now, any object whatever +keeping up with the earth, but without the help of +gravity, must maintain the velocity in space of not less +than a hundred and twenty-five thousand miles an hour, +and that is not all, as the movement is not in a straight +line, any such object wishing to keep in a particular +locality, say a room, would have to be on the alert constantly, +for the earth wabbles\DPnote{** [sic]} for numerous reasons and +what seems to us, who have bodies held by gravitation +to the earth, as so quiet and smooth running that we +are never conscious of the motion for an instant, is so +simply because gravity takes care of us. Once surrender +that and undertake to depend upon some supposed +private source of energy, and one would instantly +discover he had an engineering problem of a high degree +of complexity. If one assumes, as some have +done, that such spirit is composed of, or associated +with, some sort of matter, and that navigation is accomplished +\DPPageSep{377.png}{362}% +\index{Materializations and energy}% +by an act of the will, it will not change the +foregoing factors in the problem at all. + +2. Suppose, as some have done, that disembodied +spirits lose their hold upon matter, and that they do +not remain at the earth. Then, if they remain at the +point where separation from the body took place, in an +hour the earth will have moved forward one hundred +and twenty-five thousand miles. But over the earth +there is certainly a death every minute all the time, +and such are left in the rear by the earth never to return +to them, for the movement of the earth is not a +circuit, but an apparently endless drift. Think of the +dead of the earth for the thousands of years since man +has lived upon it! On this view, the spirits might be +seen like the tail of a comet reaching backwards for +millions on millions of miles,---the trail of the dead. + +In any view, time and space and energy cannot be +ignored or ruled out. + +At \emph{séances} the reported phenomena are mostly of a +physical sort, the trance of the medium being a physico-mental +phenomenon. The phenomenon of sound implies +the expenditure of energy, it is a vibratory motion +of the air or other elastic body, and in order to produce +it some antecedent force must be spent; it may be produced +by mechanical means, or heat, or electricity, or +by the muscles. Its production does not imply any +specific method any more than articulate speech implies +a person, as Faber's talking-machine and the +phonograph prove. + +Let us consider some of the more subtle phenomena +that are reported. First, as to so-called conditions. +\DPPageSep{378.png}{363}% +\index{Organic and inorganic matter, difference between}% +One of the primal ones of these for such phenomena as +the movements of bodies and materializations, is said +to be darkness. This is of so much importance that it +must be fully attended to. To one who has not paid +any attention to what has been done in molecular +science within the past fifteen or twenty years, the +phenomena of light may and probably do seem to be +due to an unique agency, as much as heat or electricity; +and therefore he looks upon light as he looks +upon the others in the hierarchy of the physical +sciences, and expects that in its absence a potent +agency or kind of energy is lacking. That this idea +and conclusion is all wrong will be apparent when it is +recognized that \emph{what we call} light is a particular sensation +in the eye, and that to produce the sensation +\emph{there is no one antecedent that is essential}. Press the +eye with the finger in the darkest night and one will +see a ring of light with great distinctness. An electric +shock, a bump upon the head, will also give one the +sensation of light, and in the absence of other aids to +a judgment no one could tell what was the antecedent +of a given light sensation. + +Radiations from a luminous body, and reflections +from a non-luminous one, were not long ago thought to +consist of three different kinds of rays,---heat, light, and +actinic rays. It has been discovered that there is no +such distinction in fact. What a ray will do depends +upon what it falls upon. The same ray that falls upon +the eye and produces the sensation of light, would heat +another body, or do photographic work. The only +difference in rays is in their longer or shorter wave +\DPPageSep{379.png}{364}% +\index{Immortality}% +lengths, and the energy of a wave does not depend +upon its length. From this it follows that there is no +such thing as light as distinguished among forces or +forms of energy. \emph{Light is a sensation}, and in the absence +of eyes no such distinction could possibly be discovered. +Light, then, as a particular kind of agency +takes no part in phenomena outside of the eye. The +eye of man is adapted to respond to certain wave +lengths, the eyes of other animals are adapted to respond +to other wave lengths; and if our eyes were +adapted to perceive all wave lengths the whole universe +would be always light about us, every object, +whatever its temperature, could always be seen as +easily as we now see when the sun shines. + +These facts make it quite impossible for a physicist +to understand why darkness should be an essential +condition for the occurrence of such phenomena as +are described. Again, every ray of light when traced +back leads to a vibrating molecule or atom. Indeed, +light or ether waves in general all imply vibrating +atoms or molecules; and what is called spectrum analysis +is but a development of this fundamental principle, +and not only the kind of matter, but its physical +condition is revealed. If Moses had had a spectroscope +when he saw the burning bush it might have +told him the nature of that conflagration. + +So when luminous forms appear at a dark \textit{séance}, +there is first the ether waves of such length as to +affect the eye; these traced to their source must +arise from vibrating molecules, that is, matter expending +energy in the production of ether waves; +\DPPageSep{380.png}{365}% +for no matter ever shines without some source of +energy. + +If the matter that gives out the light be ordinary +matter, there is no difficulty in understanding it; for +matter can be made to shine in several ways,---by +impact, by high temperature, by electric vibrations, +by chemical reactions; and no one could tell from +the simple fact that the matter shone, what the origin +was. But it is said that these forms that are seen +and thus affect the eye, that are touched and thus +affect the sense of touch, that are warm and thus +testify to vibrating molecules, that speak and appeal +to the ear through air vibrations, are \emph{materializations}; +meaning by that that the body with its various organs +and their functions is built up \textit{de novo} out of material +at hand, as Adam was said to be made of the dust of +the ground, and as the lion that pawed to free its +hinder parts from the soil out of which it thus grew. +What are the materials that make up a human body? +Ultimately there are carbon, hydrogen, oxygen, nitrogen, +iron, phosphorous, sulphur, potassium, sodium, and +several other ingredients of less importance. From a +hundred to a hundred and fifty or more pounds of these +are needed for one full-grown person. + +Many of the materializations that have been described, +from Samuel the prophet to Katie King, have +appeared to be veritable specimens of humanity even +to avoirdupois and all that is implied in that. If the +matter of such bodies was a creation and not a collocation, +then one of the fundamental principles of +physics is simply not true; for matter can be created +\DPPageSep{381.png}{366}% +\index{Seeing, what is implied in}% +and annihilated by any spirit that knows how to find +a suitable medium. If the material is gathered from +the environment---and this sometimes is asserted---then +the difficulty is nearly as great. + +One must take notice of the difference there is +between inorganic or relatively simple chemical compounds +and those that make up the bodies of living +things,---the bones, the tissues, the muscles, the nerves, +the brain, the blood. For building up a single pound +of such tissue as muscle or of fat requires the expenditure +of energy represented by about sixteen million +foot-pounds; and as in such a body as we are supposing +there could hardly be less than twenty-five or thirty +to be so reckoned, it follows that not less than four +hundred million foot-pounds of energy is necessary, a +quantity equal to upwards of twelve thousand horsepower, +if done in a minute; and if done in half a +minute, then twice that quantity. I cannot but wonder +if those who think they have witnessed such phenomena +could have been conscious of the stupendous +amount of energy which was being evolved before their +eyes. Then dematerialization involves the annihilation +of the same amount; for it is to be remembered that +organic matter differs from inorganic in the amount of +energy absorbed. There has been either the creation +and annihilation of matter or the creation and annihilation +of an enormous amount of energy, without antecedents +and with no residuals. This is not saying that +such events have not taken place, it only points out the +factors of energy which are implied if they do happen. + +One who is unaware of such implications and phenomena +\DPPageSep{382.png}{367}% +\index{Hearing, what is implied in}% +may easily suppose the most improbable things +can take place. Those who are aware of such implications +cannot hear of such events without instantly perceiving +how almost infinitely improbable they are. + +Reports of such phenomena have never come from +any man who understood the relations of phenomena. + +Scientific men have been often told of their incompetency +to investigate so-called psychical phenomena; +but if the latter involve physical phenomena, then who +else can properly investigate them? + +This paper is not to be understood as implying that +there is no relation between the living and the dead, +for the writer does not believe that doctrine; instead +of that he thinks we are very near to a discovery of a +physical basis for immortality that will transform most +all our thinking. If spiritual communication is not +accompanied with physical phenomena in the alleged +way, it does not follow that it may not happen in other +ways that do not do such violence to our fundamental +knowledge as most of the reported cases do. The universe +is large, not much of it has been explored. We +live and move and have our being in an environment +about which our knowledge is most meagre; but our +knowledge of energy we get not only from the earth, +but from the sun and most distant stars and nebulæ, +and it is not probable that any contribution whatever +will materially modify our present knowledge of it. + +Thus far I have considered what is always implied +when physical phenomena are considered, especially +with reference to the antecedents; for instance, when +a steam-engine is run it implies the consumption of +\DPPageSep{383.png}{368}% +\index{Senses}% +fuel, which in turn implies molecular structure, and a +definite amount of energy in what is called its chemical +form. That energy is not created or destroyed by +any physical process, and, therefore, every exhibition of +energy, no matter where or when, is to be explained +solely by reference to the laws of energy which are +now so well known as to have passed out of the region +of conjecture or hypothesis. If there be any knowledge +which man possesses, which for certainty and +accuracy compares with mathematical knowledge, it is +the knowledge of physical relations. I traced out a +few cases in which the alleged phenomena were of +such a physical sort as to be easily handled, and +showed how one must look at their antecedents. That +such phenomena did take place was not denied. It +was simply asserted that when they did happen one +must reckon with the implications, unless he was prepared +to affirm that physical phenomena might happen +when physical laws are ignored and quite counted out. +There are yet some further implications it is well to +consider. They have to do with the objective structure +and qualities of the spiritual beings that are +supposed to bring about the phenomena we are considering, +such as moving objects, playing upon musical +instruments, writing upon slates, and so on. + +As such beings are always addressed as if they were +visible personages, possessing the same organs of hearing, +seeing, and so on, as are possessed by individuals +still having a material body; and as the replies to questions +never contradict such assumptions, but, on the +contrary, are confirmatory of such assumptions, it follows +\DPPageSep{384.png}{369}% +that one may properly consider what really is +implied in the assumption that spirits have eyes and +ears, because they can see and hear. When I say \emph{I +see}, I assert not only the existence of what we call +light, but the existence of an organ called the eye, the +structure of which is adapted to be acted upon by what +we call light. Light is, as we all know, a wave-motion +in the ether. It travels at the great velocity of a hundred +and eighty-six thousand miles in a second, and the +waves are in the neighborhood of only the one fifty-thousandth +of an inch long. The eye is the only +structure in the body that can perceive these waves. +It is a kind of camera, and photographic work goes on +in the retina very much as it does in the process of +photography. Then, there is the optic nerve, which is +an essential part of the apparatus, and conveys to the +seat of consciousness the impress of the molecular +disturbances which have taken place in the eye. No +one is conscious of the phenomenon of light except +through the action of this complex mechanism. Therefore, +when one says he \emph{sees}, he means that a particular +kind of disturbance has taken place in a particular physiological +structure. The term sight is never used in a +different sense from this, except when it is avowedly +used figuratively. In the absence of ether waves there +could no more be what we call sight than if there were +no eyes; both are essential. + +When, then, it is said or admitted that a spirit \emph{sees}, +not in a figurative sense, but in the sense in which we +all use the term, it is implied that a spirit has eyes, a +physiological structure, acted upon by ether waves, and +\DPPageSep{385.png}{370}% +\index{Law, physical}% +\index{Specialists}% +the nervous system behind that. It has what \emph{we} call +eyes. It will not do at all to say that such spirit has +an equivalent sense, for whatever that might be it +would certainly not be \emph{sight}. One may get a very +accurate knowledge of the presence of another person +by the voice, or by the sense of touch, but it +would be a culpable misuse of language to say of such +person that he was \emph{seen}. Sound can no more affect +the eyes than light can affect the ears. This, then, is +the same as saying that a spirit has a physical structure +for seeing similarly constituted to that in man, +and, indeed, in all organizations that \emph{see}. + +When I say \emph{I hear}, I mean that air vibrations have +affected my organs of hearing, the ears with the nervous +structure between the ear and the seat of consciousness. +There is implied in the statement not +only that sound vibrations of a definite sort have been +produced and are acting, but that they are acting upon +a certain physiological structure adapted to be affected +by gaseous vibrations. Vibrations in the ether cannot +affect the organ of hearing. The media are radically +different, and cannot be used as substitutes for each +other; and it is therefore wrong to say \emph{I hear}, unless +what I perceive reaches my consciousness through the +physiological mechanism called the auditory apparatus. +In a figurative sense one may say he hears as he may +say he sees. +\begin{verse} + \small + ``Lo, the poor Indian! whose untutored mind \\ + \PadTo{``}{}Sees God in clouds, or hears him in the wind.'' +\end{verse} + +But real seeing and real hearing imply certain distinct +\DPPageSep{386.png}{371}% +organs adapted to different physical conditions. +One cannot, by talking, affect one's eyes; nor will +light waves, as such, affect one's ears. + +Suppose, then, in a \textit{séance}, when a spirit is addressed +thus: Will the spirit please rap upon the table? and +the answer comes at once,---a rap distinctly heard. The +question was an oral one, and was produced by physical +means, regular sound vibrations, and can be heard +by such beings as are possessed of the proper organs +to be acted upon by air vibrations, that is, ears; and +by ears I \emph{mean} ears, not substitutes of any sort. What +we call \emph{speech} is absolutely impossible in a vacuum, +as much as is sound, for speech is a succession of +sounds. There are numerous substitutes for speech,---signs +made with the fingers or lips that do not appeal +to the ear; but these are not speech. If, then, spirits +\emph{hear}, it is because they have ears, organs that can be +affected by sound vibrations in the same manner as we, +the so-called living beings, can be. Moreover, do not +all testify that they can and do both see and hear? + +In like manner one may treat of the sense of feeling, +or any other sense. All imply a molecular structure, a +nervous organization, indeed, everything that goes to +make up a consciousness of the external world such as +is possessed by living beings governed by physical +laws. + +It is clear that what we call pain is immediately due +to disordered nervous structure, and in the absence of +nerves could never be known. This can be tested in a +minute by any one, by simply pricking one's finger. +Does not the destruction of the nervous tissue in any +\DPPageSep{387.png}{372}% +manner end the possibility of pain? Can a spirit +then suffer physical pain without a nervous organization? +By pain I mean what all mean by the +term, the sensation which, if severe and long-continued, +results fatally to the sufferer, because the +nervous tissue is itself destroyed. + +If some one having read so far, perhaps with impatience, +should say, ``All this may be as you say for living +beings, incorporated in a body of flesh and blood +and a nervous system, but we are not to suppose for +a moment that spirits are thus constituted, and if not, +then they are not to be supposed to be conditioned by +such physical laws as all common matter is conditioned +by. They have their own constitution, different enough +from ours, and one cannot reason from our condition to +theirs.'' To this I would reply, that if one cannot do +this, if a physicist must not carry his terms and conceptions +into this spiritual domain, for precisely the +same reason the spiritualist must not talk about a spirit +\emph{seeing}, \emph{hearing}, \emph{feeling}, and so on, unless he admits he +is talking loosely, and means by those terms only to +symbolize his conceptions, and has to employ such +terms as best convey the idea, which idea cannot be +physically true. Even then it is very difficult to understand +why, if the physical terminology is inappropriate, +any one should at a \textit{séance} ask such a question aloud as, +If John be present will he please rap on the table; for +this is \emph{sound} addressed to an ear---both of which are +purely physical things. + +An Arab may not have any difficulty in imagining a +genie that may be summoned by rubbing a cup, to do +\DPPageSep{388.png}{373}% +wonderful things, and then vanish out of relations to +everything; but no one who has studied deeply into +the significance of physical relations can possibly admit +that affairs in nature go on in such a fast-and-loose +way. + +Thus far I have considered such relations of physical +phenomena as have been found by experience to hold +good in the whole range of physics---such relations as +properly come under the domain of what is called law, +and by law I mean mathematical precision, both in the +antecedents and the results. With the exception of +the original apparition of matter and of physical energy, +there has not been found in the whole field of physics, +by any investigator of any nationality, any kind of a +phenomenon which is believed to be unexplainable on +the basis of the knowledge of physical science we +already possess. Of course, what we call explanation +is merely presenting the antecedent factors of a given +occurrence, both in quality and quantity, and a thing is +fully explained when these are given so fully as to leave +no reasonable doubt as to their sufficiency in the mind +of one who is properly well acquainted with the data; +but the data that enter into a given phenomenon are +the very things most persons know least about; and a +given explanation may be full and adequate, and yet, to +some, seem to be wholly insufficient. + +In these days one often hears about \emph{specialists}---of +their limited knowledge and inadequate preparation for +giving a judgment in other fields than their own. So it +has come to be reckoned that if a man has, by study +and investigation in a given field, made himself a competent +\DPPageSep{389.png}{374}% +judge, so as to be considered an authority in +that field, he is by so much less fitted to be heard in +the settlement of some question foreign to that field; +whereas some other man who is not known to have +done anything in any field, may be called in for judgment, +to the exclusion of the former, lest his increased +knowledge in some one department should disqualify +him elsewhere. + +Do we not hear that biologists are incompetent +judges of mental phenomena, that astronomers are not +competent in biological questions, and so on? If this +distinction be true to the extent generally assumed, +then philosophy itself is impossible; for if a man's +opinion can be good only in a small department of +knowledge, and he cannot adequately master more, how +shall we ever know the relationships that constitute +philosophy? The truth is, this is a one-sided affair +altogether, and holds true from but one standpoint. If +an astronomer propounds a chemical theory of the sun, +will it be needful in any degree that the chemist who +reviews the work shall have even studied astronomy +or paid the slightest attention to telescopes or solar +affairs? If chemical science is involved, it is for the +chemist to say whether what is propounded is adequate +or not. That is to say, the man who concerns himself +with the constitution of the sun must so far be a +chemist, but a man may be a chemist and never concern +himself about the sun. + +Again, if a biologist who is admittedly ignorant of +chemical and physical science makes statements that +plainly contradict the laws of energy as determined in +\DPPageSep{390.png}{375}% +\index{Science, no one independent}% +chemistry and physics, and if a physicist challenges the +statements, shall the latter be silenced by calling him a +specialist who may be competent enough in his own +field, but who knows nothing of biology? Or shall he +be told that physical laws may be rigorous enough in +one mass of matter, but not in another? Is it to be +believed that physical laws thus play fast and loose? +Here the arithmetic holds good, but there all is indefinite, +and would not this be a fine example of dictation +out of one's field? Physiologists tell us that ultimately +every physiological problem reduces itself to one of +chemistry and physics.\footnote + {See Appendix, \Pageref{p.}{400}.} +If this be so, is it not plain +that the one who treats broadly of biological problems +must either be a physicist or submit his work to the +criticism of a physicist? But a man may be a physicist +and never trouble himself about biological questions. + +If a social philosopher presents a scheme for ameliorating +the evils present in society, in which scheme he +plainly ignores the laws of life as determined by biologists,---as +if such laws were not the very determining +factors which must first be reckoned with,---shall not +the biologist condemn such work? and shall he, too, be +told that however much he knows of biology, he is incompetent +in sociology? Plainly, not so. But is this +process a reversible one? Can the sociologist criticise +the biologist's work unless he be himself a biologist, or +the biologist criticise the chemist's or physicist's work +unless he be so far a chemist or physicist? He certainly +cannot; and this shows that there is a certain +relationship among these subjects in which there is an +\DPPageSep{391.png}{376}% +\index{Séances, phenomena at}% +order of dependence. In order to fully understand and +explain a sociological problem, a knowledge of psychology +is essential; a working knowledge of biology, +or the laws of life, and no adequate knowledge of this +can be had without a preparation in chemistry and +physics. + +In this there is nothing new, but it is generally +ignored by most persons who treat on broad questions. +It is plain that every kind of a question is, in the last +analysis, referable to the laws of physical phenomena, +and from these there is no appeal. There are not +many who like this, it is true; but the test for truth +is not what one likes or dislikes, but whether the +proposition is in accordance with the best and most +fundamental knowledge we have. Some of those fundamental +truths discovered within the past fifty years, +and not questioned by any one who can stand an +examination on them, were given on \Pageref{page}{356}; and +whoever sees, or thinks he sees, a phenomenon which +he interprets in a way which plainly contradicts or +ignores those laws, does not so much have a contention +with any man as with science itself. If those laws are +not irrefragably true, then we have no science at all, +no philosophy, knowledge is scrappy, and what we call +the interdependence of phenomena is a myth. + +Some of the phenomena alleged to happen at spiritual +\textit{séances}, such as levitation of human bodies, writing between +closed slates, the moving of matter without contact, +and so forth, are said to be as thoroughly proved +as any of the facts of the fundamental knowledge I +have treated. Such a statement cannot have come +\DPPageSep{392.png}{377}% +from any one who knows how the knowledge I spoke +of was obtained, or how it may be verified by anybody +who cares to take the pains. None of it depends in +any degree upon anybody's dictum. If any one has +doubts as to the constitution of water, he can determine +it himself in half a dozen different ways. If +he doubts that the earth is eight thousand miles in +diameter, he can measure it in several ways. If he +thinks a pound of coal does not have eleven million +foot-pounds of energy, he can himself try it and be satisfied. +Any one can satisfy himself by himself; assistance +of others is only a convenience, not a necessity, +and the fundamental statements are now believed by +so many because so many have tested them, and all +have reached the same conclusion. Furthermore, great +commercial enterprises are founded upon some of them, +as when so much limestone and coal are mixed with a +given ore of iron for its reduction. So if such alleged +facts be true, it cannot be true they are as thoroughly +proved as the ones I stated, and they will not be so +proved until each one can be verified in like manner. + +There is another excellent reason for denying that +they are proved in any scientific sense. All physical +phenomena, so far as they have become a part of physical +science, have been examined and reported upon by +physicists; and both phenomena and their interpretation +have been the subject of remorseless criticism, +and have been adopted, if at all, on \emph{compulsion}; their +acceptance has been a matter of last resort. This is +true in all departments. Why should one believe that +the world turns round unless there is no other possible +\DPPageSep{393.png}{378}% +\index{Growth of crystals}% +way to explain and account for all the facts which must +be reckoned with in any explanation? The theory itself +is so remote from the common experience of mankind +that nobody suspected it for thousands of years, and it +is not at all obvious to one who is not acquainted with +phenomena out of the range of ordinary experience. +The form of the earth, the aberration of light, the +apparent change of latitude, and so forth, have to be +considered even more than the recurrence of day and +night. For most of the purposes of life it does not +matter whether it turns round or not, and most men +have no interest in the question further than that it +accords or not with their other beliefs and feelings. +But the answer to the question, ``Does it turn?'' is +not one that can be settled by submitting it to the vote +of the world. The judgment of one Galileo is worth +more than that of all the rest of the world on that +point. Once admit that no department of science is +independent of other departments, and that no phenomenon +occurs independent of relations which must +be satisfied by any attempted explanation, and it follows +that no explanation of an event should be adopted +and be considered a part of science, unless it is shown +to be in agreement with what is known. Hence, if an +event is reported which appears to be out of relation +with those established relations which there is general +agreement upon, there is the best of reasons for thinking +that either the event did not happen, or that it did +not happen as reported, especially if the one reporting +it is unacquainted with the variety of ways in which it +is possible to do the same thing. If one sees a wheel +\DPPageSep{394.png}{379}% +\index{Physicists, prepossessions}% +turning round but does not see its connections, how can +he tell whether it is turned by muscular action or water-power +or wind-power or gravity or heat or electricity +or magnetism, every one of which is capable of turning +a wheel? Even if he can see the connections, he cannot +always tell what makes the wheel go without further +investigation. Air and steam will make a water motor +go as well as water itself, and the presence of electrical +devices would not insure that the wheel was turned by +electricity, and the absence of such electrical devices +would not insure that it was not driven by electrical +agency. Hence the testimony of witnesses only, even +though they were otherwise competent, would be of +little weight in deciding what made the wheel go. If +the question were one of any importance it could be +determined only by a competent investigator with +proper appliances, and unhindered by restrictions of +any sort. One cannot trust his sense of sight implicitly. +Many persons have lost fingers because the +buzz saw looked as if it was still; and it is easy with +the zoetrope, and in other ways, to produce the impression +of movements that are not taking place; so it +might be that after all the wheel was not turning, or +even that there was no wheel at all. + +Admitting, for the argument's sake, that the alleged +phenomena at \textit{séances} are real occurrences and must +be accounted for, there are certainly three different +possible ways:--- + +1. By more or less skilfully devised tricks, and fraudulent +only in the attempt to make others believe they +are not tricks. To be certain they are not the results +\DPPageSep{395.png}{380}% +of manipulative skill on the part of some one, only a +skilful juggler might be able to find out. It is known +that hundreds have been thus imposed upon; and skilful +jugglers, such as Hermann and Maskaline, who have +investigated many such, declare themselves satisfied +that the whole of it is trickery. + +2. Suppose some of the surprising things done are +not the results of conscious duplicity, then it may be, +as most interested persons contend, the work of disembodied +spirits who, through the agency of mediums, +do apparently the most absurd and irrational things, +but are never willing or able to do the simplest reasonable +thing to satisfy a competent judge; who mutter no +end of maudlin rubbish, add nothing of wisdom or +knowledge to mankind, and justify Professor Huxley +in saying that if such is the state of the dead we have +another good reason against suicide. + +3. There are a small number who think some of the +\emph{phenomena} to be genuine, but who attribute them not +to spirits, but to some obscure physical force not yet +understood, and but little investigated. This is the +attitude of Professor Crookes, and of the Milan experimenters. + +As to the class that is satisfied with the spiritistic +interpretation, it may be remarked that such an explanation +is in accordance with the attempts of the race +to give a rational explanation of all kinds of phenomena. +In the absence of proper knowledge, what +seems simpler or more natural than to assume some intelligent +agency as the cause of any obscure event? +This it was that peopled the mountains, glens, trees, +\DPPageSep{396.png}{381}% +\index{Knowledge, rapid growth of}% +and rivers with unseen beings, watchful and interested +in the affairs of men. The more ignorant, the closer +was the fetich; the more enlightened, the higher these +agencies retreated into the sky, useful now chiefly for +literary and artistic purposes. For some reason it has +always been discreditable to be without some theory +for all sorts of occurrences, and even to-day, in the +most enlightened communities, a man is liable to be +denounced for his stupidity or his cowardice if he says, +about some matters, I don't know. It is said, however, +that some of the phenomena at \textit{séances} bear the marks +of intelligence such as do not belong to natural occurrences, +and that it is a fair inference that other minds +than the witnesses are present. When Kepler discovered +that the planets moved in elliptical orbits +instead of circular ones as had been supposed, he felt +bound to give some reasonable explanation of the facts. +He knew of nothing but intelligence that could maintain +such motions, and he therefore supposed that each +planet must have some guiding spirit. When the law +of gravitation was applied, it was found that a circular +orbit was the only unstable orbit in the system, and +that gravity alone was sufficient to account for the +order, the harmony, and all the variety of motions; so +the spirits were dismissed from further duty. When a +spider has a leg grow to replace one that has been lost, +it has been held to be due to intelligent action superior +to ordinary chemical and physical action. When a +crystal of quartz is seen to replace a part accidentally +lost, so as to complete its symmetry before it begins to +grow elsewhere, it appears as if mind was at work here +\DPPageSep{397.png}{382}% +quite as much as in the other case, only in the latter most +persons are content not to follow the implications, for +they quickly see the philosophical rocks ahead. The +real truth is that the further one pursues the causes +of phenomena the more clearly does it appear unlikely +that disembodied intelligence is behind any particular +phenomena. + +Among all those who make up the great class of +believers in the spiritualistic theory of physical phenomena, +there is not a single physicist; that is, not one +to whom one would go for an explanation of any complicated +physical process. It is assumed that he is no +better qualified to investigate \textit{séance} phenomena than +others who do not know what to expect and look out +for in simpler cases, and that he is unreasonable if he +does not accept the statements of untrained observers +as being as good as his own observations. + +It is true that he has some prepossessions. He does +not believe the multiplication table should be trifled +with. He knows that most things may be done in +many different ways, independent of appearances. He +knows a man may sometimes not perceive what is +plainly before his eyes, simply because he was not +looking for it. He deems it right to exhaust the +possibilities of the known before summoning some +unknown and hypothetical factors in any given case. +He knows it to be well-nigh impossible for a man to +give an entirely accurate account to-day of what occurred +yesterday. He knows that a photograph is a +better witness of an event, and that a stenographic +report of statements made is more reliable than any +\DPPageSep{398.png}{383}% +\index{Miracle defined}% +man's memory. He knows that the interpretations of +events by mankind have never been true interpretations, +and that the general beliefs of mankind have +never been confirmed by science in any particular, and +that, so far as anything has been settled, it has been +decided against the opinions and judgment of mankind +and its leaders. He is aware that his key has unlocked +every one of the doors in Doubting Castle that have +been unlocked, and therefore he believes that the +implications of physical science as a whole are against +any generally received interpretation of any event that +has not been subjected to its scrutiny. +%\DPPageSep{399.png}{384}% + + +\Chapter[The Relations of Physical and Psychical Phenomena]% +{XVI}{The Relations of Physical and Psychical +Phenomena\protect\footnotemark}{384} + +\footnotetext{Read before the Psychical Congress, Chicago, August, 1893.}% + +% Set manually +\SetRunningHeads{MATTER, ETHER, AND MOTION}{Physical and Psychical Phenomena}% + +\First{Knowledge} has grown apace within the past fifty +years. It is generally admitted that more has been +acquired in this time than in all the preceding centuries. +Furthermore, the knowledge thus acquired has +not been simply an addition to the mental possessions +of former days; it has instead been of such a kind as +to completely overthrow nearly all former notions of +nature and its mode of operations, and the new product +can hardly be allowed to be an outcome of the work of +earlier men. It is in the nature of a catastrophe where +old continents have sunk and new ones have arisen +from old ocean beds. + +This generation lives in a new world, with new environments, +new ideas, new explanations, new philosophy, +new ideals, and new beliefs. We have new astronomy, +new chemistry, new physics, new psychology, new natural +history, and everybody is on the \textit{qui vive} to know +what can possibly come next. This does not mean +that nature goes on in a different way from what it had +hitherto done, but that we have mentally grasped a new +\DPPageSep{400.png}{385}% +\index{Mental processes imply physical conditions}% +and transforming idea. We have reached an elevation +from which it is possible to survey a broader field, and +can interpret phenomena better because their relations +are better perceived, and because of this it is seen that +the old interpretations were all wrong, and, indeed, +were worthless, because not true. While all this is +granted readily by most thoughtful persons, there are +not a few who recognize the changed opinions in the +various sciences and philosophy in general, who are not +at all persuaded but what the present philosophy of +things, which is dubbed evolution, is only a passing +phase and may itself presently give way to some +new and possibly truer conceptions, being content to +be mildly agnostic on such matters, and willing to wait +with patience for more light. There are some who +think the new philosophy does not take account of all +the known factors, if, by chance, there may not be +unknown factors of as much or more importance than +any which have been included, and which a final philosophy +of things will certainly include; and such object +strenuously to the limitations which the current philosophy +seems to set to knowledge and to the ideals +of the race. + +The man of science hears rumors of phenomena +which are said to be as certain as any in his own field, +which he has never investigated, and which cannot +come into his category of related things. Some of +these reported happenings are as marvellous as any +miracles that have been recorded. Persons of undoubted +probity have reported phenomena taking place +in their presence which, if true, give credence to many +\DPPageSep{401.png}{386}% +things for which in the past men and women have been +burned to death as wizards and witches. Thus, I have +an acquaintance, an eminent man not given to romancing, +who assures me he has seen, in undimmed light, a +chair ten feet from any person rise as if some one had +hold of its back and come and set itself down by his +side. Something of the same kind is said to have taken +place in the Milan experiments of last fall. Mr.\ +William Crookes tells us that the weight of a body has +been changed to be more or less according to an effort +of the will of Mr.\ Home, and likewise in Milan the +weight of the medium varied as much as fifty pounds. + +Now, there have been numerous attempts to define a +miracle for the purposes of philosophy, and usually it +is not the thing accomplished so much as the means +adopted for doing it. The antecedents of the event +are supposed to be other than the usual ones which +might do the same thing. Thus, a chair may be moved +by a person who lifts it and carries it to a new place; +but the chair may be pushed by a stick or pulled by a +string to a new place, while no one touched it, and all +who have been to see Hermann, and other magicians, +have seen things move about in a surprising manner +when no one touched them. In such cases it is +believed that none but well-known means are skilfully +used to produce such displacements, and that any one +might learn the art if it were worth his while. In other +words, no one thinks he is looking at a miraculous +event at a magician's show, no matter how surprising +the thing done; but if any person should be able to +make a chair, or an object, move from one place to +\DPPageSep{402.png}{387}% +\index{Consciousness implies energy}% +\index{Mind and energy}% +another without the mechanical adjuncts of some sort +which are needed by others, by an act of will rather +than by the employment of what we call energy, such +a person is able to work what has always been called a +``miracle.'' His method of doing that thing is a super-natural\DPnote{** Only instance.} +method, which is not the gift of every one even +in the slightest degree; for any one can try and satisfy +himself as to whether he can, by any simple act of will, +make the tiniest mote in a sunbeam or the most delicately +poised needle move in the slightest degree. +This is the common experience; and because it has +been found by experience that matter never moves +except when some other body has previously acted +upon it with a push or a pull, it has come about that +we have reduced the experience to the statements +embodied in so-called laws of motion, have found them +to be justified and without any exception so far as +investigation has gone, and this, too, by a multitude of +persons for two hundred years. As modern science +rests upon a mechanical basis, as it is concerned altogether +with the phenomena of matter and the relations +of the phenomena, and as these have been found in +every case that has been fully investigated to conform +to mathematical laws rigorously, not partly or dubiously, +is it not much more probable that any other phenomenon, +no matter what, that involves matter and its +changes, does conform strictly to the general laws, +than that these laws are sometimes inoperative? + +Probably the whole thing resolves itself into this: +Are the fundamental properties of matter variable? +Some of the phenomena alleged to happen at \textit{séances} +\DPPageSep{403.png}{388}% +imply that they are. How strong the case is against +such assumption, I think is not perceived by many persons +who give credence to the happenings, but who are +not well equipped with physical knowledge. Many persons +seem willing enough to admit physical laws and +physical processes in what they take to be the field of +physics, but they hold that there are other fields just as +certain, and among such, mind, that controls matter and +its forces, and to which it is not necessarily subject; +that it is perfectly philosophical to think that mind may +exist independent of matter and its relations, and be +able in this condition to control phenomena. + +Let us examine this. Assume that every physical +process in the world should be suddenly stopped, so +there should be no change. That would mean that all +motions were stopped. There would at once be neither +day nor night, for these are due to the earth's rotation; +no light, for light is a wave motion; there would +be no heat, for heat is a vibratory motion; there +would be no chemical changes, for they depend upon +heat; there would be neither solid nor liquid nor +gas, for each depends upon conditions of temperature, +that is, of heat, which is assumed to be absent; there +would be no sight, for that implies wave motions; nor +sound, for that implies air waves; nor taste, for that +implies chemical action; nor smell, for like reason; nor +touch, for that implies pressure---the result of motion. +The heart would cease to beat, the blood to flow, and +consciousness would be stopped. Every one of the +senses would be obliterated or annihilated; nothing +would happen, because there would be no change anywhere. +\DPPageSep{404.png}{389}% +Every phenomenon in the world of sensation +would be stopped, because every phenomenon in the +physical world had stopped; which is the same as saying +that all we call sensations are absolutely dependent +upon physical changes, going on all the time independent +of our will or choice, and which cannot be controlled +in the slightest degree by anybody. Every +phenomenon of every kind, then, consists in, as well +as is dependent upon, matter and its motion, and there +is in the whole range of experience no example of any +kind of a phenomenon where matter, ordinary matter, +is not the conditioning factor. There is no known case +where force or energy is changed in degree or direction +or kind but through the agency of matter. Every kind +of a change implies matter that has thus acted. What +is called the correlation of forces means that one kind +is convertible into some other kind of energy, as heat +into mechanical energy in the steam engine. But the +engine, a material structure, is essential for the change. +What is called the conservation of energy means that +in all the exchanges energy may undergo, as heat into +light, or work of any kind, the quantity of it does not +vary. The matter, as such, does not add to, or subtract +from it; hence only a material body can possess energy, +and a second material structure is necessary in order +that the energy of the first should be changed into any +other form. So it appears there must be at least two +bodies before anything can possibly happen. + +This all means that what we call energy is embodied +only in matter, and that what we call phenomena is but +the exchange of energy between different masses of +\DPPageSep{405.png}{390}% +\index{Mind and matter}% +matter; also that these exchanges take place with +mathematical precision, else prediction would be impossible, +and computation a waste of time. + +Now, assume that the physical structure of an individual +was kept intact, and that every atom and molecule +in the body maintained its relative position after all +motions had ceased. Assume, too, that the mind or +soul, or whatever one chooses to call the conscious +individuality, was present and capable as ever of acting +upon the material structure; can a single atom be +moved in the slightest degree? If any be moved, then +energy has been expended, energy which must have existed +elsewhere or have been created \textit{de novo}. For conscious +perception, whether sight or sound or any other, +motions embodying energy are essential, as pointed out; +and hence, to produce any perception, some motions +would necessarily have to be initiated, and to initiate +them energy from some source must be supplied. +All the energy the matter had has been destroyed +according to the assumption; so, if any movement has +begun, it must have been created or produced from some +other unthinkable condition which was not energy, in +some such sense as matter is supposed to have been +created, in which something is made out of nothing. +The demand is for creative power. Admit for the +argument's sake that it is done, and matter begins to +move in any kind of a way; so far it possesses energy, +physical energy as embodied in matter. Call the +amount of it ``A.'' Now, if the original condition of +things was established, so far as the amount of energy +was concerned, which may be called ``B,'' then the +\DPPageSep{406.png}{391}% +\index{Phenomena, unexplained}% +\index{Psychics}% +whole amount of energy is ``A plus B.'' It will make +no difference in this sum if one supposes that the +original motions and energy were not interrupted; for +if, on account of mind action, any particle moves more +or less than it would have done with its original supply, +then something has been added to the store of energy +in matter, and what is called the conservation of energy +is not true. + +Until all phenomena have been examined, there will be +obscure happenings and things to be explained by some +one who can; but it is no final explanation of anything +to say, ``A man did it,'' or ``An intelligence did it.'' +What kind of changes, that is, what kind of phenomena, +the forms of energy we are now acquainted with are +capable of producing no one can now limit, certainly +not one who has not been to the pains to understand +how the simple ones take place. I have often been +told that things cannot move in certain ways, or certain +things cannot be done except by intelligent action +or guidance; but it may be remembered that Kepler +thought guiding spirits were needful for making the +planets move in their elliptical orbits. If one must +explain an obscure phenomenon, is it not wisest to explain +it in accordance with what we know rather than in +accordance with what we do not know? It is better for +one to acknowledge his ignorance of the cause of it, than +to go romancing for a reason, and repudiate all we really +do know and its implications. A juggler may do the +most surprising things before one's eyes, but if one +cares to inquire into the antecedents of anything done +he will have no difficulty in tracing it as far as the +\DPPageSep{407.png}{392}% +\index{Thought transference}% +breakfast. What is meant is, the juggler does nothing +which does not require energy,---energy of the ordinary +sort, in the same sense as if it had been required +for sawing wood or walking up the street. As for consciousness, +dexterity, and all that is implied in both, I +pointed out a little way back there could be neither in +the absence of those changes which constitute physical +phenomena; and that not only life itself, but consciousness +as we know it, would be impossible without the +exchanges in the energy embodied in the cellular structure +of the brain. In the light of what has been accomplished +in the direction of physiological psychology, it +is entirely unwarrantable to assume that even thinking +can go on in the absence of physical changes of measurable +magnitude; and this is the same as saying that +what we call intelligent action is physical at its basis. + +There is such a formal agreement as well as actual +connection between conscious life and the life of the +brain, that it is not to be supposed any one who has properly +attended to the facts will venture to deny them. +Argue as one will, it is true there is no experimental +knowledge that is a part of science, of consciousness +separable from a material structure called brain, in which +physiological changes take place as the conditions for +thinking as well as for acting. This is the only known +relation of mind and body. However this association of +such apparently different provinces is to be explained, +it is still true that for every phenomenon in consciousness +there is a corresponding phenomenon in matter. +Psychologists have pointed out that the phenomena indicate +an identity at bottom between the activity of +\DPPageSep{408.png}{393}% +consciousness and cerebral activity. To follow this out +into particulars would be interesting and perhaps profitable +to most; but the significance of it here is that even +in the psychological field, where the opportunities for investigation +are right at hand and most is known, there +is no evidence for consciousness apart from a material +structure, or that the law of conservation of energy does +not hold as strictly true here as elsewhere in physics. +So there is no experimental reason for assuming the +existence of incorporeal intelligences. There is no +psychological question that is not at the same time a +physiological question. + +Experimentally it appears that the association of mind +with matter and energy is not of such a nature that one +is at liberty to assume their dissociation, any more than +one is at liberty to assume gravitation or magnetism as +independent existing somethings controlling matter according +to certain laws. So any hypothesis invented to +account for an occurrence that is not yet explained ought +not to be in contradiction to everything else we know, +and ought not to be entertained except as a last resort; +and the hypothesis of disembodied intelligences acting +now in and now out of the field of material things is +such an one. If such phenomena really happen at +\textit{séances} as are alleged, then we have to do with affairs +strictly within the line of physics, whether such phenomena +are so-called mental or so-called physical. It is +useless to affirm that the two are such radically different +phenomena that the methods of the latter are not +appropriate in the former; and the extensive laboratories +for physiological psychology, which are now +\DPPageSep{409.png}{394}% +being established in all the larger institutions of +learning, is a sufficient denial of the proposition. + +The term psychics is intended to denote something +different from the phenomena of psychology as manifested +in a given organism. It is supposed to relate to +the sympathetic relation of one mind to that of another +quite apart from the ordinary physical relations, that is, +from the senses. As for the mind-reading as exhibited +some years ago by Brown and others, I believe it is now +agreed that it is due to the sense of touch, and cannot +be done without contact. In hypnotic work there has +to be ``suggestion,'' and most of the very remarkable +cases, such as those in France last winter, have been +shown to be gross frauds. But let it be granted that +some of it is genuine, that it is possible in some cases +to impart information and discover the thoughts of +another without the common resources, it does not +then follow that the method is extra-physical. If only +here and there is to be found an individual called a +psychic, who is thus sensitive, and it is not a race +endowment, one no more need to summon a mysterious +supernormal agency to account for it, than such is +needed for the work of Newton or Mozart. Because a +phenomenon has not been explained, and no one knows +how to explain it, is no reason at all for supposing there +is anything mysterious about it. There are any number +of phenomena throughout nature that have not +been explained, and no one knows how to explain on +the basis of what is known. Such, for instance, is the +whirlwind that crosses the field, raising dust and leaves +into the air. No one has explained the soaring of birds, +\DPPageSep{410.png}{395}% +no one knows what goes on in an active nerve, or why +atoms are selective in their associates. Ignorance is +not a proper basis for speculation; and if one must have +a theory, let it be one having some obvious continuity +with our best physical knowledge. + +What is here given is not intended to be a denial that +such phenomena as thought-transference, or even the +most surprising things such as those described in the +Milan experiments, take place. It is only intended to +emphasize the probability that whatever happens has a +physical basis, and is therefore explained only when +these physical relations are known. +\DPPageSep{411.png}{unnumbered}% +%[Blank Page] + + +\Appendix +\DPPageSep{412.png}{397}% + +\Note{Note to \Pageref{Page}{57}.} +\Pagelabel{400}% + +\First{As} to whether it is considered as known that the sum of +the interior angles of a plane triangle are exactly equal to +one hundred and eighty degrees: ``Suppose that three points +are taken in space, distant from one another as far as the +sun is from $\alpha$~Centauri; and that the shortest distance between +these points is drawn so as to form a triangle. And suppose +the angles of this triangle to be very accurately measured +and added together; this can at present be done so accurately +that the error shall certainly be less than one minute, +less therefore than the five-thousandth part of a right angle. +Then I do not know that this sum would differ at all from +two right angles; but I also \emph{do not know that the difference +would be less than ten degrees}, and I have reasons for not +knowing.'' +\AppendixCite{W.~K. Clifford:}{Aims and Instruments of Scientific Thought.} + +``If the Euclidian\DPnote{** [sic]} assumptions are true, the constitution +of parts of space at an infinite distance is as well known as +the geometry of any portion of this room. So that here we +have real knowledge of something at least that concerns the +cosmos; something that is true throughout the immensities +and the eternities. That something Lobotchewski\DPnote{** [sic]} and his +successors have taken away.'' +\AppendixCite{W.~K. Clifford:}{Philosophy of the Pure Sciences.} +\DPPageSep{413.png}{398}% + +``In this case the universe as known becomes a valid conception, +for the extent of space is a finite number of cubic +miles. If you were to start in any direction whatever, and +move in a perfectly straight line according to the definition +of Liebnitz,\DPnote{** [sic]} after travelling a most prodigious distance \ldots +you would arrive at---this place.'' +\AppendixRef{\textsc{Ibid.}} + +``It must remain an open question whether, if we had +large enough triangles, the sum of the three angles would +still be two right angles.'' +\AppendixRef{\textit{Enc.\ Brit.\ 9th~ed., Art.\ Measurement.}} + +``It is true that according to the axioms of geometry, the +sum of the three angles of a triangle are precisely one hundred +and eighty degrees; but these axioms are now exploded, +and geometers confess that they, as geometers, know not the +slightest reason for supposing them to be precisely true. +That they are exactly that amount is what nobody can be +justified in concluding.'' +\AppendixCitePage{C.~S. Peirce:}{Monist,}{vol.~i.\ No.~2, p.~174.} + +``All that we need do is to call the attention of those who +busy themselves with mental philosophy to this generalization +of geometry as one of the results of modern mathematical +research which they cannot afford to overlook.'' +\AppendixCite{George Chrystal,}{in Enc.\ Brit., Art.\ Parallels.} + +Such as care to look into the matter further will find +the subject treated in an untechnical way in the works of +W.~K.~Clifford, in the chapters on the ``Theories of the +Physical Forces,'' ``Aims and Instruments of Scientific +Thought,'' and especially the ``Philosophy of the Pure Sciences.'' +There is much on it in the \textit{American Journal of +Mathematics}, vols. \i.~and~ii., also in the ``Proceedings of the +Royal Society,'' Edinburgh, vol.~x., 1879, and in article +``Measurement,'' \textit{Enc.~Brit.} +\DPPageSep{414.png}{399}% + +\Note{Note to \Pageref{Page}{208}.} +\Pagelabel{402a}% + +In 1881 the author discovered how electric ether waves +could be produced and identified, where the vibratory rates +were as high as $4000$ or more per second, by employing +static telephones detached and removed many feet from +the inducing electric current. These gave a wave length +of $\frac{186000}{4000} = 46+$ miles long. Hertz, Tesla, and others have +since then described methods of producing them so short +as to be but a few feet long. When they have thus been +mechanically shortened so as to be but the one forty-thousandth +of an inch in length, they will be seen by the eye as +red light. + +\Note{Note to \Pageref{Page}{242}.} +\Pagelabel{402b}% + +See Maxwell's ``Theory of Heat,'' pp.~160, 161. + +\settowidth{\TmpLen}{$\dfrac{H}{S} = \dfrac{h}{T}$.} +\begin{wrapfigure}[2]{l}{\TmpLen+\parindent} +\hfill\smash{$\dfrac{H}{S} = \dfrac{h}{T}$.} +\end{wrapfigure} +\noindent $S$~and~$T$ are the absolute temperatures of the +hot and cold bodies in Carnot's engine. $H$ +and $h$ are the quantities of heat taken up and given out. +When $T = 0°$, $h = 0$, when $h$ is the equivalent of the work +done. As this is $0$ at absolute zero, no work could be done +in changing the volume of a substance at that temperature. +There can be no cohesion among the molecules or atoms, for +this would require that work should be done to separate +them. It is the temperature of \emph{dissociation}. + +This conclusion is one to which chemists and physicists +have been led by their researches. For example, Dr.\ Lothar +Meyer says, ``At the lowest temperature to which we can +attain, the majority of chemical reactions studied under +these conditions have been found to cease or to proceed +very slowly, so that it would appear to be very probable that +at the absolute zero, viz., $273°$, a temperature much below +the lowest yet attained, chemical action would cease altogether +from the absence of any form of heat motion whatsoever; +so without heat there would be no exertion of the +so-called chemical affinity.'' +\AppendixRef{\textit{Modern Theories of Chemistry}, §~211.} +\DPPageSep{415.png}{400}% + +\Note{Note to \Pageref{Page}{277}.} +\Pagelabel{403}% + +The hypothesis of a ``vital principle'' is now as completely +discarded as the hypothesis of phlogiston in chemistry. +No biologist with a reputation to lose would for a +moment think of defending it. +\AppendixCitePage{John Fiske:}{Cosmic Philosophy,}{vol.~i.\ p.~422.} + +``We can demonstrate the infinitely manifold and complicated +physical and chemical properties of the albuminous +bodies to be the real cause of organic or vital phenomena.'' +\AppendixCitePage{Haeckel:}{History of Creation,}{vol.~i.\ p.~330.} + +``The aim of modern physiology is to conceive all organic +processes as physical or chemical.'' +\AppendixCitePage{Höffding:}{Outlines of Psychology,}{p.~57.} + +``Physiologists must expect to meet with an unconditional +conformity to law of the forces of nature in their inquiries +respecting the vital processes. They will have to apply +themselves to the investigation of the physical and chemical +processes going on within the organism.'' +\AppendixCitePage{Helmholtz:}{Scientific Lectures,}{p.~384.} + +``A vital element, i.e., an element peculiar to organisms, +no more exists than does a vital force working independently +of natural and material processes.'' +\AppendixCitePage{Claus \& Sedgwick:}{Zoölogy,}{part~i.\ p.~10.} + +``In Physiology the word life is understood to mean the +chemical and physical activities of the parts of which the +organism consists.'' +\AppendixCitePage{B. Sanderson:}{Nature,}{vol.~xlviii., p.~613.} + +``Modern physiology interprets the phenomena of organic +life by means of physical and chemical laws. An appeal to +`vital force' or to the intervention of mind, it does not +recognize as an explanation of an organic phenomenon.'' +\AppendixCitePage{Höffding:}{Outlines of Psychology,}{p.~10.} +\DPPageSep{416.png}{401}% + +``Physiology thus appears as a branch of applied physics, +its problems being a reduction of vital phenomena to general +physical laws and thus ultimately to the fundamental laws +of mechanics.'' +\AppendixCitePage{Wundt:}{Lehrbuch der Physiologie,}{p.~2.} + +``It must not be supposed that the differences between +living and not living matter are such as to justify the +assumption that the forces at work in the one are different +from those to be met with in the other.'' +\AppendixCitePage{Huxley:}{Art.\ Biology, Enc.\ Brit.,}{p.~681.} + +``Zoölogy, the science which seeks to arrange and discuss +the phenomena of animal life and form as the outcome +of the operation of the laws of physics and chemistry.'' +\AppendixCitePage{Lankester:}{Art.\ Zoölogy, Enc.\ Brit.,}{p.~803.} + +``If corporal functions are mediated by immaterial +agencies, physiological science is impossible.'' +\AppendixCitePage{G.~Stanley Hall:}{Amer.\ Jour.\ Psychology,}{vol.~iii.\ p.~74.} + +``It has not occurred to me that any one now uses the +term `vital force' in any other way than as a convenient +method of expressing the sum total of the physical and +chemical activities of organisms.'' +\AppendixCite{Prof.\ E.~L. Mark,}{Harvard University.} + +``These phenomena of life, though they may not as yet be +physically and chemically explained, are certainly not to be +referred to the working of any special \emph{vital force} peculiar +to organisms\ldots. We have to do here with the same +forces and the same substances that we meet with elsewhere +in nature.'' +\AppendixCitePage{Lang:}{Textbook of Comp.\ Anat.,}{London, 1891, p.~2.} + +``Modern science has allowed the vitalistic theory (\textit{vitalismus}) +to drop; instead of by means of a special vital force, +it explains irritability as a very complex chemico-physical +phenomenon. It is only distinguished from other chemico-physical +\DPPageSep{417.png}{402}% +phenomena of inorganic nature by degree, namely, +that the external stimuli come in contact with a substance +of complicated structure, an organism, and correspondingly +produce in it also a series of complicated processes.'' +\AppendixCitePage{O.~Hertwig:}{Die Zelle und die Gewebe,}{p.~75, 1893.} + +``I know of no authority in recent years which recognizes +a distinct vital force; all students of nature, so far as I am +aware, explain all the phenomena of life by means of physical +and chemical forces.\DPtypo{}{''} +\AppendixCite{Prof.\ J.~S. Kingsley,}{Tufts College.} + +%\DPPageSep{418.png}{403}% +% [** PP: Not small-capping first index entry] + +\normalsize +\clearpage +\fancyhf{} +\cleardoublepage + +\IndexBookmark +\fancyhead[C]{\textsc{INDEX}} +\printindex + +\iffalse +Action at a distance 88 + +Absolute zero 242, 336 + +Affinity, chemical 240 + +Albumen, size of molecule 15 + +Ampère turns 209 + +Arcturus 145 + +Arc light 216 + +Atmosphere, height of 26 + +Atoms 10, 18, 19 + +Atoms, unalterable 21, 22 + +Atoms, life associated with 24, 296 + +Atoms, chemical properties 239 + +Atoms, as vortex rings 349 + +Atoms, vibrations of 243 + +Attraction, gravitative 83, 309 + +Attraction of vibrating fork 87 + +Attraction of disks 94 + +Attraction depends upon distance 85 + +Attraction of vortex rings 95, 244 +% \indexspace + +Blavatsky, Madam, pretensions of 359 + +Bonnenburger's apparatus 40 + +Boiling-point pressure 125 +% \indexspace + +Cause and effect 75 + +Camera 162, 163 + +Catalysis 248 + +Cell structure 280 + +Charles, Law of 336 + +Chemism 238 + +Chemism and heat 241, 336 + +Chemical field 247, 305 + +Chemical effects 218 + +Chemical origin of electricity 177 + +Chemical reactions depend on temperature 336 + +Cohesion, in solids and liquids 332 + +Cohesion, destroyed 333 + +Colors 165 + +Color-blindness 171 + +Color, nature of 339 + +Combustion 103 + +Conductivity, electrical 190, 192 + +Consciousness implies energy 390 + +Corti's fibres 275 + +Corn, life of 291 + +Crookes' tubes 224 + +Crystallization 245, 249, 306 +% \indexspace + +Decomposition of water 218 + +Density 6 + +Diamond, hardness of 338 + +Dissociations 131, 219 + +Dispersion 138 + +Dynamo 213 +% \indexspace + +Ear 274 + +Earth, velocity of, in space 34 + +Earth, diameter of 55 +%\DPPageSep{419.png}{404}% + +Earth, a magnet 303 + +Earth, curvature 69 + +Earth, solidity of 126 + +Egg 291 + +Echo 265 + +Efficiency of machines 213 + +Elasticity 341 + +Elasticity due to motion 39, 341 + +Elements 136 + +Energy, factors of 70, 77 + +Energy in the ether 79, 105 + +Energy. What determines transfer 214 + +Energy, unknown, preface. + +Electricity, origin of 174, 229, 354 + +Electricity, thermal 174 + +Electricity, mechanical origin 180, 230 + +Electricity, magnetic origin 181 + +Electricity, electrical origin 182, 230 + +Electrical antecedents 186 + +Electrical effects 231 + +Electrical effects, reversible 232 + +Electricity, dual 234 + +Electricity, activity 194 + +Electrical field 196, 300 + +Electrical stress 197 + +Electrical waves 198, 303 + +Electro-magnets 81, 210 + +Electric lamps 215 + +Energy of translation 64 + +Energy of vibration 66 + +Energy of rotation 68 + +Ether 26, 32, 34, 80 + +Ether, a non-conductor 191 + +Ether waves 134 + +Ether wave qualities 134 + +Ether phenomena not explained 352 + +Ether waves, their source 135, 207 + +Ether pressure 205 + +Ether rotations 234 + +Explosion products 71 +% \indexspace + +Fable, La Fontaine's 357 + +Falling bodies 60 + +Falling bodies, energy of 60 + +Fibres of Corti 275 + +Fields, physical 298 + +Fields, chemical 247, 305 + +Fields, electrical 196, 300 + +Fields, magnetic 202, 214, 252 + +Fields, mechanical 247 + +Fields, thermal 298 + +Flames 137 + +Foot-pound 60, 62 + +Food 284 + +Foster, Dr.\ Michael, quoted 296 + +Force, vital 279 + +Friction, its effects 23, 34 + +Fuels 103 +% \indexspace + +Galvanic battery 178 + +Gas, motion in 333 + +Gas, free path in 334 + +Gas, pressure in 334, 336 + +Gas, destroyed 336 + +Gaseous absorption 142 + +Geometry 56, 57 % Appendix. + +Geometry@{Appendix.} + +Geissler's tubes 223 + +Goose, work in flying 65 + +Gravitation 82, 90, 309, 347 + +Gravitation, law of 84 + +Gravity, specific 7 + +Gravity follows from structure 348 + +Growth 250, 292, 310 + +Growth of crystals 283, 381 + +Growth of lobster 283 + +Gunpowder 103 + +Guppy, Mrs. 359 + +Gyroscope 342 +% \indexspace + +Hair-cloth loom 312 + +Hardness not atomic property 338 +%\DPPageSep{420.png}{405}% + +Hearing, what is implied in 370 + +Hertz waves 344, 351 + +Helmholtz 35 + +Heat, mechanical origin of 99 + +Heat, chemical origin of 102 + +Heat, electrical origin of 104 + +Heat, radiational origin of 105 + +Heat, mechanical equivalent 109 + +Heat unit 112 + +Heat, effects 123, 254, 335 + +Heat by impact 225 + +Heat of the sun, origin of 119 + +Heat, nature of 115, 118 + +Hypothesis, needful 94 + +Hypothesis, gravitation 90 + +Hydrogen vibrations 116 +% \indexspace + +Impenetrability 340 + +Immortality 24, 367 + +Inertia 70, 345 + +Induction coils 208 + +Inductive action 183, 195, 250, 302 +% \indexspace + +Joule 110 + +Jupiter, temperature of 144 +%[**missing \indexspace] + +Kepler, the guesser 90 + +Kinetics 46 + +Kinematics 46 + +Knowledge, rapid growth of 384 +% \indexspace + +Laws not compulsory 353 + +Law, physical 373 + +Lever 317 + +Life 277 % Appendix. + +Life@{Appendix.} + +Life, definitions of 278 + +Light, a sensation 135, 363 + +Light, energy of 80 + +Light, its velocity 26, 28 + +Light, its nature 27, 80, 134, 364 + +Light waves 207 + +Lightning 185, 223 + +Lighting, electric 214, 222 + +Luminous effects 222 +% \indexspace + +Matter, living 283, 294 + +Matter, characteristic property 4 + +Matter, its definition 4 + +Matter, divisibility of 8 + +Matter, effect of temperature upon 132, 336 + +Matter, as modes of motion 331 + +Matter, states of 332 + +Mass 345 + +Materialists 351 + +Materializations and energy 365 + +Mars, atmosphere of 144 + +Mars, signalling to 217 + +Machines 312, 325 + +Magnetic field 202, 204, 214, 252, 303 + +Magnetic induction 208 + +Magnetic rotation 235 + +Magnetic waves 81, 202, 207, 344 + +Magnet, electro 81 + +Mathematics 89 + +Mechanical field 307 + +Medium, necessity for 29 + +Mental processes imply physical conditions 388 + +Meteors 21, 26, 64 + +Mercury 55 + +Miracles possible 353 + +Miracle defined 386 + +Mind and energy 390 + +Mind, a material habitat for 24 + +Mind and matter 24, 393 + +Mirrors 147 + +Microscope, magnifying powers 15, 149 + +Molecules, size of 13, 18, 46 + +Molecules, loaded 160 + +Molecules, long free path 224 +%\DPPageSep{421.png}{406}% + +Molecules, number of, in universe 124 + +Motion, kinds of 46, 48, 49, 145 + +Motion, velocity of 50 + +Motion, transformations of 314 + +Motion, molecular and atomic 49 + +Motion, laws of 70, 73 + +Motion, antecedent of 72 + +Molecular fatigue 78 + +Molecular stability 281 + +Momentum 74 + +Motor, electric 212 + +Muscles 286 + +Muscular work 67 + +Musical sounds 268 + +Musical ratios 269 + +Musical instruments 271 +% \indexspace + +Newton, Sir Isaac 30, 82, 83, 88 + +Nerves, their functions 288, 290 + +Nebula theory 97 + +Neptune, discovery of 89 + +Noise 269 +% \indexspace + +Ohm's law 189 + +Organic and inorganic matter, difference between 366 +% \indexspace + +Phenomena, nature of 59 + +Phenomena, unexplained 353, 394 + +Phenomena physical, implications + +of 354 + +Photography 156 + +Phosphorescence 226 + +Physical fields 298 + +Physical universe a machine 330 + +Physical processes, reversible 232 + +Physicists, prepossessions 382 + +Pitch 259 + +Plating, electro 221 + +Polarization of molecules 178, 219 + +Postulates of Physical Science 356 + +Power, needed for rapid movement in air 359 + +Potential, electrical 189 + +Principia 31, 70 + +Prism 138 + +Protoplasm 280 + +Psychics 394 + +Pulley 317 + +Purpurine 169 + +Push and pull 315 +% \indexspace + +Radiometer 154 + +Reflection 147 + +Retina, its functions 171 + +Reflex action 172 + +Refraction 138, 147 + +Resistance, electrical 192, 214 + +Rotations in ether 235 +% \indexspace + +Satellite 69 + +Saturn, temperature of 144 + +Science, no one independent 378 + +Senses 161, 371 + +Séances, phenomena at 362, 379 + +Seeing, what is implied in 369 + +Sirius 145 + +Silver salts unstable 159 + +Soap-bubbles 10 + +Sound, origin of 257, 360 + +Sound, characteristics 262 + +Sound, range of 263 + +Sound, velocity of 263 + +Sound, vocal 272 + +Solar system 329 + +Space 58 + +Space, navigation of 154 + +Specialists 373 + +Spiritualistic theory 360 + +Specific gravity 7 + +Specific heat 130 + +Spectroscope 139 + +Spectrum analysis 140 +%\DPPageSep{422.png}{407}% + +Spectrum, solar 138, 142 + +Spark, electric 223 + +Spirit disembodied 360 + +Stress in ether 93 + +Stress in glass 92 + +Stress, electrical 183, 197, 231 + +Stress, magnetic 181 + +Steam-engine 113 + +Steam-engine, efficiency of 114 + +Stars, their number 18 + +Stars, their distance 19, 28 + +Stars, their motions 145 + +Sun, its distance 28, 56 + +Sun, its magnitude 122 + +Sun, its heat 122 + +Sun, its age 122 + +Sun, its structure 143 +% \indexspace + +Temperature 106 + +Temperature, table 108 + +Temperature, maximum 127 + +Terminology, electrical 186 + +Telegraph 211 + +Telephone 211 + +Thermometer 107 + +Tesla ether waves 344 + +Thermometer, air 109 + +Thomson, Sir Wm. 35 + +Thermodynamics 112 + +Thermopile 176 + +Thermodynamics, electric 174 + +Thought transference 395, 311 + +Toepler-Holtz electrical machine 294 + +Top, sleep of 72 + +Transparency 146 + +Transformations of motion 321 +% \indexspace + +Universe, its size 28 + +Universe, atoms in 20 +% \indexspace + +Vacuum, a non-conductor 223 + +Vacuum 47 + +Venus 55 + +Velocities 50, 54, 56 + +Vibrations per second 52, 53 + +Vibrations, gaseous 116 + +Vibrations, sympathetic 249, 267 + +Vibrations, forced 267 + +Vital force 279 % Appendix. + +Vital force@{Appendix.} + +Vision, phenomena of 164 + +Vision, hallucinations of 166 + +Vision, energy needed for 166 + +Vision of animals 168 + +Vision, theory of 168 + +Voice 272 + +Vortex ring theory of matter 94 + +Vortex ring model 342 + +Vortex rings in air 35 + +Vortex rings, properties of 37, 72 + +Volcanoes 127 +% \indexspace + +Wave lengths of sound 265 + +Waves, electric 303 + +Water decomposition 218 + +Weight 61 + +Weights, standards of 60 + +Welding, electric 210 + +Work, standard of 60 + +Work, measure of 62, 64, 318 + +Work, muscular 67 +\fi + +\cleardoublepage +\phantomsection +\pdfbookmark[0]{Catalog}{Catalog} + +%\DPPageSep{423.png}{I}% +\renewcommand{\headrulewidth}{0.5pt} +\fancyhead[C]{\textit{Books Upon Various Subjects}} +\thispagestyle{empty} + +\begin{center} +\textsf{\Large LEE AND SHEPARD}\\[12pt] +\textsf{\large 10~MILK STREET BOSTON}\\[8pt] +\tb\\[12pt] +{\Large List of Books upon Various Subjects}\\[8pt] +\tb +\end{center} + +\Entry{QUABBIN} + +\Subentry +Sketches in a Small Town \quad With Outlooks upon Puritan Life \quad By \Au{Francis~H. +Underwood}~LL.D. author of ``Handbooks of English Literature'' +``Man Proposes'' ``Lord of Himself'' etc. Fully illustrated +Cloth \$1.75 + +\begin{Descrip} +This work purports to give an account of the progress of a small New England town; +but it is of wider and deeper import; namely, a view of the development of the narrow +and sombre Puritan into the variously gifted and accomplished ``Yankee'' of to-day. It +concerns the state of literature and art in the early part of the present century, and shows +how the fairer conditions of modern times came into being. + +In plan it is wholly unlike any modern book. It is not a town history, nor an historical +essay, nor a collection of reminiscences. Its chapters are mostly picturesque descriptions +of the old times, and show the ``rude forefathers'' at home, at church, at town-meetings, at +road-making, and in other scenes of their daily life. There are sketches of the successive +ministers, the schools, the quiltings, sleigh-rides, and other rustic gatherings,---of the +homely speech and manners, and of the complexities of Yankee character. + +It is believed that these graphic, tender, and humorous pictures will appeal to the hearts +and memories of New England people, and to their descendants along the line of migration +westward to the Mississippi and beyond. + +The illustrations are from photographs taken from beautiful scenes in ``Quabbin.'' +\end{Descrip} + +\clearpage +\Entry{UNIVERSAL PHONOGRAPHY or Short-hand by the ``Allen +Method''} + +\Subentry +A self-instructor, whereby more speed than long-hand writing is gained at +the first lesson, and additional speed at each subsequent lesson \quad By \Au{G.~G. +Allen}, Principal of the Allen Stenographic Institute Boston \quad 50~cents + +\begin{Descrip} +There is scarcely any requirement so helpful to the student, scholar, scientist, or professional +man as short-hand writing. Heretofore all methods have required so long a +time before one could become so proficient as to make it of any advantage, that men in +middle life, or busy men, have not been able to give the time to learn it; but by the ``Allen +Method'' one can almost in ``the idle moments of a busy life,'' certainly in an hour a day +for two or three months, become so expert as to report a lecture \textit{verbatim}. +\end{Descrip} +%\DPPageSep{424.png}{II}% +%Font size changes on this page +\Entry{MATTER, ETHER, AND MOTION} + +\Subentry +The Factors and Relations of Physical Science \quad By \Au{Prof.\ A.~E. Dolbear} +Tufts College author of ``The Telephone'' ``The Art of Projecting'' +etc. \quad Cloth~\$2.00 + +\begin{Descrip} +``Matter, Ether, and Motion,'' the Factors and Relations of Physical Science, by A.~E. +Dolbear,~Ph.D\@. The author in this treatise presents to his readers the principles of physical +science. The chapters are arranged as Matter, Ether, Motion, Energy, Gravitation, +Heat, Ether Waves, Electricity, Chemism, Sound, Life, Physical Fields, Machines and +Mechanism. This is a tolerably comprehensive table, and introduces the student to the +principles on which, so far as at present known, the action of the universe seems to +depend. + +Altogether this little treatise gives an insight into matters outside the common range of +serious study, and yet places the subject within reach of the student seeking for knowledge. +Although dealing with abstruse scientific topics, the style is lucid, and the matter intelligible +to ordinary thinkers and readers in search of information.---\textit{New York Commercial +Advertiser}. +\end{Descrip} + + +\Entry{THE TELEPHONE} + +\Subentry +An account of the phenomena of electricity, magnetism, and sound as involved +in its action; with directions for making a speaking telephone \quad +By \Au{Prof.\ A.~E. Dolbear} of Tufts College \quad 50~cents + +\begin{Descrip} +An interesting little book upon this most fascinating subject, which is treated in a very +clear and methodical way. First we have a thorough review of the discoveries in electricity, +then of magnetism, then of those in the study of sound,---pitch, velocity, timbre, tone, +resonance, sympathetic vibrations, etc. From these the telephone is reached, and by them +in a measure explained.---\textit{Hartford Courant}. +\end{Descrip} + + +\Entry{THE ART OF PROJECTING} + +\Subentry +By \textsc{Prof.\ A.~E. Dolbear}~Ph.D. (Tufts College) \quad New Edition revised +with additions \quad $125$~illustrations \quad Cloth~\$2.00 + +\begin{Descrip} +A Manual of Experimentation in Physics, Chemistry, and Natural History with the Porte +Lumière and the Magic Lantern; also with Electric Lights and Lamps and the Production +and Phenomena of Vortex Rings. +\end{Descrip} + + +\Entry{WHAT IS TO BE DONE--(Emergency Handbook)} + +\Subentry +A Handbook for the Nursery with Useful Hints for Children and Adults \quad +By \Au{Robert~B. Dixon}~M.D. Surgeon of the Fifth Massachusetts Infantry, +Physician to the Boston Dispensary \quad Cloth 50~cents; paper 30~cents + +\begin{Descrip} +Dr.\ Dixon, in this little ``Emergency Handbook,'' gives simple directions what to do +in a number of the most common cases that arise, either in home treatment of slight accidents, +or indispositions, or in the case of patients in more serious cases, until the arrival of +the physician. The book is worth its weight in gold, and ought to have a place in every +family library.---\textit{Providence Press}. +\end{Descrip} + + +%%%%%%%%%%%%%%%%%%%%%%%%% GUTENBERG LICENSE %%%%%%%%%%%%%%%%%%%%%%%%%% + +\clearpage +\fancyhf{} +\renewcommand{\headrulewidth}{0pt} +\cleardoublepage + +\backmatter +\phantomsection +\pdfbookmark[-1]{Back Matter}{Back Matter} +\phantomsection +\pdfbookmark[0]{PG License}{Project Gutenberg License} +\renewcommand{\headrulewidth}{0.5pt} +\fancyhead[C]{\textsc{LICENSING}} + +\begin{PGtext} +End of the Project Gutenberg EBook of Matter, Ether, and Motion, Rev. ed., +enl., by Amos Emerson Dolbear + +*** END OF THIS PROJECT GUTENBERG EBOOK MATTER, ETHER, AND MOTION *** + +***** This file should be named 31428-pdf.pdf or 31428-pdf.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/1/4/2/31428/ + +Produced by Andrew D. 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with % +% almost no restrictions whatsoever. You may copy it, give it away or % +% re-use it under the terms of the Project Gutenberg License included % +% with this eBook or online at www.gutenberg.org % +% % +% % +% Title: Matter, Ether, and Motion, Rev. ed., enl. % +% The Factors and Relations of Physical Science % +% % +% Author: Amos Emerson Dolbear % +% % +% Release Date: February 27, 2010 [EBook #31428] % +% % +% Language: English % +% % +% Character set encoding: ISO-8859-1 % +% % +% *** START OF THIS PROJECT GUTENBERG EBOOK MATTER, ETHER, AND MOTION *** % +% % +% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % + +\def\ebook{31428} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +%% %% +%% Packages and substitutions: %% +%% %% +%% book: Required. %% +%% inputenc: Standard DP encoding. Required. %% +%% %% +%% ifthen: Logical conditionals. Required. %% +%% %% +%% amsmath: AMS mathematics enhancements. Required. %% +%% amssymb: Additional mathematical symbols. 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+} + +% Miscellaneous extra formatting for individual entries +\newcommand{\etseq}[1]{\hyperpage{#1} \protect\textit{et~seq.}} +\renewcommand{\see}[2]{\textit{See} #1} + +\makeindex + + +\begin{document} + +\pagestyle{empty} +\pagenumbering{Alph} + +\phantomsection +\pdfbookmark[-1]{Front Matter}{Front Matter} + +%%%% PG BOILERPLATE %%%% +\Pagelabel{PGBoilerplate} +\phantomsection +\pdfbookmark[0]{PG Boilerplate}{Project Gutenberg Boilerplate} + +\begin{center} +\begin{minipage}{\textwidth} +\small +\begin{PGtext} +The Project Gutenberg EBook of Matter, Ether, and Motion, Rev. ed., enl., by +Amos Emerson Dolbear + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Matter, Ether, and Motion, Rev. ed., enl. + The Factors and Relations of Physical Science + +Author: Amos Emerson Dolbear + +Release Date: February 27, 2010 [EBook #31428] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK MATTER, ETHER, AND MOTION *** +\end{PGtext} +\end{minipage} +\end{center} + +\clearpage + + +%%%% Credits and transcriber's note %%%% +\begin{center} +\begin{minipage}{\textwidth} +\begin{PGtext} +Produced by Andrew D. Hwang, Peter Vachuska, Chuck Greif +and the Online Distributed Proofreading Team at +http://www.pgdp.net +\end{PGtext} +\end{minipage} +\end{center} +\vfill + +\begin{minipage}{0.85\textwidth} +\small +\phantomsection +\pdfbookmark[0]{Transcriber's Note}{Transcriber's Note} +\subsection*{\centering\normalfont\scshape% +\normalsize\MakeLowercase{\TransNote}}% + +\raggedright +\TransNoteText +\end{minipage} + + +%%%%%%%%%%%%%%%%%%%%%%%%%%% FRONT MATTER %%%%%%%%%%%%%%%%%%%%%%%%%% + +\DPPageSep{001.png}{unnumbered}% +\clearpage +\null +\vfill +\begin{center} +\setlength{\fboxsep}{12pt} +\framebox{% +\begin{minipage}{3in}%[** Hard-coded width] +\begin{center} +\textgoth{By Professor A.~E. Dolbear} \\ +\tb[0.5in] +\end{center} + +\textit{\footnotesize MATTER, ETHER AND MOTION} +\smallskip + +\hspace*{\QUAD} +\begin{minipage}{\linewidth-2\QUAD} +\scriptsize +The Factors and Relations of Physical Science \\ +Enlarged Edition\quad Cloth\quad Illustrated\quad \$2.00 +\end{minipage} + +\medskip +\textit{\footnotesize THE TELEPHONE} +\smallskip + +\hspace*{\QUAD} +\begin{minipage}{\linewidth-2\QUAD} +\scriptsize +With directions for making a Speaking Telephone \\ +Illustrated\quad 50~cents +\end{minipage} + +\medskip +\textit{\footnotesize THE ART OF PROJECTING} +\smallskip + +\hspace*{\QUAD} +\begin{minipage}{\linewidth-2\QUAD} +\scriptsize +A Manual of Experimentation in Physics, Chemistry, +and Natural History, with the Porte Lumière +and Magic Lantern \\ +New Edition\quad Revised\quad Illustrated\quad \$2.00 +\end{minipage} + +\begin{center} +\tb[0.5in]\\ +\textgoth{\footnotesize Lee and Shepard Publishers Boston} +\end{center} +\end{minipage}} +\end{center} +\vfill + +\DPPageSep{002.png}{unnumbered}% i +% title page +\frontmatter +\pagestyle{empty} + +\setlength{\TmpLen}{0.125in}% + +\begin{center} +{\LARGE \scshape Matter, Ether, and Motion} \\[\Titleskip{4}] +{\itshape THE FACTORS AND RELATIONS \\[\Titleskip{1}] +OF\\[\Titleskip{1}] +PHYSICAL SCIENCE}\\[\Titleskip{4}] +{\scriptsize\upshape BY} \\[\Titleskip{1}] +{\scshape A.~E. DOLBEAR Ph.D.} +\medskip + +\tiny\upshape PROFESSOR OF PHYSICS TUFTS COLLEGE \\ +AUTHOR OF ``THE TELEPHONE'' ``THE ART OF PROJECTING'' ETC. + +\vspace*{4\TmpLen} +{\scriptsize\itshape REVISED EDITION, ENLARGED} +\vspace*{4\TmpLen} + +\small B\,O\,S\,T\,O\,N %[** PP: One-off gesperrt] + +LEE\quad AND\quad SHEPARD\quad PUBLISHERS +\smallskip + +\scriptsize 10 MILK STREET + +\small 1894 +\end{center} + +\DPPageSep{003.png}{unnumbered}% ii +% copyright page +\clearpage +\begin{center} +\scriptsize +\null\vfill +\scshape Copyright, 1892, 1894, by Lee and Shepard \\[\Titleskip{1}] +\itshape All Rights Reserved \\[\Titleskip{1}] +\scshape Matter, Ether, and Motion +\vfill +C.~J. Peters \& Son, \\ +Type-Setters and Electrotypers, \\ +145 High Street, Boston. +\end{center} + +\clearpage +\pagestyle{fancy} +\fancyfoot{} + +\stretchyspace + +\Preface{PREFACE TO THE SECOND EDITION} +\DPPageSep{004.png}{iii}% + +\First{The} issue of a new edition of this book gives me an +opportunity to make some needed corrections, and enlarge +it by the addition of three new chapters, which +I hope will make it more useful to such as have a taste +for fundamental physical problems. The first of these, +Properties of Matter as Modes of Motion, presents +the evidence that all the characteristic properties of +matter are due to energy embodied in various forms +of motion. The second, on The Implications of +Physical Phenomena, points out what assumptions +are made in explaining phenomena. It is the substance +of a series of articles published in the \textit{Psychical +Review} in 1892 and~1893. The third, on The Relations +between Physical and Psychical Phenomena, +was read as a paper before the Psychical Congress at +the World's Fair in August,~1893. + +Judging from some of the comments made about my +statements as to Modern Geometry on \Pageref{page}{57}, and +as to Vital Force, \Pageref{p.}{279}, I have thought it would be +useful to some to see corroboratory statements; and I +have therefore added, in an appendix, a few pages of +\DPPageSep{005.png}{iv}% +quotations from some of the most eminent mathematicians +and biologists on these subjects, and from them +one may judge whether or not my statements are +correct. + +As the work is a treatise on Physics, there is no +special reason for going beyond it; but if this presentation +of the subject is any approach to the truth, there +is an important conclusion to be drawn from it. If the +ether be the homogeneous and uniform medium it is +believed with reason to be, then, in the absence of +what we call matter, no physical change which we call +a phenomenon could possibly arise in it; for every such +phenomenon is a product, and in the absence of one of +the essential factors, viz., matter, it could not be. If +matter itself be a form of motion of the ether, the ether +must have existed prior to matter; also, if the atom be a +form of energy, then must energy have existed before +matter existed. Hence there must have been some +other agency radically different from any physical +energy we know, and independent of everything we +know, which was capable of producing orderly physical +phenomena, by acting upon the ether; for a homogeneous +medium could not originate it. Some philosophers +call this antecedent power The Unknowable; others call +it God. If energy \emph{as we know it} implies antecedent +energy as we do not know it, so, likewise, mind as we +know it implies antecedent mind under totally different +conditions from those in which we find it embodied. + +In whatever direction one pursues physical science, +\DPPageSep{006.png}{v}% +he is at last confronted with a physical phenomenon +with a superphysical antecedent where all physical +methods of investigation are impotent. Such considerations +raise the theistic hypothesis of creation to the +rank of such physical theories as the nebula theory +of the origin of the solar system, and the undulatory +theory of light. +\DPPageSep{007.png}{unnumbered}% vi +% [Blank Page] + + +\Preface{PREFACE} +\DPPageSep{008.png}{vii}% + +\First{Within} the past fifty years the advance in physical +knowledge has not only been rapid, but it has been +well-nigh revolutionary. Not that knowledge that was +felt to be well grounded before has been set aside,---for +it has not been,---but the fundamental principles +of natural philosophy that were applied by Sir Isaac +Newton and others to masses of visible magnitude +have been applied to molecules; and it has thus been +discovered that all kinds of phenomena are subject to +the same mechanical laws. It was thought before that +physics embraced several distinct provinces of knowledge +which were not necessarily related to each other, +such as mechanics, heat, electricity, etc. Such terms +as imponderable matter, latent heat, electric fluid, +forces of nature, and others in common use in text-books +and elsewhere, served to maintain the distinctions; +and even to-day some of these obsolete physical +agencies are to be met in books and places where one +would hope not to find them. As all physical phenomena +are reducible to the principles of mechanics, atoms +and molecules are subject to them as much as masses +\DPPageSep{009.png}{viii}% +of visible magnitude; and it has become apparent that +however different one phenomenon is from another, the +factors of both are the same,---matter, ether, and +motion; so that all the so-called forces of nature, +considered as objective things controlling phenomena, +are seen to have no existence; that all phenomena are +reducible to nothing more mysterious than a push or +a pull. + +Some say that science is simply classified knowledge. +To the author it is more than that, it is a consistent +body of knowledge; and a true explanation of any +phenomenon cannot be inconsistent with the best +established body of knowledge we have. If physical +factors are fundamental, then theorizers must square +their theories to them. + +The text-books have not kept pace with the advance +of knowledge; and there is a large body of persons +desirous of knowing more of natural philosophy, and +especially of its trend, who have neither time nor +opportunity to read and digest monographs on a thousand +topics. To meet the wants of such, this book has +been written. It undertakes to present in a systematic +way the mechanical principles that underlie the phenomena +in each of the different departments of the +science, in a readable form, and in an untechnical +manner. The aim has been to simplify and reduce +to mechanical conceptions wherever it was possible +to do so. + +One may often hear the question asked, What is +\DPPageSep{010.png}{ix}% +electricity? but a similar question as to the nature of +heat or light or chemism is just as pertinent, although +there chances now to be less popular interest in these +than in the former; not, however, because they are in +themselves better understood, or less interesting. + +It is hoped that some of those whose interests lie +along such special lines as chemistry, electricity, and +even biology, will find something helpful in the chapters +dealing with those subjects. + +In covering so much ground in so small a treatise, it +was necessary to select such facts as give prominence +to fundamental principles. Doubtless others might +have selected different materials, even with the same +end in view, for otherwise competent persons are +generally more familiar with certain details of a given +science than with others; and I have used what was +closest at hand. + +Aside from the topics usually treated upon in a book +of physics, the reader will find a chapter on Physical +Fields, which is unique, as it extends the principle of +sympathetic action---recognized in acoustics---to the +whole range of phenomena, including living things. + +The chapter on Life, in a treatise on physics, must +justify itself; while the one on Machines points out +their functions in a more complete way than has been +done before. + +Lastly, however large the physical universe may be, +and however exact such relations as we have established +may be, it is daily becoming more certain that +\DPPageSep{011.png}{x}% +even in the physical universe we have to do with a +factor,---the ether,---the properties of which we vainly +strive to interpret in terms of matter, the undiscovered +properties of which ought to warn every one against +the danger of strongly asserting what is possible and +what impossible in the nature of things. With the +electro-magnetic theory of light now just established, +and the vortex ring theory of matter still \textit{sub~judice}, +but with daily increasing evidence in its favor, one may +now be sure that matter itself is more wonderful than +any philosopher ever thought. Its possibilities may +have been vastly underrated. + +In the book called ``The Unseen Universe,'' it is +pointed out that possibly the ether may be the medium +through which mind and matter re-act. What fifteen +years ago was deemed \emph{possible}, is to-day deemed \emph{probable}, +and to-morrow may be demonstrated; and a perusal +of that book is recommended to persons who are +interested in questions of that kind. +\DPPageSep{012.png}{unnumbered}% +% table of contents + +\pagestyle{empty} +\tableofcontents +\phantomsection +\pdfbookmark[0]{Contents}{Contents}% + + +\iffalse + +CONTENTS + +CHAPTER PAGE + +I. MATTER AND ITS PROPERTIES 1 + +II. THE ETHER 26 + +III. MOTION 44 + +IV. ENERGY 59 + +V. GRAVITATION 83 + +VI. HEAT 99 + +VII. ETHER WAVES 134 + +VIII. ELECTRICITY 173 + +IX. CHEMISM 238 + +X. SOUND 256 + +XI. LIFE 277 + +XII. PHYSICAL FIELDS 298 + +XIII. ON MACHINES.--MECHANISM 312 + +XIV. PROPERTIES OF MATTER AS MODES OF MOTION 331 + +XV. IMPLICATIONS OF PHYSICAL PHENOMENA 354 + +XVI. RELATIONS OF PHYSICAL AND PSYCHICAL PHENOMENA 384 + +APPENDIX 397 + +INDEX 403 + +\fi + +%\DPPageSep{013.png}{1}% + +\mainmatter +\pagestyle{fancy} +\phantomsection +\pdfbookmark[-1]{Main Matter}{Main Matter} + +% MATTER, ETHER, AND MOTION + + +\Chapter{I}{Matter and Its Properties}{1} + +\First{All} kinds of phenomena that we can become conscious +of through any of our senses are traceable +directly or indirectly to what we call matter. The +sense of feeling implies contact with a body of some +kind; the sense of hearing depends upon movements +of the air, which is a body of matter having certain +properties; and the sense of sight, also due to vibratory +motion, implies that matter exists, however distant, +which has given rise to the vibratory motions that are +perceived as light. So of taste and smell, actual contact +of material particles endowed with particular +properties are the conditions for exciting these sense +perceptions. Some philosophers have added a sixth +sense to the five senses we have recognized for so long +a time---the sense of weight, as distinguished from the +sense of touch; and still others have thought to distinguish +a sense of temperature---relative perceptions of +heat and cold, from the sense of touch; and if these +truly represent distinct senses, they illustrate still +further the truth that it is through the reactions of +\DPPageSep{014.png}{2}% +matter upon the nervous organizations of living things +that all of our knowledge of things about us and of +the universe as a whole is obtained. + +It might seem to one as if our knowledge of matter +should be tolerably good, accurate, and complete, seeing +that it is thrust upon us everywhere, and affects us +for good or evil continuously from the dawn of sensation +till death; yet it may truly be said that the knowledge +of matter, its properties, and the wonderful complexity +of phenomena that are due to them, which we +possess to-day was wholly unknown to all mankind +until the time of Sir~Isaac Newton, whose discovery +of the law of gravitation was the first discovery of +a universal property of matter; and by far the larger +part of the knowledge we have, has been acquired in +this century and mostly within the last half of it. The +mass of mankind is, as it always has been, without +any knowledge at all and without any desire for it. +Whatever we have is due to the work of a small number +of persons in Western Europe and America. Probably +the large majority of mankind are quite unable +to understand phenomena and their significance, yet +among the brighter and more competent individuals in +every country there is an apathy and indifference to the +subject, due, of course, to the estimate they have of its +degree of importance; and this estimate is in a good +measure due to the philosophy of things in general +held by the individual thinkers. + +When Mr.\ Emerson was told by a Millenarian that +the world was coming to an end the next day, he +declared that he could get along without it, and so it +\DPPageSep{015.png}{3}% +probably has seemed to the majority of philosophers +that the material world was a condition of things to be +endured, rather than to be understood and utilized: +that they were in it but were not a part of it. + +Knowledge has, however, increased, and the wise +ones are growing wiser; and some of the modern questions +of philosophy and psychology are now so woven +in with physical details that a knowledge of matter and +its possibilities has become to them imperative. + +There have been many attempts to define matter, +such as, whatever occupies space, or whatever affects +our senses, and so on; and there is no brief definition +that has been generally adopted. In the ordinary +affairs of life one rarely needs to make such distinctions +as are necessary in philosophical and scientific affairs, +where accuracy and clearness are of the utmost importance. +There seems to be no way to define matter +except by means of some of its properties. If we say +that it is whatever occupies space, there is implied in +the statement that the term is properly applicable to +everything that exists in space; but so far as we know +there may be any number of things in illimitable space +that are not subject to any of the physical laws, such as +a piece of wood or an air particle are known to be controlled +by. If we say whatever affects our senses, we +again are going beyond our warrant; for electricity is +capable of affecting several of our senses,---sight, taste, +feeling,---and yet there is no good reason for thinking +electricity to be matter. + +There is one property of matter that may seem to +differentiate it from everything else, and hence, if +\DPPageSep{016.png}{4}% +\index{Matter, characteristic property}% +\index{Matter, its definition}% +adopted, will enable one to be precise about his use of +the term. One part of the law of universal gravitation +is---\emph{every particle of matter in the universe attracts every +other particle}. This makes gravitation a universal property +of matter. The astronomers have observed the +movements of exceedingly distant stars to be in accordance +with this law, and there are no exceptions to it +that have been discovered. + +If, then, one adopts as the definition of matter, \emph{whatever +possesses the property of gravitative attraction}, he +will have a definition that is in accordance with everything +we know, and with the added advantage that if +there be anything else in the universe that involves +observable phenomena he will not need to confuse it +with the phenomena of gravitative matter. This is the +sense in which that term is used throughout this book. +\TBskip + +Matter presents itself to our senses in a scale of +magnitude from particles in the neighborhood of the +hundred-thousandth part of an inch in diameter, and +requiring the highest powers of the microscope to see, +to such huge masses as that of the earth, eight thousand +miles in diameter, the planet Jupiter, nearly eighty +thousand miles, and the sun, eight hundred thousand +miles in diameter, while some of the more distant stars +are probably ten times larger than the sun. The large +masses, however, are but collections of smaller ones, +each particle bringing its own properties of whatever +kinds they may be; and it does not appear that new +qualities are developed by simply changing the distance +between bodies. So the properties of matter may be +\DPPageSep{017.png}{5}% +studied exhaustively without employing specimens +inconveniently large. + +The thin stratum of gold spread upon cheap jewelry +has all the characteristics and qualities of any specimen +of gold however large; and a small test tube of +hydrogen will exhibit all the kinds of phenomena that +any larger quantity would show. For such reasons the +study of the universe of matter can be carried on in +the laboratory. The universe may be in the crucible +one holds in the tongs; whatever difference there may +seem to be, it will really be one of bigness only. + +In treatises on physics one will generally find the +properties of matter arranged in two divisions, called +essential properties and non-essential ones. Of the +former are (1)~extension, or space occupying; (2)~inertia, +or passiveness under conditions of rest or motion; +(3)~impenetrability, or total and exclusive occupancy of +its own space; (4)~elasticity, or ability to recover its +form after distortion, this, however, varying in degree +in different bodies; (5)~attraction, of which there are +several varieties,---gravitation, acting at all distances; +chemism, acting at close distances and selective in its +operation, and apparently not existing at all between +some kinds of matter, as, for instance, between oxygen +and fluorine. Chemism is also capable of complete +neutralization, and is thus in marked contrast with +gravitative attraction, which is not affected in the slightest +degree discoverable by contiguity; and lastly, cohesion, +which is not apparent except bodies are in contact, +but is the agency that holds the particles of bodies together +so they form liquids and solids of any and all sorts. +\DPPageSep{018.png}{6}% + +The so-called non-essential properties are color, hardness, +malleability, ductility, and the like, which vary very +much in different substances. Among the metals silver +is white, copper is red, gold is yellow. Diamond is the +hardest substance known, while graphite is one of the +softest, though both are composed of the same ultimate +substance---carbon. Iron is malleable, and may be +forged into any shape. Gold may be hammered out into +leaves no more than one three-hundred-thousandth of +an inch thick, but zinc is wholly unmanageable in that +way. Platinum, one of the heaviest metals we have, +can be drawn out into a wire finer than a spider's web,---a +single grain may be drawn into a mile of wire; while +bismuth, also a metal, cannot be drawn at all. + +There are other conditions of matter that offer +opportunities for convenient grouping sometimes, such +as the solid, the liquid, and the gaseous: the solid +being the one where the parts strongly cohere; the +liquid, where the parts have but slight cohesion; and +the gaseous, where the individual particles do not +cohere at all, but, being elastic, bump against each +other and rebound continually. + +Farther on it will be shown how all substances may +assume either of these conditions, inasmuch as it is +temperature that determines whether a given substance +be a solid, a liquid, or a gas. + +Density signifies compactness of matter, or the relative +\index{Density}% +number of particles in a given unit volume. If compression +be applied to two cubic feet of common air until +it occupies but one cubic foot, there is twice as much +matter in that cubic foot as there was at the outset, and +\DPPageSep{019.png}{7}% +we express that fact by saying that the density is +doubled. If twice the amount of matter is in the unit +space, evidently the weight of the matter in that space +must be twice what it was at first. So one may measure +the density of matter by the weight of a unit +volume of it compared with the weight of the same +volume of some other substance taken as unity. Thus, +if a cubic foot of water weighs $62.5$~pounds, and a cubic +foot of rock weighs $155$~pounds, the density of the rock +is~$2\frac{1}{2}$, which means that it is $2\frac{1}{2}$~times heavier than +water, and that the amount of matter in the rock +is $2\frac{1}{2}$~times greater than that of the water. Such +determinations have been made of all the different +materials that could be found, and extensive tables +have thus been constructed; but it is seen that the +appeal is to gravitation, and presumes that every particle +obeys that law, and that degrees of compactness of +matter do not affect the law. Such comparative tables, +based upon gravitation measure, are frequently called +tables of \emph{Specific Gravity}, so that density and specific +\index{Gravity, specific}% +\index{Specific gravity}% +gravity mean substantially the same thing. The following +examples of the relative densities of bodies may be +of interest:--- +\begin{center} +\TableFont% +\begin{tabular} {ll<{\qquad} ll<{\qquad} ll} +Gold, & $19$ & Diamond, & $4$ & Alcohol, & $\Z.8$ \\ +Silver, & $10.5$ & Common Stone, & $2.5$ & Ether, & $1.1$ \\ +Copper, & $8.8$ & Wood, & $\Z.8$ & Water, & $1$ \\ +Iron, & $7.8$ & Sulphuric Acid, & $1.8$ & The Earth, & $5.6$ +\end{tabular} +\end{center} +Such numbers are to be understood as signifying that +if a given volume of water weighs one pound, an equal +volume of gold weighs nineteen pounds, an equal volume +of iron seven and eight-tenths pounds, and so on. +\DPPageSep{020.png}{8}% + +Sometimes, however, it is convenient to choose for a +standard of density some body, a small unit volume of +which is much lighter than water, such as air, or more +frequently hydrogen gas, a hundred cubic inches of which +weigh $2.2$~grains. In the metric system, a litre, which +is nearly two pints is the standard of volume; and a +litre of hydrogen weighs $.0896$~of a gram. + +In chemical work this is the common standard for +gases; while for solids and liquids a cubic centimetre of +water is taken, which weighs one gram. + +\Section{DIVISIBILITY OF MATTER.} +\index{Matter, divisibility of}% + +Particles of matter as small as the hundred-thousandth +of an inch may be seen with a good microscope +as the smallest visible thing, but there is no reason for +thinking that such a degree of fineness is any approach +to the ultimate fineness of the parts into which it is +possible to divide matter. For a long time philosophers +have considered whether or not there could, in +the nature of things, be an actual limit to the divisibility +of matter, so that the smallest fragment could +not be again divided into two or more parts by the +application of appropriate means, thus making matter +infinitely divisible, at any rate ideally. + +In Mr.\ Spencer's ``First Principles'' this subject is +considered at length, and the conclusion reached that it +is impossible to conceive the existence of real atoms---bodies +that cannot be divided into halves; nevertheless, +we shall see presently that it is possible to +conceive precisely that thing. It will be best here to +\DPPageSep{021.png}{9}% +note how far division has been carried and the means +employed to effect it. + +If a bit of phosphorus be put into a solution of gold, +the gold will be set free in such a finely divided state +that the particles remain suspended in the solution, +giving to it a blue, green, or ruby color, depending +upon the degree of fineness into which it has been +broken up. Faraday estimated that the particles of +gold in the ruby-colored liquid did not exceed the five-hundred +thousandth part of the volume of the liquid. +One-eighth of a grain of indigo dissolved in sulphuric +acid will give a distinctly blue color to two and a half +gallons of water, which would be about the millionth +part of a grain to a drop of the water. + +A grain of musk will keep a room scented for many +years. During the whole of the time it must be slowly +evaporating, giving out its particles to the currents of +air to be wafted presently out of doors; yet in all this +time the musk seems to lose but little in weight. + +The acute sense of smell of the dog is well known; +for he can detect the track of his master long after the +tracks have been made, which shows that some slight +characteristic matter is left at each footfall. + +A spider's web is sometimes so delicate that an +ounce of it would reach three thousand miles, or from +New York to London. No one would think it likely +that such a web would be made up of a single row of +atoms, like a string of beads; for it would not seem +probable that such a string could have such a degree +of cohesion as spiders' webs are known to possess. + +Chemists have concluded from their experience with +\DPPageSep{022.png}{10}% +matter in its various forms and conditions that it is +really reducible to ultimate particles which have never +broken up, no matter what conditions they have been +subject to; and these ultimate particles are called \emph{atoms}. +\index{Atoms}% +The term is not now understood to signify what is +implied in its derivation, as something that cannot be +divided, only something that has not yet been broken +up into smaller parts. Thus hydrogen, oxygen, iron, +silver, are reducible to such ultimate atoms; and there +are now known about seventy different kinds of +atoms, and these are often spoken of as the elements. +Though they are excessively minute when compared +with ordinary objects of sight, yet they have a real +magnitude which the physicist has measured in several +different ways. Most of these methods are complicated, +and, in order to be understood, require a pretty +thorough knowledge of molecular physics; but the following +one may probably serve to give one an idea of +the degree of smallness which atoms must have. + +When a soap-bubble is blown, the material of the +\index{Soap-bubbles}% +film slides down the sides, making the bubble thinnest +on top. When a certain degree of thinness has been +reached at the top, colors begin to appear in concentric +rings, and these colors appear to move towards the +equatorial regions, new rings being formed at the top +as fast as room is made for them by the displacement +of the earlier ones. These colors always appear in the +same order as they are in the rainbow, namely, beginning +with the red and ending with the violet, then +another set with the same order, until there have been +ten or more such sets of rainbow tints. They are +\DPPageSep{023.png}{11}% +explained as being due to what is called interference +in the light waves that fall upon the film. Light is +reflected more or less from every surface it reaches. +Some light is reflected from the first or outer surface +of the film; some goes through the film to the inner +surface, and is there reflected back to the outer surface, +and then takes the direction that the light has which +is reflected from the first surface, so that the light that +reaches the eye from a point on a bubble comes from +both outer and inner surfaces. That coming from the +inner surface has had to travel farther than that coming +from the outer surface by a distance of twice the +thickness of the film. As light consists of waves, if +one set of waves all of a length be made to move in the +same direction as another set having the same length, +their crests may coincide and produce a single higher +wave; or the crest of one may be behind the crest of +the other at any distance up to one-half the length of +the wave itself, in which case the crest of one will +coincide with the trough of the other, and the two +waves will cancel each other, and this process is called +interference. Now, in the case of the bubble, when the +thickness is such that the distance through the film +and back again is such as to equal half a wave length +of a given kind of light, that particular wave is extinguished; +and when one of the constituents of white +light is wanting, that which is left is seen as colored +light, and the color seen must depend upon the kind +of color that has been cancelled. Red light has the +longest wave length, about one forty-thousandth of an +inch, and violet, the shortest of the waves we see, about +\DPPageSep{024.png}{12}% +one sixty-thousandth of an inch; and when these colors +are seen upon the bubble we are assured that the +interferences are produced by thicknesses due to fractional +parts of such wave lengths. As the ray must go +through the thickness twice in order to fall behind one-half +of a wave, it follows that the thickness of the film +where the last set of colors appear can be no more than +one-fourth of the wave length of the shortest wave we +can see, that is, +\[ +\frac{1}{4} × \frac{1}{60,000} = \frac{1}{240,000} \text{ of an inch.} +\] +When a bubble has reached this degree of thinness, so +that no more colors are to be seen, a rather remarkable +physical effect may be noticed. The film becomes +almost jet black, with a jagged edge well defined +between it and the brighter colored rings where the +adjacent tint is purplish. The thickness of the film +has fallen suddenly off here to about one-fortieth of +the thickness it has where the tint is visible, and the +bubble breaks in a second or two after this black patch +appears; that is, when its thinness at any point becomes +as small as +\[ +\frac{1}{240,000} × \frac{1}{40} = \frac{1}{9,600000} \text{ of an inch.} +\] +As the bubble, however, does persist for a short time, +and the thin film has cohesion enough to enable it to +support the weight of the bubble, it seems highly probable, +but is not absolutely certain, that it must be more +than one molecule of water thick at the thinnest +place, which is, as shown, only about the one ten-millionth +\DPPageSep{025.png}{13}% +\index{Molecules, size of}% +of an inch thick. If one thinks it probable that +it be, say five molecules thick in order to have the +degree of cohesion it shows, then the size of such\DPnote{** [sic]} +molecule of water out of which the bubble is made +can be but the one-fifth of the above small fraction, +which gives about the one fifty-millionth part of an +inch as the diameter of a molecule of water. + +But a molecule is not the same thing as an atom: it +is made up of atoms, chemically combined, and is +defined generally as being the smallest fragment of a +compound body that can exist and possess the physical +characteristics that belong to such body. Thus, a drop +of water possesses all the characteristics of any larger +quantity of it, and a drop may be divided into smaller +and smaller globules, perhaps a million of them, each +one being visible with a good microscope; but if the +division be carried to a higher degree, as it can be by +various methods, chemical, electrical, and thermal, the +qualities of water disappear, and two different substances, +oxygen and hydrogen, are left, both gaseous +under all ordinary conditions, and neither of them exhibiting +any properties like water or from which any +of the properties of water might be inferred. It may +be well to remark here that this is only one illustration +out of multitudes that might be named throughout the +whole domain of physical science, that the properties +of things under common observation are not simply +the properties that belong to the elements out of +which the things are built up; such properties +being the result of collocation rather than inherent +qualities. +\DPPageSep{026.png}{14}% + +The molecule of water is then a compound thing, and +is made up of three atoms,---two of hydrogen and one +of oxygen,---and therefore the actual size of an atom +of hydrogen must be less than that represented by the +above small fraction of an inch. Evidently a thing +made up of three individual parts and two dissimilar +substances cannot be spherical, and it will be well to +bear this in mind in thinking of molecular forms. One +may imagine the atoms themselves to be spheres, or +cubes, or tetrahedra, or rings, or disks, or any other +forms he likes, for the purpose of getting some sort of +a mental picture of what a molecule might look like if +it could be seen with a microscope; and it is probable +that very many persons have hoped or thought that +the microscope would sometime be so far perfected as +to enable one to actually look upon the molecules of +matter and perhaps upon their individual atoms. Let +us therefore consider the problem of how much more +powerful a microscope must need to be than any we +possess to-day, in order that one should see a molecule! +We will assume atoms to be about the one fifty-millionth +of an inch in diameter, and that when combined +into molecules they are geometrically arranged +so that the diameter of a molecule made up of a large +number of atoms is proportional to the cube root of +the number of atoms, as is the case with larger bodies, +say a box of bullets. + +A molecule of water contains three atoms, a molecule +of alum about one hundred, while, according to +Mulder, a molecule of albumen contains nearly a +thousand atoms. Then, according to the assumption, +\DPPageSep{027.png}{15}% +the molecule of alum would have a diameter +equal to +\[ +\frac{\sqrt[3]{100}}{50,000000} = \frac{1}{10,776000} \text{ of an inch}, +\] +and that of albumen would be equal to +\index{Albumen, size of molecule}% +\[ +\frac{\sqrt[3]{1,000}}{50,000000} = \frac{1}{5,000000} \text{ of an inch.} +\] + +Now, the best microscopes made to-day will enable +\index{Microscope, magnifying powers}% +one to see as barely visible a point the one hundred-thousandth +of an inch, so that such a microscope would +need to be as much more powerful than it now is as +one hundred thousand is contained in five millions, that +is, fifty times, in order to see the albumen molecule, and +for the alum molecule as many times as one hundred +thousand is contained in ten million seven hundred +thousand, that is, one hundred and seven times. Now, +one who is familiar with the microscope would probably +admit that one might be made through improved +methods of making and working glass hereafter to be +discovered, two or three, or even ten times better than +the best we have now; but the idea of one being made +fifty or one hundred times more powerful than we have +to-day, I do not think would be allowed to have any +degree of probability. The case may be illustrated as +follows: Suppose in the days of the stage-coach +some one had imagined that by some improvement in +methods of travelling one might some day travel one +hundred times faster than the stage-coach could then +go. Twelve miles an hour was not an uncommon rate +then; but one hundred times that would be twelve +\DPPageSep{028.png}{16}% +hundred miles an hour, and that is sixteen times faster +than the best we can now do, and about twenty-five +times faster than express-trains now go. As a matter +of fact, we travel about three or four times faster than +the best stage-coaches did, and, on a spurt, may go six +or eight times faster. The powers of the microscope +have not been doubled within the last fifty years, and I +suppose more time and ingenuity have been given to +the problem of improving it than will ever be given +to it in the same interval again. + +There is another and still more serious reason why +there is no probability that any one will ever see a +molecule, even though the microscope had the magnifying +power sufficient to reveal it; namely, the motions +that molecules are known to have would absolutely +prevent one from being seen. A free molecule of +hydrogen has a velocity of motion at ordinary temperatures +of upwards of a mile in a second, and its direction +of motion is changed millions of times in a +second. A microscope magnifies the movements of an +object as much as it does the object itself. An object +in the field of a microscope that should have a movement +no greater than the hundredth of an inch in a +second could only be glimpsed, so there is no possibility +of one's being able ever to see a free gaseous +molecule. Supposing one should be seized and held in +the field, even then it is to be remembered that it is in +a state of vibration, changing its form constantly on +account of its temperature, so that its wriggling would +prevent any inspection. + +Lastly, there is every reason to believe that the +\DPPageSep{029.png}{17}% +molecules of all bodies are so perfectly transparent +that they can no more be seen than can the air, even +if there were no difficulty from their smallness and +their motions. + +If the atoms of a single element like hydrogen are +so minute, so restless, and so transparent that no one +can hope to see them so as to make out their forms +and what gives them their characteristic properties, +what shall be said of the case of seventy or more elements +similarly minute and restless and transparent, +yet each one easily identified in several ways, physical +and chemical? Does it seem in any way probable that +such differences in properties as are exhibited by gold, +carbon, iron, and oxygen can be due simply to differences +in size or shape of the atom? Presumably not; +and the constitution of matter has therefore always +been a mystery to philosophers, for if one is to attempt +to philosophize upon the subject in accordance with +such other knowledge as we have, one would need to +conclude that if the different kinds of matter, the elements +as we know them, were formed out of some +prior kind of substance, as bullets and marbles are +formed out of lead and clay, then there must be as +many different kinds of substances out of which the +different elementary atoms are formed as there are +different elements, which proposition does not seem to +have such a degree of probability that any one could +adopt it. If one sought for the explanation of the +different properties by assuming that all the different +kinds of elements were formed out of one and the +same fundamental substance, then it is equally difficult +\DPPageSep{030.png}{18}% +to understand how mere differences in size and shape +could give such profound differences in quality as the +elements possess. + +Then, again, it appears that the individual atoms of +\index{Atoms}% +each element are precisely alike. One atom of hydrogen +is precisely like every other atom, so far as we +have definite knowledge. Sir~John Herschel likened +them to manufactured articles on account of their +exact similarity. A machine may turn out buttons or +hooks or wheels or coins so exactly like one another +that no one can tell them apart. It is really appalling +to think of the immense numbers of atoms of every +one of these seventy elements. It is a simple matter +to calculate how many atoms there must be in say a +cubic inch. It requires no other process than the +application of the multiplication table. If the diameter +of one be the fifty-millionth of an inch, then fifty +\index{Molecules, size of}% +million in a row would reach an inch, and a cubic +inch would contain the number represented by the +cube of fifty millions, which is +\[ +125000,000000,000000,000000, +\] +($125$~followed by twenty-one ciphers) a number which +is more conveniently represented by $125 × 10^{21}$. The +utter impossibility of conceiving such a number will +be apparent if one would try to represent to himself +what the magnitude of only one million really is. Go +out on a clear but moonless night and the heavens +appear to be filled with stars. Count all that can be +\index{Stars, their number}% +seen in a certain portion of the sky, say one-tenth, as +nearly as can be estimated, and then determine the +\DPPageSep{031.png}{19}% +number in the sky that are in sight by multiplication. +It will be discovered that only about two thousand can +be seen in the whole sky. If one million stars were to +be thus visible, it would require five hundred firmaments +as large and as well filled as the one looked at +to contain them. With the largest telescopes less than +a hundred millions of stars are visible; but what shall +one say when he learns that beyond a peradventure +the number of atoms in a single cubic inch of matter +\index{Atoms}% +of any sort is more than a million of millions times +all the stars in all the heavens visible in the largest +telescope. + +If one fancies that kind of work he may compute +the number of atoms that make up the world. Of +course it will make the number much larger; but when +written out not so much longer as one might think, for +when it is multiplied a million times it will add but six +ciphers to it. Some mathematicians have been to the +pains to compute the number of atoms there are in the +visible universe, or, rather, the number that cannot be +exceeded; for if the number stated above fills a cubic +inch, if one knows the diameter of the visible universe, +the space it occupies can readily be known in cubic +miles and cubic inches, and if all this space was filled +with atoms one could know and write down their number. +Astronomers tell us that some stars are so distant +\index{Stars, their distance}% +that their light requires as long as five thousand +years to reach us, although the velocity of light is as +great as $186,000$ miles in a second, and this distance is +to be measured in every direction about us. If this be +our visible universe, then the maximum number of +\DPPageSep{032.png}{20}% +\index{Universe, atoms in}% +atoms in it are calculable, and are stated to be represented +by the figure 6 followed by ninety-one ciphers, +or, as it is usually written, +\[ +6 × 10^{91}. +\] + +If we return to microscopic dimensions, and compute +the number of atoms, there will be in the smallest +amount of matter that can be seen with the highest +powers of the microscope, the one hundred-thousandth +of an inch, it will be seen that five hundred atoms in +a row would just reach the distance; and the cube of +$500$ is $125,000,000$, that could be contained in a space +so small as to appear like a vanishing-point and the +structure or details be utterly invisible. We have read +of spirits that could dance upon the point of a needle, +but the point of a needle would be a huge platform +when compared with this last visible point with the +microscope; and the spirit that should dance upon it +might be a million times bigger than an atom of matter, +and not be in danger from vertigo. One may be +astonished at the amount of intelligence associated +with the minute brain structure of some of the smaller +forms of animal life---say the ants; but from the above +it will be seen that so far as such intelligence is associated +with atomic and molecular brain structure, the size +of the brain in the smallest ant, though measured in +thousandth of an inch, is sufficiently large to involve +billions of atoms, and the permutations possible are +almost unlimited. The same idea is applicable to the +brain of man, and seems to indicate that such differences +in quality of mind as we see are not so much due +\DPPageSep{033.png}{21}% +to the differences in amount of brain, measured in +cubic inches, as in atomic and molecular structure. + +The work of physicists and chemists, carried on for +many years, has convinced them that none of the processes +to which matter has been subjected has affected +its quantity in the slightest degree. A definite quantity +\index{Atoms, unalterable}% +of hydrogen, or, what is precisely the same thing, +a definite number of hydrogen atoms, may be subject +to any conditions of temperature, may be made to combine +with other elements successively, forming with +them solids or liquids or gases, and no atom is +destroyed nor its individual properties changed in any +degree. Neither has any phenomenon been discovered +indicating that new atoms of any kind are ever produced +by any physical or chemical changes yet known. +Time does not alter them. Elements that have been +imbedded in rocks from primeval times, reckoned by +millions of years, when liberated to-day and tested, +exhibit precisely the same characteristics as those +obtained from other sources and that have been subject +to many artificial conditions. Sometimes a meteorite +\index{Meteors}% +reaches the earth, a sample specimen from distant +space, having moved in some orbit about the sun for +millions of years. Thousands of such bodies are in +our possession, and they have been carefully analyzed, +but no element unfamiliar to the chemist has been +found among them; and the iron, the nickel, the carbon, +the hydrogen, and all the rest of the elements that +compose them, behave in every particular like those +found on the earth. + +So far as spectroscopic evidence goes, it testifies to +\DPPageSep{034.png}{22}% +the presence of the same elements in the sun and +planets and comets; and it is as certain as anything +physical can be, that the expert chemist here would be +an equally expert chemist in the planet Mars, if he +could find a way to cross the immense space that separates +that star from us. + +These facts and conclusions are frequently stated in +such a form as this, namely, that matter cannot be created +\index{Atoms, unalterable}% +or annihilated. All that can fairly be meant by +such language is that under all the conditions at present +known, the quantity of matter remains constant; +and this proposition has a high degree of importance +in social affairs as well as in philosophy. If matter +were liable to change in its quantity or quality by being +subject to various physical conditions, all industries +involving commercial interests would be in an unstable +state. If the ton of iron ore should turn out, when +smelted, only fifty per cent of iron instead of sixty +per cent, as now,---the rest being either annihilated or +transformed into lead or gold, or something else,---the +smelting company would soon go bankrupt, even if +gold were the product instead of iron, for if gold +were liable to be produced in that kind of a way, +its value would be next to nothing as a standard of +value. + +The old alchemists sought to transmute what they +called the baser elements into gold. It is safe to say, +if it were physically possible to do it and some one +should discover the art, and it were an economical process, +commercial disaster such as the world has never +known would follow its announcement. It would be as +\DPPageSep{035.png}{23}% +if the volcanoes of the world should suddenly begin to +eject gold in the place of lava. + +Stability of physical properties is as essential for +the stability of society as the regular recurrence +of day and night; and philosophy would be impossible +if fundamental data were not in every way immutable. + +These physical principles lead to some curious and +most interesting conclusions with regard to the great +difference there is between bodies of matter of any +and all kinds that are familiar to our senses and the +atoms out of which these larger bodies are composed. +In every case, where there is a difference in movement +between two of these larger bodies made up of atoms, +there is what we call friction, which invariably results +\index{Friction, its effects}% +in wearing away some of the material of both. It is +the result of mechanical friction, to tear away some of +the surface molecules of the two bodies. Bodies in use +much, and therefore most subject to friction, become +worn out. Our clothing is a familiar example; the journals +of machinery, the tires of wheels, the sharpening +of tools, the polishing of gems, the weathering of wood +and stone,---all show that attrition removes some of the +surface materials of such bodies, but there is nothing +to indicate that attrition among atoms or molecules ever +removes any of their material. It appears as if one +might affirm in the strongest way that the atoms of +matter never wear out, are not subject to such friction +and the consequent destruction as comes to all bodies +made up of them. The molecules of oxygen and nitrogen +that constitute the air about us have been bumping +\DPPageSep{036.png}{24}% +and brushing against each other millions of times a +second for millions of years probably, and would have +been worn out or reduced, as the rocks upon the seashore +have been beaten and ground into sand, if they had +been subject to friction. So one may be led to the +conclusion that whatever else may decay atoms do not, +but remain as types of permanency through all imaginable +changes---permanent bodies in form and in +all physical qualities, and permanent in time, capable, +apparently, of enduring through infinite time. Presenting +no evidences of growth or decay, they are in strong +contrast with such bodies of visible magnitude as our +senses directly perceive. Valleys are lifted up and +become mountain-tops; mountains wear away and are +washed into the ocean; the beds of the ocean sink and +rise; and the boundaries of continents may be worn and +washed away through the incessant beatings of waves +against their coasts. Wear and tear go on in all inanimate +nature unceasingly, so that it is only a question +of time when everything we see upon the earth will +have changed beyond identification. The sun is shrinking, +and must some time cease to shine. The stars, +too, are changing likewise, because they shine, and +their places in the firmament will be vacant. All living +things grow because of change, and decay because +of more rapid change, and there appears to be nothing +stable but atoms. If it could be shown that life itself +and the mind of man were in some way associated with +\index{Mind, a material habitat for}% +\index{Mind and matter}% +atoms of some sort, as inherent properties, the hopes +\index{Atoms, life associated with}% +and longings cherished by mankind for continuous existence +\index{Immortality}% +beyond the short term of three score years and +\DPPageSep{037.png}{25}% +ten would give way to convictions as strong as one +has in any physical phenomenon whatever; the evidence +would be demonstrative in the same sense as +it is for the existence of atoms and their physical +qualities. +%\DPPageSep{038.png}{26}% + + +\Chapter{II}{The Ether}{26} + +\index{Ether}% + +\First{An} incandescent electric lamp consists of a fine +thread of carbon fixed in a glass bulb from which the +air has been exhausted. When a proper current of +electricity is permitted to traverse the carbon filament, +it becomes white-hot and gives out light like any other +hot body. Other luminous bodies are in the air, and +one might infer that the light was transmitted from the +heated body to the eye by the material of the air itself. +The light in the vacuum shows that this is not necessarily +so, for the more perfect the vacuum is made the +more freely does the light from the filament reach the +glass bulb that encloses it. One is therefore led to +infer that matter is not the agent that transmits light. +The light of the sun reaches us after travelling through +ninety-three millions of miles of space in about eight +\index{Light, its velocity}% +minutes. There are the best of reasons for believing +that the atmosphere of the earth does not reach at +most more than two hundred miles upwards from the +\index{Atmosphere, height of}% +surface, and its density at the height of only one hundred +miles is such that there would be only about one +molecule to the cubic foot. + +It is not unlikely that there are free-roving molecules +in space, as there are meteors in all directions about +\index{Meteors}% +\DPPageSep{039.png}{27}% +\index{Light, its nature}% +us, varying in size from fractions of a grain to masses +weighing some tons, but the distance apart of these +bodies is so great on the average that they cannot be +considered as either help or hindrance to the passage of +the light of either sun or stars. It is known with certainty +that what we call the light from shining bodies +is a kind of wave motion. The phenomena of interference, +which can be brought about in several different +ways, and which was referred to in the first chapter +when speaking of the colors of soap-bubbles, show +this. It is possible to annihilate two rays of light by +making one of them to follow the other in a certain +way; and one cannot conceive that two particles of matter +of any sort could annihilate each other by simply +changing their positions, but this is precisely what +happens in light. + +Wave motions of all kinds can cancel similar wave +motions; for the wave consists of periodic movements, +a crest and a trough, and when the crest and +trough of one wave are superposed upon the trough +and crest of another similar one, the result is the +destruction of both waves. The lengths of these waves +have been measured by a great many persons in various +parts of the world, and they all concur that light +can only be explained by wave motions such as they +measure. + +If there be wave motions, evidently there must be +something moved. One cannot conceive of a wave +movement when there is nothing that can be moved; +so men have been compelled to believe that there is +some medium between the sun and the earth that is +\DPPageSep{040.png}{28}% +\index{Light, its velocity}% +\index{Stars, their distance}% +\index{Sun, its distance}% +\index{Universe, its size}% +capable of wave motion, and this medium they have +agreed to call \emph{the ether}. + +If one admits the existence of ether between the sun +and the earth as the agency for the transmission of +light, he will need to do much more than that. The +sun is but about ninety-three millions of miles distant, +but most of the planets are hundreds of millions and +some of them thousands of millions of miles from us, +and the light comes from them too; so the ether must +extend through the space occupied by the solar system, +the diameter of which is six thousand millions of miles, +and to cross this space light requires nine hours, +though going at the rate of one hundred and eighty-six +thousand miles per second. + +Then there are the stars beyond our solar system, +the nearest one so distant as to require three and a +half years for the light to get to us at the same rate; +and some of these are so remote that thousands of years +are needed for their light to arrive. That light we see +from them to-day left them before America was discovered, +before Jesus was born, before the pyramids +were built, and for all we should be able to see they +might have ceased to exist long ago, though their light +continues to shine. So the ether must extend to those +most distant stars we can see, and that, too, in every +direction. There is no exaggeration in the statement +that our visible universe is so great that light requires +ten thousand years to cross its diameter. There is no +reason, either, for setting that as a boundary to its +magnitude; but wherever light comes from to us, there +must this medium, the ether, be. +\DPPageSep{041.png}{29}% +\index{Medium, necessity for}% + +But there are other and just as good reasons for +thinking there must be some medium between bodies, +even when all atoms and molecules have been removed. +For instance, everybody knows that one magnet affects +another at a distance from it, and there is no kind of +substance known that will prevent such action when +interposed between them. + +If one of these magnets be placed in the most perfect +vacuum that can be made, it still acts as it would +in the air, only with still greater freedom. One cannot +believe that one body can thus act upon another body +without some kind of a medium between them. Is it +not absurd to think otherwise? One may, if there +appears to him to be a good reason, suppose that there +is a magnetic medium or ether different from that one +employed in the transmission of light; but there is a +similar need for imagining one for the effects produced +by electrified bodies upon other bodies in their neighborhood. +An electrified glass rod will attract a pith +ball or anything else just as well in a vacuum as out of +it; and it is certain that electrical attraction and magnetic +attraction are not identical, for an electrified body +will attract one kind of thing as well as another, while +a magnet is selective in its effects, and affects iron +chiefly. Hence, if each different effect in a vacuum +is to be attributed to some different kind of medium, +there would need to be an electric ether in addition +to the other two. + +Then there is gravitative attraction, which has before +been mentioned. If it is not rational to think that one +body can act upon another body not in contact with it +\DPPageSep{042.png}{30}% +\index{Newton, Sir Isaac}% +and without some medium between them, then one is +bound to admit that the gravitative effects observed, +say between the moon and the earth, the sun and the +earth, and in every other case, are due to the action of +some medium between them. Neither is it at all needful +to be able to explain \emph{how} the medium acts thus and +thus, or even to imagine how it might, in order to firmly +believe that there must be one. + +Here are four cases of apparent action at a distance +of one body upon another, requiring some sort of an +intermediate agency; and, unless there be some good +reason for thinking there are several such media occupying +the same space apparently, it is much more +philosophical to believe it likely that one medium +exists capable of transmitting effects of the different +kinds; and especially will this appear to be truer if it is +known, as it is known, that the magnetic and electric +effects are transmitted with the same velocity as is the +light. So that physicists to-day quite concur in the +belief that what was called at first the luminiferous +ether, on account of its function in transmitting light, +is the same medium that is concerned in the other phenomena +of magnetism, electricity, and gravitation. + +It is likewise true that there are some physicists who +hold rather lightly upon this belief, taking it as a convenient +working hypothesis, and who would seem to be +ready in a minute to surrender the idea, unless it had +been demonstrated in the same way as the existence of +matter and of motion has been. But this is not the +attitude of philosophic minds. + +Sir Isaac Newton deduced from the observed motions +\DPPageSep{043.png}{31}% +of the heavenly bodies the fact that they attract +each other according to the law now known as the law +of gravitation, but he says nothing about \emph{how} bodies can +affect each other. That is, in his ``Principia'' he does +\index{Principia}% +not attempt to explain gravitation. He explicitly does +say, however, that he has not employed hypotheses in +his work, yet we know from other of his writings that +the idea of a medium was constantly in his mind. His +``Principia'' closes thus:--- +\begin{Quote} +``And now we might add something concerning a +most subtle spirit which pervades and lies hid in all +\Pagelabel{31}% +gross bodies; by the force and action of which spirit +the particles of bodies mutually attract one another at +near distances and cohere if contiguous; and electric +bodies operate to greater distances as well repelling +as attracting the neighboring corpuscles, and light is +emitted, reflected, inflected, and heats bodies; and all +sensation is excited, and the members of animal bodies +move at the command of the will, namely, by the vibrations +of this spirit mutually propagated along the solid +filaments of the nerves from the outward organs of +sense to the brain, and from the brain to the muscles. +But these things cannot be explained in few words, nor +are we furnished with that sufficiency of experiments +which is required to an accurate determination and +demonstration of the laws by which this electric and +elastic spirit operates.'' +\end{Quote} + +This shows plainly enough that he believed that +some medium, different from matter, was essential for +a mechanical conception of the phenomena he alluded +to. In a letter to Bentley he states his philosophical +judgment upon the subject in still stronger terms, and +it shows, too, the sense in which he is to be understood +when he says: ``I frame no hypotheses''---% +\DPPageSep{044.png}{32}% +which has frequently been repeated to adventurous +hypothecators as the example of the model scientific +man. Hear him! +\begin{Quote} +``It is inconceivable that inanimate brute matter +should, without the mediation of something else which +is not material, operate upon and affect other matter +without mutual contact, as it must do if gravitation in +the sense of Epicurus be essential and inherent in it.~\ldots +That gravity should be innate, inherent, and essential +to matter so that one body can act upon another at +a distance through a vacuum, without the mediation of +anything else, by and through which their action and +force may be conveyed from one to another, is to me +so great an absurdity that I believe no man who has in +philosophical matters a competent faculty of thinking +can ever fall into it.'' +\end{Quote} + +Newton uses the word \emph{Spirit} in the sense of a substance +entirely different from matter (see \Pageref{page}{31}). +Evidently Newton was so strong a believer in the +medium that we call the ether, though he could not +\index{Ether}% +work out its mode of action, that he was ready to discount +the intelligence of any man who doubted it.\footnote + {In 1708 Newton wrote thus: ``Perhaps the whole frame of nature may be + nothing but various contextures of some certain etherial spirits or vapors, condensed, + as it were, by precipitation; and after condensation wrought into various + forms, at first by the immediate hand of the Creator, and ever after by the power + of nature.'' + + These with his other acute remarks concerning what we now call the ether + lead us to infer that his mechanical instincts were more to be trusted in this field + than his more labored efforts.} + +If our knowledge of the existence of the ether is +not so positive as it is for matter, but is inferential, it +will be readily understood that the knowledge we have +of its properties cannot be very exhaustive. Some +have imagined that it was only a finer grained kind of +\DPPageSep{045.png}{33}% +matter than that we know as the elements, and that it +must be made up of atoms, though almost infinitesimal +in size. Others think it cannot be granular at all, but +forms a continuous substance throughout space. By +``continuous'' is meant that there are no interstices in +it: that it is constituted like a jelly, only not made up +of distinct parts or atoms, so there can be no such thing +as separating one part from another, leaving a vacuous +cavity or rent between them. One of the reasons for +thinking this to be the case is, that if it were made up +of finer atoms or of atoms at all, such waves as those +of light could not be transmitted by it. Longitudinal +waves, like those of sound in air, can be transmitted +by atomic or molecular structures but not transverse +waves, that is, such as are at right angles to the direction +of propagation. Some of these light waves are as +short as the hundred-thousandth of an inch, and some +are as long as the one two-thousandth of an inch, and +perhaps longer. Yet all of them are transmitted with +the same velocity in any and every direction. From +the fact that light travels with the same velocity in +every direction, it is inferred that the ether is not only +homogeneous, but its properties are alike in every +direction. As light is transmitted in straight lines, it +seems to follow that there is no difference in its quality +in different parts of space. + +That wave motions travel with such high velocity in +it has been interpreted as proving it to have a high +degree of elasticity, while the fact that it offers no +appreciable resistance to the movements of bodies of +matter in it is supposed to indicate that its density is +very small. +\DPPageSep{046.png}{34}% +\index{Earth, velocity of, in space}% +\index{Friction, its effects}% + +There are some, however, who think that such terms +as elasticity and density are not appropriately applied +to the ether. These terms signify properties of atoms +\index{Ether}% +and molecules. If density signifies compactness of +atoms, then the word could not apply to something not +composed of atoms. In like manner, if elasticity +means ability to recover form after deformation, then it +is not applicable to substances that cannot be deformed, +and it is customary to speak of the ether as +being incompressible. Still, it is certain that stresses +may be set up in it in various ways, and that these +conditions may be propagated, in certain cases in +straight lines, in other cases in curved lines, so whether +the explanation be forthcoming or not, there is no +doubt about the facts. + +There is no evidence at all that the ether is subject +to gravitative action, or that it offers any resistance to +a body moving in it. That is to say, it gives no evidence +of friction. Here is the earth rotating upon its +axis, and the velocity of rotation at the equator is a +thousand miles an hour, and if there were an appreciable +amount of friction the earth must slowly be coming +to rest like a top spun in the air. Yet the astronomers +tell us that the length of the day has not changed so +much as the hundredth of a second within the last two +thousand years. Again the earth revolves in its orbit +about the sun at the average rate of nineteen miles a +second, and if the ether through which it moves offered +any resistance to the motion, the length of the year +would be changed, but no such change has happened +in historic times. Again, such bodies as comets move +\DPPageSep{047.png}{35}% +\index{Thomson, Sir Wm.}% +\index{Vortex rings in air}% +very much faster than the earth; some have been +known to have a velocity of three hundred miles per +second when near the sun, but the comets complete +their circuits and give no evidence of slackened speed +due to friction in space. + +If, then, the ether \emph{fills} all space, is not atomic in +structure, presents no friction to bodies moving through +it, and is not subject to the law of gravitation, it does +not seem proper to call it matter. One might speak of +it as a substance if he wants another word than its +specific name for it. As for myself, I make a sharp +distinction between the ether and matter, and feel +somewhat confused to hear one speak of the ether as +matter. + +Nearly thirty years ago Helmholtz investigated, in a +\index{Helmholtz}% +mathematical way, the properties of vortical motions, +and, among others, pointed out that if a vortical motion +was set up in a frictionless medium, the motion would +be permanent, and it could not be transformed. Sir +William Thomson at once imagined that if such +motions were set up in the ether, the persistence of +their form and the possibility of a variety of motions +would correspond very closely with the properties that +the atoms of matter are known to possess. Such vortical +motions as are here alluded to, all have seen, as +they are often formed by locomotives when about starting, +if the air be quiescent. Horizontal rings, three +or four feet in diameter, may be seen to rise wriggling +into the air sometimes to the height of several +hundred feet. They may be formed also by smokers +by a vigorous throat movement forcibly puffing the +\DPPageSep{048.png}{36}% +smoke from their mouths, and they can be made +% [Illustration: ] +\begin{figure}[hbtp] + \begin{center} + \fbox{\Graphic{0.9\linewidth}{048a}} + \end{center} + \Caption{1}{Diag.\ 1.} +\end{figure} +artificially by providing a box having a hole on one +side an inch or two in diameter and the side opposite +covered with a piece of cloth. A saucer containing +strong ammonia water and another with strong hydrochloric +acid may be set inside, and dense fumes will +fill the box. If the cloth be struck by the hand, a ring +will issue from the hole, and may go forward several +feet, and its behavior may be studied. Such as are +formed in the air under such conditions present so +many interesting phenomena that it is worth the while +here to allude to them for the sake of helping the +mind to a clearer idea of how some of the properties +exhibited by matter may be accounted for.\footnote + {The method of producing these vortex rings and their phenomena are fully + explained in ``The Art of Projecting.'' By Prof.\ A.~E. Dolbear. Illustrated\DPtypo{}{.} + \$2.00. Published by Lee and Shepard, Boston.} + +\DPPageSep{049.png}{37}% +\index{Vortex rings, properties of}% + +1. The ring once formed consists of a definite +amount of the gaseous material of the air in a state of +rotation, %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}[11]{r}{1.5in} + \Graphic{1.375in}{049a} + \Caption{2}{Diag.\ 2.} +\end{wrapfigure} +and in its movements afterwards retains the +same material. It is to be noted +that the ring is formed in the air, +the white fumes serving merely to +make the ring visible. The ring +moves forward in a straight line +in the direction it is started, just +as if it were a solid body. It may +move very fast too,---ten feet a +second or more, and reach the +distant side of the room, but it +always moves of its own motion in a direction perpendicular +to the plane of the ring. + +2. It possesses momentum, and will push against +the object it hits. + +3. If made to move rapidly adjacent to a surface +like a wall or table, it will move towards it as if it were +attracted by it, and generally will be broken up by +impact against it. + +4. A light body, like a feather or thread, will be +apparently pushed out of the way in front of it, and +drawn towards it if behind it---phenomena like attraction +and repulsion. + +5. If two such rings bump together at their edges, +each one will vibrate with well-marked nodes and loops, +showing that, as rings, they are elastic bodies, and that +their period of vibration depends upon the rate of the +rotation. + +6. If two such rings be moving in the same line, but +\DPPageSep{050.png}{38}% +the hindmost one swifter so as to overtake the other, +the foremost one enlarges its diameter while the hinder +one contracts until it can go through the former, when +each recovers its original dimensions. + +7. If two meet in the same line, going in opposite +directions, the smaller one goes through the larger and +may be brought to a standstill in the air for a short +time until the other has got some inches away, when it +starts on in the same direction as before. + +8. If two similar ones are formed at the same time, +side by side, at a distance of an inch or two, they always +collide at once as if they had a mutual attraction. The +result of the collision may be the destruction of one or +both, or--- + +9. Each one may break at the point of impact, and +the opposite ends may weld together, forming a single +ring which will move on as if it had been singly formed, +or--- + +10. Instead of breaking they may rebound from each +other, but always at right angles to the plane in which +they were moving at first; that is to say, if they were +moving in a horizontal plane before impact, they will +rebound from each other in a vertical plane. + +11. Three rings may in like manner be made to join +into one. + +12. The material of the ring may often be seen to +be in rotation about the ring, while the ring, as a whole, +does not rotate at all, a rotary wave. + +13. The parts of a ring may be in a state of vibration +in the ring without changing its circular form, +somewhat as if the ring were tubular and two bodies +\DPPageSep{051.png}{39}% +\index{Elasticity due to motion}% +should move up on opposite sides till they met and +rebounded to meet below, and so on. +\Pagelabel{39}% + +All these, and some other just as curious phenomena, +may be observed in vortex rings, and may fairly be said +to be due to the properties of the rings themselves. +For instance, the vibratory motions alluded to in the +fifth show that elasticity is a property of the ring, +and that the degree of elasticity does not depend upon +what the ring is made of, but upon the kind and +degree of motion that constitutes the ring. If such a +ring could be produced in material not subject to friction, +none of the motion could be dissipated, and we +should have a permanent structure, possessing several +properties such as definite dimensions, volume, elasticity, +attraction, and so on, all due to the shape and +motions involved. + +Imagine, then, that vortex rings were in some way +formed in the ether, constituted of ether. If the ether +be, as it is generally believed to be, frictionless, then +such a thing would persist indefinitely: it would have +just that quality of durability that atoms seem to possess. +It would possess physical attributes, form, magnitude, +density, energy, that is, it would not be inert. +It would be elastic, executing a definite number of +vibrations per second. This property of elasticity has +generally heretofore been assumed to be a peculiar +endowment of ordinary matter, and one was at liberty +to imagine some matter without it because not so made. +This view implies that elasticity is a necessary property +of vortex rings; for as the velocity of rotation is +reduced, so is the degree of elasticity, and if there was +\DPPageSep{052.png}{40}% +\index{Bonnenburger's apparatus}% +simply a ring without being in rotation, it would have +no elasticity at all, neither would it have any qualities +different from the medium it was imbedded in. + +That such a quality as elasticity may be due solely to +\Pagelabel{40}% +motion, and varying with it, one may assure himself +with that piece of apparatus to be found in most collections +in schools known as Bonnenburger's. It consists +of a disk of metal, mounted in gimbals so it can +be set spinning %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}{l}{1.5in} + \Graphic{1.375in}{052a} + \Caption{3}{Diag.\ 3.---\textsc{Bonnenburger's Apparatus.}} +\end{wrapfigure} +in any plane. If +this be set spinning in a vertical +plane it becomes tolerably rigid +in that plane, and cannot be moved +out of it but by the employment +of quite a degree of pressure. If +the framework be quickly struck +by the finger while thus spinning, +the wheel will begin to rock back +and forth like the prong of a +tuning-fork, and the more rapid +the rotation the higher the rate +of vibration. When the velocity +of rotation becomes slow the +vibratory motion may be as slow +as once a second, and, of course, when the ring is not +revolving it will not vibrate at all. Thus there is fairly +good physical reason for thinking that what we call +elasticity in the atoms of matter may be due simply +to the motion they possess, and \emph{how} that may be one +can understand if atoms be vortex rings. + +One may properly ask how one vortex ring can differ +from another so there could be so many as seventy or +\DPPageSep{053.png}{41}% +more different kinds of atoms. To this it may be said +that such rings may differ from each other not only in +size but in their rate of rotation: the ring may be a +thick one or a thin one, may rotate relatively fast or +slow, may contain a greater or less amount of the ether. +The word ``mass'' in physics is used to denote a quantity +of matter as measured by its resistance to pressure +tending to move it as a whole. Thus if a pressure of +one pound be applied to two different bodies for say +one second, and one of them was moved an inch and +the other but half an inch when otherwise they were +alike free to move, we would say that one had twice the +mass of the other---its resistance to being moved was +twice as great as the other. + +In the case of the Bonnenburger's rotating disk, the +resistance to the pressure tending to move it depends +upon the rate of rotation, and a thin and swift moving +disk would offer much greater resistance than a much +larger one with a slower speed. So one might infer +that the difference in what is called mass among the +atoms of matter might be due simply to the different +speeds with which the rings rotate, rather than in the +absolute volume of ether in the state of rotation. +There are other reasons than these for thinking that +motion is the chief characteristic of matter. Chemists +have discovered that both the chemical and physical +properties of all kinds of matter are functions of their +mass or relative atomic weights, and that they may be +arranged in a harmonic series. Harmonic relations +may imply either relations of position or of motion. +But the fundamental properties of matter do not change +\DPPageSep{054.png}{42}% +by changing its position, and one is therefore led to the +conclusion that one must look to the various kinds of +motion involved among atoms for the explanation of all +their properties and all their phenomena. + +There is another very important and peculiar property +possessed by vortex rings; viz., there cannot be +such a thing as half a ring or any fragment of one. +Break such a ring in two and there is not left the two +halves; not only is the ring broken, but each part at once +vanishes into the indistinguishable substance that composed +it, and all the properties that characterized it as a +ring have vanished with it. + +This greatly aids one to understand that matter may +not be infinitely divisible. Over and over again have +philosophers asserted that it was impossible to imagine +an atom of matter so small that it could not in imagination +be again broken into two or more parts. A vortex +ring, however, shows how the thing can be done. +If an atom be a ring, when it is disrupted it is at once +dissolved into ether, and that is the end of it. There +are no fragments of the ring. + +One, however, must not infer from the above treatment +that it represents knowledge of a demonstrated +kind, for it does not. It was remarked in the first +chapter that atoms are too minute to be seen and +studied as one would study an animalcule or a blood +corpuscle, and one's knowledge must be altogether +inferential concerning them; but what knowledge we do +have, and the inferences that may properly be drawn +from it, all tend to convince one that matter and the +ether are most intimately related to each other, and +\DPPageSep{055.png}{43}% +that some such theory as the vortex ring theory of +matter must be true. + +Now, it is either that theory or nothing. There is +no other one that has any degree of probability at all. +If what is presented herewith is not the precise truth +concerning a most difficult subject, it may have the +merit of helping one to conceive the possibilities there +may be of deducing qualities from motions, and rid him +of the idea that matter consists necessarily of some +created things that have no necessary relations to the +rest of the universe beyond the properties impressed +by fiat. In the latter case one could never hope to +understand them, because there could be no \emph{necessary} +reason for their being as they are, rather than some +other way, whereas, in the former case, the mechanical +relations can be understood, and there is left the possibility +that by and by, with more light and knowledge, +one may know the physical conditions under which +matter itself came into existence. +%\DPPageSep{056.png}{44}% + + +\Chapter{III}{Motion}{44} + +\First{Everybody} has so clear a conception of motion that +there would not seem to be any difficulty in defining it +absolutely, but philosophers and others from remote +times till now have been perplexed by its problems. +How can Achilles ever overtake the tortoise, though +he runs ten times faster? How can the top of a +cart-wheel move faster than the bottom? If the sun +cannot set above the horizon and cannot set below +it, how can he set at all? In the last chapter some +phenomena were alluded to which were attributed to +motions of different kinds, and one must needs have a +definite notion of what he is talking about in order that +his words shall convey to himself, as well as others, +the information he would impart. Rest and motion are +contrasted conditions of bodies, so if a body is at rest +we say it is without motion, and \textit{vice versa}. If two persons +sit side by side in a house they may be said to be +at rest, but if they sit side by side in a railroad car they +will be at rest relative to each other as they were +before, but may be in motion with reference to things +outside the car. If, as a vessel sails past the end of a +wharf, a person on board would talk with a person +standing upon the wharf, he will walk so as to keep +\DPPageSep{057.png}{45}% +opposite the man standing still, and the two will be +at rest in relation to each other, while one will be in +motion with reference to everything on board the vessel. +Thus it appears that rest and motion are relative +terms, and can only be understood to apply to the +relative continuous position of two bodies or objects. +Hence, if there were but one object in the universe there +could be no such thing as change of position, for that +implies another body with which position may be compared +at intervals. But such a single body might have +some internal motions by which there was a relative +change of position of its parts with reference to themselves. +For instance, a tuning-fork might be at rest as +a whole with reference to all other bodies, yet its prongs +might vibrate towards and away from each other, the +centre of mass or the centre of gravity of the fork itself +not moving in the slightest degree either with reference +to itself or anything outside itself. Again, a body might +spin like a top, and there would be no change of position +of the body as a whole with reference to any other +body, nor change of position of the parts with reference +to each other, yet there would be a change of position +of the parts with reference to all bodies outside itself. +Hence, a brief definition of motion is not so easy to +give. + +One might say that motion was the change of position +of a body with reference to other bodies, or the change +of position of the parts of a body with reference to each +other, or the change of position of the parts of a body +with reference to other bodies. But these would not cover +all possible cases. There need be no trouble, however, +\DPPageSep{058.png}{46}% +\index{Molecules, size of}% +\index{Motion, kinds of}% +in particular cases, because there will always be data at +hand to determine the character and direction of the +motion. + +One may study the geometry of positions and changing +positions of mathematical points, and attend only to +rates and direction of motion of all sorts, without considering +the motions of bodies of real magnitude possessing +physical properties like matter. The science +that has to do with such ideal conditions is called \emph{kinematics}. +\index{Kinematics}% +Whenever the motions of matter are considered, +the science is called \emph{kinetics}. Of course all +\index{Kinetics}% +phenomena involve the motions of matter. Although +one sees a great variety of motions, a few examples of +particular sorts may be helpful in analyzing them. + +1. The drifting of clouds, the flight of birds, of +arrows, of bullets, of meteors, the sailing of vessels, the +running of locomotives, are examples of one kind of +motion; namely, where the change of position is that +of the body as a whole with reference to other bodies +external to it. The cloud may drift with the air, but +with reference to the surface of the earth it moves. +Where a body thus moves straight on continuously with +reference to other bodies, whether the distance moved +be long or short, the motion is called \emph{translatory} or +\emph{free-path motion}. The latter term is most frequently +applied to the movements of the molecules of a gas. +In ordinary air the distance apart of the molecules is on +the average about the one two-hundred-and-fifty-thousandth +of an inch, but the molecules themselves being +only one fifty-millionth of an inch in diameter, it will +be seen that they have a space to move in about two +\DPPageSep{059.png}{47}% +\index{Vacuum}% +hundred times their own diameter before coming in +collision with another one; and after collision their +direction is only changed when they go on to another +collision, and we say that their free path is on an average +about the two-hundred-and-fifty-thousandth of an +inch. With some modern air-pumps it is possible to +reduce the amount of air in a space so that the average +free path of a remaining molecule will be a foot or more; +but neither the size of the moving body, nor the distance +hundred times their own diameter before coming in +collision with another one; and after collision their +direction is only changed when they go on to another +collision, and we say that their free path is on an average +about the two-hundred-and-fifty-thousandth of an +inch. With some modern air-pumps it is possible to +reduce the amount of air in a space so that the average +free path of a remaining molecule will be a foot or more; +but neither the size of the moving body, nor the distance +it moves, nor the velocity with which it moves, +makes any essential difference in the specific kind of +motion: so the movements of air particles among themselves, +of billiard-balls between impacts, of a bullet on +its way to the target, and of a planet or comet in its +orbit, are all examples of the same kind of motion, +namely, translational. + +2. The swaying of the branches of trees when +moved by the wind, the swinging of the pendulums +of clocks, the movement of the piston in a steam-engine, +of the prongs of tuning-forks, the reeds and +strings in musical instruments, are examples of a different +kind of motion, inasmuch as the changes of position +relate to the body itself rather than to external bodies. +The tuning-fork is the type of them all, and together +they are called \emph{vibratory} motions. Sometimes, when +the bodies that move thus are large and the motion conspicuous, +as, for example, in the pendulum of the clock, +and the steam-engine piston, the motion is spoken of +as \emph{oscillatory}. In such cases, as in the former one, it +should be borne in mind that mere differences in the +size of bodies, or of the rate of motion, does not in any +\DPPageSep{060.png}{48}% +\index{Motion, kinds of}% +manner change the character of the motion, so the +name that is applicable to one will be equally applicable +to all. If one calls the movement of a vibrating tuning-fork +\emph{vibratory}, the same term may be applied to an +atom if it goes through a like periodic change of form, +for that is the chief characteristic of vibratory motion; +and hereafter it will appear how needful it is to bear +this in mind, for what a given amount of motion will +do will be seen to depend altogether upon the kind of +motion. + +3. The spinning-top, the balance-wheels of engines, +the wheels of machines of all kinds, the turning of the +earth, and each member of the solar system upon its +axis, are examples of another sort, where the displacement +is not, as in the last, between parts of the same +body, but a change in the relative position of each part +of a body to what is outside itself. The pendulum of a +clock swings to and fro, but its point of suspension does +not move; whereas every part of a turning-wheel is +presented to opposite parts of space in the plane of its +revolution. This motion is called \emph{rotary}, and just as in +the other two cases, I wish to emphasize the fact that +the term is properly applicable to masses of matter of +all degrees of magnitude; so an atom may spin on its +axis as well as the earth or sun, and the phenomena it +will be competent to produce by such spinning will be +very different from that produced by its vibrations or +free-path motions. + +These three kinds are all of the primary ones: all +the others we see are made up of these or their compounds. +For instance, a compound of a free-path +\DPPageSep{061.png}{49}% +\index{Motion, kinds of}% +\index{Motion, molecular and atomic}% +motion with a vibratory motion will give a wave or +sinuous motion if the direction of the vibration be at +right angles to the free path. A combination of a free-path +with a rotary may give a spiral motion, as illustrated +by the movement of a screw when pushed and +turned into a piece of wood. + +In a sewing-machine may be seen all of these kinds +of motion and some other compounds more complex +than the ones spoken of, but one may readily analyze +them into the three primary ones. + +These forms of motion have been spoken of as if +they were peculiar to matter; but it ought not to be +inferred that motion is not attributable to the ether. +Indeed, we know that some sorts of motions are propagated +in the ether. For instance, what we call light +is an example. Its form is \emph{undulatory}; and, as we have +seen above, an undulatory motion is a compound of a +rectilinear and a vibratory. A spiral movement in the +ether is also known, and it is sometimes called rotary-polarized +light: its motion is like that of a screw, and +we know that such a motion is a compound of a rectilinear +and a rotary. Rotary motions in the ether are +also known as taking place in front of magnetic poles, +and are the results of the magnetism imparted to the +iron or other substance. I am not aware that any +simple rectilinear motion is known to occur in the +ether: there may be, and likely enough is, such. + +For convenience, motions that are large enough to +be visible are called \emph{mechanical motions}, while those +too minute to be seen are often called \emph{molecular} or +\emph{atomic}. Sometimes these molecular and atomic motions +\DPPageSep{062.png}{50}% +\index{Motion, velocity of}% +are spoken of as if they were mysterious, and not to be +understood in the same sense as the larger ones that +are visible to us; but it is difficult to justify any such +distinction, and difficult to imagine that any kind of a +motion a large piece of matter may have, a small particle +or atom cannot have, and \textit{vice versa}. It would +seem probable that whoever finds a difficulty in this +cannot have strong mechanical aptitudes, and is not +gifted with an adequate scientific imagination. + +A free body of any kind and of any magnitude may +have any kind of a motion whatever, and may move in +any direction and with different velocities, but the term +\index{Velocities}% +velocity is used in different senses when applied to different +kinds of motion. Thus the velocity of an atom +in its free path, of a musket-bullet, of sound-waves, is +measured in feet per second. The velocity of vibrating +bodies is indicated by the number of vibrations they +make per second. A tuning-fork making two hundred +and fifty-six vibrations in a second is said to have that +rate of vibration, whether the actual distance moved be +one distance or another, which, of course, will depend +upon the amplitude of each individual swing; while +rotational velocity is generally specified by giving the +number of rotations per second, or per minute, or some +other unit interval of time. A top may spin a hundred +times a second, a balance-wheel of a steam-engine turn +four times, while the earth makes one revolution in a +day of twenty-four hours. The range in velocities of +these different kinds that have been measured is very +great indeed. In free-path or translational motion, +there may be the snail's pace, perhaps less than an +\DPPageSep{063.png}{51}% +inch a minute, the pace of a man walking say three +miles an hour, which is at the rate of eighty-eight feet +per minute. A race-horse may trot a mile in two +minutes and ten seconds, which is forty feet per +second. A steam-locomotive may run seventy miles +an hour, which is nearly one hundred feet per second. +A rifle-bullet may go a thousand feet, and a cannon-ball +two thousand feet in a second. The earth in its orbital +motion goes seventeen miles per second; meteors come +to the earth, from space, sometimes having a velocity +of fifty or more miles per second, while comets may +reach the velocity of nearly four hundred miles in the +same time when near the sun. These are the velocities +of bodies of visible magnitude, but some of the motions +of molecules are fairly comparable with some of these. +Thus a molecule of common air is moving in its free +path about sixteen hundred feet per second, while a +molecule of hydrogen, which is much lighter, goes +more than six-thousand feet---upwards of a mile---in the +same time. As remarked before, the free path for air +molecules having but about the two-hundred-thousandth +part of an inch, it must change its direction an enormous +number of times in a second,---as many times as +one two-hundred-and-fifty-thousandth of an inch is contained +in sixteen hundred feet; +\[ +250,000 × 12 × 1,600 = 4800,000000. +\] +Four thousand eight hundred millions of times. How +one may assure himself that such a statement is not +fabulous will be pointed out farther on; so far one +needs only to trust the multiplication table. +\DPPageSep{064.png}{52}% + +For vibratory rates there are also enormous ranges: +there are the slow oscillatory movements of swinging +pendulums of various lengths, sometimes occupying +several seconds for the execution of one vibration; +piano-strings having a range from about forty per +second to four thousand; the chirrup of crickets about +three thousand. Short whistles and steel rods have +been made that will make as many as twenty thousand +vibrations per second,---a rate much higher than can be +\index{Vibrations per second}% +perceived by most persons, though occasionally abnormal +hearing in an individual enables him to hear sounds +to which ordinary ears are entirely deaf. When the +number of vibrations per second becomes so great that +they cannot be individually seen nor heard, one must +trust his judgment and the properties of matter in +determining whether there really are any still more +rapid. It has been found by experiment that the number +of vibrations a given body can make when it is +struck so as to produce a sound depends upon its shape, +its size, its density, and its degree of elasticity. If a +steel rod, having a given diameter and length, makes, +when struck, five hundred vibrations per second, another +similar one with but half the length will make twice as +many in the same time. If one were made of something +still more elastic than steel, and of the same size, +the vibratory rate would be higher still. + +A steel tuning-fork three inches long may make five +hundred vibrations per second; if it were only the one +fifty-millionth of an inch long it would make not less +than $30000,000000$ vibrations per second; and if it +were made of a substance like ether it would make as +\DPPageSep{065.png}{53}% +many as $1000,000000,000000$---a thousand million +of millions per second. As large as this number is, +and as improbable as it would seem to be, there is indubitable +evidence that the atoms of matter do actually +make such a number of vibrations per second. +\index{Vibrations per second}% +\Pagelabel{53}% + +If one knows the rate at which vibrations are propagated +in a medium and the wave length, one can readily +determine the number of vibrations the body is making +that sets up the waves. Thus, if the velocity of sound +in the air be $1100$~feet per second, and the length of +one wave be $1$~foot, then the body must be making +$\dfrac{1100}{1}=1100$ vibrations per second: that is, the velocity +divided by the wave length will give the number of +vibrations. + +The velocity of light is known to be $186000$ miles +per second; the wave lengths of light are also known with +great precision, and are all only small fractions of an +inch. If they were only one inch long, their number +would be the number of inches there are in $186000$ +miles, or $12 × 5,280 × 186000 = 11784,960000$ per +second. In reality they are only one forty-thousandth +or the one fifty-thousandth of that. +\[ +11784,960000 × 50000 = 589,248000,000000, +\] +nearly six hundred millions of millions per second. No +one can pretend to comprehend such a number; but in +proportion as he understands the process and the data +by which such a result is reached, will he have an abiding +confidence that it is legitimate and that it expresses +the actual truth. +\DPPageSep{066.png}{54}% + +Sometimes it is convenient to know the actual space +that is moved over by a vibrating body in terms +of free-path or translatory motion, that is, how far +would the body move in the same time if, instead of +vibrating, it went on in a straight line. If the prong +of a tuning-fork moves through the one-hundredth of +an inch each swing, and vibrates one hundred times in +a second, obviously its rate of motion measured that +way would be only one inch, which would be a relatively +slow motion when compared with many others. +If the same computation be applied to atoms, however, +whose rate of vibration is so enormously high, it leads +to some very respectable translational velocities. Thus, +\index{Velocities}% +suppose the amplitude of vibration of an atom of hydrogen +be as great as one-half its diameter, that is, one +hundred-millionth of an inch, if it vibrates five hundred +millions of millions of times per second, the actual +space moved through will be +\[ +\frac{500,000000,000000}{100,000000} + = 5,000000 \text{ inches} = 80 \text{ miles,} +\] +which is more than four times that of the earth in +its orbit. It does not appear probable, however, that +the amplitude of motion is anywhere near as much +as that assumed, at any rate for ordinary temperatures; +but if it be only the one-hundredth of that amplitude +the velocity exceeds that which can artificially be given +to any visible object, as it will then be nearly a mile a +second. + +Rotary speeds have wide ranges. The earth takes +twenty-four hours to make one revolution; the moon +about twenty-eight days, and the sun twenty-six, and +\DPPageSep{067.png}{55}% +\index{Earth, diameter of}% +some others of the planets perhaps much longer than +that. Some astronomers have concluded from their +observations of the planets Venus and Mercury, that +\index{Mercury}% +\index{Venus}% +their axial rotation corresponds with their time of revolution +about the sun, being $224$~days for Venus, and $88$ +for Mercury. Tops have been made to spin eight hundred +or a thousand times per second; and if molecules +ever rotate their rate has not been measured. The +velocity of rotation, when measured as a translation, +must evidently depend upon the diameter of the body +rotating. The diameter of the earth being nearly eight +thousand miles, a point on the equator moves twenty-five +thousand miles in twenty-four hours---something +over a thousand miles an hour, or about seventeen miles +a minute. A driving-wheel of a locomotive that is six +feet in diameter will advance nearly nineteen feet every +revolution. To have a speed of a mile a minute, which +is $88$~feet per second, it must turn round $\dfrac{88}{19}=4.6$~times +per second\DPtypo{}{.} A disk $4$~inches in diameter, spinning $800$ +revolutions per second, which was the speed given by +Foucault to one of his gyroscopes, would advance, if +allowed to roll, with the speed of $837$~feet per second---nearly +ten miles a minute. + +There are some facts, and inferences we draw from +them, with regard to motion and the geometry of space +that it may be well to mention here. When we speak +of the velocity of a body at a given time we mean by it +that its rate is such that if continued for the whole +interval of the unit of time, whether it be a second, or +a minute, an hour, or any other, the body will move +\DPPageSep{068.png}{56}% +\index{Sun, its distance}% +through the whole specified distance. A body will not +need to go a mile in a minute in order to have a velocity +of a mile a minute. It may not move ten feet, yet +may have that or any higher velocity. This is obvious +enough of course. Every one trusts arithmetical processes +to lead him to correct results in velocities and +\index{Velocities}% +time and all such familiar matters. One will say +frequently, ``It is six hours to New York'' instead of, +``It is two hundred miles to New York,'' and will not +be misunderstood. Some persons have computed how +long a time it would take to reach the sun if they were +to take an express-train running at the rate of fifty +miles an hour, without stopping for food or fuel; and +they find it comes out nearly two hundred years,---a +time of transit equivalent to five generations of men. +In like manner, presuming one knows the distance to +any remote point in space, the time required to get +there at a given velocity one would call a simple problem +in arithmetic, and it is. But there is an assumption +one has to make which is rarely considered: that is, +the properties of space and of time are the same everywhere, +and that the geometry of the space in which we +\index{Geometry}% +live is a geometry that holds everywhere and always: +that its propositions are absolutely and irrefragably true +always and everywhere. We assume, because we find +them practically true on a small scale, that they are +equally true on the largest scale. + +Within the past fifty years the great geometers have +made some very wonderful discoveries---one might say, +astounding discoveries; for they tell us that we do not +know that the sum of the interior angles of a plain +\DPPageSep{069.png}{57}% +triangle is equal to a hundred and eighty degrees, +that we do not know it within ten degrees if the +triangle be a very large one, such as is formed by +the spaces between remote stars and the sun; furthermore, +we are assured that, for all we know, and therefore +for all we can reason from, space itself may be +\Pagelabel{57}% +curved so that if one were to start in what we call a +straight line, in any direction, and travel in it on and on +he would find himself after a long time coming to his +starting-point from the opposite direction; that what +one would see if his sight were prolonged in any direction +would be the back of his own head much magnified. +Methods have been proposed for discovering if it be +true or not. Some folks have called this nonsense, and +have used descriptive adjectives to express their contempt +for it; but none of those who have spoken thus +of the new geometry are themselves mathematicians, +\index{Geometry}% +and one is therefore left with the fair inference that +they did not so well know of what they condemned as +did the mathematicians who reached the conclusion.\footnote + {See \hyperref[page:400]{Appendix}.} + +Now, we all of us trust such mathematical processes +as we can ourselves handle, even when they lead us to +magnitudes and distances too great for comprehension. +All that one needs to know is, that the process is a +legitimate one and is correctly worked out. This new +geometry I have alluded to has been worked at by the +best mathematicians of all the civilized nations, and +they agree in the conclusions. They certainly would +not do so if there were the slightest apparent reason +for rejecting them; for national jealousies are too +\DPPageSep{070.png}{58}% +strong, and a sense of the value of truth too great, to +allow any such notions to gain currency anywhere if +there were any possibilities of breaking them down. + +If the space we live in and the geometric relations +\index{Space}% +are only practically true upon a small scale; if we may +have a kind of space of four or more dimensions, whether +we now can conceive of it or not, then should one understand +that spaces and distances and velocities and all +computations formed upon them, though practically +true, for all of our experience must not be pushed up +into statements that shall embrace all things in the +heavens as well as on the earth. Perhaps even the +visible universe is not to be measured by our span, +much less things invisible in it and beyond it. +%\DPPageSep{071.png}{59}% + + +\Chapter{IV}{Energy}{59} + +\First{Whenever} a body of matter having any motion +strikes another body, it always imparts some of its +motion to it, and the second body moves. The ability +one body has to move another one is sometimes called +its energy, and the amount of energy received is proportional +to the amount of similar energy the first body +possesses. A body at rest can impart no motion to +another one, so it appears that the energy a body has +depends upon its own amount of motion. Neither can +a body impart to another one more motion than it possesses +itself, and rarely or never can it do so much as +that. Inasmuch as every kind of a phenomenon is the +\index{Phenomena, nature of}% +result of the transfer of some kind of motion from one +body to another, one may rightly infer that to understand +phenomena and their relations, one must need to +know, not only the kinds of motion that are transferred, +but must also know their quantitative relations, and he +must therefore have some units and standards for comparison. +This requires some measure for the amount +of matter involved, also some measure for the motion +it has. For the former it is customary to employ a +weight. A certain mass of matter called a pound is +adopted in England and America. Exact duplicates of +\DPPageSep{072.png}{60}% +\index{Falling bodies}% +\index{Falling bodies, energy of}% +\index{Weights, standards of}% +\index{Work, standard of}% +its standard weights are made and preserved by each +nation; so as weights become worn by usage, they +may be exactly replaced. Any unit space may be +adopted, as the foot, which is common. If a pound +has been raised a foot, a certain amount of work has +been done, which is called a \emph{foot-pound}, and it is important +\index{Foot-pound}% +to keep in mind just what it signifies. If ten +pounds be raised one foot, or if one pound be raised +ten feet, the same amount of work---ten foot-pounds---has +been done; and with this as a starting-point, it +will be easy to see how energy may be measured, for +the measure of it will be the amount of work, measured +in foot-pounds, it can do. It is found by experiment +that if a body be left free to fall in the air, it will fall +sixteen feet in a second, and its velocity at the end of +the second will be thirty-two feet. If a very elastic +ball weighing a pound should fall thus in the air upon +an elastic pavement, it would rebound nearly to the +height of sixteen feet. If it does not quite reach that +height, it is because the air retards it somewhat, and +some of its motion has been imparted to the pavement +upon which it falls. Adding those losses to the height +it did rise, and it would make the sixteen feet. Now, to +raise a pound sixteen feet required sixteen foot-pounds +of work; there must therefore have been sixteen foot-pounds +of energy at the instant of impact. Its velocity +was thirty-two feet per second. Hence a body weighing +one pound, having a velocity of thirty-two feet in a +second, is capable of doing sixteen foot-pounds of work. +It is found also that if the same body falls for two +seconds, it will fall sixty-four feet, and its velocity at +\DPPageSep{073.png}{61}% +the end of the second second will be sixty-four feet,---twice +as great as it was for the fall of one second; but +the pound weight in this case will rise under similar +\index{Weight}% +conditions to the height of sixty-four feet, which is four +times higher than for thirty-two feet per second; so it +is seen that in this case, when the velocity is doubled, +the power of doing work, measured in foot-pounds, has +been increased four times, and this is generally expressed +by saying that the energy of a body is proportional +to the square of its velocity. The particular +direction in which a body moves has not been found to +make any difference in this regard, so the statement is +a general one. If a mass weighing two pounds were +dropped, as in the first instance, it would rise no higher +than if it weighed but one; but two pounds raised sixteen +feet would give thirty-two foot-pounds, so the +work would be proportional to the weight as well as to +the square of the velocity. + +The amount of matter there is in, say, a pound weight +would be just the same in one place as in another; but +the attraction of the earth upon it depends upon where +it is. At the surface, where we measure it, it has a +certain value; but at the centre of the earth it would +weigh nothing. The farther it were removed from +the surface of the earth upwards, the less would its +weight be. At the height of a thousand miles it would +be but four-fifths of a pound; at a million miles it +would be but sixteen-millionths of a pound, or only +about the tenth of a grain. + +For that reason it has become necessary to find +some measure for matter that shall be independent of +\DPPageSep{074.png}{62}% +\index{Foot-pound}% +\index{Work, measure of}% +position, and this has been found by dividing the weight +of the body at a given place by the value of gravity at +that place, and calling the quotient the \emph{mass}; so if $w$~represents +the weight of a body at a given place, and +$g$~the value of gravity at the same place, that is, the +velocity that gravity will give to a body in one second +if left free to fall, then $\dfrac{w}{g} = m$, the mass. The distance +in feet that a body will fall in a second is equal +to the square of the velocity divided by twice the value +of gravity, or~$d$, the distance,~$= \dfrac{v^2}{2g}$; and as the weight +equals~$mg$, the product of the two is $mg × \dfrac{v^2}{2g} = \dfrac{mv^2}{2}$, +one-half the product of the mass into the square of the +velocity will give the energy of a body. But it is +generally more convenient to use the weight of the +body instead of its mass. As $m = \dfrac{w}{g}$, let it be substituted +for~$m$ in the expression of energy, and we shall +have $\dfrac{wv^2}{2g} = pd$ (pressure in pounds into distance in +feet), or foot-pounds, a very convenient expression to +keep in mind if one has any problems in motion and +energy for solution. + +An example will make plain the utility of this. A +body weighing ten pounds is moving with the velocity +of one hundred feet in a second; how much energy has it? +$\dfrac{wv^2}{2g} = \dfrac{10 × 100^2}{64} = 1562~\text{foot-pounds}$; that is, it has +energy enough to raise $1562$~pounds a foot high, or ten +pounds $156.2$~feet high. +\DPPageSep{075.png}{63}% + +This is applicable to all bodies, big and little, whose +weight and velocity of translation are given. + +When a person who weighs one hundred and fifty +pounds climbs a flight of stairs---say, to the height of +ten feet---he has done $150 × 10 = 1500$ foot-pounds of +work. Whether he has gone up fast or slow makes no +difference in the amount of work done; it will only +make a difference in the \emph{rate} of doing work. Now, a +horse-power is a rate of work, and is equal to $550$~foot-pounds +a second; and hence if the above individual +climbs the stairs at the rate of four feet a second, he +will be doing $4 × 150 = 600$ foot-pounds per second, +which is over a horse-power, and indicates the +probability that he would not climb so fast. If any +one thinks he can do it, it will be worth his while to +try it. + +Work can be measured on a horizontal as well as a +vertical plane. Suppose the horses on a horse-car pull +two hundred pounds, as indicated by a dynamometer, +and the car is moved five feet in a second: the pull +into the distance measures the work done; that is, +$pd = 200 × 5 = 1000$ foot-pounds, a little less than +two-horse power. These illustrations are given because +not every one has clear enough ideas concerning the +meaning of energy and work, much less the ability to +apply them to examples that may often come up. +When one sees the long trail of a meteor in the sky, +and remembers that its velocity may be as much as +twenty or more miles per second, he will now see that +it may have a good deal of energy, though its weight be +but a few grains. +\DPPageSep{076.png}{64}% +\index{Energy of translation}% +\index{Meteors}% +\index{Work, measure of}% + +The energy of a pound moving twenty miles a second +would equal +\[ +\frac{1 × (20 × 5280)^2}{64} = 174,240000 \text{ foot-pounds.} +\] +A grain is one seven-thousandth of a pound, and its +energy would therefore be but the one seven-thousandth +of that quantity. $\dfrac{174,240000}{7000} = 24891$, which is the +number of foot-pounds of work a meteor weighing one +grain, at that velocity, may have: enough to raise a +ton twelve feet high. + +As a matter of fact, the great friction it is subject to +in its path through the air heats it shortly to incandescence, +and it is presently dissipated. If it were not for +the air, therefore, even if we could subsist without it, +mankind would be in constant danger from the flying +missiles; for though they would weigh but a little, +their velocity would enable them to do destructive +work upon everything they struck. As there are some +millions that come into the atmosphere every day, no +one could be safe from them in any place. + +The energy of a workingman is measured in the +same way; namely, by the amount of work in foot-pounds +he can do. + +One of the most direct ways of knowing this for an +individual is to ascertain the amount of earth or stones +he can load into a cart, or the bricks he can carry up a +ladder to the mason. Suppose he throws fifteen shovelfuls +per minute, each one holding ten pounds, and each +one is raised four feet high: then in a minute he has done +\DPPageSep{077.png}{65}% +\index{Goose, work in flying}% +$15 × 10 × 4 = 600$ foot-pounds of work, or $10$~per second. +This is rather a small quantity, only the one fifty-fifth of +what a horse-power would do, and most men have been +found able to do forty or fifty foot-pounds per second; +still, there is a great difference in individuals in their +working ability. Climbing, in general, is hard work +because it is continuous lifting of one's self. One who +weighs one hundred and fifty pounds, and climbs one +hundred feet, has done $15000$ foot-pounds of work; and +if he has done it in a minute, he has spent nearly half a +horse-power, which is $33000$ foot-pounds a minute. + +Once more: a bird in flying has to do work; and one +may see how much is demanded of such birds as geese, +that make long voyages through the air in the fall and +spring,---sometimes for twelve hours or more continuously. +As work is measured by pressure into distance, +one may apply it thus. Geese are known to fly at the +rate of thirty miles per hour, which is forty-four feet per +second. In flying, of course, there has to be a push +forward by means of their wings, not only to advance, +but to maintain their elevation. Supposing that a large +bird flying at this rate should have to exert a push of +one pound continually: it would be expending then forty-four +foot-pounds per second, nearly one-twelfth of a horsepower; +and to maintain such a rate for twelve hours +would imply that it had a supply of energy to start with +of $44 × 60 × 60 × 12 = 1,900800$ foot-pounds for one +day's expenditure. This does not seem at all probable, +and one may therefore infer that the pressure exerted +when going at that rate is much less. If the pressure +were but one ounce instead of a pound, the rate of work +\DPPageSep{078.png}{66}% +\index{Energy of vibration}% +would be $\dfrac{44}{16} = 2.75$ foot-pounds per second, which is +much more likely; but this supposes the bird to have a +supply of energy of $\dfrac{1,900800}{2.75} = 700000$ foot-pounds. + +In the chapter on ``\hyperref[chap:chemism]{Chemism},'' the source of the +energy of animals will be more particularly treated. + +So far the energy involved in translatory or free-path---or, +as it is more often called, mechanical---energy +has been considered; but vibratory motions of matter involve +energy also, and the same expression is applicable +as in the first case,~$\dfrac{wv^2}{2g}$. Here the value of the~$v$, +or the velocity, has to be determined by analyzing the +motion itself. This is not simply the number of times +the body vibrates, but also the extent of each individual +vibration,---that is to say, the amplitude of vibration,---and +the product of these two factors will give the +value of~$v$ needed. So if $n$~be the number of times the +body vibrates a second, and $a$~be the amplitude of the individual +vibrations, the true velocity will be represented +by~$an$, and then the expression for the energy will be +\[ +\dfrac{wa^2 n^2}{2g}. +\] +For most bodies of visible magnitude the amplitude of +vibration is so small a quantity that for frequencies of +only a few hundred per second, the velocity, measured +as a translation, is small, and therefore the energy is +small, and there are few cases where it is very important +to take it into account. + +Suppose a vibrating body has an amplitude of the +\DPPageSep{079.png}{67}% +one-hundredth of an inch, and vibrates a hundred times +in a second: the total distance moved through in a +second would be but an inch, which would be the value +of~$v$, so the amount of energy it had would depend +more largely upon the weight of the body. On the +other hand, if a body is so small that its rate of vibration +is exceedingly high, as was shown in the case of +atoms on \Pageref{page}{53}, there might be a relatively large +amount of energy involved. In the case refered\DPnote{** [sic]} to, a +velocity of eighty miles a second was computed, on +\Pagelabel{67}% +the supposition that the amplitude of vibration was +equal to one-half the diameter of the atom; and what +amount of energy is possessed by a body weighing one +grain was computed. The amount in an atom with +that vibratory rate and amplitude would be calculated +by dividing the amount in the grain by the number of +atoms in a grain. Numerically it is a very, very small +quantity, and only becomes appreciable to any of our +senses when vast numbers of atoms act conjointly. + +There are some cases where energy is apparently +expended when there is no apparent motion, as is the +case when a man holds up a weight. If the weight be +\index{Muscular work}% +\index{Work, muscular}% +a heavy one, exhaustion will be the result as much as if +energy was spent in any other way. This muscular +work is called physiological work, and for a long time +it was not understood. It is now known, however, that +when a muscle is put in a state of tension, it is in longitudinal +vibration a great many times a second. This +may be perceived by putting the end of a finger into +the ear, pressing but gently, at the same time squeezing +with the rest of the hand as if grasping something +\DPPageSep{080.png}{68}% +\index{Energy of rotation}% +tightly; a low sound will be heard, made by perhaps +no more than thirty or forty vibrations per second. +The muscles in a state of tension produce this. When +one holds up a weight---say, a pail of water---the muscles +involved yield and contract rapidly, so the weight +is really raised in a vibratory way a short distance, but +a great many times in a second; and the heavier the +weight, the more the work done, and this too is measured +in the same way as other more visible kinds. +There is good reason for believing that a book resting +upon a table is supported by the vibratory motions +going on among the particles of the table, and therefore +energy is expended to do it, and that this is supplied +by the heat present in the body; that is, the +temperature of the table is a little different from what +it would be if it did not have any weight to support. + +Walking involves the expenditure of energy in the +same way. Each step requires the whole body to be +raised somewhat. Suppose it be only an inch. A +person weighing $150$~pounds would, for each step, do +$\dfrac{150}{12}$ foot-pounds~$= 12\frac{1}{2}$. If he takes two steps per +second, then each minute he does $2 × 12\frac{1}{2} × 60 = 1500$ +foot-pounds of work. Thus one can see how physiological +processes are measurable in terms of mechanical +units. + +The energy of a rotating body is more complicated +than translational energy, because a part of the body is +at rest,---the axis; and the velocity of movement at +any point away from that is proportional to its distance +from it. In the case of the balance-wheels of steam +\DPPageSep{081.png}{69}% +engines, where the most of the weight of the wheel is +in the rim, the velocity of the latter would be equal to +its circumference multiplied by the number of turns +per second or per minute. Thus if a fly-wheel, having +nearly the whole of its weight in the rim, weighs, say, a +ton ($2000$~lbs.), is six feet in diameter, and rotates four +times a second, its velocity will be $75.4$~feet per second, +and its energy will be $\dfrac{wv^2}{2g} = \dfrac{2000 × 75.4^2}{64} = 177661$ +foot-pounds, an amount of energy which is stored up, +\Pagelabel{69}% +and may be drawn upon to prevent fluctuations in +speed to which engines in workshops are liable. + +If a body having rectilinear motion be left to itself +in the air, it will speedily be brought to rest, for gravity +will bring it to the earth whether it be moving this way +or that. The air, too, will retard its motion, and would +ultimately bring it to rest if nothing else did, as it +would either of the other kinds of motion. If, however, +one could contrive to give to a body above the atmosphere +a sufficient velocity in a tangential direction, the +body would become a satellite, and revolve round the +\index{Satellite}% +earth. The curvature of the earth is about eight +\index{Earth, curvature}% +inches to the mile, and such a body would then need to +move a mile in a horizontal direction in the same time +it falls eight inches in order that it should continue to +go about the earth. As it takes about two-tenths of a +second to fall this distance, its velocity would need to be +five miles a second to prevent it from falling to the +earth; this velocity would carry it quite round the earth +in a little less than an hour and a half. + +Thus it is seen that, in order that matter should +\DPPageSep{082.png}{70}% +\index{Energy, factors of}% +\index{Motion, laws of}% +possess energy, it must have motion of some kind; +indeed, that energy has two factors, mass and motion. +When either of these is zero, there is no energy. This +is a consideration of great importance both in a scientific +sense and a philosophical one. One may often +hear it said and read it in carefully written books that +matter and energy are the two realities or physical +things in the universe, and energy is spoken of as if it +were an entity, or something that might exist though +there were no substance to move. If energy be a +product, and motion be one of the factors, then in the +absence of this there is no energy. This perhaps will +be seen still clearer after considering what are called +the laws of motion, which were first formulated by +Newton, and which, in conjunction with the law of +gravitation, were the fundamental principles that +enabled him to produce the ``Principia,'' which is what +\index{Principia}% +to-day we would call a treatise on mechanics. + +Of course, the science of mechanics is applicable to +motions of matter of any magnitude and in any place; +and Newton chose to follow out his newly discovered +principles into astronomy to the largest extent, and it +remained for later generations to employ the same principles +in other directions, largely molecular and atomic. + +The first law of motion is, that whether a body be in +a state of rest or of motion, it will remain in that state +of rest or motion until compelled by the action of some +other body upon it to change its state. This is sometimes +expressed by saying that all matter has \emph{inertia}, +\index{Inertia}% +\Pagelabel{70}% +or an inability to move or change its direction or velocity +if it has motion. This appears to be experimentally +\DPPageSep{083.png}{71}% +\index{Explosion products}% +true of all bodies whose magnitude and state +we can see. But it may very well be doubted if the +ordinary conception of the inertness of matter be true. +Many of the facts of chemistry indicate that matter in +its atomic form is not altogether so helpless as it has +been supposed to be. A stone may lie in the road for +an indefinite time and no one would suspect it possessed +any energy to do anything, and so of any other kind of +matter. Here is a piece of charcoal. Has it inertness in +any extreme sense of that word? Here is some sulphur +and some nitrate of potash; they, too, will lie as +quiescent as the coal and as long. Pulverize them and +mix them together, and we have powder the energy of +which would wreck a building. The products of the +explosion are gaseous mostly, and the carbon, the sulphur, +and the nitrate of potash have vanished as such, +and have entered suddenly into new combinations; +they have developed also a large amount of heat, while +at the beginning their temperature was that of other +bodies around them. This source of energy must have +been resident in the atoms; and if it is perceived that +for a body to have energy it is necessary for it to have +motion of some sort, it will be apparent that the +material itself must have possessed a large amount of +motion, even when it appeared to be at rest. If one +thinks that the law of inertia might still apply to atoms, +and that they cannot individually move except as they +are acted upon by other atoms, and even then only as +much as by the measure of the motion thus imparted, +he had better figure out to himself the energy of such +explosions per molecule, and see if anything initially +done will account for it. +\DPPageSep{084.png}{72}% +\index{Motion, antecedent of}% +\index{Top, sleep of}% +\index{Vortex rings, properties of}% + +When the mechanism of a clock is running, the +motion may be traced to a falling weight, and the work +done is measured by the product of the weights into +the distance it falls as the clock runs down; but in +the case of the powder, though the amount of energy +developed by the explosion is definite, it is not measured +by the work done in pulverizing and mixing and igniting +it. The case is much more nearly analogous to +that of a sleeping man. While asleep he would neither +move nor stop moving unless some other agency acted +upon him, any more than would a stone or other mass +of matter; and in that sense he would be inert, yet no +one would think of calling a sleeping man inert, except +in a very loose sense. + +Furthermore, there is an experimental analogy that +may help one to see a little deeper into this. Every +one knows what is meant by the ``sleep'' of a spinning +top. It appears to be absolutely at rest, and may not +even hum; but touch it, and the effect upon it will be +out of all proportion to the slightness of the touch. + +It has been observed as a property of vortex rings that +they have a tendency to move forward in the direction +of their axes, and when prevented from going forward +they press upon the body that arrests them. If they +be brought to rest, and then the barrier be removed, +\emph{they, of their own accord}, start on in the same direction +as if pushed from behind. Such a body cannot be +said to be inert without modifying the common meaning +of the word. + +This is not alluded to here as proving anything; but +inasmuch as the vortex-ring theory of matter has a good +\DPPageSep{085.png}{73}% +\index{Motion, laws of}% +probability in its favor, this property I have mentioned +helps one to understand how the atoms might be other +than inert, and yet large bodies of them together exhibit +that property with the rigorousness our observations +upon such bodies demonstrate. Suppose each +atom had the ability to move forward of its own impulse +when not acted on by any other atom. If there +were a million atoms joined together, no matter how, +provided they were promiscuously faced, they would +mutually neutralize each other's ability to move in any +direction, and the resultant of the whole would be that +passivity which we call inertness. + +We may by and by see that there may be still other +good reasons for thinking matter not to be so passive +as it has been often assumed to be. + +The second law of motion is, when two or more +bodies act upon a third body, the effect of each is the +same as if it alone acted, and the combined effect is +called the resultant; and the third law is, that action +and reaction are always equal and opposite in direction. +This third condition of action, or the relation of +motions in two bodies, is of a high degree of philosophical +importance, perhaps not more so than the others, +but of so much that it is worth while to attend to it +more particularly than to the second law. If a rope be +tied to the wall and one pulls upon it so as to make it +taut, the wall pulls back in the opposite direction as +much as the arm pulls forward. A spring-balance +attached to the wall would indicate the strength of the +pull, the pull of the arm representing the action, and +measured by the muscular vibration, as already described, +\DPPageSep{086.png}{74}% +and the pull of the wall representing the +reaction, and equal to the action in quantity and maintained +by molecular vibration. Imagine the action of +the arm to be steadily increasing in quantity: the +reaction of the wall would correspondingly increase +until the molecular tension could no longer be increased, +and either the rope would break, the hook be pulled out +from the wall, or the wall itself be broken away; but in +no case could the action exceed the reaction or \textit{vice +versa}. Now, if the amount of matter in the arm were a +constant quantity, as well as that of the rope, the hook, +and the wall, then it would follow that all the physical +changes noted in either the one or the other, so far as +energy is concerned, must be due to the motions involved +on either side. And if action and reaction be +equal, and the quantity of matter be uniform, then the +amount of motion involved must be equal on the two +sides. If a body in motion strikes another body, and +the second one is set in motion, the amount of motion in +the two will be just equal to the amount of motion +in the first. The amount of motion gained by one +body is just equal to that lost by the other, and there +has been simply an exchange of motions, one having +gained, the other lost; the one that gained being the +one that had less, and the one that lost having had +more, than the other one. In books of physics it is +customary to speak of the amount of motion a body has +as its \textit{momentum}; and it may be measured by multiplying +\index{Momentum}% +the mass of the body by its velocity, and oftentimes +one may read that in the physical exchanges that are +all the time happening in matter the momentum is +\DPPageSep{087.png}{75}% +conserved; that is to say, is neither increased nor +diminished. Seeing, therefore, that the amount of +matter is a constant quantity, and the momentum a +constant quantity, it follows that the amount of motion +is constant. Motion is conserved as well as matter. If +the amount of matter in the universe be constant, then, +according to this statement, the amount of motion must +be constant, and the amount of energy constant also. + +It is generally agreed that this statement concerning +energy is true, and one hears often about the law of +the conservation of energy. It seems to be less clearly +recognized that the third law of motion implies the conservation +of motion, provided matter is itself a constant +quantity. But there is another condition of things that +is as uniform as any other condition of things in +nature that has not been recognized as a law, and yet it +deserves to be perhaps as much or more than most +others, since, in our experience, it is never known to +vary; it is this: Wherever there is an interchange of +motions between two bodies, the transfer is always +from the one having more to the one having less. As +exchange of motions implies transfer of energy, it follows +that all transfers of energy of any given kind are +from bodies having more to those having less. + +Cause and effect are always determined by such a +\index{Cause and effect}% +disposition of things, though not every one has apparently +seen that questions involving what they please +to call causes and effects presume a kind of antecedent +and consequent that always work both ways at +the same time, for there is no such thing as an isolated +phenomenon. If everything takes place so and so +\DPPageSep{088.png}{76}% +because there is an exchange of motion going on, +then this thing that now moves faster than it did has +been acted upon by a body that had more motion in +this direction than the former one had, and it has +imparted some of its motion at the expense of its own +energy. If one inquires what caused the increased +velocity to this body, it may be said it was caused by +the impact with another body. In like manner one +may inquire what caused the slowing-up motions of the +second body, and the answer still must be, the same +impact with the first body. So, for every phenomenon +there is a corresponding and complementary phenomenon, +which it is just as appropriate to consider as a +cause as it is the first, and either element is just as +much a cause as the other, and in each and every case +all there is involved are exchanges in the amount and +kinds of motion in matter. + +There remains now the consideration of a topic +which those who have studied physical subjects only a +little must be more or less familiar with. The term +``potential energy'' has been much employed within the +last twenty years to express a certain condition of matter +that renders it a source of energy when no motion +is supposed to be involved: thus, where a weight is +raised, like that of a clock, or of a stone raised to the +roof of a house. By falling, either of them can be +made to do work; but so long as they remain raised +and are apparently quiescent, their stock of energy is +measured by their weight into their height, i.e., foot-pounds; +and this is said to be \textit{potential energy}. Examples +of this sort are numerous. The wound-up spring +\DPPageSep{089.png}{77}% +\index{Energy, factors of}% +of a clock or watch, a bent bow, compressed air or +steam, powder, nitro-glycerine, and the like explosives, +coal, wood, and other kinds of fuel, are all varieties of +so-called potential energy. Let it be remembered that +we have in natural phenomena matter and ether and +space and time and motion. If matter and ether be +substances, then the product of one into the other +would signify nothing; it would be physical nonsense. +So likewise would be the product of matter into space +or time; and yet if matter is to be possessed of energy, +and motion is \emph{not} one of the factors, then either space +or time must be, and no one can imagine how energy +can in any way depend upon time as a factor, and there +is no degree of probability that it is or can be so; and +hence, though we had no hint of how it might be, one +would need to avow his belief that in some way motion +was involved in every case where physical energy was +involved, for in any case where it had been hitherto +possible to trace it, it had been found to be present as +a factor in precisely the same relations as in all other +known cases, and hence he would avow a disbelief in +the existence of potential energy in any other than a +loose sense for a condition where the character of the +motion involved was obscure. This would imply that +all energy is kinetic, whether the character of the +motion was determined or not. This view is now held +by those who have taken the pains to think out the +necessary relations that are involved in this subject. + +In the last edition of the ``Encyclopædia Britannica,'' +Professor Tait, who contributed the article on ``Mechanics,'' +says, ``Now, it is impossible to conceive of a truly +\DPPageSep{090.png}{78}% +\index{Molecular fatigue}% +dormant form of energy whose magnitude should depend +in any way on the unit of time; and we are therefore +forced to the conclusion that potential energy, like +kinetic energy, depends in some unimagined way upon +motion;'' also, ``The conclusion which appears inevitable +is that whatever matter may be, the other reality +in the physical universe which is never found unassociated +with matter depends in all its widely varied forms +upon motion of matter;'' and in another place, ``Potential +energy must in some way depend upon motion.'' + +It was pointed out (on p.~67) that what was called +physiological work is now known to depend upon +the vibratory state of muscles in a state of tension. +Before that explanation was known, one might have +called such, potential energy, if it had not been for the +sense of fatigue felt by one who was doing such physiological +work that forbade him to assume that actual +energy was not employed to maintain such a stress; +and when it becomes evident, as it has, that one cannot +press upon a table, or pull upon a rope, or bring about +in any way a push or a strain upon matter, without +varying the temperature of the body, it is no longer +difficult to understand that all changes of that sort +upon matter result in atomic and molecular stresses, +for they are placed in abnormal positions as well as +stretched muscles, and their energy is spent in a similar +manner. There is a curious phenomenon exhibited +by all bodies that are made to do atomic and molecular +work for a considerable time. They become exhausted, +like living things, and require rest to recover their +properties. Thus, a tuning-fork, if kept artificially +\DPPageSep{091.png}{79}% +\index{Energy in the ether}% +vibrating for some time, will stop almost instantly +when the driving force is stopped, though at the outset +it would continue to vibrate for a minute or more when +left to itself. This is caused by what is called the +fatigue of elasticity: the body loses some degree of its +elasticity, and requires time to recover it. I have called +the phenomenon curious. Perhaps it is no more so +than any other phenomenon manifested by matter; but +it is so similar to what is so characteristic of living +things, that it almost excites one's sympathy. One +can have compassion for an overworked and exhausted +horse, but an overworked tuning-fork! The expression +would seem to be wholly inapplicable, but the fact is as +stated. The only difference between the cases is, one +has nerves, and becomes conscious of the exhaustion, +the other not. + +So far, both motion and energy have been considered +as related to matter, and matter as defined in the first +chapter, as distinguished from the ether, though immersed +in it, and can by no means be isolated from it; +but energy exists in the ether as well, as we are assured +by many phenomena. That light requires about eight +minutes to come to us from the sun has been proved in +numerous ways. When it gets to the earth it is found +to be able to impart energy to the matter it falls upon: +it may heat it and affect it in other ways that are +measurable, so energy gets to us from the sun, and is +eight minutes in transit in the ether. If we do not +call ether matter, and it has been shown that there are +good reasons for not doing so, then it follows that +energy exists outside of matter, and it is a proper line +\DPPageSep{092.png}{80}% +\index{Light, energy of}% +\index{Light, its nature}% +of inquiry to learn what shape the energy exists in, +and what mechanical conceptions are appropriate when +thinking about it. In matter one may isolate motions +of various sorts. A mass of matter, say, like a baseball, +may have translatory motion: it may vibrate or it +may spin. In each case one may contemplate the kind +of motion, and compute the energy involved in the +movement, and this is true for atoms as well as larger +masses; but when the substance is not made up of +discrete parts, but is absolutely homogeneous with no +interstices, and apparently incapable of changing either +its position or its form, as there is good reason for +thinking to be the case with the ether, it becomes +\index{Ether}% +much more difficult to picture to one's self just what is +happening when motion of any sort is involved. As +has already been said, we know that light consists of +waves, measurable quantities, and we know how much +energy reaches the earth from the sun and falls upon a +square mile or square foot. There have been several +estimates of this quantity, and it is found to be equal to +about one hundred and thirty foot-pounds per second for +each square foot section of sunshine. This signifies, of +course, that that is the amount of energy in a column +of ether one foot square and a hundred and eighty-six +thousand miles long, for that is the amount that arrives +per second. So one may calculate the amount of energy +there is in a cubic mile of sunlight to be about twelve +thousand foot-pounds, and also that the amount given +out by the sun in a second is about four millions of +foot-pounds, or nearly seven thousand horse-power for +each square foot of the sun's surface. All of this energy +\DPPageSep{093.png}{81}% +\index{Electro-magnets}% +\index{Magnetic waves}% +\index{Magnet, electro}% +is handed over to the ether, which distributes it in all +directions as undulatory movements which we call light. +Such wave motions do not exhibit anything like what +we call momentum as waves in water or air always do, +and they are therefore in striking contrast with waves +in matter. Moreover, being waves, having the amplitude +at right angles to the direction of propagation, +they must be compounded of two motions,---a rectilinear +and a vibratory one,---and not a simple one such +as a particle of matter may have. + +The ether is capable of being affected by other +motions of matter than simply the vibratory one of +atoms and molecules. + +Whenever an electro-magnet is made, it reacts upon +the ether in such a way as to affect other matter that +chances to be in the range of ether so affected. It +appears as if the ether were thrown into a state of +stress which it retains so long as the magnet retains its +property; and this condition extends to an indefinite +distance in all directions. If such an electro-magnet is +made and unmade by opening and closing an electric +current in its coils, there will be formed a set of electro-magnetic +waves in the ether which will travel outwards +from the magnet in a manner similar to light-waves, +only they will have an enormous wave length. If the +circuit be closed but once a second, the waves will be a +hundred and eighty-six thousand miles long; for a wave +in the ether travels in it with a velocity that depends +solely upon the property of the ether to transmit disturbances, +and not at all upon the source of the disturbance. +That such an electro-magnetic wave possesses +\DPPageSep{094.png}{82}% +\index{Gravitation}% +\index{Newton, Sir Isaac}% +energy, and can do work, one may satisfy himself by +observing the motions produced by them upon magnetic +needles within the affected space. + +In like manner an electrified body puts the ether into +a different kind of a stress from the magnet; and when +this is done periodically, as it may be by an induction +coil, and in other ways, electrostatic waves are set up, +and these too travel with the speed of light, and are +capable of affecting matter to a great distance, thus +showing that the ether may possess energy in an electro-static +form, as distinguished from the electro-magnetic +and light. There are some physicists who think these +last two to be identical, and the reasons for their +opinion will be given in a subsequent place. + +It only remains to point out that whatever the nature +of gravity may be, there can be very little doubt that +the ether is intimately concerned in it, as Sir Isaac +Newton supposed was the case. But if it is, and ether +is the agency by which one mass of matter is able to +affect another mass, then ether is in a state of stress +produced by the atoms of matter all the time, and +therefore in some way gravitative energy is lodged in it. +As the ether is so universal in its extension, one cannot +but see that it is a storehouse of an almost unlimited +amount of energy of many kinds; so that if every +particle of matter were instantly annihilated, there +would still be a universe filled with energy, though it +might not be serviceable, because lacking the conditions +for transformation into useful forms. This may +be said to be one of the functions of matter---the transformation +of the energy it gets from the ether. +%\DPPageSep{095.png}{83}% + + +\Chapter{V}{Gravitation}{83} + +\index{Attraction, gravitative}% +\index{Newton, Sir Isaac}% + +\First{That} all bodies will fall towards the earth if raised +above its surface and left unsupported everybody +knows and must always have known, for it is a fact +thrust into everybody's notice constantly and as long +as he lives. Also that bodies resting upon the earth +require energy to be spent in order to raise them +from it is equally well known. Thus all bodies act as +if they were attracted by the earth, and the weight of +a body is the measure of the attraction of the earth +upon it. + +One not unfrequently comes across statements by +authors implying that Newton was the discoverer of +this attraction which is called gravitation. This is a +mistake: not only was this idea common in Newton's +day, but the word itself was in extensive use. Kepler +had affirmed that the sun attracted the earth and the +planets, and Galileo had busied himself very much +with the study of attraction of the earth upon bodies. +The problem that Newton had before him was not +as to the existence of gravitative action, but what +was its law of operation and the limits of it, if it had +any limits. The familiar story of the fall of the apple +leading to the great discovery is generally believed to +\DPPageSep{096.png}{84}% +\index{Gravitation, law of}% +be mythical; at any rate, other facts well authenticated +do not accord with that story. When he was twenty-three +years old he undertook to apply the law as we +now have it, to the moon, using the size of the earth +and the moon's distance from it, as they were then +best known. The result satisfied him that his surmise +could not be the law, if the measure of the earth then +had was accurate. This was in 1666. In 1683 he +learned of some new measures recently made of the +magnitude of the earth, indicating it to be larger than +had been supposed. Then, with the new measures for +data, he made a new computation. It was then, when +he saw that the results were to prove his conjecture, +and he perceived the immense importance of the discovery, +that he handed over the unfinished work to an +amanuensis, because he was too much agitated to complete +it. If the discovery was made when he first +thought of putting the idea to the test, it is strange +that his emotional excitement should have been postponed +for seventeen years. Evidently it was at the +latter date when he thought he had made the discovery. +It was the \emph{law} of gravitation that Newton discovered, +and that it was universal. Every particle of matter +attracts every other particle; and the strength of this +attraction varies as the mass of each, and inversely as +the square of the distance between them. Thus, if at +the surface of the earth gravitation gives a weight of +one pound to a body, at the distance of ten radii of the +earth $= 40000$~miles, the weight would be $\dfrac{1}{10^2}$, one-hundredth +of a pound, and at the distance of the moon, +\DPPageSep{097.png}{85}% +\index{Attraction depends upon distance}% +or sixty radii of the earth, the body would weigh but +$\dfrac{1}{60^2}$=one thirty-six hundredth of a pound, and would +fall towards the earth in a second but $\dfrac{1}{3600}$ of the distance +it would fall at the surface of the earth, where it +is about sixteen feet. One thirty-six hundredth of sixteen +feet is about the one $\dfrac{1}{224}$ of a foot, which is +therefore the departure from a straight line the +body at the distance of the moon must make per +second to move round the earth. The mutual attraction +of these bodies at that distance is sufficient to produce +this amount of deflection, and hence accounts for +the rotation at that distance. When the same mathematical +relation is applied to the planets, comets, and +meteors that revolve about the sun, it is found to be +applicable to every one of them; and in the depths of +space in every direction are to be seen multitudes of +stars revolving about each other in similar manner, and +hence it is concluded that gravitation is a universal property, +and the law is applicable throughout the universe. + +There are other kinds of attraction that matter +exhibits, such as electric and magnetic, that follow a +part of the above law, but do not the other part. The +law regarding the distance is true for electrified bodies, +but the mass of the bodies does not enter as a controlling +condition. So it appears that the variability of +attraction with the distance is a geometrical condition, +and depends upon the property of space, and is not +peculiar to any physical phenomenon. Sound, light, +\DPPageSep{098.png}{86}% +heat, electricity, magnetism, as well as gravitation, +exhibit the property, as do circles and spheres. The +peculiar thing about gravitative attraction is that it +depends upon the masses of the attracting bodies, and +is not modified in the slightest degree by the interposition +of any substance of any magnitude between the +attracting particles or masses. In this particular it is +strikingly unlike magnetic attraction. If, for instance, +a piece of iron is brought between two magnets that at +a distance are attracting each other, the strength of +their action upon each other is decidedly less. The +strength of the attraction of the sun is just as great +upon a particle in the centre of the earth as for any +similar particle at an equal distance that is not +shielded. + +There have been numerous attempts in the past to +account for gravitation. It has been imagined that +space was full of particles swiftly moving in every direction +that produced a pressure upon all bodies by their +impact; that each body shielded other bodies in a measure, +and hence the pressure produced upon the adjacent +sides would be less than elsewhere, and, as a consequence, +each body would be pushed in the direction of +an adjacent body. But a push represents expended +energy, and this would imply that the moving particles +must be losing energy at the expense of their velocity; +and as no such particles are known, and if there were, +their velocity would have to be so much greater than +that of light, there is no degree of probability to be +allowed for the idea. The effect of vibrations upon +the ether has been a very common manner of attempting +\DPPageSep{099.png}{87}% +\index{Attraction of vibrating fork}% +to explain gravitation. It has been observed that if +light bodies are brought near to a vibrating body like a +tuning-fork, they are apparently attracted by it so long +as the vibratory motion continues; and the action is +explained by the rarefaction produced by the vibratory +motion, which reduces the pressure in the space about +the body, so when another body is brought near the +pressure is greater on the remote side than it is on +the side adjacent, and thus the body is pushed towards +the one vibrating. It is known that all the atoms of all +bodies are in a state of vibration at all temperatures; +and hence it was inferred that the pressure of the ether +must be reduced next to their surface, so that between +two atoms or molecules the pressure must be less than +external to them, and hence the pressure of the ether +will crowd them together. This idea has been worked +out by a large number of persons in different countries. +There are two fatal objections to this hypothesis: +First, it would make the attraction of gravitation +dependent upon their temperature, and there is no evidence +to show that temperature makes any difference; +and second, that the velocity of gravitative action is the +same as that of light. There is an abundance of astronomical +evidence, that if it has any velocity at all it +must vastly exceed that of light. If it were as much +as a million times greater, astronomical phenomena +would exhibit it plainly. + +Seeing that every particle of matter in the universe, +affects every other particle in a certain and definite +way, no matter what the distance between them, there +must be either the possibility that a body can act upon +\DPPageSep{100.png}{88}% +\index{Newton, Sir Isaac}% +another one at a distance without any medium between +them,---which is called action at a distance,---or there +\index{Action at a distance}% +must be a medium which is first affected by the bodies, +and which in turn reacts upon other bodies in it. +What Sir Isaac Newton thought of these contingencies +was cited in a former chapter (see \Pageref{p.}{31}). It +is now generally felt to be not only essential for consistent +mechanical thinking, but that in some way the +ether which is known to exist must have some essential +part in the phenomenon. It has been the subject +of curious speculation why Newton should so strongly +state his belief in the existence of a medium for the +propagation of physical conditions, and yet in his work +on light he should adopt the corpuscular theory---that +light consisted of emanations, which was a practical +denial of the hypothesis of the ether. The explanation +of the anomaly is probably in the fact, that he +could treat in his mathematical way the ideal corpuscles, +while he could not so treat the ether hypothesis of +waves. His work was developed with ideas he could +handle; and the outcome of it was that the science of +light was retarded by his misconceptions for a hundred +years, for every one now who knows anything about it +knows that Newton's hypothesis was a wrong one. +There are some persons who would curb the imaginations +of others in physical things by quoting Newton's +dictum, ``Hypotheses I do not touch,'' but they omit to +mention that Newton's work on optics was altogether +based upon a hypothesis that has wholly broken +down. Every one of the explanations he gave of +such phenomena is worthless, and no one gives attention +\DPPageSep{101.png}{89}% +\index{Neptune, discovery of}% +to them except for their historic relations to the +science. + +It has been thus in other lines. A symbolic representation +of things such as offers the possibility of +mathematical treatment has been seized and worked out +to great length, when the actual phenomena pretended +to be treated gave no countenance to the conceptions. +Such has been the case in electricity and magnetism and +heat. The mathematicians fought Ohm's, Faraday's, +and Joule's mechanical conceptions until death stopped +them. + +It is certainly true that all physical phenomena are +subject to strictly mathematical conditions, and mathematical +processes are unassailable in themselves. The +trouble arises from the data employed. Most phenomena +are so highly complex that one can never be +quite sure he is dealing with all the factors until +experiment proves it. So that experiment is rather a +criterion of mathematical conclusions and must lead +the way. Mathematics is a deductive science, yet the +\index{Mathematics}% +number of physical facts or phenomena that have been +discovered by its aid is so small that they may almost +be left out of the count. There is the discovery of the +planet Neptune, that has been spoken of as a triumph +of mathematical science, yet one of the most competent +mathematicians that ever lived---Professor Peirce of +Harvard---declared that it was only a lucky find, for the +computations would apply just as well to a planet $180°$~from +it. The conical refraction of light is another +one. Altogether they make but a small figure and +are unimportant. The law of gravitation was discovered +\DPPageSep{102.png}{90}% +\index{Gravitation}% +\index{Hypothesis, gravitation}% +\index{Kepler, the guesser}% +by trial, and although its importance is second +to none other yet discovered, it happens that it is one +of the very simplest and least complicated with other +laws we know of; but an explanation of how it can act +thus, or why it exists at all, or what its antecedents are +if it has any, these are questions that are matters for +the guessers, like Kepler, who kept guessing until he +guessed right, and so discovered what are known as his +laws. Meanwhile definite mechanical conceptions of +what the phenomena to be explained are like may be +helpful to those interested in them. + +Suppose two bodies, \textit{A} and \textit{B}, a certain distance apart, +and they so react upon each other that they tend to +mutually approach each other. Given a medium, ether, +can one imagine stresses set up by either body in the +ether that will be capable of affecting the other? + +Imagine a large space like a room occupied by glass +of uniform texture and properties throughout. If relieved +of gravitational property, the cohesion of all +its parts shows that every particle is in some sort of +stress, no matter what the origin of that may be. Now, +suppose there could suddenly be created somewhere +near the middle of the glass a bullet or a marble. It +would displace so much glass as would be equal to its +own volume, and the result of that would be that the +glass about it would be subject to a new stress, which +would be greatest, at the surface of contact of the +marble, and would be less as that surface is receded +from inversely proportional to the square of the distance +of the point of observation. If the glass be imagined to +be indefinitely great in magnitude, then the stress would +\DPPageSep{103.png}{91}% +extend in every direction through the whole extent of +it, and at any assignable point would still be in accordance +with the inverse law, diminishing outward. +Imagine now another similar marble to be created at +the distance of a foot from the first. Inasmuch as it +displaces so much glass it will set up a new stress in +the latter, and this stress must also be transmitted +throughout the whole mass as in the first instance. +Now, here will be two independent stresses overlapping; +and on account of the nature of the stress, it will be +greater between the marbles than it will be anywhere +else, because there the sum of the stresses will be at a +maximum. If one can now for the moment imagine +that the glass was of such constitution as to permit a +motion to the marbles, in any direction, when there was +a stress tending to move them, it would be obvious +that the marbles would separate from each other as the +medium, the glass, was under greater tension between +them than in any other direction.\footnote + {Such bodies might be said to have \emph{negative weight}.} +And if the glass +thus mobile was indefinite in extent and without friction, +the two marbles would continue to separate indefinitely. +The energy making them thus to move comes directly +from the medium, which in turn got it from the bodies +themselves when they were thrust into it, no matter +how. Such a phenomenon as separation in a manner +like the above is exactly opposite in character to that +of gravitation, but it points at once to a consideration +of the condition necessary to be similar. It was the +forcing of new material into space already occupied +with other material that developed the stress and led +to the above results. It will be necessary to find a way +\DPPageSep{104.png}{92}% +\index{Stress in glass}% +to develop a stress \emph{towards} a point instead of away +from it. + +Suppose, then, that instead of having a created something +imbedded in it, a cavity of equal volume to the +marble should be produced in its place. As part of the +material of the medium has been annihilated, there will +now be a less stress at its bounding surface than there +was when it was occupied with material, and the +direction of the stress will now be towards the cavity. +That is, the stress will be less there than anywhere +else in the glass; and this, too, if measured, will be found +distributed like the other, inversely as the square of the +distance from the origin. Let another similar cavity +be produced in the neighborhood of the first, and the +two stresses will overlap, and there will be less between +them than in any other direction. Let us imagine now +that the glass was mobile enough to permit the movement +of either of these cavities in any direction towards +which there was any pressure, and they would approach +each other because pushed by the stress in the glass +more towards each other than in any other direction. +If one of these cavities were larger than the other, one +would expect that the corresponding stress would be +greater, and so there would be a stress that for direction +and the resultant movement would correspond with +what is observed in the phenomena of gravitation. + +But such a conception as that of a vacuum as constituting +what we call the atoms of matter has no mechanical +validity at all. Atoms have not only volume, they +have mass, and that requires energy to displace. One +cannot imagine that the displacement of an absolute +\DPPageSep{105.png}{93}% +\index{Stress in ether}% +vacuum, if such a thing could be done, would require +any energy, for there would be no mass to move. + +Suppose, however,---instead of imagining, as was +done, the entire volume of the marble to be destroyed,---that +in some way the volume of the glass marble had +suddenly been reduced, no matter how, and that the +diminished volume was retained,---the material had been +condensed. This would bring about the same relative +condition of stress to the condensed portion, so that +there would be less adjacent to it than elsewhere, the +measure of it being the actual amount of condensation +represented in the body. What would be true of one +would be true of others,---an indefinite number,---and +no number of such stresses would in any manner interfere +with or neutralize that of others. At any point of +the space filled with such glass each such condensation +would have produced its effect at the outset, and if the +glass were practically limitless in extent this relationship +would be maintained so long as the reduced +volumes remained constant. + +So far has been considered a condition of things +somewhat analogous to gravitation; and to apply it one +needs to imagine the ether to be substituted for the +glass and the atoms of matter for the imagined condensation, +and also that the two, the ether and atom, +are capable of mutual reaction. + +There have been some physicists who have imagined +that the atoms of matter were condensations in the +ether, but I am not aware that any very satisfactory +reasons have been given for thinking so. That in itself +would be no reason for rejecting the idea in the +\DPPageSep{106.png}{94}% +\index{Attraction of disks}% +\index{Hypothesis, needful}% +absence of a better and more consistent one. For +scientific purposes a poor hypothesis is better than +none at all. + +A very large amount of scientific work has been +done by employing hypotheses that are now known to +be wrong. A working hypothesis is needful. If it be +wrong, one will by and by find it out and be able to +amend it, or replace it by a better. If it be right, it +will be vindicated, and will justify itself, and be generally +adopted. + +Until we know more definitely than is now known +what the constitution of matter really is, one can only +guess and try; and among the multitude of interested +workers in all civilized countries there will be some +who will guess right to the advantage of all. + +If, then, one adopts the vortex ring theory of matter, +\index{Vortex ring theory of matter}% +and endeavors to trace the mechanical conditions that +might obtain with such kind of atoms, he would be +led to inquire whether a vortex ring does or does not +exhibit any evidence of condensation in the material +that is in rotation; that is, does the material of the ring +occupy the same space while it is in rotation as it does +when not? + +There are several phenomena that seem to show that +it occupies less space. The reduction of pressure +in its neighborhood shows a rarefaction there, and the +mutual approach of such rings and of other light bodies +in their neighborhood indicates the same thing. If +one rotates a disk rapidly, any light bodies in front of +it will tend to approach it even from a distance of +several inches. If a dozen disks five or six inches in +\DPPageSep{107.png}{95}% +\index{Attraction of vortex rings}% +diameter are set loosely an inch apart upon a spindle a +foot long, so that they may be rotated fast, yet left free +to move longitudinally upon the spindle, they will all +crowd up close together as the pressure is less between +them than outside. If one can imagine the spindle to +be flexible and the ends brought opposite each other +while rotating, it will be seen that the ends would +exhibit an apparent attraction for each other, and, +if free to approach, would close up, thus making a +vortex ring with the sections of disks. If the axis +of the disks were shrinkable, the whole thing would +contract to a minimum size that would be determined +by the rapidity of the rotary movement, in +which case not only would it be plain why the ring form +was maintained, but why the diameter of the ring +as a whole should shrink. So long as it rotated it +would keep up a stress in the air about it. So far as +the experimental evidence goes, it appears that a vortex +ring in the air exhibits the phenomenon in question. +There is no doubt at all that two vortex rings in the +air attract each other, for they will mutually approach +if free to do so, and the explanation is plain that there is +reduced pressure between them; in other words, the +characteristic motion of the ring reduces the air +pressure about it, so that another body within that field +is pushed towards the place where the pressure is +least. The reduction of the pressure about any ring +must evidently depend upon the amount of material +embodied in it, and more especially the degree of +rotation which it has. A small, thin but rapidly +rotating ring might produce as great a rarefaction about +\DPPageSep{108.png}{96}% +it as a much larger one with less velocity, hence there +is something about it that corresponds to what is called +mass. It is not \emph{simply} an amount of material, but the +\emph{energy} the material has, which gives it its characteristic +properties. + +Analogy must not be mistaken for identity. There +is so great a difference between the properties of the +air and other gases and those of the ether that one +cannot affirm that what holds true of one must hold +true of the other; yet that is what is generally done by +such persons as those who try to show the properties +of the ether to be identical with those of matter. + +We know what conditions are necessary in order that +a ring should be formed in the air, and one of them is +that there must be gaseous friction. If that were not +the case a ring could not be formed. If the ether be +the frictionless medium it is generally supposed to be, +one would not know how to make a vortex ring in it. +On the other hand, the reason a ring in the air is so +soon destroyed is because of friction; and hence if one +were made in some unimagined way in the ether it +would continue to exist indefinitely, but how it could +act at all upon the ether surrounding it would be a +mechanical puzzle, and that is the present state of the +case. The puzzle is no greater with the conception of +a vortex ring than if the atom were made up in some +other way, and therefore that objection is not peculiar +to this hypothesis. It has been confessedly a puzzle +to see how the vibratory motions of atoms and molecules +could set up transverse waves in the ether if the +ether be without friction; nevertheless, they do set up +\DPPageSep{109.png}{97}% +such waves. A common objection to all attempts that +have been made to account for gravitation by means of +the motions of the atoms themselves is that it not +only requires a constant expenditure of energy, but that +the velocity of transmission must be so much greater +than that of light. Light is transverse vibratory movement. +A direct longitudinal wave may be much swifter +than the other. A pull upon a taut rope will travel +much faster in it than will a wave produced by a transverse +movement of the hand. + +It is not to be understood that what is presented here +is given as a proof that gravitation is but a simple +mechanical condition of things. It is probable that +every one who thinks about it believes that its explanation +is purely mechanical. Some perhaps are pessimistic, +and doubt that man will ever be able to understand +its mysteries, but pessimists are not discoverers. They +frequently so chill the air about them that more hopeful +ones, who are not persuaded that the end has yet +been reached, are sometimes deterred from venturing +into fields where they have to pass such self-constituted +gate-keepers. + +There are few physical problems of any generality +and complexity that are abruptly and completely solved +by one person. Tentative steps must be taken, and +much labor is oftentimes spent upon ideas that by and +by are proved to be worthless. A good deal of the +work done by Laplace upon the Nebula theory was +\index{Nebula theory}% +of that sort; yet all astronomers hold the Nebula theory +in some form: what the exact process was, if solely +mechanical, may be interesting, but not very important +from a philosophical standpoint. +\DPPageSep{110.png}{98}% + +So one may hold that gravitation is a mechanical +action, and in some way explainable on mechanical +principles, even if he does not see how at all. + +This chapter may help some to see not only what +the character of the problem is, but what factors are +present, and how somewhat similar phenomena may be +reproduced at will; but the radical distinction that +exists between the ether and matter must always be +kept in mind. +%\DPPageSep{111.png}{99}% + + +\Chapter{VI}{Heat}{99} + +\index{Heat, mechanical origin of}% + +\First{Heat} and cold are two words we apply to contrasted +sensations, either of which may imply comfort or discomfort; +and what is meant by either word in a given +case depends altogether upon what the sensation is +compared with. Thus, one would speak of a day when +the thermometer indicated one hundred degrees in the +shade as being a hot day, while if his cup of coffee had +the same temperature it would be called cold; so the +terms imply only roughly some departure from a +standard of comfort. To obtain more definite knowledge +of that physical condition which gives us the +sensation we call heat, it is necessary to attend to its +origin and its effects upon other bodies. + +\Section{I. MECHANICAL ORIGIN.} + +When a blacksmith hammers a small piece of iron, +like a nail, upon his anvil, it becomes too hot to hold, +and it even may be made to glow, red-hot, by the +repeated blows of the hammer. If a bullet be shot +against a target and be quickly picked up, it is found to +be hot; and in general the impact of any two bodies +always results in heating both of them. In the above +cases both the hammer and the target are heated, but +\DPPageSep{112.png}{100}% +on account of their size the degree of heat is not so +noticeable as it is with the smaller bodies. + +In like manner if the knuckles be rubbed briskly +upon one's sleeve, the sensation of heat becomes +unbearable in a very brief time. The friction of the +surfaces develops the heat, as may be learned by +taking a button or some similar object, and in the same +brisk manner rub it on the sleeve or other convenient +surface, and it will get too hot to be safely touched +against the skin. On a larger scale the brakes upon +railroad-cars exhibit the same quality when they have +been applied for a few seconds. The sparks that may +be seen flying from them in the dark is testimony to +the same thing; while the car-wheel boxes are often so +heated by the constant friction when the lubricating +oil is wanting, that the cotton waste takes fire, and +even locomotives may be delayed by their hot journals. +This source of heat is so common that instances may +be cited indefinitely. It is universally true that the +friction of one body moving in contact with another +heats them both, and the heat developed depends upon +the pressure and the velocity of the moving surfaces. +It is true not only for solids, but for liquids and gases +as well, and the friction of solids moving in either +liquids or gases. An extreme case of the latter kind is +illustrated by the shining trail of a meteor when it +enters the atmosphere. Its velocity is very great---twenty +or thirty miles a second---and the friction of the +air is so great on account of the high speed that it +renders the surface of the meteorite red-hot, and some +of its molecules are ground off as they would be if it +\DPPageSep{113.png}{101}% +were held against a swift turning emery-wheel that +scatters the sparks in the air. The luminous trail consists +of these heated particles. If the body is not large, +and most meteors are quite small, they may be entirely +ground to powder and dissipated before they can reach +the earth. Most meteors in this way rarely pass +through more than fifty or sixty miles of our atmosphere +before this happens. + +Another mechanical source of heat is compression. +Let a bullet be hard squeezed in a vise, or in any other +% [Illustration: ] +\begin{figure}[htb] + \begin{center} + \Graphic{4in}{113a} + \end{center} + \Caption{4}{Diag.\ 4.} +\end{figure} +way, and it is found that its heat is perceptibly increased. +Small differences of this sort may be easily detected +by the use of the thermopile and galvanometer. + +The rubbed button or pounded or squeezed bullet +placed upon the face of the thermopile shows the presence +of an amount of heat which the sense of heat +would %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}[11]{l}{.5in} +\null\hfill\Graphic{.25in}{114a}\hfill + \Caption{5}{Diag.\ 5.} +\end{wrapfigure} +never detect. Gases exhibit the heating effect +through pressure in a high degree. Before the invention +of friction matches, which are themselves good +\DPPageSep{114.png}{102}% +\index{Heat, chemical origin of}% +examples of the production of heat by friction, metallic +tubes, closed at one end with a tight-fitting plunger to +be worked by hand, were in common use for lighting +fires. A bit of punky wood was fixed to the +end of the plunger, and the latter was then +quickly driven to the bottom of the tube. The +air was compressed to so great an extent that +the heat developed became sufficient to ignite +the punk. The same heating effect of compression +may be shown by the thermopile and galvanometer +by compressing the air with an air-condenser, +and permitting the air thus condensed to +strike on its exit upon the face of the pile. + +Thus impact, or \emph{sudden} stopping of mechanical +motion, friction, or the \emph{gradual} stopping of mechanical +motion and condensation, or compelling molecules +to occupy less space, all of them of a purely +mechanical nature, result invariably in heating the +matter that is subject to the action. + +\Section{II. CHEMICAL ORIGIN.} + +The heat that results from the combustion of fuels +of all sorts is due to the chemical changes that take +place. When coal burns, its substance, carbon, is +entering into combination with the oxygen of the air, +and a new chemical product is formed called carbon +dioxide, which is a gas; and the change is accompanied +by the production of a large amount of heat, which we +utilize for our comfort or for the various arts that +depend upon heat as an agent. Wood, alcohol, the +various oils,---everything capable of burning, and which +\DPPageSep{115.png}{103}% +may be called fuels---are, in the process of burning, +\index{Fuels}% +undergoing what is called oxidation, in which new +chemical compounds are formed and which are nearly +all gaseous. Thus the products of the combustion of +\index{Combustion}% +wood, alcohol, coal-oil, etc., are always carbon dioxide +gas, and the vapor of water; and the heat developed is +proportionate to the amount of these produced. + +But combustion is not the only chemical source. If +sulphuric acid be mixed with water, the compound +becomes very hot although it is liquid. The two +substances enter into an intimate chemical combination. +A pint of each mixed together will not make a quart, +but will fall short of that volume a good deal when +they have cooled. This shows that condensation has +taken place; and, knowing that condensation produces +heat when brought about in other ways, one might have +suspected that chemical condensation would result in +a similar development of heat. + +Some substances when in a finely divided state, +though what we generally call solids, are capable of +entering into combination with each other at a very +rapid rate and then develop a great deal of heat. +Such a substance as gunpowder, a combination of carbon, +\index{Gunpowder}% +sulphur, and the nitrate of potash, when intimately +mixed, will combine with explosive violence, and great +heat results from it, as shown by the attending flash +and the scorching effects it produces upon some bodies +that do not happen to be destroyed by the explosion. +All chemical reactions whatever involve in some degree +temperature changes; and by so much one might be +led to suspect that there might not be so great a +\DPPageSep{116.png}{104}% +\index{Heat, electrical origin of}% +difference between the mechanical \DPtypo{souces}{sources} of heat at +first considered and the more obscure chemical ones as +one might think who attends only to the more prominent +features of the two. If one should adopt for +a basis of his philosophy that like causes produce like +effects, what shall he say when he sees the same effect +produced by pounding with a hammer, condensing a +gas, and burning a piece of wood? Either unlike causes +can produce similar effects, or fundamentally these +three processes are the same. We will attend to that +question more at length farther on. + + +\Section{III\@. ELECTRICAL ORIGIN.} + +As a chapter is to be given to electricity and its +phenomena, it will be sufficient here to point out that +wherever a current of electricity is flowing in a conductor, +there heat is invariably produced. The heat in +an electric arc is so great that all known substances are +either fused or volatilized in it. Gold, platinum, the +ruby, are easily reduced to the liquid form, and the +diamond slowly wastes away, being oxidized like a piece +of coal. Electric furnaces are now in use where the +most refractory substances, like clay, are reduced, and +the metal aluminum extracted from it. So long as it +cost so much to produce electricity as it did before the +dynamo was perfected, no one could afford to use it for +heating purposes. Now there will shortly be electric +heaters in houses, replacing stoves for cooking and +furnaces for warmth. The electrical current can be +brought on the wire where it is wanted, and the heat +developed from it to any degree desired. Electricity, +then, is another source of heat. +\DPPageSep{117.png}{105}% +\index{Energy in the ether}% +\index{Heat, radiational origin of}% + + +\Section{IV\@. RADIATIVE ORIGIN.} + +When one stands near a blazing fire the warmth felt +does not come from the heated air between the fire +and the person; for when one shields his face or hands +the warmth ceases to be felt, though the temperature +of the air might be the same in both cases. + +In like manner sunshine warms the earth, although +between the sun and the earth there is an enormous +space without air or other matter, through which the +sun's rays come producing warmth \emph{when they get here}. +This process of giving out rays to the ether independent +of matter, which is possessed by hot bodies, is called +radiation. It has been shown that all bodies are at all +times giving out such radiations; and oftentimes the +radiation itself is called radiant energy, sometimes it +is called light, and sometimes simply ether waves. +Here we do not attend to the origin of the waves, but +to the fact that when such waves fall upon matter they +result in heating it, and therefore radiation must be +looked upon as a fourth source of heat. + +I would again suggest the thought presented a page +or two back, as to the similarity or dissimilarity of each +of these four kinds of origins of heat,---mechanical, +chemical, electrical, radiant. They appear to be utterly +unlike each other, yet their effects upon matter are identical, +always thus and never different, so far as our experience +goes. Evidently there must be some factor +common to them all; and if this could be known for any +one of them, it would throw light upon all the rest. If +we take, for instance, the mechanical origin of heat, +\DPPageSep{118.png}{106}% +say, impact, which is one of the most obvious, and note +the factors present, it is plain there are but two; +namely, a mass of matter with a certain measurable +amount of motion of the translational variety. These +two embody the energy represented by the impact, and +of these the translational motion is destroyed when the +heat appears. The other factor, the mass of matter, +remains constant. The motion that was seen needs to +be accounted for; and as the heat that appears is the +result of that motion, it appears probable that in some +way the translational motion has been transformed into +some other kind of motion, not that it has been annihilated. + + +\Section{TEMPERATURE.} +\index{Temperature}% + +If a pint of boiling-hot water be mixed with a pint +of ice-cold water, the mixture will have all the heat +there was in the pint of hot water, but it would not +injure the hand thrust into it. The heat that was in +one pint has been distributed through two pints, and +hence each pint has one-half the heat that was in the +hot pint. A red-hot bar of iron will be cooled by being +thrust into a pail of water. The water will be heated, +and will have all the heat the bar lost; but as it is distributed +through so great a volume of water, the +amount of heat in a cubic inch of it will be but a small +proportion of the whole. + +The word ``temperature'' is used to denote the degree +of heat there may be in a unit volume of a substance, and +this is measured by means of thermometers in which +the property that heat possesses of expanding the volume +of bodies is made to indicate their degree of heat. The +\DPPageSep{119.png}{107}% +standard for this is an arbitrary one altogether. In the +common Fahrenheit thermometer there is a tube of glass +\index{Thermometer}% +with a bulb upon it filled with mercury. This, when put +into ice-water, acquires the same temperature, and the +mercury stands at a certain height in the tube, which is +marked. Then it is put into boiling-hot water, where +the mercury expands and reaches another height in the +tube, which is also marked. The space between the +two marks is divided into one hundred and eighty equal +parts, and the same scale of division is carried beyond +in both directions. A point thirty-two of these divisions +below the mark of the melting ice is called zero; +so between it and the boiling-point are two hundred +and twelve divisions, called degrees. The centigrade +thermometer is more generally used in scientific work. +In this the space between the freezing and boiling +points is divided into one hundred equal parts, called +also degrees. A centigrade degree is $\dfrac{9}{5}$~larger than a +Fahrenheit degree. The scales of either may be extended +indefinitely for the measurement of temperatures +departing from the more usual ones. For a lower +limit one cannot use the mercury below about forty +degrees below zero; for it freezes at that temperature, +and no longer follows the same law of contraction. As +alcohol does not freeze, thermometer tubes filled with +it are used to indicate such low temperature. In the +Arctic regions, and even in Siberia, the temperature +falls to fifty or sixty degrees below zero not infrequently +in winter, but temperatures have artificially been produced +as low as $400°$~below zero. +\DPPageSep{120.png}{108}% + +For the higher limits mercury thermometers can be +used for higher temperatures than alcohol, for the latter +boils and becomes vapor at~$174°$. The following table +of temperatures may be interesting:--- +\begin{center} +\TableFont% +\begin{tabular}{p{3in}@{\ }r}%[** PP: Hard-coded width] +Absolute zero \dotfill & $-460°$ \\ +Lowest degree artificially produced \dotfill & $-400°$ \\ +Lowest degree measured in Siberia \dotfill & $-72°$ \\ +Mercury freezes \dotfill & $-39°$ \\ +Water freezes \dotfill & $32°$ \\ +Blood in man \dotfill & $98.6°$ \\ +Temperature observed in India \dotfill & $140°$ \\ +Alcohol boils \dotfill & $174°$ \\ +Water boils \dotfill & $212°$ \\ +Lead melts \dotfill & $612°$ \\ +Mercury boils \dotfill & $650°$ \\ +Red heat visible in dark \dotfill & $1000°$ \\ +Silver melts \dotfill & $1873°$ \\ +Gold melts \dotfill & $2200°$ \\ +Iron melts \dotfill & $2700°$ \\ +Platinum melts \dotfill & $3600°$ \\ +\end{tabular} +\end{center} +\index{Temperature, table}% + +Gases, like liquids and solids, are increased in volume +by heat when permitted to expand. If not permitted, +the pressure upon the walls of the containing vessel is +increased; and it is found that this pressure is proportionate +to the temperature, and also that the pressure +diminishes about~$\dfrac{1}{273}$ for each centigrade degree of cooling, +starting at the freezing-point of water. If, therefore, +a gas could be cooled from that point $273°$~centigrade, +it would have no pressure, as it would have no +temperature. Such a degree has never yet been reached; +but all phenomena having any bearing upon the subject +\DPPageSep{121.png}{109}% +indicate that at~$-273°$ there is no heat: it is an +absolute zero. The molecules %[** PP: Width-dependent line break] +% [Illustration] +\begin{wrapfigure}{r}{0.5in} +\null\hfill\Graphic{0.25in}{121a} +\Caption{6}{Diag.\ 6.}% +\end{wrapfigure} +would have no translational +motion, otherwise they would produce +some pressure upon the walls of the vessel that +contained them. Air thermometers may be +\index{Thermometer, air}% +made with bulbs blown upon the end of a glass +tube. A small drop of water in the tube will +be pushed in or out as the temperature varies, +and is much more sensitive than ordinary thermometers; +but barometric pressure affects it +and renders it unfit for common use, but its indications +are proportionate to the absolute scale; +that is, the volume of the air at the melting-point +of water will be increased or diminished~$\dfrac{1}{273}$ +by every change of one degree in cooling or heating, +or~$\smash[t]{dfrac{1}{490}}$ if the degree be Fahrenheit. + + +\Section{MECHANICAL EQUIVALENT.} +\index{Heat, mechanical equivalent}% + +For a long time it was supposed that heat was a kind +of substance that ordinary matter could absorb and +emit. It was sometimes called caloric; and that word is +in common use to-day, but not in the sense it originally +had. Sometimes it was spoken of as one of the imponderables---a +substance without weight. Now there is +only one imponderable recognized, that is the ether. Sir +Humphry Davy and Count Rumford found they could +produce an indefinite amount of heat by the friction of +one body upon another; and that implied if heat was a +substance of any sort, that any piece of matter contained +an infinite amount of heat, else one could get +\DPPageSep{122.png}{110}% +out of a body what was not in it. These two men concluded +that heat was a kind of molecular motion, and +that what their experiments showed was that friction +only transformed the mechanical motion into molecular +motion, which was called heat. + +The old conceptions had got so thoroughly incorporated +into both the thoughts and the writings of others, +that they could not easily be dislodged, and men went +on as they had done. It was easier to do that than to +change notions and terms that were familiar for others +that were strange, even if true. A whole generation of +men had to be buried before any attention was paid to +what had been proved in the early part of the century. +Soon after 1840 it occurred to a number of persons in +different countries that if heat were but transformed +mechanical motion there should be some quantitative +relationship between them that might be discovered; +that is, a given amount of mechanical motion ought to +produce a definite amount of heat, and \textit{vice versa}. +This was worked out in the most complete and satisfactory +way by Joule of England. His method consisted +\index{Joule}% +in churning a definite amount of water and observing +the rise in temperature in it. The churn paddle was +driven by a known weight falling a known distance, and +therefore the work done in driving the paddles was +known in foot-pounds. In this way he found that $772$~pounds +falling one foot would heat a pound of water +one degree, and he called this number the mechanical +equivalent of heat. In like manner it is said that when +a pound of water loses one degree in temperature, it has +lost energy enough to raise $772$~pounds one foot high. +\DPPageSep{123.png}{111}% +This relationship renders it easy to determine the +amount of work a given amount of heat can do, and +also the temperature that will be acquired by a given +amount of water when a definite amount of work is +done upon it. But the scientific importance of this +new step is much greater than its practical utility. +Before that time men had thought there were such +things as \emph{forces}, independent of each other; and such an +idea as mutual convertibility had not dawned upon any +philosophic mind. Physical philosophers were so much +misled by their terminology and the accompanying +notions, that Joule's work, though demonstrative, made +no impression upon them for several years, and it was +refused a place in the transactions of their society for +seven years. The reason for this common hostility to +new knowledge is probably not far to seek. When one +has achieved distinction in his line of work, especially +in physical science, he is likely to possess his own philosophy +of things, in which not a small part of the data +is symbolic and is represented in mind only by a name; +and if this chances to suggest something mysterious, as, +for instance, an imponderable, the less is one likely to +attempt, or suffer others to attempt, to displace it by +definite mechanical conceptions. To change one's +fundamental conceptions necessitates a change in his +philosophy throughout,---a change that is not only difficult, +but highly \DPtypo{distaseful}{distasteful}; and one ought not to expect +a welcome to a man whose work necessitates such a +change. + +Within the present century the advance in all directions +has been such as to give definite mechanical +\DPPageSep{124.png}{112}% +\index{Thermodynamics}% +conceptions and relations where before only ghosts and +genii were supposed to do duty; and what can a man do +when his genii have been slain and he must now depend +upon~$mv^2$? To become acquainted with his new associate +is generally the last thing he sets himself about. +It was with Joule as it was with all the prophets and +discoverers. Joule, however, was young, and he lived +to attend the funeral of all his detractors. + +That heat and work are mutually convertible is now +called the first law of thermo-dynamics; and it has led +directly to a knowledge of the working-power there is +in fuels, and made the duty of steam-engines and other +sources of power beautifully simple. + +The amount of heat needed to raise the temperature +of a pound of water one degree Fahrenheit is called a +\emph{heat unit}. The amount of heat needed to raise the +\index{Heat unit}% +temperature of a kilogram of water one centigrade +degree is sometimes called a calorie, and this is a +unit in common use. It is found by careful experiment +that a pound of coal when burnt gives up $14500$ +\emph{heat units}, or would raise the temperature of $100$~pounds +of water~$145°$, or to any other equivalent. A +pound of hydrogen, in like manner, burning with oxygen, +will give $61000$ units, a pound of wood about +$7000$, and so on. Each different substance has its own +equivalent of such heat units. As each unit will do +$772$ foot-pounds of work, a pound of coal, when burnt, +will give $14500 × 772 = 11,194000$ foot-pounds of +work, and so on for any other. This equivalency is +independent of time or place. Whether the coal burns +fast or slow makes no difference. When wood is +\DPPageSep{125.png}{113}% +burned in the fire it develops its work-power fast; but +when it slowly rots it is undergoing the same process, +oxidation, and the same amount of heat is developed, +though at no time does the temperature appear to be +above that of surrounding things. The food we eat possesses +its mechanical equivalent, which is the maximum +amount of work it would enable one to do. If bread +and butter were used for the fuel of an engine, it would +develop about $21000$ heat units (or calories) per pound, +and this is equal to $772 × 21000 = 16,212000$ foot-pounds, +and it has the same value when used for food; +and thus one may know approximately the amount of +energy he is supplied with from day to day; also, he +may compare the amount of work he does, in lifting, +walking, or otherwise, in a day with the food equivalent +absorbed. Some of this is, of course, used to +maintain the temperature of the body, the circulation +of the blood, and so on---conditions that are tolerably +constant. + + +\Section{THE STEAM-ENGINE.} +\index{Steam-engine}% + +The steam-engine is a machine for utilizing the +heating-power of fuels, and, when complete, consists of +furnace, boiler, and engine. The furnace transforms +the energy of the fuel and air into heat units in the +boiler, and the engine transforms this into the work of +whatever sort it may be applied to. + +Evidently the efficiency of such an engine must depend +upon how large a proportion of the heat units it +utilizes compared with the heat units supplied to it. +Steam-engines permit the steam to escape into the air +\DPPageSep{126.png}{114}% +\index{Steam-engine, efficiency of}% +generally with a temperature higher than boiling water, +and that means a great waste of unused heat; for the +steam in the engine loses temperature proportionate to +the work done by it, and, as stated before, the steam +pressure is proportionate to its absolute temperature, +not its temperature as indicated by common thermometers. +And the absolute temperature on Fahrenheit scale +will \DPtypo{he}{be} found by adding~$460$ to the indicated temperature. +Suppose, then, an engine-boiler delivered steam +to the engine at $248° \text{ Fah.} = 708 \text{ absolute}$, and on exit +from the cylinder it was $212° \text{ Fah.} = 672 \text{ absolute}$, then +the proportionate amount of work done compared with +the whole supplied would be $\dfrac{708 - 672}{708} = \dfrac{36}{708}$, or only +about five per cent of the heating-power of the fuel. +Higher efficiency must be looked for chiefly by using +steam at higher temperature and, therefore, higher pressure, +which would increase the value of the numerator. + +The efficiency of engines is generally given in the +amount of coal required to maintain one horse-power +per hour. A horse-power for an hour is equal to +$33000 × 60 = 1,980000$ foot-pounds; and the coal required +varies from about two pounds in the best engines +to six or eight pounds, locomotive engines generally +being less efficient. As one pound of coal when burnt +has an equivalent of $11,194000$ foot-pounds of work, +two pounds will give $22,398000$ foot-pounds. When +that maintains a horse-power for an hour, or $1,980000$ +foot-pounds, the efficiency is $\dfrac{1,980000}{22,398000} = 8 \text{ per cent}$. +This appears very low; but it is to be remembered that +\DPPageSep{127.png}{115}% +\index{Heat, nature of}% +the coal is seldom anywhere near pure; that much heat +escapes by the flues without heating the water; that +much is lost by heating the engine, boiler, and the +pipes, etc., that does no good, and most of that that does +go through the engine escapes to the air without having +done any work; and it cannot be helped, for steam condenses +to water at~\DPtypo{$212$,°}{$212°$,} and is no longer able to do +steam service. In reality, such an efficiency is relatively +high. + + +\Section{AS TO THE NATURE OF HEAT.} + +It has been pointed out that it was concluded early +in the century that heat must be some kind of motion, +because its production depended solely upon antecedent +motion, and that later the quantitative relationship +between the two was accurately defined. The +\emph{nature} of heat was ascertained, but the particular kind +of motion that gave it its characteristics was not made +out; that is, whether the motion was one of free path +of the molecules,---a swinging to and fro in space,---or +a true vibratory motion, such as a change of form of +the molecules and atoms that made up the heated body, +or a rotation of them, or a combination of any or all of +these, was unknown. At first the conjecture prevailed +that it was an oscillatory motion of the molecules +among themselves even in a solid body; but after the +discovery of spectrum analysis it became apparent that +the atoms and molecules were in a state of true vibration, +and their temperature depended upon the amplitude +of that vibration. If one will remember that the +atoms of matter are certainly elastic, and are not solid, +\DPPageSep{128.png}{116}% +\index{Hydrogen vibrations}% +\index{Vibrations, gaseous}% +and will also picture to himself what mechanically +must happen when such a body is struck in any manner, +that it \emph{must} vibrate, for the same reason that any +visible elastic body must vibrate if struck, he will see +quite clearly the condition of things among elastic +atoms that collide with each other so many times per +second. + +That they do thus vibrate is proved by the spectrum +of substances in the gaseous state where between impacts +they have time to vibrate a great number of +times per second. At ordinary temperatures and density +a gaseous molecule of hydrogen, having a mean free +path of about the two-hundred-and-fifty-thousandth of +an inch, and moving at the rate of $6000$~feet per +second, will collide with its neighbors $17750$ millions +of times per second, but its spectrum shows that it +makes $450$~millions of millions of vibrations in the same +interval, so that in each interval between impacts it +would be able to make $\dfrac{450,000000,000000}{17750,000000} = 25352$, +more than twenty-five thousand vibrations. + +Now, imagine a number of bells suspended by cords +of equal length from the ceiling, but not so near as to +touch each other. Suppose each bell to have the same +musical pitch as every other one, and now let one of +the outer ones be pulled away from the rest and forcibly +swung back among them; presently every bell +among them would be set swinging by the impact of +others upon it, and each impact would cause each bell +to sound its own particular pitch, and the elasticity of +each individual one would maintain that vibration in +\DPPageSep{129.png}{117}% +some degree until the next impact, when it would be +strengthened, and one would hear along with the +bumping of the bells the sound due to the pitch of +the individual bells. Something very like this goes on +among the molecules of the gas. Their vibratory +movements we cannot hear, but with the spectroscope +they are detected and measured. Now, hot bodies cool +by radiation---the giving-off of just such waves in the +ether as we are describing,---and the fact that such cooling +molecules of a gas give out constant wave-lengths, +as is shown by their spectrum lines, is proof that the +vibrations that originate the waves +are not %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}{r}{1.25in} +\Graphic{1.25in}{129a} +\Caption{7}{Diag.\ 7.} +\end{wrapfigure} +free-path or oscillatory motions, +but true atomic ones, due to a +\emph{change in form}. How this can be is +easily seen by considering the change +in form made by any vibrating body, +say, a ring. Let the heavy lined ring +represent an elastic atom: if it be subjected to impact it +will assume an elliptical outline, and go through a series +of phases represented by the dotted lines. This change +of form, and uniform vibration, is a mechanical necessity, +and is independent of the size or particular form a +body may have. It is this kind of motion that embodies +the energy represented by the temperature of +an atom or a molecule, and the temperature varies with +the square of the amplitude of this motion; and two +bodies have the same temperature when their molecules +have the same vibratory energy. A single molecule in +free space would radiate all its heat away, and thus be +reduced to absolute zero, if it were not continually +\DPPageSep{130.png}{118}% +\index{Heat, nature of}% +receiving from other bodies an amount that depended +upon its nearness to them and their own amplitude of +similar motion. Hence the temperature of a body +depends upon the amplitude of vibration of its molecules, +and not upon any translatory or oscillatory or +rotatory motions. This is not saying that molecules +that are heated do not have other motions than the +vibratory ones constituting their temperature, but +when they do have others it is at the expense of the +vibratory, and therefore has reduced the temperature; +and such free-path motion as all gases have, and which +produces pressure upon the walls of vessels, is maintained +by the vibratory. It is not heat, but the result +of heat, in the same way as the translatory motion of +a bullet is not heat, but the result of heat. Most books +on heat do not make the distinction here made, but +combine the heat-motion of the molecules themselves +with the translatory motion they have, calling the sum +of them the heat of the gas. So long as one is concerned +only with the energy involved in the actions it +will make no difference; but if one analyzes the process +for the factors it is plain that there are two distinct +kinds of motion---one of them capable of setting +up waves in the ether, the other not, for it is not known +that any free-path or translatory movement of a body +ever disturbs the ether; and if distinctions of such +marked characters as these exist, and one of them involves +temperature and ether waves, and the other +does not, they ought not both to be called by the same +name. The peculiar character of the energy involved +in heat as distinguished from so-called mechanical +\DPPageSep{131.png}{119}% +\index{Heat of the sun, origin of}% +energy, is that the factor of motion is of the vibratory +sort, whereas the other is more or less translatory,---one +capable of easy transformation into ether waves, +the other incapable of such transformation, but each +of them easily transformed into the other by impact. +Equivalent velocities give the same amount of working +ability, or $\dfrac{W v^2}{2g} = \dfrac{W a^2 n^2}{2g} = P d$ (see \Pageref{p.}{69}). So it +can be understood how ordinary visible motion can be +transformed into heat, and \textit{vice versa}, as easily as one +can understand how the motion of the clapper of a bell +is transformed into sound. + + +\Section{ORIGIN OF THE SUN'S HEAT.} + +There has been much speculation as to the source of +the heat of the sun. Unless one assumes that it has +some miraculous or non-physical origin he is bound to +account for it, if at all, upon the assumption that physical +conditions and relations, such as we find at the +earth, hold good at the sun as elsewhere. + +At the beginning of this chapter the various sources +of heat were considered,---the mechanical, the chemical, +the electric, and the radiative. If these be tested as +to their sufficiency to account for the temperature of the +sun, one may reach a conclusion as to the probability +of any or all of them being concerned in it and their +relative importance. + +It will be convenient to consider them in the reverse +order, and first as to radiations. In order that a body +should become heated by radiations, there must first be +some body or bodies having as high or higher temperature +\DPPageSep{132.png}{120}% +to give rise to the radiations; and in this case, if +the sun's heat came from such a source, one would need +to look for the other bodies in the universe having such +high temperature. The millions of stars shining by +their own light would at first seem to furnish the proper +source; for the testimony of the spectroscope is that +they all are highly heated, and some astronomers think +some of them to be much hotter than the sun is. One +of the conditions under which radiant energy is distributed +in space is that its amount upon a given surface is +inversely as the square of the distance from the source; +and as every one of these bodies is at such an amazing +distance away, it is only with the most delicate instruments +that their radiant energy can be measured, and a +given surface upon the earth would receive as much as +the same surface upon the sun, and the earth would be +heated from the same source as much as the sun would +be. Practically it is found to be but a very small quantity, +and hence radiation from other bodies cannot +possibly account for the sun's heat. + +Second, as to electrical currents: it may be said at the +outset we have no direct knowledge that there are such +at the sun, and from other knowledge we have of its +constitution it would appear to be highly improbable +that there were or could be electric currents there. +Electric currents imply some generator and some conductor +for their transference; and from what is known +or may fairly be inferred that every substance we are +acquainted with as a conductor of electricity which is +present in the sun---and there are a good many of +them---iron being particularly abundant, yet they are +\DPPageSep{133.png}{121}% +all at such a high temperature as to be a far reach from +the conductibility we know anything about. There +may be, but it is by no means certain, something solid +in the sun, but the most of it is as gaseous as a bubble, +and gases do not conduct currents of electricity. + +Third, chemical action is known to be the antecedent +of vast quantities of heat. It may be recalled that a +pound of hydrogen, for instance, when allowed to combine +chemically with oxygen will give out $61000$ heat +units. The atmosphere of the sun appears to be made +up of elements mostly in an uncombined form, except +in the cooler, outlying parts; that is, the temperature is +so high that chemical combination is impossible except +in exposed places where radiation can allow cooling to +take place. It is tolerably certain that chemical combinations +are taking place there whenever it is possible, +and with such combination heat must be produced, if +physical laws are in operation there as they are at the +earth, but the amount of it going on, or possible, if the +whole body of the sun were to combine its elements in +this way, does not appear to begin to be equal to the +expenditure of heat actually taking place. + +There remains only the mechanical sources of impact, +friction, and condensation. There is good evidence +that there is a large body of meteors in the neighborhood +of the sun that must be falling upon its surface. +The sun's attraction can give a velocity of nearly four +hundred miles a second to any body reaching him from +distant space, and such a velocity would, on impact, +produce heat enough to reduce the whole body to a +gaseous state almost instantly. +\DPPageSep{134.png}{122}% +\index{Sun, its magnitude}% +\index{Sun, its heat}% +\index{Sun, its age}% + +Given the mass and velocity of a body, and one may +calculate how much energy it has, and how much heat +is the equivalent of the mechanical energy. Such a +computation shows that even if the earth were to fall +into the sun, it would be volatilized in a very brief time. +If the sun's surface were solid the impact would be +sufficient to effect it almost instantly. If the shell of the +sun were liquid it would be changed more slowly through +friction, but, in the end, the result would be the same. +It does not appear, however, that there is sufficient +material that finds its way to the sun to furnish but a +small proportion of the sun's heat, so neither impact +nor friction can be admitted as sufficient agencies. +There remains but one more, namely, compression. Is +there any evidence that condensation is taking place? +The body of the sun is $866000$ miles in diameter, and +is so far away that this immense magnitude occupies +but about half a degree of arc. If it were to shrink at +the rate of a mile in twenty years, it would account for +the present rate of expenditure, but such a shrinkage +could not be observed from the earth for several thousand +years, for nothing much less than a second of arc +can be observed with certainty, and a second of arc at +the sun's distance is equal to about $465$~miles, so it would +require $465 × 20 = 9300$ years to produce an observable +effect. + +Now, if the nebula theory be true, the sun once occupied +all the space between itself and the outer boundary +of the solar system and has shrunk to its present dimensions, +a process which, if heat alone were concerned, +would require about eighteen millions of years. It is +\DPPageSep{135.png}{123}% +\index{Heat, effects}% +not probable that heat alone has been concerned, so +it is probable that the sun is older than that, but the +shrinkage will account for the heat, and it appears as +the only probable conjecture. It will be understood +that the gravitative action is the occasion of the compression, +and that the approach is constant and as fast +as the generated heat can be radiated away. It has +been calculated that at the above rate of condensation +it may be reduced to one-half its present diameter with +its present radiation rate, in about five million years, +when its density will be about twice that of water. + +From such considerations it appears in a high degree +probable that the heat of the sun is due to condensation, +the condensation is due to gravitation, and thus +one is led back to a time when the substance of the +sun and all the planets was scattered through that +immense space, the diameter of which is not less than +six thousand millions of miles. How matter came to +be thus scattered is at present an enigma. It is important +to remark here, though, that until there was impact +among atoms, and molecules were formed, there evidently +could be no such condition as what we call heat, and +until these atoms and molecules vibrated there could +be no light, that is, ether waves. + + +\Section{EFFECTS OF HEAT.} + +Once in possession of a good, mechanical conception +of the action going on in a heated body, one can proceed +to trace out the various effects of heat in all +directions. Thus to take the familiar one of pressure +in a gas. A gas is simply a large number of individual +\DPPageSep{136.png}{124}% +\index{Molecules, number of, in universe}% +molecules moving about with great velocity and bumping +against each other and the sides of the containing +vessel. Each molecule, though small, has some momentum; +but the enormous number of them in, say, a cubic +inch, five hundred millions of millions of millions, and +their relatively high translatory velocities,---say fifteen +hundred feet per second, gives them momentum which, +when spent upon the side of the vessel, gives a pressure +equal to about fifteen pounds per square inch. If one +were to hold up a shield against which many balls were +thrown per second, he would need to brace himself to +withstand the pressure that would appear to be constant. + +If the gas be heated the molecules have increased +amplitude of vibration, and they rebound from each +other with greater velocity, and strike the side with +more momentum, and hence the pressure is greater. +As the pressure is proportional to the absolute temperature, +it is plain there could be no pressure if there +was no vibratory motion. If the density of the gas +be increased by adding more molecules per cubic inch, +there must a greater number of them strike upon the +sides of the vessel in a second, which will increase the +pressure, that is, the pressure varies as the density. + +When it is said that gases have a tendency to expand, +or that they exhibit a repulsive action, all that is signified +is this; as elastic bodies, the molecules rebound +after impact, and continue on in their direction, according +to the first law of motion, until otherwise obstructed. +When a ball rebounds from the side of the house it +has been thrown against, it is not because there is any +repulsion between the ball and the house. +\DPPageSep{137.png}{125}% +\index{Boiling-point pressure}% + + +\Section{EFFECT OF PRESSURE UPON BOILING AND FUSION.} + +When it is said that the boiling-point of water is~$212°$, +it is to be understood that the pressure of the air +upon the surface of the water is fifteen pounds per +square inch. At elevated places water boils at a much +lower temperature; and when in a tight vessel, like the +boilers of steam-engines, the pressure of the steam +affects its boiling-point in the opposite way, raising it. +Thus at twenty pounds steam pressure, the temperature +required to boil water is~$228°$, at sixty pounds it is~$291°$, +at ninety pounds~$319°$, and at the high pressures +employed in locomotives of one hundred and fifty pounds +or more to the square inch, the temperature of the +steam and water is $360°$~or more. As one goes down +into a mine the pressure of the air becomes greater, +and higher temperature is needed to boil water. The +explanation of this phenomenon is that the heated molecules +of the liquid are bumping against each other in +all directions, but the surface molecules can receive +such bumps only from below and on their sides. If +there were no molecules above to beat downwards, the +surface molecules would fly rapidly up into the free +space, which would be what we call a vacuum. This +escape of the surface molecules of a liquid into the +space above is called evaporation, and the higher the +temperature of the liquid the harder the bumps, and +the more will be flipped away from the liquid and +become free rovers, having a long, free path. When, +however, the gaseous particles are numerous and strike +back upon the surface, that is, when there is a gaseous +\DPPageSep{138.png}{126}% +\index{Earth, solidity of}% +pressure upon the surface, the surface molecules are +prevented from rising, that is to say, evaporation cannot +go on so fast, boiling is prevented until more energy is +given to the water, and that means a higher temperature. + +The melting-point of substances is likewise affected +by the pressure to which they are subject, and increasing +the pressure increases the temperature needed to +fuse them. Such small variations of pressure as only +a few pounds per square inch do not make much difference, +but pressure measured by tons per square inch +makes a great deal. The condition of the interior of +the earth appears to depend upon this as a most important +factor. As one goes beneath the surface of the +earth in mines and tunnels, it is observed that the temperature +rises about one degree for every fifty or sixty feet +of descent; and it was formerly inferred from this that at +the depth of a few miles a temperature would be reached +high enough to melt the most refractory bodies, and hence +the interior of the earth was probably in a fused state +while the crust was relatively thin. Such a view took +no account of the effect of pressure upon the state of +bodies. At the depth of a mile of water the pressure +must be equal to $62.5×5280=330000$ pounds per +square foot, and as rock is $2\frac{1}{2}$~times\DPnote{** PP: Slant fraction in original} the weight of +water, the pressure must be $825000$ pounds, or over +four hundred tons; and at five, ten, or a hundred miles, +it is obvious the pressure is correspondingly greater. +A body that at the surface of the earth would melt at any +assignable temperature would require a much higher +temperature to fuse when subjected to such enormous +\DPPageSep{139.png}{127}% +\index{Temperature, maximum}% +pressure. It appears that the pressure increases faster +than the observed temperature; and hence the earth +must be solid to the centre, instead of being liquid as +formerly supposed. This makes it appear that the +phenomena of volcanoes are only local, and do not indicate +\index{Volcanoes}% +any general melted condition of the earth. If a +body that would melt at a thousand degrees on the surface +of the earth be subject to such pressure that it is +not melted when its temperature is two thousand +degrees, then, if the pressure be suddenly removed +from it, the heat it has will instantly liquefy it. This +may be the condition at the base of volcanoes, where +shrinkage of the earth's crust in some direction may +relieve the pressure in some other direction; and a +large mass of heated material may become liquid, expanding +in volume, and overflow in any direction where +there is a vent, and this would be called a volcanic +eruption. + +\Section{MAXIMUM TEMPERATURE.} + +We have considered the condition called absolute +zero, wherein the molecules have no vibratory motion +whatever; and it has also been pointed out, and it is +generally agreed, that the temperature of a body varies +as the square of its amplitude of molecular vibration. + +It has often been assumed in treating of high temperatures, +such as that of the sun for instance, that +there is no limit to the temperature to which matter +can be raised. So some have estimated the temperature +of the sun to be several millions of degrees; but +a consideration of the factors involved will show such a +\DPPageSep{140.png}{128}% +conclusion to be impossible, for the dimensions and +form of a body set a limit to the amplitude it can have. +A tuning-fork cannot have its prongs vibrate beyond +the limit where its prongs touch each other, and a +vibrating ring cannot have an amplitude greater than +one-fourth its circumference; and this degree is only +possible to a mathematical circle having no thickness. +Make a ring of a piece of twine, and elongate any +diameter until the opposite sides touch, then move the +middle points through a similar distance, and it will be +seen that the limit will be equal to a quadrant of the +circle; but if the ring be a thick one, say made of rope, +it would be less than that, and how much less will +depend upon the relative thickness of the rope to the +diameter of the ring. If the thickness of the rope +were one-fourth the diameter of the ring, then the +amplitude could be but one-half the quadrant, and so +on. Now, the atoms of matter have a definite size, and +no one has ventured to suggest that they were variable +in size in any degree; and one may, therefore, compute +the greatest amplitude such a body could have, whether +it were a circle or a hollow sphere without thickness. +If the diameter be as before stated, one fifty-millionth +of an inch, calculation shows that the greatest amplitude +it could have would be about one sixty-four-millionth +of an inch. This, multiplied by the number of +vibrations it makes per second, will give the equivalent +velocity from which its energy can be calculated. On +\Pageref{page}{67}, it is shown that the velocity of a vibrating +atom, if the amplitude be one-half of the diameter, +will be about eighty miles a second. If the amplitude +\DPPageSep{141.png}{129}% +be equal in measure to the quadrant, as is here supposed, +this velocity would be not far from a hundred +miles per second, and the energy represented by that +velocity would be the utmost energy of heat, or highest +temperature that the body could have. The pressure +of gases enables one to determine the velocity of +the particles; and when this is known at a given temperature, +the temperature at any other velocity may be +computed. + +The statement that atoms and molecules can have a +maximum temperature must not be understood to imply +that the energy they can have is fixed at that limit, +because aside from their temperature energy, represented +by their vibratory motion, they can have any +assignable translatory velocity in addition. But it does +imply that ether waves, arising from temperature, +have a fixed limit for each element; and such radiant +energy from a given source cannot be transmitted beyond +a certain rate, because its amplitude has a limit, +so that whatever actual energy the sun as a whole may +have, it cannot lose that energy by radiation faster than +an assignable rate. + +This has an important bearing upon the question of +the age of the sun. Computations have been made of +the length of time the sun can have been giving out +its energy, on the assumption that the sun is a cooling +body, and that it was formerly much hotter than it is +now. If the above statements are correct, the probability +is that the sun is as hot now as it ever was, and +that its rate of loss of heat by radiation has not been +greatly different from what it is to-day; so, instead of +\DPPageSep{142.png}{130}% +being only fifteen or twenty millions of years old, it +may be very much more. + +As the temperature of a body represents its molecular +energy, and is measured by $\dfrac{mv^2}{2}$, it follows that if two +different kinds of molecules, such as hydrogen and +oxygen, have the same temperature, they will have the +same amount of energy; but the mass of an oxygen +molecule is sixteen times greater than the mass of a +hydrogen molecule. In an equal weight of the two +there will be sixteen times more molecules of hydrogen +than of oxygen, and therefore the hydrogen will have +sixteen times the energy of the oxygen at the same +temperature. To produce a rise of temperature of one +degree in a pound, or any given weight of hydrogen, +would require sixteen times as much heat as the same +weight of oxygen would need. This difference in +thermal capacity of different substances is called their +specific heat. In general, the lighter the molecules +\index{Specific heat}% +that make up a substance, the more numerous must +they be to make up a given mass, and the higher will +be its specific heat; i.e., the more heat must be expended +upon it to produce a given rise in its temperature. +The specific heat of water is chosen as a standard +and is unity, as it is found to require more heat to +raise a given weight of it one degree than any other +substance. One heat unit will raise the temperature +of a pound of it one degree; all other substances +require but a fraction of this. From what is said, it +appears that the specific heat of an element varies +inversely as its atomic weight. The specific heat of +\DPPageSep{143.png}{131}% +\index{Dissociations}% +a substance determines the temperature it will attain +when a definite quantity of heat is supplied to it. If +a pound of hydrogen and eight pounds of oxygen are +exploded together, and not allowed to expand in volume, +$51444$ heat units calories are produced. The $51444$ +heat units would be divided among nine pounds of +water vapor, that has a specific heat under such conditions +of~$.37$. The temperature attained would be +$\dfrac{51444}{9×.37}=15450°$. This temperature is much higher +than the limit of possible combination of the two +gases, which, at about~$3000°$, are unable to combine, so +such an action could not take place any faster than the +parts could cool down to the latter temperature. If +the mixture be allowed to expand, the temperature of~$3000°$ +may not be reached, and the action of the whole +is so rapid it is called an explosion. + +\Section{DISSOCIATION.} + +When compound molecules are broken up into their +elementary constituents in any manner, the process is +called dissociation. It may be effected by electrical +action, as when water is decomposed by it, or by chemical +action, as when wood is decomposed under water, +setting the carbon free; but heat is competent to effect +the same end. At the temperature of about~$3000°$ the +existence of water is impossible, as the elements cannot +stay united, and the reason is obvious. Whatever the +nature of the attraction that holds atoms together in +chemical compounds, if the elementary atoms are themselves +in brisk vibratory motion, as we know they are, +\DPPageSep{144.png}{132}% +\index{Matter, effect of temperature upon}% +they must be straining their bonds continually to separate; +and when the amplitude of such motion reaches a +certain maximum, the impacts are so violent as to make +the atoms rebound out of each other's neighborhood, +and thus prevent cohesion. The atoms then either +enter into new combinations with others, if possible, +and if not they remain as gaseous particles, and subject +to the laws of gases. + +If one starts with a piece of ice and applies heat it +melts, and we call the liquid water. Apply more heat +and the water becomes steam, in which the individual +molecules are no longer able to cohere, because of their +energetic motions; but each molecule remains intact, +having a long free path, for a cubic inch of water +becomes nearly a cubic foot of steam under ordinary +air pressure. If still more heat be applied, the molecules +become more and more unstable until they too +are broken up in the same way and for the same reason +that the solid and the liquid forms were. When it is +no longer possible for hydrogen and oxygen to combine, +it is still possible for the atoms of each to combine +with each other, hydrogen with hydrogen and oxygen +with oxygen, forming elementary molecules \textit{H H}, and +\textit{O O}; but if a still higher temperature be applied, even +this combination becomes impossible, and the atoms +themselves become free rovers and individually independent. +Thus it is seen that the different states +of matter depend altogether upon temperature. At +absolute zero there can be no such thing as a gas, for +the molecules would have no individual vibrations and +therefore no free paths. They would probably fall to +\DPPageSep{145.png}{133}% +the bottom of the vessel and remain quiescent. It is +also probable that both liquids and solids too would +cease to exist, not that matter would be annihilated, but +a solid, a liquid, and a gas are simply each a bundle of +physical properties that depend mostly upon temperature, +and those properties would probably disappear +with the disappearance of the conditions upon which +they depended. +%\DPPageSep{146.png}{134}% + + +\Chapter{VII}{Ether Waves}{134} + +\index{Ether waves}% +\index{Ether wave qualities}% +\index{Light, its nature}% + +It has already been stated in what has preceded this +that translational motions of matter are not competent +to originate ether waves, and that vibratory motions +of both atoms and molecules can originate them. A +consideration of the origin, transmission, and effects of +such ether waves constitutes the subject-matter of what +is called the science of light. The word ``light'' is +commonly used to signify that agency in nature which +is capable of affecting the eye and causes vision, or the +sensation of sight, and until within a very few years +has been supposed to be a peculiar kind of a wave +motion in the ether quite distinct from other waves +known to exist which were competent to produce heating +and chemical effects, so such waves as were known +from their effects were called heat waves, light waves, +and actinic or chemical waves, according as they heated +bodies, produced light, or brought about chemical reactions. +These three sorts of waves were supposed to +coexist generally, but were capable of being separated +from each other so there could be a beam of either +without the others. This is now known to be a mistaken +view, for what a given ether wave will do depends +upon what it falls on rather than on its own peculiarity. +The same waves that fall upon the eye and produce the +sensation of sight will heat other kinds of matter, and +\DPPageSep{147.png}{135}% +\index{Ether waves, their source}% +\index{Light, a sensation}% +if they fall upon a surface of molecules that are unstable, +that is, in which the atoms that make up the molecules +are not strongly cohesive, the molecules are +disrupted by the waves, and the atoms enter into new +combinations, and this process is called a chemical process; +and while it is true that some waves will not produce +vision, there are none that will not produce both +heating and chemical effects, so there is no such distinction +among ether waves as was supposed, and this +leads to another conclusion also; viz., if there is no +such distinction between waves, then there is no such +thing as light at all, unless we classify all rays as light, +whether they can produce sight or not, which is sometimes +done to save explanations, but it leads to the +anomaly that there is such a thing as dark light, which +is absurd. There will be no difficulty whatever if light +be defined as a sensation merely, and the waves competent +to produce the sensation be called visual waves. +Up to the present time, however, the old terminology +is quite generally adhered to in spite of the difficulty of +reconciling the old signification with the new knowledge. +There is no single word that signifies ether +waves in general, and independent of the effects that +may be produced in specific cases, and for that reason +this term has been adopted. The word ``light'' is +entirely inadequate, and likely to mislead one not well +versed in the phenomena. + +\Section{ORIGIN OF ETHER WAVES.} + +The source of ether waves of all degrees whatever +is the vibratory motions of atoms and molecules as distinguished +\DPPageSep{148.png}{136}% +\index{Elements}% +from their translatory, or free-path motions, +but their rates of vibration are determined by their +atomic weights. An atom of hydrogen, for instance, +has a different rate from oxygen, for the same reason +that two tuning-forks, though made precisely alike, +would have different rates if one were made of steel +and the other of aluminium. If they have different +rates, then the number of waves produced by them per +second will be different, and as all waves travel in the +ether with the same speed, namely, $186000$ miles per +second, the length of the waves produced by them +must be different. + +There are about seventy different elementary atoms, +each setting up its characteristic waves in the ether all +the time. It is to be remembered that all atoms and +molecules are always to be considered as hot bodies; +that is, bodies having some temperature, and mostly +a long way above absolute zero; and also that their +energy of this kind may be spent upon the ether. If +the waves from one molecule have more energy than +those given off by a second molecule upon which they +fall, the second one absorbs some of it so as to have its +own temperature raised until it is the same as the other; +that is, until the energy given off by them both is +equal. And this is universally true. Matter is continually +exchanging energy in this way, always tending to +bring about equality of temperature. But the number +of vibrations a body makes does not need to be the +same as that of another body in order to possess the +same amount of energy, for the energy depends upon +both mass and velocity. If the mass be small, the +\DPPageSep{149.png}{137}% +velocity must be greater, and \emph{vice versa}. And thus it +is that the seventy elements that make up the kinds of +matter we know are everywhere and at all times setting +up ether waves, each kind its particular rates, when not +otherwise interfered with. + +There is, however, a qualification that must be added +that has a high degree of scientific importance. Every +elementary substance is vibrating at several rates at the +same time, as do piano-strings, bells, and musical instruments +in general. Every particular rate of vibration +produces its own waves, and thus each atom and +molecule is continually producing, when not interfered +with, its own characteristic set of waves. This must +make the ether waves from the different kinds of matter +exceedingly complex, and disentangling them correspondingly +difficult; yet it has been done. + +When we look at luminous bodies, like the sun or +stars, or flames, or gas, they seem to differ from each +\index{Flames}% +other in brightness and sometimes in color, as is seen +in fireworks. A flame of alcohol has a bluish tint, a +little salt in it makes it yellow, some lithium makes it +red, and copper, green or bluish, while sunlight is white, +as is the electric light. If one looks through a common +prism at the landscape the edges of objects appear in +rainbow tints, and with the colors arranged in the same +order, while at the same time the shape of things is +more or less distorted. If a beam of sunlight be sent +directly through such a prism, a patch of colors may be +seen on the floor or wall, and this is called a solar +spectrum; and if this light of different tints has its +wave length measured, it appears that the red light has +\DPPageSep{150.png}{138}% +a wave length of about the one forty-thousandth of an +inch, and the violet light at the other extreme a wave +length of about the one sixty-thousandth of an inch, +while the intermediate tints range regularly from the +one to the other. There is in this spectrum that can +be seen an almost infinite number of wave lengths; +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{150a} + \end{center} + \Caption{8}{Diag.\ 8.---Visible Solar Spectrum.} + \index{Spectrum, solar}% +\end{figure} +there is no break among them apparently. The same +thing holds true of a spectrum produced by letting the +light from a lamp or candle go through the same prism: +\index{Prism}% +the tints, their order, and their wave lengths are found +to be the same. The prism then receives ether waves +of any or all wave lengths, and separates or disperses +them in the order of their wave lengths. In doing this +it deflects the longer waves less than it does the shorter +ones. The deflection of the waves from their original +course is called \emph{refraction}, and the separation from each +\index{Refraction}% +other so as to produce the spectrum is called \emph{dispersion}. +\index{Dispersion}% +A prism effects both at the same time, and thus enables +one to isolate at will any particular tint or part of the +spectrum; and if one takes a single narrow portion in +any such spectrum, he has a bundle of light rays of +uniform wave lengths, and he may then determine their +value. In this way the wave lengths of the different +colored parts of the spectrum of sunlight have been +found to be as follows:--- +\DPPageSep{151.png}{139}% +\begin{center} +\TableFont% +\begin{tabular}{ll<{\qquad\qquad}l} +Red, & about & $39000$ to the inch +\\ +Orange, & \PadTo{\text{about}}{\Ditto} & $41000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Yellow, & \PadTo{\text{about}}{\Ditto} & $44000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Green, & \PadTo{\text{about}}{\Ditto} & $47000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Blue, & \PadTo{\text{about}}{\Ditto} & $51000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Indigo, & \PadTo{\text{about}}{\Ditto} & $54000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +Violet, & \PadTo{\text{about}}{\Ditto} & $57000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +\multicolumn{2}{l}{Extreme visible, about} & $60000$ \PadTo{\text{to }}{\Ditto}\PadTo{\text{the }}{\Ditto}\PadTo{\text{inch}}{\Ditto} +\\ +\end{tabular} +\end{center} + +A spectroscope is an instrument composed of a prism +\index{Spectroscope}% +mounted between two tubes, one of them having an +adjustable slot for the light to be examined to pass +through on its way to the prism, the other being a short +telescope to magnify somewhat the image of the +spectrum that %[** PP: Width-dependent break] +%[Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{151a} + \end{center} + \Caption{9}{Diag.\ 9.---Spectroscope.} +\end{figure} +it may the better be seen. With this, +light from any source may be examined. Light made +up of all wave lengths that can be seen shows as +a complete spectrum, while any light made up of but +a part of these gives a corresponding incomplete +spectrum. The flame of an alcohol lamp, or a Bunsen +\DPPageSep{152.png}{140}% +\index{Spectrum analysis}% +gas-flame, gives but little brightness and not much to +produce a spectrum; but a little salt in the flame gives +to it a bright yellow tint, and shows in the spectroscope +a single narrow band of yellow light in the same place +as the yellow seen in sunlight, and therefore having the +same wave length. Such a beam made up of waves of +one wave length is called homogeneous light. This +sodium light has a wave length of about the one forty-four-thousandth +of an inch. With other more refined +methods, which cannot be described here, sodium is +found to have other wave lengths beyond both the red +and blue ends, and which cannot be detected by the +eye alone. Hydrogen, another element, gives a bright +red line and a blue line that are easily seen; and several +others may be detected with more delicate apparatus. +In this manner all the elements have been attentively +studied during the past thirty years, and many treatises +may be found that give full particulars of the processes +and results. The substance of knowledge obtained by +the study of the spectra of the elements may be briefly +stated to be,--- + +1st, Each element has its own vibratory rates at +a given temperature, and sets up corresponding ether +waves; some of these can be seen, and others require +more complicated apparatus to discover. + +2d, In order that the characteristic vibrations of any +atoms or molecules may take place, it is necessary that +they be allowed a free path to vibrate in; in other words, +they need be in the gaseous state. If they be crowded +together, as they are in solids and liquids, they have no +chance to vibrate without interference. A pailful of +\DPPageSep{153.png}{141}% +school-bells might make a jangling noise, but would give +no particular pitch or characteristic sound of any of the +bells, and only when not interfered with for a part of the +time at least could one give out its true sound. This +gaseous state is generally obtained by igniting in flames +or by the electric spark the substance to be examined. +In an electric arc all substances are volatilized, and may +be then studied with the spectroscope to great advantage. +Sometimes substances that remain in the gaseous +state at ordinary temperatures, such as hydrogen, oxygen, +chlorine, etc., are hermetically sealed in glass tubes, +after rarefication, in order to obtain long free paths, and +are lighted up by means of electric discharges through +them. + +3d, On account of the lack of vibratory freedom, the +molecules of solids and liquids give out vibrations of all +wave lengths, for every partial and incompleted movement +disturbs the ether; and there are all degrees of +these, but the energy of the shorter ones is rarely great +enough to affect the eye, and hence are not visible at +ordinary temperatures. If a body like a cannon-ball be +gradually heated in the dark, it will presently begin to +glow with a dim red tint. If looked at through the +spectroscope, only red light on the extreme red border +can be seen. As the temperature rises, additional +shorter waves appear, and the spectrum broadens to the +orange, then the yellow, and so on; the ones already +showing growing brighter meanwhile, until the ball is +in a bright glow, and a full continuous spectrum is produced. +As the ball cools, the reverse holds true; and +the violet waves are the first to disappear, then the blue, +\DPPageSep{154.png}{142}% +and lastly the red vanishes from sight. Still the ball is +much too hot to safely touch, and continues to cool by +giving off ether waves differing from the rest only in +being too long to affect the eye. They still are refracted +by the prism, and an invisible spectrum is produced, +and this spectrum has been traced out to ten +times the length of the visible spectrum. +%[Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{154a} + \end{center} + \Caption{10}{Diag.\ 10.---Complete Solar Spectrum.} +\end{figure} + +The sun, an electric arc, and other solid hot bodies, +\index{Spectrum, solar}% +give out similar long, invisible spectra. + +In like manner, where the body is white-hot, and giving +out the shortest waves the eye can see, there can still +be found, a long way beyond that limit, waves that can +do photographic work, which is but a kind of molecular +dissociation. + +4th, Where waves of a given length are made to pass +through a gas having similar vibratory rates, or capable +of producing waves of the same length, the molecules +of the latter will absorb such waves, and therefore stop +their progress, especially if they have more energy than +the waves the absorbing gas can give out. So if sunlight +containing the same yellow light as that of sodium +gas be made to pass through the latter, it will be stopped; +and if this be done where there is a spectrum of sunlight, +the yellow will be cut out from it, and there will be +but a black line instead. This is called gaseous absorption, +\index{Gaseous absorption}% +and is an illustration of what was said a little way +\DPPageSep{155.png}{143}% +\index{Sun, its structure}% +back about the exchange of energy always going on. +The absorbing power of a gas has a significance like its +radiations, and indicates its presence as well. + +The yellow light of sodium gas has a definite place +in the spectrum; and hence if one perceives those wave +lengths in a gaseous spectrum, he knows that sodium +must be present in a state of incandescence, giving rise +to the waves. But if the light from a white-hot cannon-ball +were to be sent through that same vapor, and afterwards +examined with a prism, the yellow light would be +absent, and the absence would still proclaim the existence +of sodium vapor. + +Hence, if an incandescent body gives a continuous +spectrum, it must be a solid or a liquid; the molecules +must be so compact that the individual vibrations are +prevented, and only irregular ones can be made. If a +discontinuous but bright line spectrum is shown, the +matter must be in a gaseous state, and the molecules +have free path. + +If a bright spectrum have black spaces or bands +across it, there is indicated a solid or liquid incandescent +body shining through gas that acts by absorption +upon it, and thus both the solid and gaseous conditions +are detected, as well as the nature of the substance in +the gaseous state. + +This knowledge has been applied to the discovery of +the substance and condition of the sun and other celestial +bodies, and it is concluded that the sun has a solid +or liquid surface as a shell to a gaseous interior, and +that the atmosphere of it consists of the various +elements that make up the body of the sun in so highly +\DPPageSep{156.png}{144}% +\index{Jupiter, temperature of}% +\index{Mars, atmosphere of}% +\index{Saturn, temperature of}% +heated a condition as to keep them in a vaporous or +gaseous state. The characteristic spectroscopic lines of +about forty elements have been found there. Some of +the elements have a very large number of spectroscopic +lines. Iron, for instance, has several hundred lines. +Hydrogen is particularly abundant. Perhaps the most +important discovery due to the spectroscope has been +this: that there are a very large number of gaseous +bodies, called nebulæ, in the heavens; some of these fill +immense spaces; they are in a condensing state, and +all of them are mostly made up of hydrogen. This +discovery gave an additional probability to the nebula +theory of the origin of the solar system, for it showed +that process in its various stages in more distant +parts of space: and in addition to that, it has led to +the surmise that in some way some of those we now +call elements are really compounds of more elementary +substances, probably hydrogen; but that is a speculation +merely, for there is no other than such spectroscopic +evidence that anything like transmutation of what we +call elements into others can take place. + +The spectroscopic examination of the other members +of the solar system has shown that Mars has an +atmosphere like ours, holding watery vapor in it; +that Jupiter is red-hot; that the temperature of Saturn +is probably much too high for any such living things +as exist on this earth---and in this way has answered +the question so interesting to most thoughtful persons +as to whether the planets are inhabited or not. Jupiter +certainly cannot be inhabited by any such beings as we +are, for the temperature would destroy all organic things. +\DPPageSep{157.png}{145}% +\index{Motion, kinds of}% +\index{Stars, their motions}% + +Velocities of translation can also be measured when +as high as two miles a second or more, by the displacement +of spectroscopic lines towards one or the other +end of the spectrum. If a star is approaching us, the +wave lengths are shortened a small quantity, and that +changes the position of a line towards the blue end, +while recession makes it longer and moves it towards +the red end, so it has been found that Sirius is receding +\index{Sirius}% +at the rate of nineteen miles per second; that Arcturus +\index{Arcturus}% +is coming towards us at the rate of sixty miles +per second. In like manner is shown that the sun, and +with him the whole solar system, is travelling in the +direction of the constellation Hercules at the probable +rate of about sixteen miles per second. + +Now, all this presupposes that the principles established +in the laboratory for substances there investigated +are applicable wherever such matter exists; +for instance, that the spectrum of sodium and of hydrogen +and iron, which depends upon temperature and +pressure, is as reliable if the light comes from a body +a million miles or a thousand million miles away as if it +came from only one mile or a foot distant. If it be +thus widely applicable, then do we have the best of +testimony that matter, its conditions, and its laws are +the same everywhere, and that the earth is a fair specimen +of the rest of the universe. + + +\Section{OTHER PHENOMENA OF ETHER WAVES.} + +Whenever a line of ether waves---which is generally +called a ray, whatever the wave length may be---falls +\DPPageSep{158.png}{146}% +upon matter, the ray may be either absorbed, transmitted, +or reflected. Neither of these results takes +place singly in any case. There is no known body, for +instance, that can wholly absorb all the rays that fall +upon it, nor wholly transmit or reflect them. If a body +should be able to absorb all the rays that fall upon it, +we should not be able to see it unless itself were a self-luminous +body, for we only see other than self-luminous +objects by means of the light reflected from them, +and such a body would reflect no light, and hence could +not be visible. + +Bodies which absorb most of the rays that fall upon +them we call black and opaque; that is, a body that +reflects but a small portion of the waves that are incident +upon it is a dark or black body, because we see +but little of it. If it reflected none at all, it would be +quite invisible. In like manner, a perfectly transparent +body would be one that would neither absorb nor +reflect any rays, and for that reason would be quite as +invisible as space itself. The air is perhaps as near an +approach to perfect transparency as anything that can be +\index{Transparency}% +named; yet if it reflected no rays at all, there would be +nothing of the diffused light that is now so plentiful on +the clearest day, but there would be only what would +come direct to us from the sun or other luminous body. +We call clear glass and water transparent because objects +can be plainly seen through them; and a sheet of hard +black rubber we call opaque, for nothing whatever can +be seen through it, nevertheless it has been shown +that waves longer than those that affect the eye, go +through such hard rubber as easily as the shorter ones +\DPPageSep{159.png}{147}% +we call light go through glass, hence transparency and +opacity are terms only relative to particular kinds of +waves. All kinds of matter reflect more or less of the +waves that fall upon it. This reflection is merely the +\index{Reflection}% +change in direction of the ray; but it always follows a +definite law, keeping to its original plane, and making +the angle of reflection equal to the incident angle. +The surfaces of most bodies are very rough, and the +rays are reflected in all directions, because the points +upon the surface face in so many ways. This will +be obvious to one who looks at the surface of paper or +of wood with a magnifying-glass. The smoother a surface +is made, the nearer will all the incident rays take +the same direction on reflection. Mirrors are thus +\index{Mirrors}% +made of smooth glass or metallic surfaces, and are +plane, convex, or concave; but whether they are made +with plane or curved surface, the rays reflected always +follow the above law. + + +\Section{REFRACTION.} +\index{Refraction}% + +So long as ether waves fall perpendicularly upon any +surface of any kind of matter, the rays go straight on +into it if they be not reflected or absorbed at the surface; +there is no change in the direction, but the velocity of +transmission is less in all kinds of matter than it is in +the ether. In glass it is only about two-thirds as fast, +and in water about three-fourths. When the ray meets +the surface at an angle, it is bent out of its course more +or less, depending upon the kind of material it falls +upon, and also the angle at which it meets it. This +change of direction, when entering a new medium, is +\DPPageSep{160.png}{148}% +called refraction, and this property is possessed by all +kinds of matter, solid as well as liquid and gas. The +refraction for a given angle of incidence is more for a +liquid than for a gas, more for a solid like glass than for +water or other liquids, and more for a diamond than for +any other known substance. The same rule that obtains +when the waves enter a medium, holds when it leaves +it; the direction it will now take will depend upon the +angle the rays make with that surface and the character +of the medium into which it enters. Thus, if a +ray meets a piece of plain glass at an angle, say, of~$45°$, +some of it will be reflected, making an angle of~$90°$ +with the incident ray, and some of it will be refracted +into it, making an angle with the original direction, and +continue on in a straight line until it meets the next +surface, when it will again assume its original direction: +but when the second surface is not parallel with the +first, as is the case with the prism, the direction may +depart still more from the original; and the shorter the +wave length, the more the deflection. It is this property +that is made use of in spectroscopes, microscopes, +and telescopes. A lens has one or both surfaces +curved, so as to be convex or concave, depending upon +the use it is to be put to,---a convex glass converging +the rays, and a concave one separating them,---and +almost any degree of either of these may be obtained +by proper curvature. + +Both microscopes and telescopes are so common, and +descriptions of them are to be found in so many places, +that they need not be described here. The inquiry is +often made, why still more powerful microscopes and +\DPPageSep{161.png}{149}% +\index{Microscope, magnifying powers}% +telescopes are not made so as to reveal the very smallest +and the most distant thing. The utility of a +microscope depends upon how plainly it is able to +make minute objects visible; and the more a given one +magnifies an object, the smaller the portion that can be +seen and the less light is available for the purpose, and +when the objects are so small as the few thousandths +of an inch, the light waves interfere with each other at +the edges, and produce colored fringes that cannot be +got rid of altogether, and very small objects become +indistinct for that reason. Microscope lenses are +marked as $1$~inch, $\dfrac{1}{2}$~inch, $\dfrac{1}{10}$~inch, and so on, meaning +by the fraction the approximate distance it must be +brought to the object in order that the latter may be +seen. The higher the power, the shorter this distance. +A one-tenth inch objective may magnify an object a +thousand diameters and perhaps more, so that a blood +corpuscle having a diameter of only one three-thousandth +of an inch may appear about three-tenths of an +inch in diameter, and the details of its coarser structure +may be very well seen; but if there be a minute +point upon it, still indistinct because it is minute, and +a still greater magnifying power required to see it, and a +$\dfrac{1}{20}$~objective be taken, the actual magnifying power +may be five thousand diameters. But now one is +approaching the dimensions of wave lengths themselves, +and the agent necessary for observing introduces +its own complications, producing distortions and +color fringes about the point to be studied, and no way +\DPPageSep{162.png}{150}% +has been found of obviating this. Objectives have +been made having a focal length of only the $\dfrac{1}{50}$~of an +inch and one having only the~$\dfrac{1}{75}$, but no work of any +importance has ever been done with them. The best +of the microscopic work has been done with lenses that +magnify no more than one thousand diameters. It is +said that the best microscopes will show an object that +is no more than about the one hundred-thousandth of +an inch in diameter, but it appears simply as a point or +a line, and no details of its structure can be seen. +Fine rulings upon glass have been made that are known +to have this degree of fineness, because the mechanism +that rules them can be gauged to that degree; but +many persons cannot see these in a microscope, though +others can. So within the limits of the visible not a +little depends upon the acuteness of vision, and there +is a great difference among individuals in this respect. +On account of the properties of the ether waves themselves +in their relations to each other, it does not +appear probable that much improvement is possible to +the microscope. This does not imply that we may not +know more of the minute structure of bodies than we +do now, for there are other sources of knowledge of +minute quantities than simply direct eyesight, which +are just as reliable, perhaps more so. A good chemical +balance will weigh to the millionth part of the load. +Whitworth showed that it was possible to measure to +the millionth of an inch by touch. The spectroscope +will indicate the millionth of a grain by the tint of the +\DPPageSep{163.png}{151}% +gas flame, and the color of a drop of water is appreciably +changed by the one three-millionth of a grain of +fuschine. Some substances, like essential oils, sulphuretted +hydrogen, and the odors of flowers, can be +perceived when the quantity is certainly less than the +fifty-millionth of a grain. + +Any day may bring tidings of new instrumentalities +that help in the solutions of the interesting questions +concerning molecular structure that are now quite out +of our reach. Let it be granted that the problems are +altogether physical ones, such as are justified by the +known mechanical relations of energy, and one may +wait with patience. Let one assume that some or any +of them are not mechanical, and he not only is in danger +of having to revise his judgment in some degree any +day, but he reasons against the significance of all the +knowledge we have of matter and its energy. + +The larger a lens is the more light can go through it: +a lens two feet in diameter will let four times as much +light through it as one only one foot in diameter. As +remote objects, like the distant stars, appear dim on +account of their great distance, it becomes needful to +concentrate the light from a much larger area than that +of the pupil of the eye. If the pupil be one-tenth of an +inch in diameter, a certain amount of light from a star +may enter it. A lens one inch in diameter would concentrate +at its focus $100$~times as much, and one a +foot in diameter, $14400$~times more; and hence the +object would appear so much brighter. Along with +this apparent brightening of the star, it is apparently +brought nearer and enlarged. There are limits to the +\DPPageSep{164.png}{152}% +size and useful magnifying power of telescopes as well +as to those of microscopes. The magnifying power +of telescopes depends very largely upon the eye-pieces +used, and the shorter their focal length the more do +they magnify. The large lens, called the objective, +serves mostly to collect a large amount of light. It is to +be kept in mind that the movements of bodies are magnified +as much as their apparent dimensions, and when +there are any movements of the body surveyed, or of +the instrument itself, distinct vision becomes correspondingly +difficult. + +With the telescope the chief trouble comes from +movements of the air, which are rarely of uniform quality +and motions. Not only its transparency, but its degrees +of density caused by heat and wind, are varying all the +time; and these seriously interfere with telescopic work. +If a magnifying power of say~$100$ be employed, these +disturbing causes are increased in proportion, and with a +power of~$1000$ nothing can be distinctly seen. Suppose, +however, the air be in best condition for observations, +and a power of~$1000$ be put upon the moon. As +the moon is about $240000$ miles away, this magnifying +power would have the effect of bringing it $1000$~times +nearer, or as it would appear to the eye if it were +but $240$~miles away. Now, an object $240$~miles away +can reveal no interesting details at all; anything much +less than half a mile square could not be distinguished +unless it were a very bright or very dark spot. Powers +as high as~$8000$ have been used; and such a one would +bring the surface of the moon as it would appear if it +were about thirty miles distant, which might show a +\DPPageSep{165.png}{153}% +city, a large town, a lake, and the difference between +field and woodland, yet nothing satisfactory was seen +for the reasons mentioned, so for most astronomical +work a magnifying power of only a few hundred is +used; seldom more than five hundred. When large +telescopes are set on elevated places like the Lick +Telescope on Mt.~Hamilton in California, some of the +troubles from disturbed air are obviated, and it is hoped +something more may be learned about our nearer astronomic +neighbors. But these large telescopes collect +so much more light that stars so distant as to be quite +invisible with smaller glasses become plainly visible +with them. With the unaided eye no more than $5000$ +or $6000$~stars can be seen in the whole heavens, with +an opera-glass as many as $100000$ become visible, while +the Lick telescope, with an object-glass three feet in +diameter, shows nearly $100,000000$. Each increase in +the size of the telescope adds to the number of visible +stars, and one cannot but wonder if their number be +infinite, or if there be a boundary to the universe of +matter. Though the visible boundary of our universe +has been greatly extended by the invention of the telescope, +nothing has been descried anywhere but matter +and motion: there has been nothing added to our knowledge +but the sense of bigness. Instead of only a few +thousand of hot and flaming stars, there are hundreds +of millions of them, made of the same kinds of matter, +having the same kinds of motions, controlled by the +same laws, and nothing animate in any of them more +than in a bowlder in the wall. Clifford said he wished +they were farther off. The problems of astronomy are +\DPPageSep{166.png}{154}% +\index{Space, navigation of}% +interesting studies in mechanics, but are not inviting to +those most interested in life and mind. Herschel and +Chalmers and Dick and Mitchell are dead. The +knowledge already gained has destroyed both their +arguments and hopes, and has left the inhabitants of +this earth the possessors of the universe, yet unable to +take possession. + +If there are inhabitants in Mars they are as unable to +traverse space as we are; and the possibility of our yet +being able to do that is not half so unlikely as it seemed +to be but a very few years ago, since it evidently requires +for accomplishment but a directed reaction against +the ether; and we already know how to produce the +reaction by electrical means; and every point in space +has the energy for transformation. + +It is generally agreed that the so-called attraction of +a magnet for its armature is really due to the pressure +of the ether upon the latter, and it may be as great as +two hundred pounds to the square inch. + +An electro-magnet without an armature is therefore +reacted upon by the ether to that degree. When this +reaction can in any way be neutralized at one pole and +not at the other, the ether reaction will push the magnet +backwards, and the navigation of space will at once +become mechanically possible. + + +\Section{THE RADIOMETER.} +\index{Radiometer}% + +It is a familiar enough fact that when sunshine falls +upon a surface the latter becomes heated. In general, +the darker the color of the surface the more rapidly %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}{r}{1.5in} + \Graphic{1.5in}{167a} + \Caption{12}{Diag.\ 12.---Radiometer.} +\end{wrapfigure} +does +the temperature rise; and some bodies, when thus exposed +\DPPageSep{167.png}{155}% +for some time, become unbearably hot. We are +able to say that the surface molecules of such a body +are in a brisk vibratory movement; that they have more +energy than other bodies with less temperature. If one +imagines the condition of things when the molecules of +the air impinge upon such a heated surface, he will understand +how they must bound away +from it with greater velocity than +they struck it with, and if with +greater velocity, then with greater +energy. As action and reaction are +equal, it must kick back upon the +surface as it leaves it, thus tending +to make the surface move in the +opposite direction; and a large number +of such impacts must give a resultant +backward pressure. If the +surface be a small one, the increased +pressure in the air in front will +travel round to the other side at +the rate of eleven hundred feet in a +second in ordinary air; so the pressure +will be equalized in a very short +interval of time. If the air be rarefied +in front of such surface to such a degree that the +free path of the molecule is many times greater than +its ordinary length, that pressure cannot get round +nearly so fast, and there will consequently be a constant +backward pressure, produced by the molecules that impinge +upon it and become heated by contact with it. +The pressure per square inch is very slight, as it is +\DPPageSep{168.png}{156}% +produced by a relatively small number of molecules; +but it may be made apparent by mounting some disks, +blackened on one side, upon a pivot in a glass bulb, +and, after exhausting a large part of the air, hermetically +sealing the bulb. Such a device is called a radiometer. +When put where sunshine, or the light from +the flame of a lamp or candle, or even the heat of the +hand, may fall upon it, the vanes begin to rotate, the +blackened side backing away from the source of the +energy. This movement was at first interpreted as +being due to the actual pressure produced by light +waves, but further investigation showed that idea to be +wrong. The movement comes from the transformation +of the motions of ether waves, first into heat, and +second into the translational mass motion observed. +The radiometer is, therefore, a machine for transforming +ether waves into visible mechanical motions. + + +\Section{PHOTOGRAPHY.} +\index{Photography}% + +It has already been explained how heat acts upon +molecules, increasing the amplitude of the vibrations of +the atoms that make them up, and, if carried to a sufficient +degree, is able to quite destroy the molecular structure +and enable the component atoms to enter into new +combinations. The degree needed for this depends upon +the kind of molecules. Some molecules are so stable +that only the very highest temperature we can produce +can break them up. Others are so feebly cohesive that +the least touch will cause them to go to pieces, and +sometimes with explosive violence, as is the case with +what are called fulminates, compounds of nitrogen with +\DPPageSep{169.png}{157}% +silver or with mercury; and sometimes the same result +is reached by ether waves, whose number per second is +such as to set one of the ingredients into sympathetic +vibration and thus decompose the compound, doing it +at a slower rate than the others. Nearly all complex +molecules are decomposable in this way, and the process +is going on all the time in nature where there are organic +things to act upon, but the process is usually +slow. + +When shingles are first laid they have a fresh surface +and new appearance, which is presently lost by +the exposure. Take a freshly planed piece of soft +pine or other white wood, and fasten to the surface a +piece of paper cut into any shape or design,---a circle, +a star, or the like,---and set the wood where the sun +can shine on it for a few days. When the design is +removed the figure will be plainly seen on the wood by +the difference in tint between its surface and that part +which the sun has shone upon. The latter is much +darker. This is an example of photographic action, +as is the color of fruit, etc.; for if a design is pasted +upon a green apple, which is red when ripe, the design +will protect the surface from the action of the light, +and will therefore appear upon the apple in a light tint. +Diagrams and letters may be fixed thus upon fruit of +any kind. Discolorations of all sorts, due to ether +waves or light, may properly be called photographic +action, both fading and darkening, as when the skin +becomes tanned. For practical purposes some compounds +of silver are generally employed, because they +are more sensitive to the action of visible waves than +\DPPageSep{170.png}{158}% +most other substances. They have the property of +being easily disorganized by waves whose length +ranges from about one forty-five-thousandth of an inch +to those in the neighborhood of the seventy-thousandth +of an inch, some of these being visible waves, the +others being too short for visibility. When a surface is +prepared with some one of the sensitive salts of silver,---generally +the iodide or the bromide,---and a picture +of an object produced by the lenses of the camera +is allowed to fall upon it, the decomposing action is +proportional to the amount of light and shade in the +different parts; and, when the plate thus exposed is +placed in certain chemical solutions called developers, +the decomposition is completed and the products dissolved +out, leaving a coating of pure silver, with a +thickness proportional to the chemical action that has +taken place. This gives, then, a correct likeness of +the picture that was in the camera. Formerly it took +a long time to produce such a picture, a person having +to sit still for half an hour or more. More and more +sensitive preparations were produced, until now a good +picture can be taken in less than the thousandth of a +second; and the practice of the art has become a great +industry. There are many preparations in common +use for taking such pictures, but nearly all of them +have silver for the chief constituent. It may be +remarked that silver compounds are remarkably unstable. +Silver is not easily oxydized\DPnote{** [sic]}, for it remains +untarnished for an indefinite time, as exemplified by +coins and jewelry. But there are plenty of other compounds +that may be used. Thus the common blue-print\DPnote{** Hyphenated across page, no other instances.} +\DPPageSep{171.png}{159}% +\index{Silver salts unstable}% +is a compound of iron. The salts of chromium +are also sensitive to such waves. + +It was remarked that the salts of silver are sensitive +to ether waves between quite a wide range in wave +lengths, but the longest of them is in about the middle +of the visible spectrum. They reach from there into +the region beyond the violet. Yellow and red waves +are incapable of affecting such a preparation, while the +waves that are the most efficient for it are the blue +ones. +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{171a} + \end{center} + \Caption{13}{Diag.\ 13.---Photographic Range for Silver Salts.} +\end{figure} + +Other substances have a different range, and a curious +chemical discovery has shown that silver molecules +may be loaded; that is, may have attached to them in +a temporary way some other kinds of molecules that +render them sensitive to waves of any length. If an +ordinary photographic plate has a solar spectrum +thrown upon it, there will be no indication of action +below the green; but, if aniline be added to the sensitive +coating and the plate be then exposed in the same +way, the action will now be seen to have gone on to a +distance below even the longest red wave that can be +seen. In this way photography has shown that the +spectrum of most incandescent bodies is much longer +than the visible part of it in both directions. It was +the observation that photographic action took place +\DPPageSep{172.png}{160}% +\index{Molecules, loaded}% +most strongly in the blue part of the solar spectrum, +and in the region beyond, that led to the belief that +light waves and chemical rays were, in some way, +unlike each other. From what has been said it will be +seen that the reason for the different action was due to +the character of the material used. When a molecule +is made bigger or heavier in any way, longer waves can +affect it more; and that is the significance of the so-called +loaded molecule. In reality, the whole molecule +is made more complex and bigger, and longer waves +can shake its atoms loose. + +It is to be hoped that all can understand that there +is nothing mysterious about photographic action; that +it is as simple in its mechanical principles as anything +can be. One may not be able at once to say in +any given case which atoms or which parts of a molecule +are loosened by the vibratory strains. In this one +it may be the nitrogen, in another it may be the silver, +and in still a third it may be oxygen; but in each case +the mode of action is the same, and it may be said to +be mechanical throughout. + + +\Section{VISION.} + +Our various senses differ much in their mode of +action, and require for excitation not only each its +proper stimulant, but degrees of remoteness from +actual contact to the most distant points. Thus the +sense of touch requires absolute contact of a body: so +also does taste,---the sugar or the salt must dissolve +upon the tongue. A distance of but the tenth of an +inch between the sugar and the tongue will be absolutely +\DPPageSep{173.png}{161}% +prohibitive to the consciousness of sweetness. +The sense of smell requires the actual contact of the +gaseous molecules upon the nasal membrane, but currents +of air and gaseous diffusion secure to us this condition, +so that the emanating body itself may be at +some distance, and yet we become conscious of the +bank of violets, the cup of coffee, or the chemical laboratory. +This sense, therefore, enlarges our field, so to +speak, and permits us to be conscious of bodies out of +our immediate reach. The sense of sound still farther +enlarges the space that can react upon us. But the +loudest sounds, such as the roar of cannon and thunder, +lose their intensity shortly, and can rarely be +heard beyond a few miles. If our endowment of +senses stopped with these, we should really be quite +\index{Senses}% +limited in our possible knowledge; for as we can know +only what comes into our experience, how small the +possibilities of existence would be to us! What we +could touch, taste, smell, and hear we could know something +about, though we were unconscious of any lacking +sense. We should need some apparatus that could +make us conscious of the most distant things as well +as those close at hand. We should need just what we +have got,---the sense of sight, that extends the field of +experience and of interest to us to the boundaries +of creation. The other senses give us information of +contiguous things, but sight brings the universe itself +to our consciousness. + +The sense of touch is diffused all over our bodies. +There is no such thing as an organ of touch. The +senses of taste and smell are restricted to localities and +\DPPageSep{174.png}{162}% +to organs that have other functions as well. Only sound +and sight have specific organs, having no other function +than to respond to sonorous and optical motions, and +thus they have a peculiar dignity in the physiological +mechanism; and precisely because the eye and ear have +these mechanical functions do they come into the domain +of physics. They are machines by which certain forms +of motion are transformed into others suitable for nerve +transmission to the seat of consciousness. + +It has often been pointed out that the structure of +the eye is like the camera of the photographer. In each +\index{Camera}% +there is a chamber~\textit{a}, having a lens in front, which has +a length %[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{174a} + \end{center} + \Caption{14}{Diag.\ 14.} +\end{figure} +of focus adapted to the distance between it and +the back of the chamber, so that the image of objects +external to it will be produced by it upon the back of +the chamber, where there is in each a sensitive coating +so affected by the light as to make an impress. In the +camera this action has been explained as chemical +reaction when molecular dissociation results, proportionate +to the amount of light that falls upon any part +of the surface exposed. + +In each there is an arrangement for altering the focal +distance of the lens. In the camera it is a ratchet-wheel +that moves the lens towards or away from the +back. In the eye there are muscles attached to the +\DPPageSep{175.png}{163}% +edge of the lens that by contracting make the pliable +lens less convex and so increase its focal length. For +the camera %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}[15]{r}{2.25in} + \Graphic{2.25in}{175a} + \Caption{15}{Diag.\ 15.---Photographic Camera.} +\end{wrapfigure} +there is +\index{Camera}% +an exchangeable diaphragm +having perforations +of various +sizes to admit more +or less light through +the lens. In the eye +there is a colored +muscular disk called +the iris, that contracts +or expands in +an automatic way so +as to expose more or +less of the lens to +the light. The functions +of the two devices are identical. + +The energy possessed by the ether waves that fall +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{175b} + \end{center} + \Caption{16}{Diag.\ 16.} +\end{figure} +upon the sensitive photographic plate is spent in doing +\DPPageSep{176.png}{164}% +\index{Vision, phenomena of}% +the molecular work of disintegration. In the eye all +the energy is stopped at the sensitive back coating +called the retina, and must of course be accounted for +in some physical way. In the camera all the energy of +the waves is spent in precisely the same kind of a way; +that is, there is no such distinction as what is called +color in it: and color photography---that is, the direct +picture of objects in their proper, natural tints, such +as we know they have, upon the sensitive plate---has +not been accomplished, for the probable reason that the +colors of the molecules that are the result of the decomposition +of the silver compound are either transparent +or blueish black. In the eye, the distinction between +wave lengths which we denominate color sensation is +very pronounced. + +The sensations are so much complicated with the +processes that induce them that it is not always easy to +keep in mind the purely physical side or the subjective +side while treating of them. + +The following are some of the more common phenomena +of vision which must be taken into account in forming +any judgment or theory of it. + +When a firebrand is swung round and round it +leaves an apparent luminous trail, the length of which +depends upon the rapidity of motion. This is called the +persistence of vision, and indicates that the sensation +does not cease instantly after the source has gone. If +the brand be swung round at the uniform rate of once +per second, the length of this luminous trail will be a +rough measure of the duration of the sensation after it +is once excited. Thus, if it appeared to be one-quarter +\DPPageSep{177.png}{165}% +of the circle, the sensation must last for one-fourth +a second. For impressions not very bright the sensation +lasts but about the tenth of a second. If, however, +the object looked at be very bright, like the sun, for an +instant, the sensation may last for many seconds; and, +in general, the older the person the longer does it last. + +Different colors also have different degrees of persistence. +\index{Colors}% +Violet, blue, and green soonest fade out, and red +is the last to vanish for most eyes. This signifies that +wave length has in someway to do with the persistence. +When a bright colored object, like a bit of red paper, +is put upon a sheet of white paper and steadily looked +at for a few seconds, and is then suddenly removed while +the eyes are kept fixed upon the same place, the image +of the red paper will still be seen, but it will appear with +a green tint, and will fade out in a few seconds. A +green piece of paper, or any green object looked at in +the same manner, will give an image in red. Blue ones +give yellow, and yellow blue; and these tints seen in +this way are called complementary to each other, as it is +found by combining such together they produce the +sensation of white light. Whiteness is therefore a compound +sensation. Formerly, it was thought that white +was only produced by the composition of all the colors +of the spectrum in the same proportions they exist in it; +but the same sensation of whiteness can be produced +by red, green, and violet, and by blue and yellow. This +is not to be understood as applying to pigments or +paints, but to light itself. + +If one looks at a strongly lighted object intently for +a few seconds, and then turns his eyes to a dimly +\DPPageSep{178.png}{166}% +\index{Vision, hallucinations of}% +\index{Vision, energy needed for}% +lighted drab surface, he will be able to see, sometimes +in a surprisingly realistic way, the same object against +the new background. If it be a person looked at, +the features may even appear in a startling way. +The size of the subjective figure will depend upon +the distance of the background, being larger the more +remote that is. Age and health have much to do +with the persistence of such sensations\DPtypo{}{.} Young and +vigorous persons seldom notice them until they +carefully look for them; while older ones, and especially +weakened ones, may be much troubled by +them. Some nervous systems react upon the eye itself, +and give rise to similar images there; and these subjective +images have not unfrequently been mistaken for +objective persons living or dead. The color a given +object appears to have is not unfrequently modified by +what colors the eye has been resting upon the instant +before, and hence two persons may look at once upon +the same picture and see it in very different tints. + +As ether waves are the source of the sensation, it is +obvious that a certain number of consecutive waves +must be necessary to affect the eye; that is to say, it is +not in the least probable that a single wave of any +length could produce a sensation. How many are +needed is not known, but one can determine somewhere +near what the number must be if he knows how +brief a time is sufficient to produce a sensation. It is +said that some flashes of lightning have been found to +occur in less than a millionth of a second, and those +may produce a very strong sensation. + +If there are five hundred million million vibrations per +\DPPageSep{179.png}{167}% +second, as we know there must be to give such a sensation, +in the millionth of a second there must be five +hundred millions; if the brightness were reduced ten +thousand times and it were still visible, there must +then have been not less than fifty thousand waves: and +this is equivalent to saying that the eye could perceive +light if it lasted no longer than the ten thousand +millionth part of a second, which is probably true. +But there is another condition; namely, the \emph{energy} +of the waves must be sufficient to effect a physical +change in the eye; and we know that the energy of +such ether waves varies with the square of their amplitude. +If, then, any wave whatever has not energy sufficient +to produce the necessary physical disturbance in +the eye, it could not produce vision. And this is the +most probable reason that we do not see in what we +now call darkness. It has been shown that all matter +at all temperatures is vibrating and setting up ether +waves, and also that in all liquids as well as solid +bodies there are vibrations due to their atomic and +molecular interference; and, theoretically, there must +be vibrations of all wave lengths at all times and in all +places, but at low temperatures the shorter waves, +though not absent, would have but small energy, and, +as the body becomes hot and the shorter ones acquire +more, it is done at the expense of the energy of the +longer ones, for the light given out by an incandescent +lamp increases faster than the supply of energy to produce +it. It therefore appears as a necessary conclusion +that the reason we cannot see in the dark is not so +much because the waves of proper wave length are +\DPPageSep{180.png}{168}% +\index{Vision of animals}% +\index{Vision, theory of}% +entirely absent, as that they have too little energy to +affect our eyes. Other animals, such as rats, mice, +owls, bats, and the like, can see where it appears to us +to be pitch dark. They must, therefore, have eyes +adapted for longer wave lengths than are ours, or else +the sensitiveness of their eyes exceeds ours. As +they see readily in the daylight, it is certain they are +adapted to such waves as our eyes are; and, if ours +were sufficiently sensitive, or had a greater range in +effective wave lengths, there would be no such condition +as darkness. That is the same as saying that +darkness is in us rather than being a condition external +to us. + + +\Section{THE THEORY OF VISION.} + +When it was discovered that the sensation of whiteness +could be produced by combining three different +colors,---red, green, and violet,---it was inferred that +there were probably three sets of nerves that were spread +as a fine net-work over the retina so that either of these +rays might fall at any point in the field of vision upon +it and so produce the sensation. At the same time, +when one or two of them were absent, the other nerve +ingredient would be present to be affected; and, furthermore, +each one of these three nerves was sensitive to +quite a wide range of wave lengths, and their overlappings +gave perception without any break from the +extreme red to the extreme violet. In this way color +perception could be explained. This view was adopted +as a working hypothesis; and there was no other proposed, +although there was no evidence whatever for the +\DPPageSep{181.png}{169}% +existence of three sets of nerves having different properties. +It has, however, lately been discovered that +the retina secretes a substance called purpurine, on +\index{Purpurine}% +account of its purple tint, which is very rapidly +bleached or decomposed by the action of light. That +is to say, it possesses photographic properties in a +marked degree. This discovery has led to the view that +vision may be altogether due to photographic action, +and the older view has been about abandoned. The +details of this theory have not yet been all worked out, +but the purport of it may be briefly stated. + +Given the purpurine spread over the retina: this +would be its sensitive coating corresponding to the silver +preparation upon the photographic plate. The +action of the light upon it being the same in character, +decomposes it into simpler molecular compounds. The +optic nerve is certainly spread over the retina, and the +purpurine is in its meshes, and any disturbance taking +place in this substance must correspondingly affect the +ends of the nerves imbedded in it. Given the disturbance +that can affect the optic nerves, and it is transmitted +at once to the base of the brain and there interpreted +as light sensation. The differences there might +be in the amount of disturbance would be the differences +that are called brightness or intensity. If molecules +are disintegrated, as in photographic action, there +must be a relatively large amount of free-path motion +resulting from the wave action in the eye, and the +amount of it proportional to the energy expended. +Such an effect would give a general sensation of light, +probably, also, effects of light and shade, so the forms of +\DPPageSep{182.png}{170}% +bodies would be readily enough seen. It would also +account for persistent effects; for, when molecules are +made to move fast or slow, they do not cease instantly +on the removal of the source of the motion, but they +continue to thus move until their energy has been +reduced to that of the surrounding medium. With +simple purpurine there appears to be no more possibility +of chromatic effects than there is in the common +silver preparation on the photographic plate. Suppose, +however, the purpurine to be not a simple kind of a +body, or made up of only a single kind of molecules, +but instead made up of as many as three different +kinds having as many different molecular weights, and, +therefore, capable of being reacted upon by three different +wave lengths. Call these three substances \textit{a},~\textit{b}, +and \textit{c}~purpurine. Let \textit{a}~be such as red waves can +decompose, \textit{b}~such as green ones can decompose, and \textit{c}~such +as only the short purple ones can break up or +shake up. If these are uniformly mixed together and +spread over the eye, then red waves would shake up +the red constituent, but would leave the others alone; +and the same would hold true of the others. If one +has been looking at red-light wave lengths, the \textit{a}~purpurine +would be used up, but the \textit{b} and~\textit{c} would still be +present unimpaired; and now, when white light is again +looked at, the \textit{b}~and~\textit{c} would be acted on strongly because +they are present in greater quantity. The resulting +sensation would be the compound of these two +reactions, which, as is well known, is a greenish tint. +In a like manner, each of the others when used up +would leave the same field fresh with the other constituents, +\DPPageSep{183.png}{171}% +\index{Color-blindness}% +\index{Retina, its functions}% +and so give the complementary tints; and in +this way chromatic effects of all sorts can be accounted +for. + +Some persons are color-blind; that is, they are +unable to distinguish some colors; and this defect is +usually for red rays. Such a color-blind person will be +unable to see the red end of the spectrum, and the +colors of it will appear to leave off in the yellow or +orange. The old explanation was that the red sensation +nerves were absent. The newer explanation is +that the \textit{a}~ingredient of the purpurine is wanting either +partially or altogether. + +Of course it is to be understood that the products of +decomposition by light in the eye are removed and +fresh material secreted in its place by the organ itself +in a manner similar to the removal of waste tissue and +its repair in any other part of the system. + +The function of the retina, then, would appear to be +the secretion of the sensitive substance needed for +vision, instead of itself being the sensitive substance. + +Such an explanation of vision makes the eye still +more like the photographic camera than appears in its +outward form and mechanical functions. And thus one +is able to trace the forms of motion that constitute the +heat and the temperature of a body through its resultant +ether waves to the molecular break-ups at the ends +of nerve fibres, whence the characteristic motions are +transmitted to the base of the brain, to be interpreted +thus or thus, according to position, number, and energy. +We begin with motion, we end with motion at the +seat of consciousness, and there we stop. It is vibratory +\DPPageSep{184.png}{172}% +in the hot body it starts from, it is undulatory +motion in the ether, it is oscillatory in the disrupted +molecules, and a longitudinal wave in the nerve. +Whether it is discharged from further service at the +base of the brain, or is stored up in some way as experience, +no one can say; but it is certain that a relatively +large amount of molecular energy finds its way constantly +to the brain, and some of it is re-employed as +reflex action, giving rise to voluntary and involuntary +\index{Reflex action}% +muscular and secretory processes, as when one winks, or +dodges a threatening motion before the will can act, or +laughs or weeps at sights and sounds. In either case +the result is the physical expression of a physical antecedent, +with an intermediate mental quality called +emotion. + +The eye may then be said to be a machine for the +transformation of ether waves into interpretable molecular +or atomic motions, and its function ceases at the +ends of the optic nerve. +%\DPPageSep{185.png}{173}% + + +\Chapter{VIII}{Electricity}{173} + +\First{The} industrial applications of electricity are now so +extensive and varied that every one is acquainted with +them in some measure, and yet fifteen years ago there +were millions of persons in the civilized nations who +had never seen an electrical phenomenon with the exception +of lightning. The apparently capricious behavior +of lightning, together with the attractions and repulsions +exhibited by electrified bodies, were phenomena +so different in character from any other, that it came +to be looked upon as a very mysterious force. Fifty +and more years ago it was classed with heat and light +as one of the imponderables. To-day even the question +is often asked, What \emph{is} electricity? with the +emphasis on the word ``is,'' as if one knowing enough +might describe it as he might describe a genii or an +object having specific qualities that might be isolated +from everything else. Some have thought it to be a +fluid, some two fluids, some vibratory molecular motion, +some a property of matter, some a motion in the ether, +some the ether itself; and, lastly, some have concluded +that we do not and never can know its nature. +Hence, to-day there is no generally received notion +concerning its nature. +\DPPageSep{186.png}{174}% +\index{Electricity, origin of}% +\index{Electricity, thermal}% +\index{Thermodynamics, electric}% + +Still, one may know a great deal about the agent +itself,---how it originates, what it will do, and its relations +to other phenomena,---and not concern himself at +all as to the nature of it. Heat and many of its laws +were well known before any one knew or even suspected +what its nature was. The law of gravitation +is known and applied on the scale of the universe without +demanding any explanation of the phenomena, and +it is equally true that our knowledge of electricity is +very extensive and accurate, and doubtless what we do +not know to-day we may know to-morrow. + + +\Section{ORIGIN OF ELECTRICITY.} + +It is here to be assumed as known, that various +instruments, such as electrometers and galvanometers, +are employed to detect the presence of electricity, and +descriptions of them will not be given. Attention will +be paid chiefly to the conditions that are present when +electricity is generated. + +\Section{1. THERMAL ORIGIN.} + +When two different metals, such for instance as copper +and iron, are touched together, they are found to be +electrified; that is, an electrometer shows the presence +of electricity. A piece of copper wire twisted to a +piece of iron wire always becomes thus affected, but +the effect is so slight that only delicate and sensitive +apparatus will detect it. Wires of any of the metals +under similar circumstances exhibit the same phenomenon, +but in different degrees. This electrification is +but transient; in a few seconds it has vanished. If the +\DPPageSep{187.png}{175}% +junction of the metals is heated by the fingers, or in +any other way, the electrical condition is maintained +indefinitely. If one will imagine such a compound wire +bent into a ring so the ends nearly touch each other, +it could be shown that the ends attract each other, the +attraction being but slight. Here we are not so much +concerned about the measure of what is taking place +as with its character. If the ends of the wires be +allowed to touch, and the twisted junction be kept warm, +a current of electricity will continue to circulate through +the ring; and, if the ends be connected to a galvanometer +of sufficient delicacy, the needle would be +continuously deflected, so long as the junction was +warmer than the outer ends of the wires; and the deflection +of the needle would be found to vary with the +difference in temperature between the inner and outer +junctions. Some metals, such as bismuth and antimony, +when fastened by solder, or in any other way, give much +stronger effects with a given temperature at their junction. +Such a combination is called a thermo-electric +pair. By joining a number of such together, so that +alternate ends may be heated at once, the electrical +effect is increased proportionally: two will give twice, +and ten ten times as much, and so on. When a number +of these are nicely compacted together and provided +with binding-screws, they are called thermo-electric +piles, and are of service in some investigations. It is +not necessary, however, to have two different metals in +contact to obtain the same kind of effects. If a piece +of soft iron or platinum wire be wound into a close coil +about a lead-pencil and the ends of it connected to a +\DPPageSep{188.png}{176}% +galvanometer, a current of electricity will traverse the +circuit when one end of the coil is heated in a flame. +If the other end be heated, the current will go in the +opposite direction. The twisting of the wire into +the coil produces a strain among the molecules that +changes the physical properties to a slight extent: the +density is altered. It therefore appears that in this +case, as in the cases with two different substances, we +have two \emph{physically} \DPtypo{diferent}{different} +bodies, though of +the same element. The +facts may be generalized +by saying that, %[** PP: Width-dependent break] +%[Illustration] +\index{Thermopile}% +\begin{wrapfigure}{l}{2.5in} + \Graphic{2.5in}{188a} + \Caption{17}{Diag.\ 17.---Thermopile.} +\end{wrapfigure} +whenever two differently +constituted bodies +are placed in contact +with each other, electricity +is generated, and +is maintained so long +as there is a difference +in temperature between +the junction and the external +ends. + +If one inquires for the +origin of such manifestation as the first case, when two +different metals are placed in contact, attention must +be directed to the actual molecular condition of the +two metals. Suppose them to have the same temperature,---as +they have different atomic weights their +vibratory rates cannot be the same,---and when the +surfaces are put in contact there must be a re-adjustment +\DPPageSep{189.png}{177}% +\index{Chemical origin of electricity}% +of their molecular motions, for each will interfere +with the other. This disturbance of molecular rates +is a disturbance in their relations of energy, and +furnishes the energy for the electrical phenomenon +that ensues. When equilibrium is restored, as it may +be shortly, there is no longer any electrical exhibit. + +When heat is applied so as to keep the junction continually +hotter than the other parts, the first effect is +continuous; for as each element has its own proper +vibratory molecular rate, which is increased by the +heat, the interference is kept up and an electrical current +results, which the heat is spent to produce and +maintain. One needs to have in mind what is signified +by heat as vibratory atomic, and molecular motion, in +order to clearly perceive what is expended in the +thermo-electric pile. The face of the pile, when it is +generating a current of electricity, does not acquire +that temperature it would acquire if it was prevented +from producing a current by having the wires detached. +Hence the amplitude of vibrations is lessened by the +electrical work done, and we may say that heat has +been converted into electricity, a thermal origin. + + +\Section{2. CHEMICAL ORIGIN.} + +When a piece of copper is dipped into a vessel of +water, and a wire leading from it is connected to a +proper electrometer, it is found to be electrified to a +certain degree. If a piece of zinc be substituted for +the copper, it too indicates a still greater degree; and +now let both be placed in the same water and connected +by a wire, and a current of electricity will flow through +\DPPageSep{190.png}{178}% +\index{Polarization of molecules}% +the wire, as in the case with the thermopile. This +current will be a transient one, or very slight, if the +water be pure; but if a little acid like sulphuric be +added to the water, the current may be relatively a +strong one. If, %[** PP: Width-dependent break] +% [Illustration] +\begin{wrapfigure}[11]{l}{1in} + \Graphic{1in}{190a} + \Caption{18}{Diag.\ 18.\break Galvanic Cell.} +\end{wrapfigure} +instead of the zinc and copper, any +other two metals be taken, the results will differ from +the former only in degree. Zinc and copper, +or zinc and carbon, are generally employed, +because those have been found to +give better results than other available elements; +and such a combination of metals, +with some solution, acid or alkaline, which +is capable of \DPtypo{disolving}{dissolving} one or both of the +metals, is called a galvanic battery. A single +\index{Galvanic battery}% +jar with its proper elements is called a cell; and by +the addition of cells additional effects may be produced; +that is, with two cells twice, and with ten cells +ten times the effect. + +As with the thermo-pair, one may inquire what conditions +were known to be present that could furnish an +antecedent to the electrical current that results. This +is answered by pointing out, as in the other case, that +there are two substances differing in their physical qualities, +copper and water, or zinc and water, and molecular +rearrangement at their junction must necessarily +result. More than this. It is known that the zinc and +oxygen have a strong affinity for each other. The oxygen +is combined with hydrogen to form the water, and +in water the molecules are without any definite arrangement: +they face in all directions, and move about with +the greatest freedom, with but little, if any friction. +\DPPageSep{191.png}{179}% +When zinc is placed in it, the attraction of the zinc for +the oxygen part of the molecule must result in making +every water molecule in proximity to the zinc swing +round so as to present its oxygen side to it. This orientation +of the liquid molecules is called their polarization. +The attraction between the two is not quite +strong enough to disrupt the water molecule; but the +addition of sulphuric acid weakens the attraction between +the hydrogen and oxygen, and enables the oxygen +to seize a zinc atom, and both combine with the sulphuric +acid to form the sulphate of zinc. Here we +have chemical reactions such as always result in exchange +of energy; for the sulphate of zinc has less +molecular energy than the zinc, the water, and the +acid, in the same way that carbonic acid gas has less +energy than the carbon and oxygen gas that formed +it. There has been, then, a molecular change accompanied +by the development, first of heat and second +the generation of electricity; for if the electrical current +be not allowed to flow, the battery cell will itself +heat up more than it otherwise would do. There are +chemical, thermal, mechanical, and electrical phenomena +here, which may be perceived by carefully thinking +of the successive steps in the process. The distinctive +thing here is to bear in mind what the characteristic +antecedents of the electrical phenomena are. What are +the chemical, the thermal, the mechanical factors, except +special forms of exchangeable molecular motions? +So one may say that in a galvanic battery chemism or +heat has been transformed into electricity. Though +the mechanism of transformation is different, yet the +same factors appear as in the thermopile. +\DPPageSep{192.png}{180}% + + +\Section{3. MECHANICAL ORIGIN.} +\index{Electricity, mechanical origin}% + +When a piece of glass or of wax is rubbed with a +cloth or catskin, the two substances subject to the +friction become endowed with a new property which +they do not otherwise exhibit. If a glass disk be +mounted so as to %[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{\linewidth}{192a} + \end{center} + \Caption{19}{Diag.\ 19.---Static Electrical Machine.} +\end{figure} +be rotated, and proper connections +made to it, as in the common Static Electrical machine, +a current of electricity may be maintained by maintaining +the friction, and all the electrical phenomena may +be produced that can be with electricity from any other +source. They are identical, but the source is the friction +of dissimilar substances. It will be recalled that +dissimilarity in substance was the condition in each of +the former cases; but in this, mechanical friction is the +\DPPageSep{193.png}{181}% +\index{Electricity, magnetic origin}% +\index{Stress, magnetic}% +second factor. In the chapter on heat it was pointed +out, and it is a familiar enough fact everywhere, that +heat is always the immediate result of friction. So in +this mechanical source, with apparatus so dissimilar in +all outward form to both thermopile and galvanic battery, +we still have precisely the same molecular conditions +that were operative in them to produce electricity,---two +dissimilar substances, and heat or a kind of motion +that results at once in heat. + + +\Section{4. MAGNETIC ORIGIN.} + +If a wire of any sort be placed across the pole of a +magnet, and held quiet there, no electrical effect will +be noted; but if the wire be moved toward or away from +the pole, it will become electrified, and if one end of it +be connected to an electrometer the movement of the +needle will indicate it. If the two ends of the wire be +connected to a galvanometer, whenever the wire is thus +moved in front of the magnet pole a current will flow +through the circuit, and the movement of the needle +this way or that will indicate the motion of approach or +recession. The strength of this current will vary with +the rapidity of the motion of translation of the wire +through the space in front of the magnet; and the wire +through which it goes becomes heated. This is the +same as saying that the mechanical motion of translation +of the wire is converted into heat in a manner as if +it had been subject to ordinary friction there; and as a +matter of fact, it is found to require more energy to +move the wire in such a space when the ends of the wire +are in contact, than it does when they are not. This +\DPPageSep{194.png}{182}% +\index{Electricity, electrical origin}% +shows that the material of the wire is subject to some +restraint under such conditions and in such positions, +and the degree of restraint depends upon the distance +it is from the magnet, as well as upon the strength of +the magnet itself. Hence the different parts of the +wire are in different physical states. And this is just +what is exhibited by the twisted wire in the case of +the thermal origin; and when motion is imparted to the +wire, the degrees of stress in it change, and a current of +electricity is the result. That such a stress is really +present in the wire can be proved in several ways, +which only need to be alluded to in this place. First, +the electrical resistance of a wire is greater when in +front of a magnet than elsewhere; and second, the +phenomenon known as Hall's, in which a current of +electricity going through a conductor is deflected from +its course in the neighborhood of a magnet. So we +have, in this magnetic origin, two bodies with different +physical constitutions and external motions impressed +upon them, which gives the electrical product +observed. + + +\Section{5. ELECTRICAL ORIGIN.} + +Imagine two wires parallel to each other and a foot +apart. If an electrical current from any source is made +to traverse one of them, a corresponding current will +be initiated in the other, but in the contrary direction. +In a like manner if a constant current be kept in one +of the wires, and the other one be moved towards and +away from the other, currents will be set up in it. +Their direction will depend upon whether the motion +\DPPageSep{195.png}{183}% +\index{Inductive action}% +\index{Stress, electrical}% +be approach or recession. The effect is the same +whether either or both move at the same time. The +effect is similar to the one described under the head of +Magnetic Origin, showing that in some way the space %[xref] +about a wire having a current of electricity in it is substantially +similar to that about a magnet. The process +is called electro-magnetic induction in both cases, and +the explanation is the same in this as in the other. It +will be well, however, to point out that there are steps +in this process that need attention for the sake of mechanical +clearness. + +Given say, an electro-magnet, through which a current +can be sent at will, and so be made magnetic, +and with the wire in front of it as before. There is +now no magnetism and no electricity in the wire. +Make the iron magnetic, and the current is at once induced +in the other. I say at once, but this does not +mean instantaneously. It takes a short time for the +effect of the magnet upon the ether to travel to the wire +and affect it. As no electricity escapes from the electro-magnetic +circuit, the electricity observed in the wire, +or second circuit, is generated in it, and the \emph{immediate} +antecedent of it was the stress in the ether which was +produced by the magnet. Hence an electrical current +can arise from a proper kind of stress in the ether, no +matter how that is produced, as one of the factors; the +other factor being motion of some sort, mechanical or +otherwise. The steps are, an electric current in a conductor, +an electro-magnetic effect of the current upon +the ether, the reaction of the ether upon the second conductor. +Let these steps be kept in mind always when +\DPPageSep{196.png}{184}% +thinking about inductive action, and there can then be +no confusion from trying to imagine how electricity +gets from one circuit to another when they are insulated +from each other. + + +\Section{6. PHYSIOLOGICAL ORIGIN.} + +There are certain kinds of fish that are capable of +giving powerful electrical shocks to men and animals. +They are provided with special organs for this purpose, +but they have not been the subject of much study for +several good reasons. First, they are only to be found +in a few localities, and are difficult to obtain; and second, +their electrical qualities cannot be studied except +when they are alive; and when they are living and +healthy their shocks can kill both men and animals, +and few are willing to incur the risk. Both mankind and +animals in general can give rise to electrical currents. +By grasping with the thumb and finger of both hands +the terminal wires from a delicate galvanometer, a current +is indicated,---a part often due to thermo-electric +action, and a part to physiological action,---and it will +vary with the tightness of the squeeze of contact and +the person experimenting, some developing much more +relatively than others. It also varies with the parts of +the body in contact with the wires. This physiological +effect is always extremely minute, and is not to be +mentioned beside the amount necessary to effect the +remarkable things said to be done by personal electricity, +such as moving chairs, tables, etc. I do not +think any one has been found whose physiological +electricity could do so much as raise a grain the tenth +of an inch. +\DPPageSep{197.png}{185}% + +The various processes continually going on in the +body, such as breathing, digestion, blood-circulation, +and muscular motions of all sorts, and under conditions +of different temperatures, different material, different +chemical reactions, are quite sufficient to account +for all that has been observed in this direction. + + +\Section{7. ATMOSPHERIC ORIGIN.} + +The origin of lightning, so far as details go, has +\index{Lightning}% +never been satisfactorily accounted for. It is obviously +not an affair that can be investigated in any very scientific +manner, for one can never control any of the conditions +when it arises. + +Some have thought it due to the condensation of +electrified vapor molecules condensing into drops of +water, the degree of electrification increasing with the +size of the drops. How the original electrification of +the molecules was produced is not explained by such. +There is no doubt but that a large amount of energy is +often involved in a stroke of lightning, judged by its +sudden destructive work. The immediate source of +this energy is the question\DPtypo{}{.} There is no doubt but +when a gas or a vapor is condensed into a liquid, a +notable amount of energy is liberated in motions of +some sort; for it requires energy to be spent upon water +to produce the vapor. This is given back when the +process is reversed. This energy has often been called +latent heat. If this process goes on faster than it can +be conducted away, it must either be transformed, or the +process must stop\DPtypo{}{.} We know, too, that heat motions +are most freely transformed into electrical by the phenomena +\DPPageSep{198.png}{186}% +\index{Electrical antecedents}% +\index{Terminology, electrical}% +of the thermopile and the galvanic battery, +and it is not improbable that this is the source of the +atmospheric electricity. It is certain that where it +originates there are two differently constituted kinds of +matter,---the air and the water; and it is equally certain +that there are some vigorous exchanges of motion, both +in the form of wind and heat, and these are the conditions +present in each of the cases where our knowledge +is most complete. + +One may then fairly conclude from the analysis of +all the known sources of electrical development, that +motion of some sort is the antecedent in every case. +This motion may be the sort called mechanical, or that +called molecular or atomic, as heat, but it is always a +factor; and the amount of electrical energy developed +in every case is equal to the \emph{immediate} mechanical, +chemical, or thermal energy which disappears when it +is produced. If one admits that the quantity of energy +in phenomena is constant, that the quantity of matter +is constant, there is but one variable factor, and that is +motion. If mechanical motion is transformable into +heat, and heat into electricity, and some known form of +motion is the invariable antecedent to the production +of electricity, it does not need a very profound logician +to say, \emph{so far}, the nature of electricity is known. + + +\Section{ELECTRICAL TERMINOLOGY.} + +Every particular science and art has some technical +terms to give precision and definiteness to its processes +and its laws, and the advances made in any science +depend very largely upon exact signification of its +\DPPageSep{199.png}{187}% +terms. The late rapid development of electrical science +is due in a large measure to terminology, adopted +about twenty-five years ago; for it enables a man not +only to know what he himself is talking about, but also +to understand others, and that was not the case before. +A system of units and names for them are matters of +the first importance. How these were derived need not +be stated here, but it is needful for every one now to understand +the significance of the more common of them. + +Imagine a wire in front of you with an electrical current +traversing it from left to right. If it travels in that +direction it is because the electrical pressure is less +towards the right than in the opposite direction, just as +water flowing through a pipe towards the right travels +thus because gravitative pressure is less in that direction +than in the other. Gravitative pressure is measured +in pounds, electrical pressure is measured in \emph{volts}. + +If the pressure at the left of the wire were increased +in any way, there would be an increased current of +electricity in the wire, just as there would be more water +go through the pipe if the head or gravitative pressure +were increased. The rate of water flow might be measured +as so many cubic inches or cubic feet per second. +The rate of electrical flow is measured in \emph{ampères}. + +If the water pipe were a large one, and the pressure +the same, more water would flow through it than if it +were a small pipe of the same length. In like manner +a thick wire will permit more electricity to flow through +it with a given electrical pressure than a thin one. The +water pipe is said to oppose friction to the movement +of water. +\DPPageSep{200.png}{188}% + +A conductor of electricity is said to offer resistance +to the flow of electricity. No name has been given to +any unit of frictional resistance, but electrical resistance +is measured in \emph{ohms}. + +A definite quantity of water flowing at a given rate +will be emptied from the pipe in a second or a minute. +So will a definite quantity of electricity go through +the wire in a second or a minute. The quantity of +water thus flowing would be measured as so many cubic +feet, or so many gallons; the quantity of electricity is +measured in \emph{coulombs}, a coulomb being an ampère per +second. Where the rate of flow of an electrical current +is given in ampères, the quantity will be found by +multiplying the ampères by the number of seconds the +flow has continued. Thus a ten ampère current in an +hour will have conveyed $10 × 60 × 60 = 36000$ coulombs. + +There are also measures of capacity. The cubic inch, +the cubic foot, the pint, quart, bushel, and so on, are +measures of volume or capacity: any of them may be +adopted as a unit, and when accuracy is required all are +reducible to the cubic inch as a standard. Thus in a +gallon there are $231$~cubic inches. + +In electricity the unit of capacity is called a \emph{farad}, +and it represents the capability of an electrical device +to receive and hold a definite amount of electricity +under the standard conditions of pressure. Thus, when +under a pressure of one volt it holds one coulomb, the +capacity of the apparatus is said to be one farad. +Actually a piece of apparatus of sufficient size to hold +that quantity has to be so enormously large that a much +smaller one was requisite for convenience, and consequently +\DPPageSep{201.png}{189}% +\index{Potential, electrical}% +the microfarad, or the one-millionth of the farad, +has been more generally adopted. + +As work may be got out of a flow of water, the +amount of work depending upon the pressure and the +rate of flow, so may work be got from an electric current, +the amount depending upon the pressure, volts, +and the current, ampères. The product of these factors, +volts into ampères, is called \emph{watts}; and the mechanical +value of one watt is such that $746$~is equal to +a horse-power, which, as before stated, is $550$~foot +pounds per second. The working power of a watt is +therefore $\dfrac{550}{746} = .735$ of a foot pound per second. + + +\Section{OHM'S LAW.} +\index{Ohm's law}% + +%[** PP: Putting upright variables in math mode] +This is simply that the current in an electric circuit +may be determined by dividing the electric pressure in +volts by the resistance in ohms. It is customary to use +symbols for each of these factors, $E$~or E.M.F. (electro-motive +force) for the pressure in volts, $R$~for the resistance +in ohms, and $C$~for the current in ampères, so Ohm's +Law when thus written reads $\dfrac{E}{R} = C$. Recurring to the +idea of a wire in front carrying a current of electricity +from the left to the right, and also the statement that +the electrical pressure is greatest at the left as the +cause of the current towards the right, it is well to +remark here that the electrical pressure at any particular +point in a circuit is sometimes spoken of as its +potential. If the potential at some other point in the +circuit be different from the first, the current will flow +\DPPageSep{202.png}{190}% +\index{Conductivity, electrical}% +from the higher towards the lower. The difference of +potentials may be measured in volts, and expressed as~$E$ +in Ohm's Law. + +There is a very wide difference among different substances +in their ability to transmit electricity. Some +transmit it freely, and are called good conductors; others +transmit it but slowly, and such are called poor conductors. +All solids, and liquids possess some degree of +conductivity; but some of them, such as glass, rubber, +and wax, are so poor in conductivity as to be called non-conductors. +The term non-conductor came into use +before the refined methods now in use for measuring +conductivity were known. It is now believed that +the only non-conductor of electricity is the ether. If +this be the case, then it appears that all the so-called +electrical phenomena in the ether are to be looked upon +rather as the results of electrified matter upon the +ether, than the presence of electricity in the ether, just +as radiations or ether waves are the results of actual +vibrations of atoms and molecules. Conduction, then, +is a general property of matter, and differs in degrees, +that difference depending upon both the kind of element +considered and its molecular combination. Thus, +copper is an excellent conductor; but if copper be +chemically combined with sulphur or with oxygen its +conductivity is greatly impaired. + +Conduction, too, implies contact, physical contact, +as in the case of heat; hence solids and liquids may +continuously conduct electricity, while gases can conduct +no faster than their individual molecules can move +in their free-path motions, and the rate of electrical +\DPPageSep{203.png}{191}% +\index{Ether, a non-conductor}% +loss is so slow from this source, that for telegraph lines +of hundreds of miles in length it is neglected as being +of no practical consequence. Neither is moist air +much better, and for the same reason. In all cases +where dampness appears to affect the working of electrical +apparatus, the loss is due to the moisture deposited +upon the surface of the apparatus, which thus +forms a thin conductive coating. A Leyden jar may +retain its charge for months if protected from a coating +of moisture, which, of course, it could not do if +either the air or the ether were conductors in any ordinary +sense of the word. + +The words conduction and conductivity represent the +property possessed by matter to become electrified by +mere contact with another body that is electrified; but +the terms do not have a very high scientific importance +now, for a much more convenient term is employed in +place, the term resistance, which is the reciprocal of +conductivity, that is, the greater the one the less the +other proportionally. The substance having the highest +degree of conductivity has the smallest degree of +resistance. Resistance is measured in ohms, and is of +two sorts; viz., specific and dimensional. Specific resistance +is that resistance which depends altogether +upon the nature of the particular element considered, +and may be determined for any element by measuring +the resistance of a cubic centimetre of it. + +Tables of conductivity and of resistance of wires +are common, and the following one gives the relative +values of a few of the elements for comparison. The +standard of conductivity being silver and reckoned as~$100$. +\DPPageSep{204.png}{192}% +\index{Conductivity, electrical}% +\index{Resistance, electrical}% +The standard of resistance being a column of +mercury $106$~centimetres long and one millimetre +square, which has a resistance of one ohm. The numbers +given are the resistances in ohms and fractions of +a wire $1$~metre long ($39.37$~inches) and one millimetre +($\frac{1}{\DPtypo{15.4}{25.4}}$~of an inch) in diameter. +\begin{center} +\TableFont% +\begin{tabular}{l<{\qquad}>{\qquad}r@{}l<{\qquad}>{\qquad}r@{}l} +\scriptsize\llap{SU}BSTANCE. & + \multicolumn{2}{c}{\scriptsize\llap{CONDU}CTI\rlap{VITY.}} & + \multicolumn{2}{c}{\scriptsize\llap{RE}SISTA\rlap{NCE.}} +\\ +Silver, & $100$& & &$.021$ +\\ +Copper, & $99.$&$9$ & &$.021$ +\\ +Gold, & $80.$& & &$.027$ +\\ +Aluminium, & $56.$& & &$.037$ +\\ +Zinc, & $30.$& & &$.072$ +\\ +Platinum & $18.$& & &$.116$ +\\ +Iron, & $17.$& & &$.125$ +\\ +Lead, & $8.$&$5$ & &$.252$ +\\ +German Silver,& $8.$& & &$.267$ +\\ +Hard Carbon, & $1.$& & $50$&$.00$ +\\ +Graphite & $0.$&$01$ & \multicolumn{2}{c}{Very variable.} +\\ +\end{tabular} +\end{center} + +The resistance of most liquids, and of such substances +as are used for insulating wires, is so very great +that they are given in units called megohms, each a +million ohms. The following represents the resistance +of a few bodies in such terms, the volume being one +cubic centimetre:--- +\begin{center} +\TableFont% +\begin{tabular}{l<{\qquad\qquad}r} +\qquad\scriptsize SUBSTANCE. & \scriptsize\llap{RESISTANCE} IN \rlap{MEGOHMS.} +\\ +Ice, & $284.$ +\\ +Water at freezing-point,& $150.$ +\\ +Mica, & $84.$ +\\ +Gutta Percha, & $450.$ +\\ +Hard Rubber, & $28,000.$ +\\ +Paraffine, & $34,000.$ +\\ +Glass, & $3,000,000.$ +\\ +Air, & Infinite. +\\ +\end{tabular} +\end{center} +\DPPageSep{205.png}{193}% +These must be read as so many millions of ohms. +Thus, ice\DPnote{** [sic], no verb} $284$ millions. Thus can be seen within what +wide limits this electrical property of matter ranges, +and also its significance as a factor in Ohm's Law, and +why some substances can be practically used as insulators +when in reality they possess a certain degree of +conductivity. Thus, glass is called an insulator. But +if there were a difference of potential or pressure on +opposite sides of a piece of glass one centimetre thick, +equal to $3,000000$ of millions of volts, there would be +a current of one ampère passing through for +\[ +\frac{3,000000,000000}{3,000000,000000} = 1 +\] +In no artificial way can we produce such a voltage as +that; but it is the opinion of some physicists that the +voltage of lightning may rise as high as some thousands +of millions. Under ordinary commercial voltages of +only a few thousands, the current would be insignificant. +Suppose it were $50,000$ volts, then +\[ +\frac{50,000}{3,000000,000000} = \frac{5}{300,000000} = \frac{1}{60,000000} +\] +of an ampère. + +Dimensional resistance is of more practical importance, +for by making a conductor larger its resistance +becomes less. When the cross section of a wire is doubled, +the resistance is reduced one-half. When the +diameter of it is doubled, it is reduced to one-fourth,---a +relation which may be stated as follows: The resistance +of a conductor varies inversely as its cross section, +or the square of its diameter if it be a wire; so by +making a relatively poor conductor large enough, it may +\DPPageSep{206.png}{194}% +\index{Electricity, activity}% +transfer as large a current as a much better specific +conductor of smaller dimensions. In the table it is +shown that the resistance of copper to that of iron is as +$.021$ to~$.125$, or that the latter is six times the former. +If, then, the section of the iron wire be made six +times larger, it will have the same degree of conductivity +as the copper. This means that one pound of +copper is worth nearly six pounds of iron for electrical +conduction; and whether the one or the other should +be employed in a given place depends chiefly upon the +relative costs. It is a commercial rather than an electrical +question. The resistance of all conductors varies +with their length. + +Temperature also affects the conductivity of nearly +all bodies. Some have their conductivity increased +by heat, as is the case with carbon; others have their +conductivity increased by cold. Thus, the conductivity +of copper at $100°$~below zero is increased nearly ten +times. + +An idea of the relative magnitude of the factor of +resistance in common electrical work may be gained by +knowing that a mile of ordinary electric arc-light wire +generally has a resistance of about two ohms; telegraph +and telephone wires five or six ohms, and often +more, per mile. If there be a current of ten ampères +going through a mile of wire that has a resistance of +one ohm, then Ohm's Law enables one to determine +what is the difference in pressure between the ends; +for $\dfrac{E}{R} = C$ and $E = RC = 1 × 10 = 10\text{ volts}$. So if any +two of these factors be known, the other may be computed. +\DPPageSep{207.png}{195}% +\index{Inductive action}% +The $E$~gives the available electrical pressure; +the $R$~gives the conditions under which it can work, +and the $C$~gives their resultant, the available current, +while the product of~$EC$ gives the activity, or rate at +which energy is expended in the circuit, while if this +product be divided by~$746$, the horse-power of the circuit +will be given. + +The further significance of Ohm's Law and its utility +will be given farther on, when considering the relation +of electrical energy to mechanical energy. + + +\Section{INDUCTION.} + +It has been pointed out that the term conduction +signifies the transferrence\DPnote{** [sic]} of electricity from one body +to another by contact,---contact in the sense that the +molecules of solids and liquids are in contact when they +cohere, and when their individual vibrations cannot take +place without mutual interference. It is found that +bodies become electrified by merely being in the presence +of another body that is electrified, without material +contact, and the more perfect the vacuum between +the bodies the more freely does this phenomenon take +place. As the electrified body that thus affects other +bodies in its neighborhood does not lose any of its own +electricity, does not share it with other bodies in any +degree, and as the other bodies lose their electrification +by simply being removed to a distance, and will recover +it again by being brought back, it follows that the +action is entirely distinct from the phenomenon of electrical +conduction. A similar body electrified by conduction +will retain its condition, and distance will make +\DPPageSep{208.png}{196}% +\index{Electrical field}% +\index{Fields, electrical}% +no difference. This kind of action is called \emph{electrical +induction}. To understand what changes take place, it +will be needful to attend particularly to the factors +present. Under the head of Electrical Origin of Electricity, %[xref] +it is pointed out that an electrical current may +be induced in a circuit adjacent to another circuit in +which a current is produced in any way; and here are +similar conditions and similar phenomena. Imagine an +electrified body freely suspended in the air. If a gold-leaf +electroscope is brought within a few feet of it, its +leaves will diverge; if brought nearer they will diverge +still more; recession will cause them to collapse. This +movement of the leaves can be produced indefinitely by +changing the distance of the electrometer from the +electrified body. It is important to note here that it +requires the expenditure of energy to move the gold +leaves, though the amount may be small. If it may be +done for an indefinite number of times, then the energy +spent may be indefinitely great; and that it is not +directly derived from the electrified body itself is certain; +for the latter loses by the process none of its electricity, +and cannot lose it except by conduction. Evidently +the body has in some way modified the physical +condition of the space about it so that another body +within that space is affected somewhat as it would be if +touched by an electrified body. But the property belongs +to the space itself, and cannot be extracted from it +so long as the electrified body remains in place. This +space about an electrified body within which other bodies +assume an electrical condition is called an \emph{electrical +field}. It may extend to an indefinite distance +\DPPageSep{209.png}{197}% +\index{Electrical stress}% +\index{Stress, electrical}% +from it, and its strength has been found to vary like +gravity, being inversely as the square of the distance. +This new physical condition into which the space has +been brought by the electrified body is known to be the +effect of the latter upon the ether, and is called its electrical +\emph{stress}. It is simply the reaction of the one upon +the other, and indicates that the molecules stand in +abnormal strained positions. A mechanical idea of +what it is like may be got by pressing the hand upon +the top of a table, and then producing a twisting strain +tending to turn the table round, but without moving it. +The whole table will be subject to a stress that will react +upon the hand, a condition which will, of course, be +retained by the table as long as such pressure is kept +upon it. For the hand substitute an electrified mass of +matter, and for the table the ether in any direction +about it, and one will have a fair conception of the +electrical field. Especially so, if he will add to it that +such twisting effect can be either right-handed or left-handed, +and so produce those distinctions known as positive +and negative, which run all through electrical +phenomena. + +A body brought into this distorted field of ether is +acted upon by the latter tending to twist its molecules +into new positions with reference to each other, which +is precisely the condition that brought about the original +stress, that is to say the electrical one, with this +difference, that if the original one was right-handed +the reaction of the ether would be left-handed, or +exactly opposite that of the inducing body. This is +simply because action and reaction are equal to each +other and \emph{opposite}. +\DPPageSep{210.png}{198}% +\index{Electrical waves}% + +One can now understand how it can be that bodies +can be electrified by induction without loss of electrification +by the inducing body. There are three steps in +the process. 1st,~The body electrified in any known +manner. 2d,~Its resultant stress in the ether. 3d,~The +reaction of the ether upon the second body, +inductively electrifying it. Electricity has not been +conducted by the ether, but a stress has been, and +the ether stress has electrified the second body. By +periodically electrifying and delectrifying a body, a +series of stresses will be produced about it which will +travel outwards as a succession of waves, the velocity +of which is the same as that of light, $186,000$ miles +per second, and the wave length of which will depend +upon the number of electrifications per second. Suppose +a sphere, like a cannon-ball in free space, to be +connected by wire, so that by pressing a Morse telegraph +key in connection with any source of electricity +it could be charged and discharged at will. If the key +was closed regularly once a second, the wave produced +would be $186,000$ miles long. If it could be +closed $186,000$ times per second, the wave would be +one mile long. And if it could be closed so often that +the wave length should be but the one fifty-thousandth +of an inch, there is every reason to believe that the +eye would perceive the waves as light; not so much +because the waves were produced by electrical means, +as that the eye is capable of perceiving ether waves of +that length, no matter how they may originate. + +The analogy between heat and electrical phenomena +in the ether is very close. The ether receives the +\DPPageSep{211.png}{199}% +energy from both sources and transforms it. The +ether is not a conductor of either heat or electricity: +it is neither heated nor electrified by them, but in each +case is simply a medium for the distribution of such +energy as gets into it according to its own laws, and +quite independent of its source. When heat gives up +its energy to ether it becomes ether waves or radiant +energy, and is no longer heat: it has been transformed. +When radiant energy falls upon other matter it is +again transformed into heat. In like manner, when +electricity gives up its energy to the ether, it becomes +radiant energy also, and when this falls upon other +matter it is again transformed into electricity. I have +been thus particular to enlarge upon induction, and +point out the factors present, in order to make it clear +how entirely distinct the electrical condition in matter +is from the electrical effect of it upon the ether. It is +from a failure to keep these distinctions in mind that +so many have been mystified by electrical phenomena, +and so many different theories have been propounded +as to its nature. + +In all our experience electricity originates in matter, +and whatever the particular character of the phenomenon +\emph{in matter}, it ought to have a different and distinct +name from the effect of such phenomenon upon the +ether. If such endowment of matter be called electricity, +then it is not proper to use the same word for +its stress, or wave effect, in the ether, and this for +precisely the same reason as is allowed to hold good in +heat phenomena. Formerly ether waves were called +heat, afterwards heat waves, now radiant energy, for it +is known that there is no heat in the ether. +\DPPageSep{212.png}{200}% + + +\Section{EFFECTS OF AN ELECTRICAL CURRENT---1. MAGNETISM.} + +If a wire through which a current of electricity is +passing be twisted into a loop or ring, it is found that +the loop acts in all ways like a magnet. Its sides have +polarity; and if it be so mounted as to be free to +assume any direction, it will move so its sides face the +north and south. If a piece of iron be placed in the +ring, the magnetic effect will be greatly strengthened. +Soft iron, however, loses its magnetic property as soon +as the current stops. A piece of steel will retain some +portion of the magnetic condition, and so is called a +permanent magnet. A given current of electricity +will make a much stronger magnet of a piece of soft +iron than it will of a piece of steel, and this is explained +by saying that the iron is more \emph{permeable} to +magnetism than steel is. Once in possession of a +magnet, one may proceed to study its physical properties +in many ways. That a magnet possesses poles; +that it can attract and hold to itself iron, steel, nickel, +cobalt, and affects other substances but slightly; that +it is attractive to unlike poles of other magnets, and +repulsive to similar poles,---and so on, are phenomena +so widely known that they need not be described here. +Only such phenomena will be considered as will be +helpful to an understanding of the constitution of a +magnet, and its relation to electricity and to the space +about it. + +The magnetism of a magnet seems to reside chiefly +near its ends, for these will sustain bits of iron, but +near the middle it will not; and when a small compass-% +\DPPageSep{213.png}{201}% +needle is moved around a bar magnet, it points towards +one end or the other, except when near the middle, +where it sets itself parallel. When such a bar magnet +has a sheet of paper laid upon it, and iron filings are +sprinkled upon the paper, the filings are arranged in +curious curved lines, starting from one pole and traceable +to the other, and quite around the magnet on both +sides. This %[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbt] + \begin{center} + \Graphic{3.5in}{213a} + \end{center} + \Caption{20}{Diag.\ 20.---Magnetic Lines.} +\end{figure} +arranging power of the magnet extends in +every direction about it, as one can satisfy himself by +trying the same experiment with the magnet turned on +different sides. If one will compare the direction of +these lines of filings with the positions of the needle, +he will see that the needle assumes the same direction +at any given place. Near the poles the lines all converge +to it, and opposite the middle the lines are parallel +with the magnet. If the magnet be of a U~or +horse-shoe form, the lines will be found still to extend +from one pole to the other, some straight, some curved +\DPPageSep{214.png}{202}% +\index{Fields, magnetic}% +outwards, but always forming a curve such as to touch +each pole of the magnet. While the filings are in the +position described, let the paper be gently tapped with +a pencil so as to jostle them slightly, and they will +begin to close up in such a way as always to shorten +themselves, and presently they will form a dense mass +between the poles, adhering to the latter as a solid +piece of iron would do. + +Such phenomena show that the magnet in some way +reacts upon the space about it, so that iron and other +magnets there are affected, just as an electrified body +affects the space about it, as has been described. This +space about a magnet within which such effects are +produced is called the \emph{Magnetic field}, which may be +\index{Magnetic field}% +said to be the stress in the ether produced by a +magnet. Like the electric stress, it extends to an +indefinite distance from the magnet, and travels with +the velocity of light; so if a magnet was charged and +discharged once a second, a wave motion would be set +up: the wave length would be $186,000$ miles long, and +if it could be charged and discharged so fast that the +waves were but the one fifty-thousandth of an inch in +length, it is very probable they would be perceived as +rays of light, and the magnet would be a luminous +body. Such waves are called electro-magnetic waves. +\index{Magnetic waves}% +At present the shortest waves of this sort, that can be +artificially produced, are several inches long, but it +seems highly probable that before long some way will +be discovered of making them of the required length +for vision. + +If a test-tube filled with iron filings be held near a +\DPPageSep{215.png}{203}% +delicate suspended magnetic needle it will be found to +give no indication of polarity, one part will act just +like any other part, and the magnet will be equally +attracted. Bring the test-tube against the poles of a +strong magnet for a few seconds, and then it will be +shown that the filings have become magnetic, and now +one end of the tube will attract one pole of the needle, +while the other end will repel the same end. Shake +up the filings well, and the polarity will be destroyed. + +Stir up iron filings with melted wax, and pour into a +paper mould, so as to form a stick the size of the finger, +or larger. If this be tested for magnetism, it will be +found without any; but magnetize it as if it were a +piece of steel, and it will be found to retain it, becoming +a permanent magnet. If a layer of iron be electrically +deposited upon a brass wire in a magnetic field, +the wire acts like a magnet. All these phenomena go +to show that what is called polarity or magnetism is +due to the \emph{positions of the molecules}, rather than upon +some sudden endowment which the molecules receive +and may lose. Imagine every molecule of iron to be +a magnet, having its poles or faces, then if in a mass +of them, such as makes up a piece of iron or steel, +all be made to face one way and keep such position, all +will act in conjunction to give polarity to the mass. +When some molecules face one way, and others adjacent +to them face the opposite way, they will but +neutralize each other, so the external evidence of +magnetism will be destroyed. How atoms may be +magnets and exhibit polarity may be imagined by considering +the phenomena of vortex rings again. In the +\DPPageSep{216.png}{204}% +ring all the motion on one side is towards the middle +of the ring inwards, on the other side all the motion is +outwards, so the properties of the two sides are opposite. +Each such ring must have its own \emph{field}, which +may extend to an indefinite distance from it, and may +be represented roughly by the diagram in which the +curved lines show the same features before described +as belonging to a magnetic field. When two or more +\index{Magnetic field}% +are facing the same way, and are in contact, these lines +cannot re-enter the ring except by going round the +second one; and when many are in line they must go +round them all, in which case the %[** PP: Width-dependent break] +%[Illustration] +\begin{figure}[hbt] + \begin{center} + \begin{minipage}[b]{1.25in} + \Graphic{1.25in}{216a} + \Caption{21}{Diag.\ 21.---Field of a Ring.} + \end{minipage} +% + \begin{minipage}[b]{1.5in} + \raisebox{12pt}{\Graphic{1.5in}{216b}} + \Caption{22}{Diag.\ 22.---Coinciding Fields.} + \end{minipage} +% + \begin{minipage}[b]{1.25in} + \Graphic{1.25in}{216c} + \Caption{23}{Diag.\ 23.---Opposing Fields.} + \end{minipage} + \end{center} +\end{figure} +direction of the lines +will be precisely those observed about a straight bar +magnet. +\Pagelabel{105} %[** PP: Label to p. 105 seems to point here] + +When they all face one way, as in diagram~22, the +resultant will be at~A, the sum of the outgoing movements, +and at~B, the sum of the ingoing ones, and +polarity at A and~B will be at a maximum. If they face +in different ways, each will tend to cancel the other, +and there will be no external field; as in diagram~23. +\DPPageSep{217.png}{205}% +\index{Ether pressure}% + +If two such atoms be brought face to face, each will +be blowing against the other; their fields overlap, and +the stress is increased between them, and they are +crowded away from each other,---a phenomenon called +repulsion. The opposite condition obtains when they +face the same way and are near together, with the +result that the stress is lessened between them, and +they are pushed together by it; and this is called +attraction. + +There has been growing the conviction for a long +time that the atoms of all substances are magnetic; but +\Pagelabel{205}% +when they combine into molecular groups they are +turned about so their magnetic fields neutralize each +other, and thus it happens that most molecular compounds +show no polarity. But every substance whatever +is attracted by a magnet, and will move up to it if +the magnet be a strong one. Brass, lead, stones, oats, +corn, and wood will all be affected alike by a strong +magnetic field, being pushed towards the magnet in the +same way as iron, though not in the same degree. The +pressure of iron against a magnet, due to the magnetic +field, may be as great as a thousand pounds per +square inch. + +When a piece of iron is brought near to a magnet, +and it becomes a magnet by induction instead of by +contact, it is to be understood that its molecules are +rotated into similar positions by the action of the +magnetic field upon it, not that magnetism has gone +from the magnet to the iron; and when it requires a +pull, and therefore work, to move a piece of iron away +from a magnet, it is against the ether the work is done. +\DPPageSep{218.png}{206}% + +It was stated at the outset that a loop of iron through +which an electric current is passing is a magnet, and +previous to that it was pointed out that an electric %[** PP: Width-dependent break] +%[Illustration] +\begin{wrapfigure}{l}{1.75in} + \Graphic{1.75in}{218a} + \Caption{24}{Diag.\ 24---Iron Filings about Electric Current.} +\end{wrapfigure} +current in a wire has a field +that extends indefinitely out +from it. If such a wire be +dipped in iron filings, they +form rings round it, showing +that the polarity is at right +angles to the wire. Now, if the wire with the iron +filings clinging about it be made into a loop, it will +be seen at once how the polarity of the different +segments is all in one direction inside the ring, and +opposite to that on the outside the ring, and the +structure will be a forcible reminder of a vortex ring. +If several similar turns be taken in the wire, and they +all be brought near together so as to form a helix, it +will also be seen that these conspire together to set a +boundary to the field on the inside, but allow indefinite +expansion to it outside; so if one should draw the lines +for it as iron filings would be arranged by it, he will +have the precise lines of a magnet, while the ring +structure will be, on a large scale, just +what was described on an atomic scale +as constituting a vortex ring magnet; +and the only thing lacking to complete +the analogy is the conception of a rotary +motion in the wire at right angles to its length. + +%[Illustration][** PP: Moved down to avoid LaTeX warning] +\begin{wrapfigure}{r}{1.25in} + \hfil\Graphic{1in}{218b}\hfil + \Caption{25}{Diag.\ 25.---Adjacent Turns.} +\end{wrapfigure}It has been found that when a current has been +started in a conductor, a torsional impulse is given to +the latter in such a sense that if one looks along it in +\DPPageSep{219.png}{207}% +the direction of the current the twist is in the direction +of the hands of a clock. So there is direct confirmatory +experiment showing that the nature of the motion in +an electric circuit is rotary in such a way that the +whole circuit may be considered as a vortex ring; and +as it is the matter of the conductor that is thus rotated, +it follows that electrical current motion is rotary, as +heat motion is vibratory. + +Allusion has been made to the opinion now current that +ether waves or light are electro-magnetic phenomena. +\index{Ether waves, their source}% +\index{Light waves}% +\index{Magnetic waves}% +How this can be may be understood by considering a +magnet of any form, with its surrounding field. If the +form of the magnet be changed, the shape of the field +will be correspondingly changed; and as this extends +out indefinitely into space, it follows that a succession +of changes of form would set up waves through the +whole of that space. Now, a magnet is an elastic body, +and if it be struck it will vibrate and produce a sound. +The vibration implies a change of form, and that in +turn a set of waves radiated into space. As the field is +an ether field, the waves will be ether waves. Now +assume that atoms are themselves elastic magnets, each +with a field indefinitely extended, and it follows that +the vibrations produced by impact, or in any other +manner, will set up corresponding waves in the ether, +the wave length depending upon the vibratory rate of +the atoms. Thus ordinary radiant energy, or light, +would consist of undulations in a magnetic field. + +Of course it will be perceived that vibrations of any +electro-magnetic body, large or small, would induce +similar waves, differing only in wave length, so there +\DPPageSep{220.png}{208}% +\index{Magnetic induction}% +would be in the ether wave lengths of all dimensions, +\Pagelabel{208}% +from the shortest possible to those millions of miles +long. It is now an important physical problem how to +produce such that shall be of the dimensions capable of +affecting the eye. + +\Subsection{Induction Coils.} +\index{Induction coils}% + +One or more loops of iron, through which a current +of electricity is flowing, is an electro magnet. When +iron is placed in the loop, it condenses the magnetic +field, and it may be made as much as thirty times +stronger than it would be without the iron. When a +magnetic field is produced inside a loop of wire, the +reverse effect %[** PP: Width-dependent break] +%[Illustration] +\begin{wrapfigure}{l}{1.75in} + \Graphic{1.75in}{220a} + \Caption{26}{Diag.\ 26.---Electro-Magnetic Induction.} +\end{wrapfigure} +happens, and a +current is generated in the +opposite direction. Suppose +a short rod of iron to have a +single turn of wire at each +end about it, one of them, +as~A, to be so connected to a source of electricity +that a current through it may be produced by closing a +key, the other one to be a closed circuit, as shown. If +a current be established through~A in one direction, a +current will be induced in~B, as indicated by the arrow. +There will be in the loop of the A~circuit a certain +electro-motive force,~$E$. A nearly equal electro-motive +force will be induced in loop~B. If there were two +loops at~B instead of one, the electro-motive force would +be twice that in~A, and for $n$~turns it would be $n$~times. +The current in~B will depend upon the resistance in its +circuit; that is, it will be $\dfrac{E}{R}=C$, according to Ohm's +\DPPageSep{221.png}{209}% +Law. The size of the wire in B~circuit will not make +any difference in the value of~$E$ in it. That value will +depend only upon the magnetism of the bar, and the +magnetism in the bar will be measured by the product +of the current into the number of turns of wire in +the circuit~A. And this product is called the \emph{ampère +turns}. The ampère turns will be nearly equal in the +\index{Ampère turns}% +two circuits. This process of obtaining electrical +currents in a second circuit by two transformations is +of great use in the electrical industries, and the device +is called an induction coil or transformer. The charging +circuit is called the primary, and the discharging +one the secondary. By making circuit~A of a small +number of turns of thick wire, so as to allow strong +currents in it, and having circuit~B consist of a great +number of turns, the electro-motive force may be +raised almost indefinitely. Suppose there be $100$~turns +in the \textit{A}~circuit,\DPnote{[** Italicized in orig, not sure why]} and a hundred thousand in the \textit{B}~circuit, +then for every volt in the A~circuit there may be +nearly a thousand volts in the B~circuit; and this is the +construction in those instruments known as induction +coils, with which so called jumping sparks are produced, +and represent sometimes a million or more volts. On +the other hand, it is sometimes desirable to change a +high electro-motive force to a lower one; and this may +be done by reversing the connections and making the +primary current go through a great number of turns, +and taking the induced current from the smaller number +of turns in the other circuit. Definite reduction in +either way may be effected by making the ratio of the +number of turns in the two circuits the reduction +\DPPageSep{222.png}{210}% +\index{Electro-magnets}% +\index{Welding, electric}% +wanted. That is to say, if there are $100$~volts in +the primary circuit, and only ten are wanted, make the +secondary of one-tenth the number of turns in the primary. +If a thousand volts are wanted, make the secondary +with ten times the number of turns in the primary. +It should be remembered, also, that two turns of wire in~B +have twice the resistance of one turn, and the current +induced will be reduced to one-half. If there be one +hundred turns, it will be reduced to one-hundredth and +so on. Hence, in the large induction coils for high electro-motive +forces, the current is necessarily a small one, +while in the transformers in which the reduction is to +lower values of~$E$ than are in the primary, the current +may be very great indeed. This is the case in Thompson's +Welding Apparatus. The secondary has but a +single turn of heavy copper, while the primary has many +thousands, and the current in the secondary may be +thousands of ampères. As the heating effect is proportional +to the square of the current, it is plain that +such large currents have enormous heating power. + +All such devices require either intermittent or alternating +currents to operate them, for there is no induced +current in any circuit when the inducing magnetism is +not changing. A constant magnetic field induces no +electrical changes. + + +\Subsection{The Electro Magnet.}\DPnote{** [sic] No hyphen} + +This is generally considered as consisting of a helix +of insulated wire about a piece of soft iron, and may be +either a straight bar, or crooked in any convenient form, +its function being to produce a magnetic field when a +\DPPageSep{223.png}{211}% +current circulates in the wire, and to lose it when the +current stops. This it does only partially, for all iron +when once it has been magnetized becomes more or less +permanently magnetic; hence there is only a difference +in degree between an electro magnet and a permanent +magnet. Until within a few years the electro magnet +had its most extensive field of usefulness in telegraphy. +It was combined with a piece of soft iron near its poles +called its armature, which was so mounted that the +magnetic field made it to move towards the magnet, and +a retractile spring pulled it away when the field was +absent. The movement of the armature was employed +to receive signals. In some cases the movement recorded +itself, and sometimes its prompt motion produced +a sound, a succession of these being arranged into a +telegraphic alphabet. + +If one has a good idea of a magnetic field and its +action upon a piece of iron in it, he will be able to +understand all the various combinations of forms and +functions of electro-magnetic devices, however much +they may apparently be disguised. Thus, the magnetic +telephone is an electro magnet with an armature +\index{Telephone}% +of such size and flexibility as to be capable of much +quicker movements than ordinary telegraph instrument +\index{Telegraph}% +armatures, the whole boxed so as to be convenient +to hold to the ear. A common telegraph sounder +acts in precisely the same way, though not so well, for +the armature is too heavy, and one cannot concentrate +its effects upon the ear on account of its form. An +electric bell also produces its ring by having a hammer +fixed to the armature, so as the latter moves in response +to the electric field it strikes the bell. +\DPPageSep{224.png}{212}% +\index{Motor, electric}% + +An electric motor, in the largest sense, consists of a +device for transforming electric into mechanical motions; +and the relation sustained between an electro +magnet, its field and an armature, is such as to do it +directly. A telegraph sounder is thus a simple motor, +for the armature moves visibly in response to the electric +current. If a wire be wound about the armature, +there is an induced current in it, as in an induction coil, +and for the same reason; and the movements of the +armature towards and away from the poles of the electro +magnet, called sometimes the field magnet, give +rise to currents in the armature coil. If a current +from another source is sent through the armature coil, +it gives polarity to the armature itself, and the reaction +between it and the poles of the field magnet is still +stronger, and the mechanical motions are still more +energetic. The armature thus wound with wire is obviously +an electro magnet itself, and when it is so +mounted as to be capable of rotating between the poles +of a fixed electro magnet, a continuous rotation may +be kept up. + +The current in the fixed magnet is steady, and therefore +maintains a steady magnetic field. The current +in the armature magnet is changed in direction by the +motion of the armature itself, and is effected by a device +called a commutator. The efficiency of such a +motor may be as high as $90$\%~or more. That is, for +every horse-power of electrical energy turned into it, it +will give back nine-tenths of a horse-power in actual +work. The small space they occupy for the working +capacity, when compared with a steam-engine for the +\DPPageSep{225.png}{213}% +\index{Efficiency of machines}% +same work, the small amount of attention they require, +and their freedom from the dirt inseparable from an +engine, commend the electric motor as a substitute +for the engine in most places where power is wanted +and an electric current can be had; for it is to be +remembered that fifty horse-power can travel through +a wire that can go through a gimlet-hole, while a steam-plant +for the same work would require a large boiler +and engine as well as a big chimney. + +When the armature of a motor is made to turn by +mechanical means, the shifting positions in the magnetic +field develop electric currents in its coils. Such +an armature cannot be turned as freely when the field +magnet has a current in it as it can when it has not, +and the energy spent in making it turn appears as a +current. The device is called a dynamo, which may be +\index{Dynamo}% +said to be a machine for transforming mechanical motion +into electrical motion. The steps are mechanical +motion, magnetic field, electrical current; while in the +motor they are simply the reverse,---electric current, +magnetic field, mechanical motion. + +The efficiency of a dynamo is very high indeed. It +can transform~$95$\% of the power applied to it into +electrical power, and in this particular it is one of the +most perfect machines in existence. There is absolutely +no room for any important improvement in the +dynamo as regards its efficiency. A good steam-engine +may transform ten to fifteen per cent of the energy +turned into it. A windmill may give fifty, a turbine +water-wheel ninety, but when a dynamo gives ninety-five, +it shows that the coming man has a margin of but +five per cent for improvement in its efficiency. +\DPPageSep{226.png}{214}% +\index{Energy. What determines transfer}% +\index{Fields, magnetic}% +\index{Lighting, electric}% +\index{Resistance, electrical}% + +Thus the magnetic field, which is simply the ether in +\index{Magnetic field}% +an abnormal condition of stress, is the common agency +between mechanical motions and electrical phenomena, +and transfers energy one way or the other. All that +determines whether it shall be one way or the other is +simply which side has the excess of energy; for energy +of a particular sort always goes from the body having +more to one having less. Which side has the excess +is determined solely by the mechanical conditions +present. + + +\Subsection{Electric Lighting.} + +An electric current always heats the conductor +through which it is passing. The amount of heat depends +upon the strength of the current, and varies as +the square of it. In a given circuit with a uniform current, +the current has the same value, and therefore the +same heating power, in every part of that circuit; but +the temperature to which a body will be raised by a +given current depends upon its own constitution, its +size and electrical resistance. Connect together three +wires of copper, iron, and platinum, each a foot long, +and of the same diameter, and make them a part of the +same circuit, so that the same current shall flow through +them. If the current be increased gradually, the iron +wire will grow appreciably warm, more current will +make it hot; platinum wire will be only warm; +while the copper wire will not have its temperature +much changed. Still more current will make the iron +red-hot, the platinum uncomfortably hot, and warm +appreciably the copper; and more current will fuse the +\DPPageSep{227.png}{215}% +\index{Electric lamps}% +iron, perhaps make the platinum red-hot, but the copper +may not yet be uncomfortably hot. This heating +effect in a given wire is found to be proportional to its +resistance: the iron wire having the greater resistance +is most heated, and the copper having least, is least +heated; hence to obtain a high temperature with a +given current, a conductor must be chosen that has a +relatively high resistance. Resistance, however, varies +with the cross section inversely, so a small wire must +be taken if the temperature of incandescence is to be +reached with a small current; and a current that will +raise half an inch of a wire to a white heat will raise a +mile, or any other length of the same wire, to the same +temperature; but the longer a wire is, the higher must +be the electro-motive force in order to get the same +current. For a given length of a wire the electrical +energy spent in it will be found by multiplying its resistance +by the square of the current,~\DPtypo{$RC,^2$}{$RC^2$,} which will +give the products in watts, of which $746$~equal a horsepower. +Metals are liable to fuse and become useless, +so that wires of carbon, made by heating organic fibres +in the absence of air, as in making charcoal, are substituted +for metals. They fuse only at extremely high +temperatures; and being enclosed in a vacuum in bulbs +of glass they cannot burn up as carbon does when exposed +to the air when red-hot. This is the electric incandescent +lamp. Most of them are so prepared that a +current of about three-fourths of an ampère is required +to properly light them, and this will be got when the difference +of potentials between the lamp terminals is kept +at a certain figure, so that lamps are specified by the +\DPPageSep{228.png}{216}% +number of volts they require, rather than the current; +thus there are $50$~volt lamps, $110$~volt lamps, and so on. +Now, such lamps take ordinarily about four watts for a +candle, so a twenty candle-power lamp requires eighty +watts, and that means $\dfrac{746}{80}=9.3$ such lamps to the +horse-power. Such lamps may last for a thousand or +more hours. If a stronger current be used, they shine +brighter, but their life is shortened. There is a process +of slow disintegration going on in these lamps +all the time. The surface molecules slowly evaporate +under the vigorous vibratory movements present, and +the carbon vapor thus formed sticks to the inside surface +of the bulbs, giving them the familiar blackened +appearance. + + +\Subsection{The Arc Light.} +\index{Arc light}% + +If an electro-motive force of forty or more volts be +maintained in a circuit, and the circuit be broken at +some place and the ends separated a small fraction of +an inch, the current does not cease, and is maintained +between the ends by what is termed an arc, where the +temperature is so very great that almost all substances +are reduced to vapor at once. All metals are fused and +dissipated there. Carbon does not fuse there, but is +slowly burnt up. The ends of the carbon reach a temperature +higher than can be reached in any other +known way, and the light they then give out is called +the arc light. The rate of expenditure of energy in +that small space where the brightness is, is generally +some less than a horse-power. The current employed +\DPPageSep{229.png}{217}% +\index{Mars, signalling to}% +is about nine and a half ampères, and the electro-motive +force about forty-five volts; hence $9.5 × 45 = 427.5$ +watts, and such a lamp may be equal to $800$~candles, +though they are generally rated as $2,000$ candle-power. + +By increasing the current the brightness increases, +and there is no especial limit to the amount of light +that may in this way be produced. With parabolic reflectors +the light may be concentrated into a powerful +beam. The inhabitants of Mars could see such a one, +and it could be used for signalling between the two +planets if the Martians had a similar one. + +Seeing that the temperature to which a given conductor +can be raised by a current is determinate, one +can arrange for heating on any scale. There is no +other reason than the relative cost of electric heating +compared with the ordinary method with fuels, why it +should not be in common use to-day. In most places +the dynamo for the production of the current would be +run by a steam-engine, requiring in its turn a furnace; +and it is cheaper to use the fuel direct for heating, than +to transform the energy so many times, each time with +some loss. A common furnace is much more economical +of energy than a steam-engine. But if ever electricity +is obtained directly from combustion in an economical +way, as there is some reason for thinking possible, +electrical heaters will displace stoves and the common +furnaces in the house. So the same current that +lights the house will serve for cooking and warmth. +\DPPageSep{230.png}{218}% +\index{Water decomposition}% + + +\Section{2. CHEMICAL EFFECTS.} +\index{Chemical effects}% + +When a current of electricity is passed through +conducting liquids capable of being decomposed, such +as acidulated water, and solutions containing more or +less of the metallic elements, decomposition of the solution +results, with the additional curious phenomenon +that one of the elements of the decomposed compound +appears at one terminal, and the other element at the +other. Thus, if water be the liquid, hydrogen appears +at one place and the oxygen at another. If the two terminals +of an electric circuit were on opposite sides of the +Atlantic Ocean, and a current were sent through the +circuit, hydrogen would appear on one side and oxygen +on the other. The oxygen is set free at that terminal +at which the current reaches the liquid. The direction +of the current being determined in the ordinary conventional +way. Bring the wire carrying the current over +and parallel to a suspended magnetic needle. If the +current be going from south to north, the north pole will +be deflected to the west. If the current be going from +north to south, the south pole will be deflected to the +west. Hence, if one looks along a wire in the direction +of the current, oxygen will be given off at the next +terminal if it dips in water. It may be convenient to +know that when a battery is employed as a generator of +electricity, hydrogen is set free at the terminal of the +battery from which the current flows, and oxygen at +the other end of that conductor. + +The decomposition of water may be taken as a type +\index{Decomposition of water}% +of electro-chemical work; hence, when the mechanical +\DPPageSep{231.png}{219}% +\index{Dissociations}% +\index{Polarization of molecules}% +conditions present where decomposition is going on are +understood, they may be applied to any other case. + +Under the head Chemical Origin of Electricity it %[xref] +was pointed out that the same factors which gave rise +to the current also arranged the molecules of the liquid +so that the oxygen sides of them all faced the same way, +towards the zinc, which of course necessitates that the +hydrogen sides should all face in the opposite direction. +The other terminal of the battery tends to bring about +a similar condition of things, so that between the terminals +the molecules are all polarized or brought into an +orderly arrangement. The direction of the electric +current in such an arranged body of molecules in the +liquid is from the zinc to the oxygen---oxygen, hydrogen, +oxygen, hydrogen, and so on to the last molecule +in the line, the hydrogen face of which is against the +other terminal. So far this represents molecular arrangement, +not molecular or atomic cohesion. There +is good reason for thinking that dissociation of atoms +in such molecules is going on all the time in some +degree, on account of their incessant and vigorous vibratory +motion. Such motion must tend to disrupt +the atoms so that at any given instant there would be a +relatively large number of atoms in the liquid already +free and quite indifferent as to whether they recombine +with the same or other atoms the next instant. If there +be another agency present, like an electrical current, +adding its energy tending to disruption, not only would +a larger amount of dissociation take place, but when at +one end of the line one element of the molecule, like +oxygen, enters into a new combination which is more +\DPPageSep{232.png}{220}% +stable under the conditions present, the remaining hydrogen +will combine with the oxygen of the adjacent +molecule when that molecule is broken up, and so on +along the whole line, leaving the hydrogen of the last +liquid molecule to be freed against the other plate of +the battery. This means that there is an exchange of +partners among all the molecules of the liquid that take +part in the current, else some of both oxygen and hydrogen +would be set free elsewhere than at the terminals, +which never happens. + +Now, all molecules are combinations of atoms in +definite proportions by weight, and it is therefore to be +expected when such decompositions as the above take +place the products will be found in the same proportions. +It is the necessary outcome of the operation. So for +every one part by weight of hydrogen set free, eight +parts of oxygen will be liberated; and for a like reason +twice the volume of hydrogen as of oxygen. + +If a current of electricity be led through any liquid +which it can decompose, and the material of the terminals +be some substance that neither of the constituents +of the molecule can combine with, both of the elements +will be set free. Platinum is such an element; and if +terminals be made of that, and dip into a tank of water, +the current polarizes the molecules precisely as in the +battery, and decomposition takes place in the same way,---oxygen +being set free at the in-going terminal, and +hydrogen at the out-going one. If the solution contains +molecules of metallic salts of copper, nickel, iron, silver, +gold, etc., the metallic side of the molecule faces in the +direction of the current, the same as the hydrogen in +\DPPageSep{233.png}{221}% +\index{Plating, electro}% +the former case; and as a consequence, the metal is deposited +upon the out-going terminal, whatever that may +be, and the other constituent of the molecule is set free +at the in-going terminal. For example, the sulphate of +copper is a compound of copper and sulphuric acid. +Where it is subject to decomposition by an electric +current, the copper is deposited at the one terminal, and +sulphuric acid at the other. If both the terminals be +made of platinum, one will be covered with copper, and +the other will be surrounded with the acid, and all the +copper in the solution may be taken out. If the in-going +terminal be itself of copper, the sulphuric acid +set free will itself dissolve off the copper as fast as the +acid is set free, and in this way the solution will be kept +saturated. The metal may be deposited on any other +metal. It is in this manner that electro-plating of all +sorts is done. Each different metal requires different +treatment from the others as to solution, electro-motive +force, current per square inch section, and so on for the +best results. To decompose water, as much as one and +a half volts are necessary to initiate it, but copper salts +require only a small fraction of one volt. The amount +of decomposition in a given time, say a second or an +hour, depends upon the current employed. A current +of one ampère will in an hour decompose only about +fifteen and four-tenths grains of water, liberating one +and seven-tenths grains of hydrogen. The weight of +other elements set free or deposited by an ampère per +hour is determined by multiplying the weight of hydrogen +set free by the electro-chemical equivalent of the +element, and this is either equal to its atomic weight, or +\DPPageSep{234.png}{222}% +\index{Lighting, electric}% +is one-half or one-third that. Thus, the electro-chemical +equivalent of gold is $\dfrac{196.6}{3} = 65.5$, of silver $\dfrac{108}{2} = +54$\DPtypo{}{,} of copper $\dfrac{63}{2} = 31.5$, of nickel $\dfrac{57}{2} = 28.5$, and so on. +So the amount of gold that will be deposited by an +ampère in an hour is $1.7 × 65 = 111.35$ grains; of silver +$1.7 × 54 = 91.8$ grains and so on. This shows a +definite relationship between electricity and chemical +reactions. + +It is to be kept in mind that when substances combine +there is always some transformation of energy, +and heat is either absorbed or given out. When +hydrogen and oxygen combine there is a large amount +given out, $61,200$ heat units for each pound of hydrogen. +When, therefore, water is decomposed so as to +set free one pound of hydrogen, the same amount of +energy must be spent to do it. The electrical energy +spent in a decomposing cell is, therefore, reducible to +the heating effect, and may be calculated as such. + + +\Section{3. LUMINOUS EFFECTS.} +\index{Luminous effects}% + +When an electric current passes from one conductor +to another through the air an electric arc is produced, +and great heat and light are developed there. An arc +is generally about an eighth of an inch long. By +having a higher electro-motive force one may be made +several inches long. The arc itself consists of the +incandescent molecules of the air in its path mixed +with some of the disintegrated particles of the carbon +of the terminal. When an arc is formed in a partial +\DPPageSep{235.png}{223}% +\index{Geissler's tubes}% +\index{Spark, electric}% +\index{Vacuum, a non-conductor}% +vacuum the character of the phenomenon is very much +changed. Instead of being concentrated into a narrow +space, it spreads out into an oval form, the size of +which depends upon the degree of exhaustion. The +terminals may be separated to a much greater distance; +the light becomes less intense, and shows as a kind of +glowing gaseous globe, and this may extend to the +walls of the glass vessel in which it is produced. + +If the vacuum be made very perfect, no current can +be got through it; for the ether is a perfect non-conductor. +Even the spark from an induction coil that +will jump several feet in the air will not jump a quarter +of an inch in a vacuum. The jumping ability of +an electric spark or current depends upon its electro-motive +force. A thousand volts will jump but +about the one-hundredth of an inch in common air, +and ten thousand volts only about one-tenth of an +inch. From such experiments it has been concluded +that a flash of lightning probably has an electric pressure +\index{Lightning}% +reckoned by hundreds of millions of volts, but +there is some doubt about the calculation for such +exceedingly high voltage. Glass tubes provided with +platinum terminals hermetically sealed, and from which +the air has been partially removed, when connected +with the high voltage terminals of an induction coil +exhibit phenomena that depend altogether upon the +degree of exhaustion in the tube. If the air pressure +%[** PP: Width-dependent break] +% [Illustration] +\begin{figure}[hbtp] + \begin{center} + \Graphic{4in}{236a} + \end{center} + \Caption{27}{Diag.\ 27.---Crookes's Tube. Long Free Path.} +\end{figure} +\index{Crookes' tubes}% +be removed to about the one-hundredth of the normal +pressure, the discharge appears as a broad band of +purplish light between the terminals; if the reduction +be to the thousandth, the light fills the tube. Still +\DPPageSep{236.png}{224}% +further reduced, the discharge appears broken up into +striæ, or bright disks, their distance apart depending +upon the degree of exhaustion, and they measure +roughly the length of the free path of the gaseous +molecules. If the exhaustion is carried to a very high +degree, this free path may be made as long as the tube, +\index{Molecules, long free path}% +or longer. This means that a molecule may move +from one end of the tube to the other without coming +into collision with another one. + +When a molecule touches upon the electrified +terminal, it is impelled from it with great velocity, +quite like that exhibited in the radiometer, and probably +\DPPageSep{237.png}{225}% +\index{Heat by impact}% +for the same reason. It moves away from the +terminal in a straight line in obedience to the first +law of motion, and continues on till it strikes another +molecule, or the surface of the tube, and it shines as it +moves, on account of its vigorous internal vibrations; +for each gas gives its characteristic spectral lines when +thus made incandescent. Where they strike upon a +thin piece of platinum they may make it red-hot by +impact, and where they strike upon the +% [Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{4in}{237a} + \end{center} + \Caption{28}{Diag.\ 28.---Crookes's Tube. Platinum made Red Hot by Impact.} +\end{figure} +walls of the +glass tube the latter is made luminous with a phosphorescent +glow, and may be made red-hot, and so +softened as to bring about a collapse of the tube. +These tubes are known as Crookes's Tubes, and their +phenomena are extremely interesting from the insight +they give into the behavior of matter under all sorts +of conditions. With a set of these tubes, the laws of +motion, kinetic energy, sound, heat, light, electricity, +and magnetism may be illustrated in a way unapproachable +\DPPageSep{238.png}{226}% +with any other simple and cheap apparatus. The +long free path, and inability to turn a corner when +projected from an electrified terminal, show the first +law of motion and inertia. The impact of the molecules +may make a wheel turn round,---an example of +energy as good as a windmill. The intermittent beats +upon the sides of the tube produce a sound, the pitch +of which is the same as that of the vibrations of the +induction coil. The heating of the tube and its contents +shows the transformation of free-path motion +into vibratory molecular motion. The luminousness +of the gas, and the phosphorescence of the tube, show +\index{Phosphorescence}% +the transformation of the electrical energy into the +vibratory molecular kind, at a rate capable of affecting +the eye. The phosphoresence\DPnote{** [sic]} itself showing the conditions +needed for producing it; the origination of the +motions in the tube showing the relation of electricity +to the other forms of motion developed; the deflection +of the stream of electrified molecules by a magnet +illustrating the effects of a magnetic field upon a +current of electricity. The fact that such streams of +molecules are projected from an electrified terminal +solely by impact there, is shown by their returning to +it when there is nothing in front of it to expend their +energy upon, as a ball returns to the earth when +thrown into the air, which is the case when but one +terminal is connected with the induction coil; and, +lastly, such a tube will be lighted up by being merely +in the neighborhood of an induction coil, or rather in +a varying electric field. They may be insulated and +several feet away from such induction coil or a Holtz +\DPPageSep{239.png}{227}% +or other similar machine and yet be internally lighted +every time a spark passes, which shows that the luminousness +seen in the tubes is not necessarily due to any +electrical current present, because in this case there +can be no electrical current. + + +\Section{THE NATURE OF ELECTRICITY.} + +There have been many theories proposed to account +for electrical phenomena, yet to-day there is no one +that is generally held, even as a provisional one, among +physicists. Some have even abandoned the hope of +mankind ever being able to reach a consistent theory of +it. The case has been the same in the history of heat, +of light, and of magnetism; yet text-books of to-day do +not hesitate to state what is the nature of each of these. +Electrical phenomena have greater variety, and the +apparent dual character oftentimes present has served +to give a perplexing degree of complexity to them. +The writer has thought that a summation of the principal +factors present in electrical phenomena might be +helpful to some in their endeavor to find some physical +explanation without having to assume something \textit{sui +generis}, which has no other necessity for being except +the very dubious one of accounting for a certain phenomenon. +Caloric, light corpuscles, and vital force +were such visionary creations; but further knowledge +has enabled science to dispense with all of them, leaving +nothing in their places but what was known to +exist before; namely, matter, ether, and their motions. +Such a steady course of reduction to these factors +leaves one with the fair presumption that it will likely +\DPPageSep{240.png}{228}% +fare the same way with any other agencies that have +been imagined to account for phenomena, though the +latter may, for the time being, seem not reducible to +simple mechanics. + +There are certain \textit{a~priori} reasons for thinking that +in electrical matters, as in all other physical agencies, +only matter, ether, and motion are concerned. No one +has ventured to identify ordinary matter and electricity, +which cuts down the possibility to one of the remaining +two. + +If it be admitted that matter is not altered in quantity +by any process to which it may be submitted, and +also that the amount of ether and energy in the universe +are constant, it follows that all the different phenomena +exhibited by matter are due to the different +kinds of motion it may have; for \emph{motion is the only +variable factor}. On such a premise one can fairly +maintain that no matter how obscure and puzzling a +phenomenon may be, its explanation lies altogether in +its characteristic motions, and, when they are fully +made out, there will be no more to learn about it. If +so much be granted, one has got on a long way towards +the final answer to the questions, What is the nature of +heat? what is the nature of light? what is the nature +of electricity? Two of these are settled, and no one +thinks of asking as to their nature. The nature of +heat was settled by Rumford and Davy, that it is a form +of motion in matter. The nature of light was settled +by Young and Fizeau, that it is a form of motion in +the ether. What remained to be done was simply to +discover the particular kind of motion in each case. +\DPPageSep{241.png}{229}% +\index{Electricity, origin of}% +Spectrum analysis and photography have since given +us the particulars. Electricity is on precisely the same +philosophical basis; and, in the absence of evidence of +the existence of some other physical factors than matter, +the ether, and motion, one would be entitled to the philosophical +opinion that \emph{electricity must be some form of +motion}. What the particular form is may be a subject +of investigation, but not the nature of it. + +It is my purpose to show, \emph{first}, that in every case +where electricity is produced motion of some sort is +antecedent to its production; \emph{second}, that in every +case the effect of electricity is to produce motion of +some sort, and that itself is annihilated in doing it in +precisely the same sense as motion of any other sort is +annihilated when it is transformed. + +1. \emph{As to its origin}. When the face of the thermopile +is heated and electricity is produced, we know that +vibratory molecular motion is the condition for its appearance. + +In a galvanic battery the molecular exchanges by +which zinc is dissolved and oxidized, and hydrogen is +set free, are well known, and also the heat equivalent +of such re-actions; and they are measured in heat units, +which in turn may be made the measure of the electricity +developed. + +When glass or wax or other substance becomes electrified +by friction, the word itself expresses the condition +necessary for producing it. Mechanical friction +is the antecedent. + +When a conductor is moved in a magnetic field and +becomes electrified, the effect depends absolutely upon +\DPPageSep{242.png}{230}% +\index{Electricity, mechanical origin}% +\index{Electricity, electrical origin}% +the motion. Stop that and all evidence of electricity +disappears. + +The same thing is true when electricity is developed +by so-called induction in a field produced by a neighboring +body that is electrified in any way. The continuous +production of it implies continuous motion of one or +the other body. + +In dynamos of every variety of form the mechanical +motion turned into them is the antecedent, and the +energy of the engine spent in turning the dynamo has +its full representation in the electric energy developed, +and when there is no motion there is no electricity. + +In the physiological development there are always +chemical, thermal, and mechanical motions, which are +spent to produce what electrical phenomena appear, +whether in mankind or in animals. + +In the air and in the earth there are changing temperatures, +condensations, etc., which signify molecular +motions. + +Some crystals, like tourmaline, become electric by +heating; some, like mica, become electric by splitting; +and so on. Every one implies that some kind of motion +has to be spent to develop the electrical condition, and +in each case the particular kind of motion that has +been spent to produce it has been \emph{spent}; that is, it has +been transformed in the same sense that the translatory +motion of a bullet has been transformed into vibratory +when it strikes the target. The electricity thus appears +as the representative of the kind of motion that +has been destroyed. + +Some have imagined that electricity was a kind of +\DPPageSep{243.png}{231}% +\index{Electrical effects}% +\index{Stress, electrical}% +dual matter, which was broken up by the various processes +described, or that some substance was transferred +from one place to another, so that there was +more than the normal amount in one place and less in +another. Even such conceptions do not get rid of the +idea of motion being the chief characteristic, for the +separations are the ideal embodiments of motion, and +in this case the measure of it; so nothing whatever is +gained, either in clearness or simplicity, by such invention. + +2. \emph{The effects of electricity} are to bring about mechanical +motions of some sort. + +The stress into which the ether is thrown by either +an electrified or magnetized body is a change of position +of adjacent parts with reference to each other, +and the fact that this stress travels with the velocity +of light shows that motion is the essence of it. The +re-action of the stress in the ether upon other matter +in it always results in the motion of the latter. If the +whole body can move, it will do so, and mechanical +motion is the immediate effect. If it cannot move as +a whole, its molecules are twisted into new positions, +so that motion, either molar or molecular, is the result. + +As the electric current in a conductor always heats +the latter in every part, one has but to reflect upon the +character of heat motions to perceive that some kind +of motion must be the antecedent of it. Consider a +short portion of wire through which a current of electricity +flows. It becomes warmer and now radiates +faster into space. It is losing motion by imparting it +to the ether. Trace back the ancestry of the ether +\DPPageSep{244.png}{232}% +\index{Electrical effects, reversible}% +\index{Physical processes, reversible}% +motion, and it appears as vibratory motions of the +molecules of the conductor, thence as electrical current, +thence as armature rotations of a dynamo, thence to +the engine movements, thence to the furnace and the +chemical re-actions going on there. There is no question +as to the nature of the factors in all of these but +one. Call the chemical re-actions \textit{A}, the engine \textit{B}, +the dynamo \textit{C}, the electricity \textit{D}, the heat \textit{E}, and the +ether waves \textit{F}. With the exception of \textit{D}, each one is +known to represent a certain kind of motion, molar or +molecular, and all in a consecutive series. Is it not +difficult to conceive that the step \textit{D} can be anything +different in character from the rest of the series, and, +whether understood or not, must represent some phase +of motion? To think otherwise is to think that motion +can have some other antecedent than motion. Whoever +sets himself in earnest to this problem will see +there is but one answer to it. + +So heat effects, light effects, chemical effects, as +well as the direct mechanical ones shown in Crookes's +Tubes, or otherwise, will lead to precisely the same +conclusion that \emph{electricity represents an intermediate +molecular kind of motion}, having definite motions +for its antecedent, and definite motions for its consequent, +and so must itself be some peculiar form of +motion, differing from the others as they differ among +themselves, and nothing beyond that. It may also be +remarked that every form of motion which is capable, +under definite mechanical conditions, of developing +electricity, electricity is itself capable of producing. +The processes are all reversible. If heat will produce +\DPPageSep{245.png}{233}% +electricity, electricity will produce heat. If chemical +re-actions produce electricity, electricity will produce +chemical re-actions, and so on of all the rest; so if they +be reducible to motions, so must electricity. + +Such considerations make logically certain what the +nature of electricity is; but they do not indicate what +the character of the motions is that gives it identity, +and distinguishes it so radically from other well-known +kinds of motion. In the chapter on ``Motion'' it is +pointed out that there are three fundamental kinds of +motions,---translatory, vibratory, and rotary,---and +that with these all the various complicated motions of +mechanical processes may be produced. It is also +pointed out that for convenience we call those motions +mechanical that are on a scale of visible magnitude, +but such as cannot be seen are called molecular and +atomic. It is plain, in this case, that the motions must +be on a molecular scale, for no motions are directly +perceived in electrical phenomena any more than in +heat phenomena; so there remains for consideration +what evidence there is for the motion being molecular +and therefore of matter, or of the ether. + +It appears that when certain kinds of work, such as +friction, are spent upon a mass of ordinary matter, electricity +is developed, and we say the body is electrified. +The body in this condition at once re-acts upon the +ether about it; and it has happened that some persons +have given most attention to this effect of the electrified +body, and the phenomena that may result from it, +and have called \emph{it} electricity; while others have given +more attention to the condition of the matter that +\DPPageSep{246.png}{234}% +\index{Electricity, dual}% +\index{Ether rotations}% +induced the ether stress, and they have called \emph{that} +electricity; while the greater number have hopelessly +confused the two, calling both by the same name, just +as formerly heat and ether waves were both called +heat. It is plain that a physical condition of things in +matter requiring a name ought not to be designated by +the same term as that physical condition in the ether +which is the result of the first. One is, therefore, +justified by the logical necessity of making a distinction, +in adopting the name electricity as applicable to +one and not the other, and also in calling the phenomenon +in matter by that name and denying its applicability +to any effect of it wherever it is plain there has +been a transformation. Thus it would be as illogical +to call ether waves set up by an electrified body electrical +waves, as it would be to call the swinging of a +pendulum that was actuated by electrical attractions +electrical vibrations. + +We are, therefore, now reduced to the sole consideration +as to the character of those molecular motions +which differentiate electricity from heat and free-path +motion; and here the apparent dual character, which +has been so puzzling, helps at once to an understanding +of it. + +For many years it has been merely a matter of convention +that a current of electricity is said to move in +a certain direction in a wire. It has often been noticed +that there is an apparent current in both directions +from any electrical source; and one has been called a +positive, the other a negative, one; yet the current, +reckoned either way from its source, is always the +\DPPageSep{247.png}{235}% +\index{Magnetic rotation}% +\index{Rotations in ether}% +same at a given point, and has not unfrequently been +considered as made up of two currents moving in +opposite directions. + +If one will take a limp rope a few feet long and tie +its ends together so as to form a ring, and, holding it +in his two hands, will begin to twist it in one direction, +he will see the twist start in opposite directions at his +hands, and each one can be traced quite round the ring, +neither interfering with the other; yet one is a right-handed +twist, the other a left-handed one; and one +might call one a positive and the other a negative current. +There will be as much twist in one part of the +rope as in any other, and the rate of rotation at the +hands will be the measure of the amount of motion, +and, consequently, of the energy that is in the circuit. +For a rope substitute a wire, and for the hands a +battery or a dynamo, and the analogy is complete, +except that no rotation is seen in the wire as a whole; +so, if there be rotations, they must be of molecules and +not of the mass. Molecular motions must, of course, +be inferential. It is so for heat. The waves called +ether waves imply vibrations of matter; and, if there +be any known rotary motions in the ether, they would +imply molecular rotations for the same reason. It is +conceded that in every electro-magnetic field the ether +is in a rotary motion, and in numerous books it is +pictured as a whirl both about a magnet and a wire +carrying an electric current. The rotation of an electric +arc in a magnetic field shows it, and the twist +given to a polarized ray of light in passing through it +also shows it; and it has been so interpreted for years. +\DPPageSep{248.png}{236}% +The twist given to a conductor through which a current +is flowing, which has been before alluded to, also +gives direct evidence of the same condition; so the +phenomena confirm the conjecture that the phenomenon +in matter which is called \emph{electricity is a phenomenon +of rotating molecules}, in the same sense as the +phenomenon called heat is a phenomenon of vibrating +molecules. + +If the atoms in molecules, and the molecules themselves, +were absolutely fixed in position so as to have +no individual freedom of motion, there could be neither +vibration nor rotation; but the vibrations tend continually +to separate them, and hence between impacts +there is freedom for rotary slip, if there be any tendency +to do so. In an electro-magnetic field the ether +stress re-acts upon molecules in it so as to rotate them +upon some axis tending to set them in certain position +with reference to it. This action will be stronger upon +an atom or molecule immediately adjacent to an electrified +molecule than to one more distant, and one may +therefore infer that the process called conduction, +where heat is the immediate effect of an electric current, +is really an induction effect, and depends directly +upon the ether rather than upon the direct mechanical +effect of one molecule upon another; for such mechanical +action would make the rotation of adjacent molecules +to be opposite in direction, whereas in an electric +current all are in one direction. There is, therefore, +impact and slip, impact and slip; each impact knocking +the molecule out of the position the induction had +set it in, and each arrest of the slip resulting in increasing +\DPPageSep{249.png}{237}% +the amplitude of vibration, and hence raising +the temperature of the conductor. Hence, the explanation +of the transformation of electrical energy +into heat energy. An electric current is, therefore, +not a simple phenomenon, but is considerably complicated, +involving motions of both molecules and the +ether; the molecular motion depending directly upon +the re-action of the ether stress produced by an adjacent +molecule rather than upon mechanical contact. +The electrical condition called static being itself a +compound of abnormal molecular position and stressed +ether, is the condition which, while being propagated +in a conductor, constitutes an electric current, propagated +in the ether, constitutes an ether wave. +%\DPPageSep{250.png}{238}% + + +\Chapter{IX}{Chemism}{238} + +\label{chap:chemism}% +\index{Chemism}% + +\First{The} atomic theory of matter was held in some form +by ancient philosophers, but the reasons they assigned +for their opinion were not such reasons as have led +men of the present day to adopt that theory to the exclusion +of all others. Modern chemical analysis enables +one to reduce compound substances to their elementary +forms, and out of those to build up numerous +other substances with entirely different qualities. +Each such elementary form can be isolated, its properties +can be studied, and by compounding them one can +at will produce thousands of substances, each with its +own distinctive qualities. Some of the more thoughtful +men of all ages have pondered upon the fundamental +questions of physical science, and they have guessed +how it might be: some guessed this way, some guessed +that, and none of them gave a sufficient reason. It +would be very remarkable if, among a multitude of +guessers, some did not guess nearer right than others; +but such lucky guessing hardly entitles one to the +honor of being the founder of a philosophy that had +to wait for later men and entirely different methods to +substantiate it. And this is the real state of the case +in nearly all departments of knowledge. Ask any chemist +\DPPageSep{251.png}{239}% +\index{Atoms, chemical properties}% +to-day why he holds the atomic theory of matter, and +he will reply that he can isolate the elements, and by no +process yet discovered can they be more finely divided; +that he can measure their individual magnitude and +weigh them, prove their existence in the sun and stars; +so that the weight of evidence is exceedingly great. +He will never think of assigning any such reasons as +the early philosophers gave for their teaching. Many +of the properties of bodies of visible magnitude depend +upon the number and arrangement of the molecules +that compose them, but the properties of atoms are +fundamental and not subject to change. All substances +are identified by means of their properties, and the +chemical properties of atoms are among the most important. +Not only do atoms combine together in groups +called molecules, consisting of two or more atoms, but +they combine in definite proportions by weight, and only +so; and these proportions are called the atomic weights +of the elements, and are known for all of them; so +that molecules are compounds of definite constituents, +definite weight, and possessing definite properties. For +instance, water is made up of hydrogen and oxygen, two +parts by weight of hydrogen and sixteen of oxygen; +and as to its properties, such as density, specific gravity, +conditions at different temperatures, etc., all are familiar +with. Most of these properties of bodies are called +physical, but by chemical properties is meant the +ability of atoms to enter into definite combinations +with other atoms, to form new compounds and develop +new properties. The chemist is concerned with such +atomic exchanges, called re-actions, and notes the conditions +\DPPageSep{252.png}{240}% +\index{Affinity, chemical}% +under which they take place, and some of the +new qualities that appear, such as its physical condition, +as to being a solid, a liquid, or a gas at certain +temperatures, its crystalline form, if it has any, its +behavior with polarized light, and so on. + +Underneath all chemical re-actions there lies the +question as to why atoms combine at all. At first it was +explained as due to an attractive force,---chemical attraction, +possessed by all atoms, but in different degrees +by different elements. When it became known that +this acted in definite selective ways, it was called chemical +affinity, but was still supposed to be a peculiar +force unrelated to other forces supposed to exist, such +as heat, light, electricity, and so on. In the progress of +knowledge, it became apparent that these latter phenomena +were so directly related to each other that they +were capable of being transformed one into the other, +and then the expression ``correlation of forces'' began +to be used. A further analysis showed them to differ +from each other chiefly in the character of the motion +involved in the phenomena; and so forces, as such, have +been banished from physical science, leaving not even +a single primal force; for as each one can be changed +at will into any of the others there is simply a closed +chain of phenomena, no one of which can be called an +elementary one more than any other. + +Chemical phenomena have been found to be a part of +the same grand division, and the term ``chemical affinity'' +has itself been in a measure supplanted by the +term ``chemism,'' which is now used to signify the +quality possessed by atoms to enter into definite combinations; +\DPPageSep{253.png}{241}% +\index{Chemism and heat}% +and its explanation is to be found by noting +the factors present when atomic and molecular exchanges +take place, and these have been found to be all +physical without exception. There is a large field +known as chemical physics with which one needs to be +acquainted in order to understand simple chemical +operations; namely, the effects of heat, light, and +electricity in bringing about chemical changes. + +When hydrogen combines with oxygen to form water +the process is called a chemical one; but, as has been +pointed out in the subject ``Heat,'' there is a definite +amount of heat given out by the combination of a definite +amount of the elements; and in like manner the +dissociation of the elements in water requires the expenditure +of energy proportionate to the amount decomposed. +This too is called a chemical process, but +the conditions for doing either are purely physical, depending +absolutely upon heat. The elements cannot +combine when heat cannot be given out, and cannot be +separated except by an equal expenditure. What is +true for this example is true in degree for all other +chemical re-actions; physical energy is involved in every +change and is the condition for the change. The first +law of thermo-dynamics states the quantitative relation +between heat and mechanical work; viz., that it is measurable +in foot pounds, and is equal to $772$ foot pounds +per pound degree, and this is called a heat unit. Now, +the chemical combination of a pound of hydrogen with +oxygen gives $61,000$ heat units, and is therefore at once +measureable in foot pounds, showing a direct relation +between chemical re-actions and heat or work. +\DPPageSep{254.png}{242}% + +It has also been discovered by experiment that in the +absence of heat chemical re-actions cannot go on, and +this has led chemists to the conclusion that at absolute +zero chemism does not exist. There is not only no +selective action, but no cohesion among atoms, and all +molecules would fall to pieces---that is, to atoms, quite +dissociated---at absolute zero. Instead of requiring +\index{Absolute zero}% +\Pagelabel{242}% +$61,000$ heat units to dissociate a pound of hydrogen +from water, it would not require any, for if the atoms +do not cohere, no work would need to be done in order +to separate them.\footnote + {See Appendix, \Pageref{p.}{400}.} %[** PP: Original reads p. 399] + +From this, then, it appears that chemism is determined +by heat, and does not exist in the absence of +temperature. When it is developed it manifests itself +in selective ways, and in the formation of definite compounds; +and it therefore is a proper subject of inquiry +as to how the temperature of atoms can give such selective +qualities to them. This requires a reconsideration +of the distinctive quality of heat itself. It has been +pointed out that this consists in the internal vibratory +motions of atoms and molecules, as distinguished from +translatory and rotary motions; that the evidence for +this comes, first, from the fact that a body of any size +possessing any degree of heat---that is, having a temperature +above absolute zero---is constantly exchanging +its energy with the ether, and that the rate of the exchange +depends upon the temperature; and, second, that +translatory motions of bodies in ether do not require +the expenditure of energy, or, in other words, that for +such motions the ether is frictionless. This is the +same as saying that, where the heat of a body is lost by +\DPPageSep{255.png}{243}% +\index{Atoms, vibrations of}% +radiation, it is the internal vibratory motion alone that +is lost, not its translatory velocity. Consider a body of +any magnitude whatever, having any temperature whatever, +and moving at any assignable velocity in space. +After an interval it will have lost some of its temperature +by radiation, and, if it moves long enough, it might +lose it all, reaching absolute zero; but its translatory +velocity will not therefore be reduced in any degree. +Hence, in considering the heat in a body, independent +of any other motions it may have, one has only to do +with its internal vibratory movements, and that the +temperature of a body, say an atom, is measured by +the amplitude of its vibration, and is proportional to the +square of that amplitude. + +If, therefore, chemism is directly related to heat, one +must attend to what must be going on in an atom, not +groups of them. + +To say that an atom vibrates is to say that it is +changing its form, and to explain how changing its form +can result in such selective properties as atoms exhibit +is to explain chemism by the mechanics of the motion +involved. Whether atoms have one form or another +will make no difference in this argument, which is that +the result is due to change of form, whatever that may +be; but, for making the subject mechanically clear, some +form may be adopted, and one can do no better than to +choose that form which now has most probability in its +favor judged by other phenomena; that is, the vortex-ring, +which has been treated under the head of ``The +Ether.'' + +When such a body vibrates in its simple way it +\DPPageSep{256.png}{244}% +\index{Attraction of vortex rings}% +elongates alternately on two axes at right angles to +each other; that is, the change in form is from a circle +to an ellipse, so as to assume first a horizontal, then a +vertical elliptical form, as shown in the cut. Such +%[Illustration: \textsc{Diag.~29.}] +\begin{wrapfigure}{l}{1.25in} + \Graphic{1.25in}{256a} + \Caption{29}{Diag.\ 29.} +\end{wrapfigure} +changes are due to the elasticity of +the ring, and are brought about in +such an atom by impact, by friction, +and by absorption of ether waves. +Whether produced in one way or +another, they represent absorbed energy +and exhibit it as heat, the temperature +of a given one depending upon the amplitude +given to it by a definite amount of energy however +applied. + +Such changing forms imply nodes and loops in the +vibrating body, positions of minimum and maximum +motions; and when the vibratory rate is the fundamental +one,---that is, the lowest rate the body can have,---there +will be four of each, the nodes being the positions of +minimum change of form. Such nodes may be seen in +vibrating bodies of all sorts,---strings, bells, rods, pipes, +and rings. The size of a body makes no difference in +this characteristic, and it therefore may be affirmed of +atoms as well as of any other magnitudes. + +%[Illustration: ] +\begin{wrapfigure}{r}{1.5in} + \Graphic{1.5in}{258a} + \Caption{30}{Diag.\ 30.} +\end{wrapfigure} +Let it be admitted that vibrating atoms can cohere +for any reason, it will be seen that an atom such as +represented could only have other atoms attached to it, +and be in a stable condition, when they were at the +nodes; and in this case four might be so attached and +no more, if they were approximately of the same size. +Such places in atoms might be called bonds: they would +\DPPageSep{257.png}{unnumbered}% +% [Illustration: ] +\begin{figure}[hp] + \begin{center} + \Graphic{3.75in}{257a} + \end{center} + \caption{Geometrical Forms of Snow Flakes.} +\index{Crystallization}% +\end{figure} +\DPPageSep{258.png}{245}% +be definite in number, position, and strength. If the +other attached atoms were themselves +vibrating, they +would each have their own +nodes; and if they were free +to turn into any position, one +might be sure that the nodes +of each would be in contact, +and that the loops of the vibratory +motions would be where +space to move in without interruption +was free. Such a combination +of atoms might be called a molecule. It would +consist of a definite number of atoms, each with its own +atomic weight; and if the strength of +the cohesion depended upon the vibratory +motion, it is easily seen that when +there was quiescence in that there +would be disruption or dissociation. +%[Illustrations] +\begin{figure}[hbt] + \begin{center} + \hfil + \begin{minipage}{1.25in} + \Graphic{1.25in}{258b} + \Caption{31}{Diag.\ 31.} + \end{minipage} + \hfil + \begin{minipage}{1.5in} + \Graphic{1.5in}{258c} + \Caption{32}{Diag.\ 32.} + \end{minipage} + \hfil + \end{center} +\end{figure} +Moreover, when there was such a nodal +bond it would be like a hinge, and two thus united +could swing upon it; while if three were thus united +and two were to swing upwards, +they would meet at a node on +each and stick together for the +same reason the other nodes did, +thus forming a symmetrical and +stable figure against which other +similar ones could be built up, +node against node indefinitely. A +hexagonal figure would result. If four were attached +to the primary nodes, and each was to swing up ninety +\DPPageSep{259.png}{246}% +\index{Chemical field}% +\index{Fields, chemical}% +\index{Fields, mechanical}% +degrees, there would be formed a sort of cubical box +without a lid; but at the top will be presented four +open nodes, upon which the four nodes of any other +similar one might be placed: and thus could a cubical +structure be built by addition of similar forms indefinitely. +Such symmetrical forms are called crystals. + +Of course all this presupposes that there is some +good mechanical reason for atomic cohesion, that is in +some way dependent upon temperature; and to make +this clear it is needful, first, to call to mind some phenomena +of a similar sort on a larger scale. + +It is well known that if a light body be brought near +a vibrating tuning-fork, the latter acts as if it attracted +it, for the light body will move towards the fork. The +same thing is true of other vibrating bodies, and the +explanation is that the vibratory motion reduces the +pressure about the body. Thus, suppose the hand to +move to and fro; as it moves forward the air in front +of it is somewhat condensed, while that behind it is +partially rarefied; when the hand returns the same +thing happens. The air follows up the hand because +the pressure is reduced next the hand, and if the hand +could swing back and forth, faster than the air could +return to it, there would be formed a perfect air vacuum; +and that means that the pressure would be +nothing at the hand and fifteen pounds per square +inch at a distance from it. Hence any body placed near +the hand would be subject to a pressure greater on its +remote side than on the side adjacent to the hand, and +would be pushed by it towards the hand. This would +be a phenomenon similar to attraction, the movement +\DPPageSep{260.png}{unnumbered}% +%[Illustration: ] +\begin{figure}[hp] + \begin{center} + \Graphic{\linewidth}{260a} + + \scriptsize CRYSTALLINE FORMS.\\[6pt] + \begin{minipage}{\linewidth} + The above figures illustrate very clearly the molecular arrangement in crystals of + various kinds. \textit{A}~represents a cross section of Brazilian Topaz, as shown in polarized + light. \textit{B}~is a hollow faced cube of salt, and \textit{C}~a similar hollow faced octahedron of + copper sulphide. They show that the cohesive strength is greater on the edges than + elsewhere. Some crystals, when being dissolved, leave a complete skeleton of themselves + the last to disappear. \textit{D}~is a skeleton crystal of silver from Scotland, where the + structure consists of a series of minute octahedral crystals adhering to each other in + such directions as would build up a single large octahedral crystal if filled out. + \end{minipage} + \end{center} +\end{figure} +\DPPageSep{261.png}{247}% +\index{Crystallization}% +\index{Vibrations, sympathetic}% +towards the vibrating body being due directly to the +pressure of the medium, while the difference in the +medium would itself be directly due to the vibratory +movement. The amount of such difference in pressure +is evidently determined by the degree of vibration. +Now, if one can imagine a similar condition of things +about an atom vibrating in the ether, he can understand +how its vibratory movements might reduce the ether +pressure adjacent to it in a way proportional to the +movement, and also how at the nodes such effect would +be at a minimum, and at the loops at a maximum, so +there would be produced what is called a field. As the +condition that produced it was one of mechanical +motion, one might call the field a mechanical field, for +mechanical effects of translatory motion result from it. + +When such an effect takes place among atoms one +might distinguish it as a \emph{chemical} field, for it would +bring about mutual cohesion among atoms, and the +nodes would determine the positions of stable combinations; +and a molecule so built up would require an +amount of energy spent upon it to break it up equivalent +to the energy spent, to produce the field, or, in +other words, equivalent to the heat in the atom. + +It is here to be noted that when atoms combine in +this way each one retains abundant space for its heat +movements, so its temperature may be varied within +considerable limits without interfering with molecular +stability. And, if the vibratory movements continue, +then each molecule will have its own field, which will +be the resultant of all the fields of the atoms that are +combined thus to make the molecule. The field of a +\DPPageSep{262.png}{248}% +\index{Growth}% +\index{Inductive action}% +molecule will then have a form which will depend +absolutely upon the number and arrangement of the +constituent atoms, and will extend to some distance in +space beyond the geometric boundary of the molecule +itself. + +The presence of such a chemical field must affect +other chemical fields in the neighboring space where +the fields overlap, hindering or facilitating the exchange +of atoms in other molecules, because lessening the +pressure holding them together. There are many +examples of this kind of action known. It is called +catalysis, which signifies the action of a given substance +\index{Catalysis}% +in bringing about chemical reactions without +itself being changed. For example, the binoxide of +manganese, when mixed with the chlorate of potash, +greatly facilitates its decomposition by heat, though +the binoxide is itself not decomposed. Pure zinc is +dissolved with difficulty by sulphuric acid; but a little +mercury or iron, or other so-called impurity, enables it +to be dissolved freely. Hydrogen and oxygen gases will +not combine when simply mixed; but a little spongy +platinum placed in the mixture will at once bring about +the combination, but will itself suffer no chemical +change. These gases will also slowly combine in the +presence of mercury when kept at the temperature of~$305°$. +In glass vessels without the mercury no combination +at that temperature occurs, but on raising the temperature +to~$448°$ it combines very slowly. In smelting +operations a flux has a similar function, and in some +cases the boundary line of such action can be observed. +Some re-actions take place at a different rate near the +\DPPageSep{263.png}{249}% +sides of the vessel that contains the solution than away +from it, and some mixtures of substances in solution +will separate from each other except within a short distance +from the surface. Such phenomena show that +the mere presence of some substances is sufficient to +profoundly affect chemical re-actions. The chemical +field of substances gives a consistent explanation of +catalysis. There is another class of phenomena well +known, but hitherto without any rational explanation; +viz., some supersaturated solutions seem unable to initiate +the process of crystallization, but the smallest crystal +of the substance starts it, and the whole body is +solidified in a few seconds. Here it is evident that the +crystal, taken as a nucleus, had a field that compelled +other and similar molecular groups to arrange themselves +in similar order. This is a phenomenon of such +importance as to warrant some attention here. When +two tuning-forks having the same pitch are separate +from each other a distance of several feet, and one of +them be made to produce a sound, the other one will be +made to sound likewise by the action of the sound +waves in the air upon it. The effect is called sympathetic +vibration. Other forks having different rates of +vibration will not be similarly affected, so the vibrations +in the air select out the particular fork having the same +rate as the one vibrating, and cause it to enter into a +similar state of vibration. So it appears with a magnet. +Any magnetic bodies in its field become magnetized +there; that is, they are brought into the same physical +state as the body that incited the field. Such physical +fields, then, are capable of compelling bodies in them +\DPPageSep{264.png}{250}% +\index{Fields, magnetic}% +\index{Magnetic field}% +\Pagelabel{252}% +to assume the same state of motion or similar position, +or both, as the body that produced the field, provided +the substance itself be constituted molecularly like the +first,---and this simply by being in proximity, not by +contact. It is a kind of induction, common through +the whole domain of physics. In the organic world of +living things the phenomenon of growth is manifested +by what are called cells, which are symmetrical groups +of molecules, as crystals are, only much more complex. +Growth consists in the formation of similar cells out of +suitable molecular constituents in the neighborhood. +Each different part of a plant or animal has a different +cell structure. If, therefore, it be conceded that each +cell has a field, which is the resultant of all the elements +that make it up, it will be seen how such field +must act upon other matter within it, compelling it to +assume a form similar to the cell that produces the +field; that is, to form a similar cell adjacent to itself. +Such formation is called growth; but the similarity in +form and function, when appearing among plants or +animals, has been considered as due to heredity, a term +that has a definite enough meaning, but which has not +been supposed to be due to mechanical necessity but +to some super-physical agency not amenable to purely +physical laws and conditions. It is possible to pursue +this much further and to show that cell structure itself +may be modified by molecular fields, and how stability +of form and function are possible with some and not +with others,---how what in natural history is called +variability, reversion, and other phenomena of the sort, +are explicable as due to the same factors that \DPtypo{organizes}{organize} +\DPPageSep{265.png}{251}% +atoms into molecules, and molecules into crystals. +Every one interested in the fundamental questions of +chemistry will be able to follow out in many ways the +mechanical conceptions here introduced, and compare +what he knows of chemical re-actions with them. It +will be especially helpful for one to draw upon paper +such ideal atomic rings with their edges touching, and +marking where the nodes must be. Such diagrams as +the one on \hyperref[fig:30]{p.~\pageref{fig:30}, fig.~30}, thus drawn, cut out, and the +parts bent up until they touch each other, will probably +surprise one at first to find how the nodes will be +brought adjacent to each other and therefore into a +stable position. + +So far it has been assumed that there will be in the +ether about a vibrating atom an effect comparable with +the effect produced in air about a tuning-fork or other +vibrating body that is producing sound waves. One +might be satisfied that there was such an action, even +though he were not able to explain it, provided there +were good reason for the assumption. The case is the +same as for a magnetic field within which magnetic +phenomena take place, though a magnetic field cannot +be isolated. It is the same for the existence of the +ether itself: it is inferential, but from a large body of +phenomena of different sorts, all corroborating the hypothesis; +so one is satisfied. When a magnet acts upon +a piece of iron not in contact with itself, we explain the +action by the magnetic field; and, if a body acts chemically +upon other bodies not in immediate contact, controlling +their motions and positions, as is the case, the +same kind of an assumption is to be entertained. If a +\DPPageSep{266.png}{252}% +\index{Heat, effects}% +reasonable explanation for the existence of the field +can be offered, all the better, though no one holds more +lightly upon a magnetic field because he cannot explain +it. In the chapter on magnetism it is remarked that +there is good reason to think that atoms of all kinds +are magnets. If that be the case, then every atom has +a field of its own, wherever it may be; and it would +seem likely that this magnetic field of atoms was the +underlying factor in the so-called chemical field; and it +is therefore well to analyze the phenomena, having that +magnetic field in mind. + +A single magnet of any form will have its field +under all conditions, and the \emph{shape of the field will be +determined by the form of the magnet}. If the magnet +were of sufficient size, there would be no difficulty in +locating it by its field, even though the magnet itself +could not be seen. A number of magnets arranged +promiscuously would so neutralize each other's fields +as to have no residual field, and in order to detect the +existence of magnetism it would be needful to get very +close to an individual magnet. When a steel magnet +is dissolved in an acid all evidence of the existence of +magnetism disappears, for the iron molecules are now +separated from each other and are scattered promiscuously +through the solution. Any disturbance whatever +that disarranges the magnetic arrangement of +molecules destroys the evidence of the magnetic field, +except at very short distances. When a piece of iron +is heated to redness it cannot be made magnetic in +the ordinary sense; for the vigor of the vibratory movement +continually knocks the molecules into new positions, +\DPPageSep{267.png}{253}% +and therefore changes their resultant fields, +leaving but a neutral effect upon outside bodies. + +As chemical re-actions take place in liquids or gases, +and only exceedingly slow in solids, it follows that in +them one has to deal with molecules in all positions,---that +is, an entirely disordered arrangement, and such as +would exhibit no evidence of magnetic field, even though +every atom was itself a strong magnet; and this condition +of neutrality would be constant so long as the +temperature kept up so much mechanical disturbance +as to prevent any systematic arrangement. Yet it is +to be borne in mind that the magnetic field of no one +has been \DPtypo{distroyed}{destroyed}: it is as strong, as far reaching, as +ever; but it is masked by overlying fields,---that is all. +Let any one of them suffer any change at all, and the +effect of it would be felt throughout the whole space +the field would occupy if there were no other one in +its neighborhood. + +Now, when the form of a magnet is changed, it +changes the form of the magnetic field---that is, the +distribution of the stress that constitutes the field; and, +when an atomic magnet vibrates, it is changing its +form; and as a result its field is changing at the same +rate. A multitude of such independent magnets, all +changing their forms and fields, would be sending out +waves into the ether; but they would be caused by and +measured by their heat motions, not by their magnetic +condition simply; and the effects of these waves at a +distance from their source would be practical uniformity +unless the waves were very long. For such short ones +as are produced by atomic and molecular vibrations +\DPPageSep{268.png}{254}% +there could be no ordinary indications of a magnetic +field such as are exhibited in the movements of bodies +of visible magnitude. Long waves of precisely the +same sort caused by motions of a slower rate might +make magnetic needles move. Thus, magnetic needles +upon the earth have been observed to move at the +same instant that solar disturbances have been witnessed +through a telescope, which indicates that the +waves were long ones, giving a magnet time to move +one way before it was impelled to move in some other +way. + +This condition of practical neutrality on account of +the rapidity of the change at a distance from the magnetic +body would not hold true in close proximity to +the body itself; for the changes in the field will not +only be actually greater there, but the fact that there +are nodes and loops necessitates changes in the stress +at the surface of the atom, and renders it possible for +the actual magnetism to assert itself and act upon +another very near to it which it cannot have in any +degree a little farther away, the actual distance being +comparable with the diameter of the atom itself. Hence, +atoms close by would have certain magnetic effects +upon each other in the nature of selective effects, on +account of the uniformity of the stress at the nodes, +and the number of nodes would determine the possible +number of cohesive attachments. So one may fairly +presume that the vibratory motions such as constitute +the heat motions of atoms are the physical conditions +that underlie chemical combinations and give to them +their quantitative character, their selective property, +\DPPageSep{269.png}{255}% +\index{Sound, origin of}% +and their symmetrical form into which they arrange +themselves. + +This gives a rational account of so-called chemical +attraction, and makes it clear how the laws of thermo-dynamics +are related to chemical re-actions. It reduces +the whole scheme to one of the mechanics of vibrating +magnets; and the evidence that atoms are such magnets +does not rest upon the necessity of the conception for +the hypothesis, but upon much confirmatory experiment +that has led physicists to the conclusion that +they are such, in a manner quite independent of what +phenomena might be deducible from matter with such +a constitution. In conclusion, it may be added that, +although the idea of ring-formed atoms has been +adhered to in this explanation, it is not to be understood +that the same explanation would not apply to +atoms constituted in any other manner; for all that is +implied in the above is that whatever their form and +substance they are magnets, and that they are so elastic +as to be capable of internal vibratory movements---that +is, of changing their forms in a periodic way; +and of this there appears to be no reasonable doubt. +When several such are combined together the resultant +motions and their effects become very complicated, and +therefore difficult to disentangle; but that would be no +reason for not holding a well-grounded conviction that +all chemical phenomena are truly physical, and referable +to fundamental mechanical laws, and are fully explained +when these mechanical conditions are pointed out. +%\DPPageSep{270.png}{256}% + + +\Chapter{X}{Sound}{256} + +\First{The} term ``sound'' has two very different sign\-i\-fi\-ca\-tions,---one +a physiological one referring to a sensation +in the organ of hearing, the other the physical cause of +the sensation. When one has the sensation of sound, +of course he usually infers that it was caused by some +external physical condition that has in some way impressed +itself upon his auditory apparatus; and, to one +who has thought but little about it, it is difficult to get +rid of the idea that sound is a something which exists, +whether it be heard or not. That is, there would still +be sound though there were no ears, that a tumbling +pile of books in a deserted house would make a racket +if no one did hear it. On the other hand, one may +call that sound which is capable of being heard; and +when those conditions are investigated it is found, in +all cases, to be some kind of a mechanical impulse, or +succession of impulses, generally in the air, which may +be traced from the ear to some body which is found to +be in a state of vibration. The latter is called a +sounding body, and the air is called a sound conductor; +but these conditions are not necessary for the +sensation of sound. One may not infrequently hear +what is called ringing in the ears, that has its origin +within the head, and, perhaps, in some cases independent +\DPPageSep{271.png}{257}% +\index{Pitch}% +of any of the auditory apparatus, like some +nerve disturbance even at the base of the brain itself. +Hence there is a distinction between hearing and the +cause of hearing, and the latter does not necessarily +imply anything external to the listener. One may be +deaf so that no conditions external or internal will +produce the sensation. As the sensation itself can +give no infallible testimony as to what causes it, it has +come about that the physical conditions which may be +heard as sound have been investigated, and the science +of sound, or acoustics, has been developed quite independent +of the sense of hearing, the latter being only +a convenient instrumentality in the investigation, not +an indispensable one. In this sense sound is the +science of the vibratory movements of elastic bodies, +and one may inquire first as to the origin of such +movements. When one body strikes upon another, +motion is imparted to the latter. If enough motion is +imparted, it may move visibly, and we then call such +motion mechanical. Though it does not visibly move, +yet energy has been spent upon it in some degree, and +must be represented by some degree of motion which +at first it did not have. If a pencil be struck upon the +table, one may be as sure that energy has been spent +upon it as if it had been struck with the fist, only +less in amount. + +When molecules are compressed together so as to +increase the density, and retained in such closer compactness, +heat is always the result; that is, the molecules +themselves have their amplitude of vibration +increased: but when molecules are compressed quickly, +\DPPageSep{272.png}{258}% +and the pressure be as quickly removed, the compressed +molecules at once rebound to their original +position with a velocity that depends upon the degree +of elasticity the body has, and, like a swinging pendulum, +do not stop at once when they have reached that +position, but go beyond a little, and thus oscillate back +and forth. Each molecule pushes against its neighbors, +and they upon theirs, and so on, the motion travelling +outwards from the point of disturbance in every direction, +with a velocity that is proportionate to the temperature; +that is, the vibratory rate of the molecules +themselves, which, as pointed out in the chapter on +heat, is exceedingly great. + +This particular kind of movement is called longitudinal; +that is, it is to and fro in the direction in +which the disturbance travels, and depends altogether +upon the properties of the body that is struck, and not in +any degree upon the initiating cause. When the table +is struck with the pencil the sound heard is different in +quality from that given out by a similar stroke upon +the window or a tumbler. It differs also in duration. +The latter may continue to be heard for some seconds, +while the former is brief. Every elastic body has some +particular vibratory rate, which depends upon its size +and shape as well as the material it is composed of. +A stretched string or wire, a board, a lath, a bridge, +a house, for examples, all have individual rates of +motion, into which they can be brought by some well-directed, +sudden push. When a strong wind shakes a +house, the shake is the vibratory rate of the building, +and may be as low as one or two per second. In +\DPPageSep{273.png}{259}% +general, as bodies are smaller their rate of vibration +increases, until it becomes greater than thirty or forty +per second, when the effect can be heard. Stones +have an individual pitch, or rate of vibration, so that +by selection one may get a set to represent the musical +scale when struck. Smooth bits of laths of different +lengths give out their pitch when dropped upon +a table; and, with a properly graded set, tunes may be +played by dropping them successively. The rate of +vibration, or pitch, of a table is relatively high---several +hundred per second; and a pencil knock distributed +over so large a body, and by it to the floor, reduces its +strength very fast. The tumbler has its motions +symmetrical, therefore of greater amplitude, and last +longer. A tuning-fork struck and held in the fingers +near the ear will be heard for a much longer time than +if the stem be held against the table, as any one may +satisfy himself by trying. In the latter case the +motions are conducted away freely, in the former case +not so freely. In the former case the sound appears +louder to the ear, because the air, in contact with the +vibrating table, receives vibratory motions from it as +well as directly from the fork; and so the air motions +are re-enforced, and the energy is dissipated so much +the more rapidly. + +The idea in all this is that, so far as sound consists +in vibratory motions, energy is involved, and is distributed +in accordance with mechanical laws; the size, +density, and elasticity of the sounding body being the +factors which determine the rate at which the distribution +can go on. +\DPPageSep{274.png}{260}% +\index{Sound, characteristics}% + +If the motion be properly mechanical, any agency +that can originate such motions can give rise to sound. +One might ask himself here if it be likely that any +kind of motion, or form of energy, cannot produce it. +If it be remembered that motion is the antecedent of +motion in all known cases, one will perceive that +sound might have a variety of antecedents, as it has. +To the mechanical ones alluded to might be added +all cases of percussion, impact, friction---indeed, the +whole range of mechanical motions. Any agency that +can change the form of a body can cause sound vibrations. + +That heat can directly produce sound is shown by +the roar of fire in furnaces; and tubes having a burning +gas-jet in them may give out a loud sound. In +these cases it is the body of air that is caused to +vibrate energetically\DPtypo{}{.} + +When a beam of light falls upon a body that can be +heated by it there is a re-action between the surface and +the air, in which the surface is pushed slightly backwards, +as indicated by the \DPtypo{radiometre}{radiometer}. If a beam is +allowed to fall intermittently upon such a surface, it +will be thrown into vibrations as if it had been struck, +and will give out a sound, the pitch of which depends +upon the number of interruptions per second. Such a +device is called a radiophone. + +A current of electricity sent through a conductor in +an interrupted manner makes the wire give out a sound. +The current heats the wire, expands it slightly, and +cools as suddenly when the current is stopped; so the +succession of currents results in sound. In like \DPtypo{manmer}{manner}, +\DPPageSep{275.png}{261}% +\index{Sound, range of}% +\index{Sound, velocity of}% +a current of electricity going through an electro-magnet +causes a click at the instant of making and +breaking the current. This is occasioned by the +change in position of all the molecules. A succession +of these may keep up a continuous hum. + +The electric spark itself always produces a snap of +brief duration, for short sparks from induction coils +and electric machines; but, when the spark is a long +one, like a flash of lightning, the sound may be prolonged +several seconds. Along the line of the flash +the air is greatly heated for a very brief time, and it +therefore rapidly expands. The quick cooling produces +a collapse of the heated column of air, with the consequent +noise. The duration of the thunder does not +signify that the lightning lasts such an appreciable +time, but that a part of it was a distance away, and that +time was taken for the sound to come from the more +distant place. + +That chemical action can give rise to sound is proved +by the explosion of gunpowder and other explosives, +solid and liquid. In these cases a large amount of gas +is suddenly formed, and at a high temperature; it displaces +the air quickly and forms a great wave. One +may often feel the wave of compression produced by +a cannon go by him, even at the distance of several +hundred feet from it. These examples show that heat, +light, electricity, magnetism, and chemism are directly +related to mechanical motions because competent to +produce them under appropriate conditions. If motion +be the antecedent of any given motion, and any of +these may be the immediate antecedent of mechanical +\DPPageSep{276.png}{262}% +motions such as sound, what shall be said as to the +nature of each of these physical agencies? + +\Section{CHARACTERISTICS OF SOUND.} + +As sounds may be produced by any of the physical +agencies, it does not matter, except for convenience, +what ones are adopted. Usually mechanical motions +are most convenient, and for musical purposes either +percussion, or currents of air. We speak of high +sounds and low sounds, and we find by experiment that +those called low are produced by fewer vibrations per +second than those called high. If sounds are considered +as vibratory movements, then it is evident there is +practically an infinite range of them; for there may be +any rate, from one a year or a thousand years all the +way to such vibrations as atoms make, measured by +millions of millions per second. There is no good reason +for drawing a boundary-line at one point rather +than at another, and saying that all vibratory movements +beyond this rate are not to be considered as +sound, yet it is convenient for some purposes to confine +the range to such as can be heard. + +When a succession of impulses follow each other at +such a rate as just to produce a continuous sensation of +sound, it is found to require from twenty to thirty per +second. It differs very much in individuals. In the +young it requires more, as the organ of hearing acts +more promptly than it does in the old. A less number +than these is heard as a tremble. From this as a minimum +one may go through a series, running from the +lowest sound produced by a piano---about forty per second---to +\DPPageSep{277.png}{263}% +\index{Echo}% +\index{Wave lengths of sound}% +the highest one of about $4,000$ per second. +Many insects make much higher sounds than this. +Such differences in the rate of vibration are called differences +in pitch; and, for musical purposes, a standard +of pitch has been adopted, making the middle~C of +the piano give from +%*[Illustration: ] +\begin{wrapfigure}{r}{1.25in} + \Graphic{1.25in}{277a} + \Caption{33}{Diag.\ 33.} +\end{wrapfigure} +$256$~to~$261$ vibrations. +The pitch of a sound may be +specified by giving its vibratory rate. +The pitch of men's voices ranges +from $100$~to~$150$ vibrations in conversation. Ordinary +whistling is produced by from $1,000$ to~$3,000$ or~$4,000$. +The squeak of bats is in the neighborhood of~$5,000$. +Beyond these figures it is difficult to hear anything,---not +because the vibratory motions are not produced, but +because they have too little energy to affect the ear. +Occasionally aurists find abnormally sensitive ears capable +of hearing sounds with a pitch as high as fifty or +sixty thousand, but ordinary persons have a limit in +the neighborhood of $20,000$; so it is customary to say +that the range of hearing of mankind is from thirty +per second to about $25,000$: but it should always be borne +in mind that the chief reason for not having a greater +range is in the difficulty of giving sufficient amplitude +to such very rapid changes. As the pitch rises the +amplitude decreases for a given amount of vibratory +energy. One might attribute the relatively low vibratory +rate of the maximum which the ear can perceive +to the lack of delicacy of the apparatus itself, which +would be true enough in an absolute sense; but the actual +sensitivity of the ear is really something wonderful, +for a piece of apparatus that is altogether mechanical +\DPPageSep{278.png}{264}% +in its mode of operation. It has been found that the +ear can hear such sounds as are produced by small +whistles at the distance of several hundred feet; and, if +the amplitude be computed,---assuming that it varies +inversely as the square of the distance---it is found to +be comparable with the diameter of a molecule, or less +than the ten-millionth of an inch. One who understands +the necessity for vibratory motions in elastic +matter will readily conclude that between the highest +number the ear can perceive, say $50,000$ per second, +and the lowest rate capable of affecting the eye ($400$ +millions of millions), there is an enormous gap; and man +has no organs for perceiving the intermediate ones. + +Experiments made in various ways have shown that +the velocity of sound waves in air is about eleven hundred +feet per second, and varies with the temperature, +being only $1,090$~feet at the freezing point of water, +increasing or diminishing about two feet per second for +each degree above or below that; and this is true for +sounds of all degrees of pitch. If it were not so, +music could not be heard at any distance from its +source. Suppose a tuning-fork makes one hundred +vibrations in a second. At the end of the second the +first wave would have got say eleven hundred feet +away, while the last wave would have just been completed; +or between the fork and the more distant wave +there would be a series, one hundred in all, reaching +eleven hundred feet. It follows that each wave would +be eleven feet long, or the velocity of transmission +divided by the number of vibrations. The wave length +of sounds can be measured in several ways, and of +\DPPageSep{279.png}{265}% +\index{Vibrations, sympathetic}% +\index{Vibrations, forced}% +course the product of the wave length into the number +of vibrations gives the velocity of sound in any conductor. +An idea of the actual wave length for common +sounds may be had thus: If the middle C of the piano +makes $261$ vibrations per second, and the velocity in +the air of the room be $1,140$ feet, $\dfrac{1140}{261} = 4.36\text{ feet}$, +as the length of the air wave, and for a man's voice it +will be about $\dfrac{1140}{125} = 9.1\text{ feet}$, while the highest note +on a piano will be $\dfrac{1140}{4000} = .285\text{ foot}$, or $3.4\text{ inches}$. In +water the velocity is four times greater than in air, in +wood about twelve times, and in steel about sixteen +times greater; and this will give a corresponding increase +in the wave length. This velocity of sound in +air is, roughly, about a mile in five seconds, or twelve +miles a minute; and at this rate nearly a day and a +half would be needed to go round the earth. + +Air waves, like water waves, are reflected when they +come against a more solid body. Such reflections of +air waves are called echoes. The mere fact of reflection +does not change the length of the wave, as the +pitch of a sound is not altered by having its direction +changed. The law of sound reflection is the same as +that for the reflection of energy in general; viz., the +angle of reflection is equal to the angle of incidence. +Neither does reflection change the velocity of sound +waves. + +The phenomena of echoes are familiar to every one, +for walls, houses, wood, and hills all echo sounds; and +one may roughly determine the distance to such an +\DPPageSep{280.png}{266}% +\index{Musical sounds}% +echoing surface. As one approaches such surface the +time between producing a sound and its return is +shortened, until, when about sixty feet from it, the two +so blend that the echo is no longer heard with distinctness. +The sound has then travelled $120$~feet. + +When sounds are produced at the ends of tubes the +walls of the tube prevent, by reflection, the scattering +of the waves, and the whole motion is kept in nearly +parallel lines, and with slight loss in strength; hence the +utility of speaking-tubes. If the tube be a short one, +and stopped at one end, a new phenomenon appears +for sounds having a wave length about four times the +length of the tube. The sound is much strengthened. +A tuning-fork making say $435$~vibrations per second will +have a wave length of about thirty-one inches. If it be +held while it is vibrating over a tube or vessel of any +sort, between seven and eight inches deep, the increase +in the strength of the sound will be very marked. The +motion in the air is so much swifter than the prongs of +the fork that, while one prong is beating downwards +and thus producing a condensation in the air, the wave +reaches the bottom of the tube; there it is reflected, and +gets to the top just as the prong of the fork has returned +to its normal position. As the fork continues +upward, forming a rarefaction, the rarefaction also +travels down the tube, and is reflected so as to get +back when the prong has returned to its normal position; +so for a complete vibration of the fork the air +wave has travelled four times the length of the tube. +It is possible in this way to make quite accurate measurements +of either the wave length of a sound, its +\DPPageSep{281.png}{267}% +\index{Musical ratios}% +\index{Noise}% +velocity, or the number of vibrations a sounding body +makes per second. This phenomenon is called resonance; +and it is the chief factor in wind musical instruments, +such as flutes, organ-pipes, and the like. +Resonance in general means the ability of a body to be +thrown into sound vibrations by sound waves, and there +are two well-marked cases that need to be considered. +When the stem of a vibrating tuning-fork is held upon +a table the sound in the air is much louder, for the +whole table is made to vibrate at the same rate as the +fork. The table will resound loudly to forks of any +pitch. Such vibrations as are different in pitch from +that belonging to the body itself are called \emph{forced} vibrations. +Resonance of this sort is the function of the +sounding-boards of pianos, the bodies of violins, guitars, +and other similar instruments. + +If two tuning-forks have the same pitch, and one of +them be made to sound, the other one will presently be +made to sound also, though it be several feet away from +the former one. The air waves act upon it like a +pusher upon one swinging; at each return a little more +energy is added, until the amplitude has become great +enough to make the sound audible. Such vibrations +are called \emph{sympathetic}, for they are only effective upon +bodies whose own rate of vibration is the same as that +of the sounding body. Raise the damper to the piano +and sing a sound of any particular note, then listen. +The same note will be heard prolonged by the piano. +The particular string which can give that pitch of sound +has been thrown into similar vibrations, and continues +to sound as it would if caused to in any other way. +\DPPageSep{282.png}{268}% + +The air as a body is too large to have a vibratory +rate of its own, and, consequently, all sounds in it are +properly called forced vibrations; but, when it is confined +in cavities, resonance becomes apparent, and +sympathetic vibrations may be so strong as to be deafening. +That is the case often in locomotive furnace-flues +when the door is opened. One may hear it a mile +or two. The resonance of large rooms sometimes +renders it very difficult to understand a speaker in +them. + +The prolonged sound of thunder has been often explained +as due in some measure to echo from the clouds, +but it is doubtful whether clouds do echo sounds. No +one ever hears the sounds of bells, whistles, or cannon, +or other strong sounds, coming from the clouds, as +would be the case if they reflected sounds appreciably. + +When a single key of a piano is struck, there is produced +what is called a musical sound. There is a definite +pitch that is maintained. Strike half a dozen +adjacent keys at once, and the effect is what is called +a noise, though each component by itself would give a +pleasing sound. A load of stones when tipped from +a cart makes a great racket; yet each stone, if struck +with a hammer, may give out a distinct musical sound. +Nearly every body has its own musical pitch; but, if a +number of bodies with different unrelated pitches are +listened to at once, the effect upon the ear is a discordant +one, and is called a noise. + +When, however, two or more musical sounds whose +pitches stand in a simple ratio to each other are heard +together, they blend so as to form a pleasing combinational +\DPPageSep{283.png}{269}% +\index{Musical instruments}% +sound. Thus, if one makes twice as many vibrations +per second as the other, the sound is a very +smooth musical one, and one is said to be the octave of +the other. If middle C of the piano makes $261$~vibrations, +the octave above will make~$522$, and the octave +below~$130.5$; and these may all be heard at once as a +musical sound. In music an octave is divided up into +eight parts called tones; and these are sung as \emph{do}, \emph{re}, +\emph{mi}, and so on. If a string be stretched between two +points and the distance measured, the sound it will +produce may be called \emph{do} of the scale. If the string +be now shortened by a bridge so as to produce the note +\emph{re}, and the length of the string be again measured, its +length will be found to be eight-ninths of the length +of the first, the note \emph{mi} will be four-fifths, \emph{fa} three-fourths, +\emph{sol} two-thirds, \emph{la} three-fifths, \emph{si} eight-fifteenths, +and the next \emph{do} one-half. As the number of vibrations +a stretched string will make is inversely as its length, +it follows that these fractions inverted will represent +the relative number of vibrations produced by each +member of the musical scale when compared with the +beginning or fundamental one. The following shows +the letters of the musical scale, with their ratios and +vibration numbers for the middle octave of the piano. + +\begin{center} +\TableFont% +\begin{tabular}{cccccccc} +C & D & E & F & G & A & B & C \\[1ex] +& $\dfrac{9}{8}$ & $\dfrac{5}{4}$ & $\dfrac{4}{3}$ & $\dfrac{3}{2}$ & $\dfrac{5}{3}$ & $\dfrac{15}{8}$ & $\dfrac{2}{1}$ \\[2ex] +261 & 293.62 & 326.25 & 348 & 391.5 & 435 & 489.37 & 522 +\end{tabular} +\end{center} + +The meaning of this is that $\dfrac{9}{8}×261 = 293.62$, and +so on, so that the notes of the musical scale stand in +\DPPageSep{284.png}{270}% +\index{Sound, vocal}% +\index{Voice}% +simple ratios to each other; and, if one has the vibration +rate of any one of them, he can compute any +others. Of course any octave above this one will have +simple multiples of these numbers for their vibration +numbers. + +But these numbers signify more than simply this: +they signify that, when a second one is sounding with +C, it will make the number of vibrations represented by +the numerator of the fraction; while C is making the +number indicated by the denominator. Thus, G makes +three vibrations while C makes two. The sounds are +concordant one-third of the time, and the effect is a +pleasing tone. On the other hand, D makes nine while +C makes eight, and the two are in accord but one-eighth +of the time; and the effect is displeasing, and is called +discordant. The smaller the ratio the more musical +and harmonious the sounds; and music is made up of a +succession of sounds standing in such relations to each +other, and, when different ratios are employed, it is only +for contrast, and return is quickly made to these ratios. +The ear will not long tolerate a departure from them. + +It has been stated that sympathetic vibrations would +cause a given body to vibrate. Press down gently a +base C on a piano, so as not to make it sound. Now +strike the C above it, holding down the key for a second +or two. On letting up the latter the sound of the +latter will continue to be heard, but coming from the +lower key, as can be learned by letting up the key, when +it will cease to be heard. If the G above the struck C +be now struck with the same low C held down, the +sound of the G will be heard from the base string, and +\DPPageSep{285.png}{271}% +so one may go up, finding eight or ten strings, each one +of which will make the low C string vibrate, giving out +the sound of the higher string. It is found that each +one of the strings able to do this has a vibration number +which is a simple multiple of the lowest one. The first +one is the octave, making twice the number; the second +one is the fifth of that octave, making three times the +number; and so on, to the upper limit of the piano. + +This means that a piano string is capable of vibrating +in a number of rates,---two, three, four, and so on, times +its own lowest rate, which is always called its pitch. +It is also found that this process is reversible; that is, +if each one of these keys in turn be held down and the +lowest one struck, they will each be set vibrating; and +this shows that the struck string vibrates itself in the +several different pitches represented by the multiples +of its fundamental rate. The sound of a piano string is +therefore a compound sound. In such a compound +sound the lowest one is called the fundamental, and the +others the over-tones, or harmonics. Some of these +harmonic sounds are likely to be stronger than others; +and some may even be so much more energetic than +the fundamental as to nearly drown the latter, so as to +make the pitch of the string to appear an octave or +more higher than it really is. The number and relative +strength of the harmonics in a compound sound make +the difference in the quality of sounds. In all such +instruments as pianos, violins, guitars, and the like +string instruments, the number and strength of the +over-tones depend in a large measure upon how and +where the strings are struck and made to sound. A +\DPPageSep{286.png}{272}% +\index{Ear}% +piano string plucked near its middle point gives a different +sound from what it will give if plucked near one +end, and different in each case if plucked by the fingernail +and by the finger. So the quality of sound can be +much modified by mechanically varying these factors. + +In other musical instruments the sounds are also +compound in a similar way, differing in the number and +strength of the higher harmonics. Some have the +even harmonics, as the second, fourth, sixth, and so on, +stronger; some have the odd ones---first, third, fifth, +etc.---stronger; some have few, and some many. A +flute has but one or two, a violin has twenty; and thus +the character of the sounds of musical instruments is +explained. + +As for the voice, the sound is produced by the vibrations +of what are called the vocal chords, which are +fixed at the junction of the trachea and æsophagus, and +through which all the air to and from the lungs has to +go. These chords are modified in tension by muscles +at will, and so change the pitch of the vibrations. The +cavities of the throat, the mouth, and nose act as resonators +for these sounds and seem to strengthen some +of the constituents, thus giving prominence to certain +ones to the exclusion of others. That the mouth acts +this way may be observed by pursing the lips as if to +produce the various sounds of ah, oo, o, snapping one +cheek with the finger. These sounds will result; +while, with a little trial, one may thus snap a tune +which may be heard through a room, merely altering +the size of the mouth cavity. The cavity of the nose +is as important as that of the mouth. When this cavity +\DPPageSep{287.png}{273}% +\index{Corti's fibres}% +\index{Fibres of Corti}% +is small and narrow, there is produced what is called +a nasal sound. When this is prominent, and is not the +result of a cold, as is sometimes the case, the trouble +is a physiological one, due to the bad shape of the +resonating cavities rather than to careless habits, as is +often assumed by some teachers of expression. Some +different pitch of the voice in ordinary speaking might +be adopted, and thus in some measure prevent the disagreeableness +of the nasal sounds, but no amount of +painstaking can altogether prevent it. That structure +and its acoustic effects are an inheritance in some parts +of the world, as are crooked noses, thick lips, black +eyes, and broad heads in other and different parts of +the world, and is no more to be legislated away than +are these other physiological peculiarities. Neither is +it a proper subject of ridicule, more than lameness or +defective vision. + +If the bell of a locomotive be rung while it is swiftly +approaching one, the pitch of the sound rises until the +engine has reached the observer. As it retreats the +pitch lowers, and the difference in pitch becomes +greater as the velocity of the engine is greater. The +explanation of the phenomenon is, that one judges of +the pitch of a sound by the number of vibrations that +reach the ear per second. Suppose an observer be +distant eleven hundred feet from a source of sound of +one hundred vibrations per second. If both observer +and source remained in place, one hundred vibrations +per second would reach the ear of the observer, and +there would be one hundred more on the way to his +ear. If the observer should continue to go that whole +\DPPageSep{288.png}{274}% +distance of eleven hundred feet to the source of the +sound in one second, he would not only receive all he +would by standing still, but in addition all that were +on the way to him,---two hundred vibrations in all,---or +just twice the number that would reach him if he +remained in place. Now, twice a given number of +vibrations represents a difference in pitch of an octave. +The sound he would hear would be an octave higher +than the sounding body was actually making. Any +less velocity than that supposed would make a corresponding +less difference in pitch, but such velocities as +railway trains have may make a difference in the pitch +of more than a musical tone. Of course, if the sounding +body and listener be separating, a less number of +vibrations will reach his ear, and the pitch will be correspondingly +lowered. One may roughly determine +the velocity of a train of cars by noting the change in +pitch of bell or whistle. Thus, if the difference be, +say a musical semitone,---one-sixteenth,---then the +speed of the train is one-sixteenth the velocity of sound +in air, one-sixteenth of $1,125$~feet, which gives seventy\DPtypo{-}{ }feet +per second, or forty-seven miles an hour. + +The ear is a complicated structure of tubes, muscles, +cartilages, bones, fibres, and nerves. The external +part, or conch, is of but little service in hearing in man, +for it cannot be directed, as can the ears of horses and +cattle. If it stands out from the head so as to have +some use as a collector, it is supposed to be in abnormal +position; but it is not much needed in any case. +The orifice of the ear is known as the tympanum, a +tube a little over an inch in depth and about a quarter +\DPPageSep{289.png}{275}% +\index{Life}% +of an inch in diameter. At the inner end it is covered +with a thin membrane called the drum of the ear. On +the inner side of this membrane, there is attached to +the middle of it a bone fixed to a kind of hinge, so that +any movement of the drum of the ear, in or out, makes +this bone to move in a similar way. Then follows a +network of bones and cartilages, and a set of fibres +known as Corti's, of different lengths, and whose function +has been supposed to be for sympathetic vibrations. +%[Illustration: ] +\begin{figure}[hbt] + \begin{center} + \Graphic{3.5in}{289a} + \end{center} + \Caption{34}{Diag.\ 34.---The Ear.} +\end{figure} +There are in the neighborhood of $4,000$ of these +fibres, each one adapted to vibrate at a different pitch. +Then follow the nerve terminals and the acoustic +nerve itself, which goes to the base of the brain, where +its function as an acoustic instrument ends with the +delivery of its peculiar motions, interpreted by consciousness +as sound. + +It is easily seen that the whole structure is one +adapted to receive vibratory motions from the air, +within prescribed limits, and transmit them inwards +\DPPageSep{290.png}{276}% +\index{Life, definitions of}% +where they can be interpreted. The tube itself possesses +resonating properties like any other tube. The +membrane is shaken to and fro by sound vibrations, +and this movement is handed on to each distinct part +until the nerve itself is shaken. From beginning to +end, it is only the transfer of a particular kind of +motion,---what is called mechanical,---perhaps transforming +it from longitudinal to transverse vibrations. +That it is so extremely sensitive as to be affected appreciably +by motions so slight as the ten-millionth of an +inch is a marvel, and shows that mechanical motions of +translation, though on a scale of molecular magnitudes, +is able, through the proper avenue, to affect the mind +and develop consciousness, which experience enables +the individual to interpret by direct inference. + +Let one reflect upon the facts furnished in great +abundance by physical science,---that all the data which +comes to the mind through consciousness, and which +furnishes what is called experience, is simply motion +of some sort. Touch, producing pressure upon the +surface of the body, finds a suitable nerve to transmit +to the base of the brain that kind of a disturbance; +sight, another kind of disturbance to the optic nerve, +transmitted to the same place; hearing, still another +kind of motion given to another kind of nerve running +to the same headquarters. So, by means of motions +of various sorts man determines his place in the +universe, and learns how he may adjust himself to it. +%\DPPageSep{291.png}{277}% + + +\Chapter{XI}{Life}{277} + +\First{Any} scheme of physics which fails to present that +great body of physical phenomena exhibited by living +things, both vegetable and animal, must be incomplete. +Many of these phenomena have seemed to be so remote +from ordinary mechanical operations that, in the +absence of definite knowledge concerning them, their +origin, factors, and relations to subsequent phenomena, +it is not to be wondered at that they were long thought to +be due to some peculiar force residing in a living thing, +\index{Force, vital}% +\index{Vital force}% +\Pagelabel{277}% [** PP: Note to p. 277 clearly points here] +\Pagelabel{279}% +which was not to be attributed to the general endowments +of matter, but only to be found in certain organized +forms of matter, which organization it had itself +built up as a \emph{habitat}. It was conceived to exist apart +from any material organization as a kind of entity. +The difference between a living and a dead animal was +thought to be simply one of the presence or absence +of that entity called life. It was thought to be able to +effect changes in matter which the ordinary physical +and chemical forces could not possibly do; and many +of the chemical products of living things were supposed +to be formed only through its agency; and still +more than that: it was held to be capable of ``suspending +the action of chemical laws.'' That the stomach +\DPPageSep{292.png}{278}% +\index{Cell structure}% +\index{Protoplasm}% +itself was not digested by the gastric juice it secreted +was held to be proof of its control over chemical +operations. + +There have been many attempts to define life, but +the efforts have not been very successful. Thus Kant +defines it as ``an internal principle of action;'' Treviranus, +``the constant uniformity of phenomena under +diversity of external influences.'' Bichat, ``Life is the +sum of the functions by which death is resisted.'' +Duges calls life ``the special activity of organized +beings.'' De~Blainville's and Compte's definition runs +thus: ``Life is the twofold internal movement of composition +and decomposition, at once general and continuous;'' +and Spencer's is ``the continuous adjustment +of internal relations to external relations.'' It will be +observed that in all of these what is described is a +series of processes, or a body of functions belonging to +certain structures, rather than an entity,---a description +of what life does rather than what it is. + +Analogous difficulties were met in the attempts to +define other of the so-called physical forces. Thus +light was supposed to be a created something. The +corpuscular theory of it represented it as consisting +of particles of some sort that ordinary matter could +absorb and eject, and which, therefore, had an existence +independent of matter. The establishment of its +being but wave motion in the ether completely destroyed +the notion of its having an objective, independent +existence. + +Heat, too, was supposed to be a kind of imponderable +matter, and certain phenomena in ordinary matter +\DPPageSep{293.png}{279}% +\index{Molecular stability}% +depended upon its presence or absence; it, therefore, +was supposed to be an entity, and to have an independent +existence. Experiment showed it to be but a +particular kind of motion, so the idea that there was +any such thing as heat was abandoned. + +Electricity and magnetism were supposed to be +fluids; and some of the early terminology still survives +in popular speech to-day, as when one reads that the +electric fluid struck a tree or entered a house. Nevertheless, +nobody now believes that either of them is +a fluid, or has an existence independent of matter. + +The regular movements of the planets were thought +to require intelligent directive power to keep them in +their orbits; but now the gravitative property of matter +itself is held to be quite sufficient to account for all +the observed facts, and the extra material directive +force is held to be an entirely unnecessary assumption. + +The discovery of the conservation of energy, covering +every field that has been investigated, led to the +growing conviction that there are no special forces of +any kind needed to explain any phenomena. What +seemed probable forty years ago, to those who were +conversant with the facts,---that vital force as an entity +has no existence, and that all physiological phenomena +whatever can be accounted for without going beyond +the bounds of physical and chemical science,---has +to-day become the general conclusion of all students of +vital phenomena; and vital force as an entity has no +advocates in the present generation of biologists.\footnote + {See Appendix, \Pageref{p.}{400}.} +The +term has completely disappeared from the science, and +is only to be found in historical works; and every +\DPPageSep{294.png}{280}% +phenomenon which was once supposed to be due to it +is now shown to be due to the physical properties of a +particularly complex chemical substance known as protoplasm, +which is the substance out of which all living +things, animals and plants, are formed. This protoplasm +is entirely structureless, homogeneous, and as +undifferentiated as to parts as is a solution of starch, +or the albumen of an egg. Minute portions of this +elementary life-stuff possess all the distinctive fundamental +properties that are to be seen in the largest +and most complicated living structures. It has the +power of \emph{assimilation},---that is, of organizing dead food +into matter like itself,---and, consequently, what is +called growth. It possesses the ability to move---that +is, of visible, mechanical motion, which is technically +called \emph{contractility}; and it possesses \emph{sensitivity}---that +is, ability to respond to external conditions. + +It was formerly thought that the cell was the +physiological unit, a cell having walls differently constituted +from the substance enclosed, also a nucleus; +but as the microscope was improved, and anatomical +research continued, it became evident that the cell, +with its more or less complicated structure, was itself +built up by the structureless protoplasm. As before +stated, it is a highly complex substance, chemically +considered, made up of many atoms of carbon, hydrogen, +oxygen, and nitrogen, with a small number of +atoms of sulphur and phosphorus,---more than a thousand +of them in one molecule; and there appears to be +a great number of varieties of it. A small pellicle of +this substance, like a minute bit of jelly, without any +\DPPageSep{295.png}{281}% +\index{Growth of crystals}% +\index{Growth of lobster}% +\index{Matter, living}% +parts or organs, possesses its various attributes in equal +degree in every part. Any particular portion can lay +hold upon assimilable material, or digest it, or be used +as a means of locomotion; so that what are called +tissues of animals and plants are only the fundamental +properties of the protoplasm out of which they have +been built---thrown into prominence by a kind of division +of labor. The protoplasm organizes itself into +cells and tissues in the same sense as atoms organize +themselves into molecules, and molecules into crystals +of various sorts, having different properties, that depend +upon the kind of atoms, their number and +arrangement in the molecule. + +The greater the number of atoms in a molecule the +less stability does it have, and especially is this the case +with molecules containing nitrogen. Many of its compounds +are so unstable as to be liable to explosive +disruption. This fact makes it easy to understand how +there exists, in a mass of such molecules no larger than +the minute ones seen in the microscope, conditions for +internal motions in the nature of explosions. + +Let it be granted that atoms are in the neighborhood +of the fifty-millionth of an inch in diameter; then, +if a thousand of them are organized into a molecule, its +diameter would be about the five-millionth of an inch. +A speck of protoplasm, one ten-thousandth of an inch +in diameter, would require not less than five hundred +such molecules in a row to span it; and there would be +no less than one hundred and twenty-five millions of +such molecules in the small mass. Some of these molecules +would be less stable than others on account of +\DPPageSep{296.png}{282}% +\index{Food}% +the internal motions that all the time are present. +Physical disturbances, external to such a mass, such as +temperature, ether waves of light, and chemical re-actions +of any sort, and so on, can induce and add to the +disruption and other changes going on, and visible motions +might be expected to follow. + +That such external agencies can bring about visible +motions of microscopic particles has long been known. +A few small bits of camphor dropped upon the surface +of clean water in a saucer will begin to move about in +a remarkable way. They will spin round, and travel +from place to place, and dodge each other in a manner +strongly like living things. A little gamboge, which is +a reddish-yellow gum used as a pigment, if rubbed up +in water and looked at through a microscope, will be +seen to have its particles in constant motion like animalcules. +This is known as the Brownian movement, +and is caused by temperature changes between the +particles and the water. Such phenomena are rather +extreme cases of the re-action of external molecular conditions +upon a small mass of matter, resulting in mechanical +motions. In protoplasm there is added to +these same external ones others of the nature of molecular +explosions within the mass, and together they +give rise to a number of effects, in which the transformed +energy shows itself in redistributing the molecules, +absorbing additional material, and movements of +other sorts. + +Biological researches within the past few years have +added vastly to our knowledge of protoplasm and its +properties; and there is no longer any question that its +\DPPageSep{297.png}{unnumbered}% +%[Illustration: ] +\begin{figure}[hp] + \begin{center} + \Graphic{\linewidth}{297a} + \label{fig:frost} + \end{center} +\begin{minipage}{\linewidth} +\scriptsize% +The above picture is copied from a photograph. It represents the plume-like +forms assumed by water when crystallized in a basin. The similarity it presents +to vegetable forms is very striking. One may often see on frosty window-panes +fantastic imitations of organic things which forcibly suggest vitality. They are +too common to be considered coincidences. +\end{minipage} +\end{figure} +\DPPageSep{298.png}{283}% +\index{Muscles}% +qualities are the expression of the various movements, +chemical and physical, and belong to it simply as a +chemical substance. Chemists have synthetically +formed out of the various elements a vast number of +substances that were not long ago believed to be formed +only by living things; and there is but little reason to +doubt that, when they shall be able to form the substance +protoplasm, it will possess all the properties it is now +known to have, including what is called its life; and one +ought not to be surprised at its announcement any day. + +Some of the phenomena exhibited by bodies called +inorganic, such as minerals of many kinds, possess +properties that are very like those supposed to belong +solely to living things. A spider or a lobster will have +a new leg or claw grow to replace one lost in any way. +In like manner a crystal will replace a corner or side or +any defacement so as to complete its symmetry before +it will begin to grow elsewhere, and this in cases where +the crystal has been defaced or incomplete for millions +of years, as is found to be the case sometimes in geological +specimens. Such phenomena have led some of +the most thoughtful and best informed naturalists to +query whether the evidence we have does not lend +much support to the theory that \emph{matter itself is alive}, +and that the difference we observe in things is simply +one of degree rather than of kind. See \hyperref[fig:frost]{opposite page}. + +In the brief space of this chapter, only an outline of +the relations between vital and physical phenomena can +be given, and of these, only a few of the more prominent +ones. It will suffice to show that such phenomena +as assimilation and growth, movement and irritability, +\DPPageSep{299.png}{284}% +or sensitivity, have antecedents of physical energy in +the same sense as the movements of an electric motor +have physical antecedents in electric currents, dynamos, +steam-engine, and furnace. + +The food of an animal consists almost altogether in +highly complex molecular compounds. It may be said to +be matter stored with energy. A pound of bread may +have the mechanical equivalent of twelve thousand heat +units, and if burnt in an engine would be better for +heating purposes than a pound of coal. When this has +been digested, and has done its work in the body, the +excreted products are of course equal in weight to the +original pound, for no kind of a physical or chemical +process affects the quantity of matter in any degree; +but the products themselves represent much less complex +compounds, and the energy has been distributed +through the body, carrying on its various operations. +There is, first, that of ordinary movement, which can be +measured in foot-pounds, as work of any kind may be. +The blood in the arteries and veins has to depend upon +a kind of hydraulic apparatus to keep it in motion. +The temperature of the body demands a supply of heat +measurable in heat units to maintain it, while the +repair and waste going on through the whole body of +all animals implies a distribution of the material necessary +for the maintenance of the integrity of the tissues, +as well as a separation and removal of the used-up material; +that is, the material that has lost all its available +energy. The energy for doing all this of course comes +from the food, so the question is not as to its source +and quantity, but it is, How is this transformation of +\DPPageSep{300.png}{288}% +\index{Nerves, their functions}% +energy in the body effected? Is it direct, or is it indirect? +This is the same as asking as to the mechanism +in the body, by means of which energy supplied is transformed +to meet the various wants of the body. + +Roughly, there are five different kinds of motion to +trace the antecedents of in the body of any of the +higher animals. First, there is the common mechanical +motions of the bony framework, which transport the +body from one place to another, or change the position +of a part with respect to the rest, as when one moves +an arm. Second, there is the motion of a muscle, +wholly different in character from the first, for the +shape of the muscle changes by contracting in length +and increasing in diameter. The muscles are so attached +to the bones that the contractions of the one +cause the others to change their positions. The muscular +contractions of the heart, arteries, and veins keep +the blood circulating; and the same is true for the processes +of digestion, breathing, etc. + +Third, there is the motion constituting the temperature +of the body, which, as has been explained, is altogether +atomic and molecular in its nature, and is, +therefore, in strong contrast with the other two. + +Fourth, there is a kind of motion that is going on +throughout the body of the nature of transpiration, in +which solids, liquids, and gases are passing through the +various membranes without rupturing them. In the +lungs there is an exchange of gases, oxygen going one +way and carbonic acid gas going the other. In all the +mucous-membrane-lined cavities there is more or less +liquid oozing through the walls continuously, and there +\DPPageSep{301.png}{286}% +is no tissue so dense but protoplasmic masses do not +move into or out of apparently with ease. They go +through the walls of veins and arteries as if the latter +were porous bodies, though no visible pores have ever +been discovered in them. + +Fifth, there is the motion in the nerves, in the nature +of a longitudinal wave, and the velocity of which is in +the neighborhood of one hundred feet in a second, +which, though it is slow compared with sound waves or +light waves, is fast when compared with the other +motions of the body. He is a swift runner who can +run at the rate of thirty feet a second for any distance. + +The contraction of a muscle is to be measured in +fractions of an inch per second. The motion of heat, +measured as a rate of conduction, is exceedingly small +in the animal body,---probably not the hundredth of an +inch per second. The transpiration, or osmotic action, +is also a relatively slow movement, so that a velocity of +one hundred feet per second, which is upwards of a mile +a minute, is really rapid. + +How and why the bone moves we know: it is because +the muscle that is attached to it contracts; but how is +energy spent to make a muscle contract? As a matter +of fact, when a muscle contracts it evolves a considerable +quantity of carbonic acid gas and water; it also +becomes acid, all of which imply chemical actions, for +these are chemical products. Carbonic acid gas and +water are the chief products of the combustion of such +material as foods, for they are made of what are called +hydro-carbons (combinations of carbon, hydrogen, and +oxygen chiefly); and when these elements re-combine, +\DPPageSep{302.png}{287}% +\index{Nerves, their functions}% +forming water and carbonic acid, there is always a relatively +large but definite amount of energy given out +in the form of heat, and this effect is independent of +time or place; that is, the same amount is developed +whether the process goes on fast or slow, or whether it +takes place in a furnace, in the body, or by slow decomposition +called rotting. When it goes on faster than +the heat can be conducted or radiated away, the temperature +rises and we say the body is hot. When the heat +generated is at once employed to do work, as in a steam-engine, +the temperature of it is reduced proportional to +the work done. When this takes place in a contracting +muscle better results follow, for conduction and +radiation within a muscle can take place at only a slow +rate; so the temperature rises, and this explains the +sensation of warmth resulting from muscular exercise. +The increase in perspiration is also partly due to the +same re-action of decomposition, as water is one of the +products. When the muscle in contracting does additional +work, as in raising a weight, a corresponding +amount of decomposition takes place, and the heat is +but transient, as it is at once transformed into the +muscular motion, which is as much mechanical in its +nature as is the movement in a steam-engine. + +The muscle is quite like a spiral spring, which may +contract upon itself and do work by contracting. + +It is not the substance of the muscle itself that undergoes +the change of disintegration, evolving water, carbonic +acid, and other products; but there is evidence +that the muscle secretes a particular substance called +\emph{inogen}, the rapid decomposition of which causes the +\DPPageSep{303.png}{288}% +\index{Corn, life of}% +\index{Egg}% +contraction. As this substance can only be replaced at +a definite rate and in a definite amount, it is clear that +the work of a given muscle is limited by the physiological +processes that precede it. The rate of work of a +muscle is then determined by the rate at which inogen +can be secreted by the muscle, and work done beyond +that rate results in muscular exhaustion, which in its +early stages is called weariness, and requires repose for +fresh accumulation. Excessive draught upon the +muscles reduces their ability to secret inogen, and their +degeneration follows. + +Muscular contraction is satisfactorily accounted for +without assuming any vital force. It has a purely +physical origin, the structure itself acting as a kind of +mechanism for transforming the chemical energy supplied +in food into the mechanical forms of energy +represented by the various movements of the body, +external and internal, which have already been mentioned. + +That physical and chemical agencies bring about new +movements is of course well understood. Especially +clear is this for such nerve actions as accompany the +special sensations of sound, sight, touch, and the rest. +That the disturbance is properly described as a movement +is apparent when it is found that it has a rate of +progression, as before stated, of from one hundred to +three feet per second. Whether such movement be +similar to a sound wave in a rod or tube, or to an electric +disturbance, makes no difference so far as the transformation +and transference of energy are concerned. +For sound there is the antecedent of vibratory motions +\DPPageSep{304.png}{289}% +\index{Growth}% +in the air; for light, waves in the ether; for touch, +mechanical pressure; for taste, chemical solution; and +for smell, gaseous substances with definite constitutions +and rates of vibration. These represent the ordinary +stimulants to action of such nerves, and so are commonly +understood to be the source of disturbance; but +every one of these so-called special nerves may be +excited to action by other agencies than the common +or normal ones, and the effect is the same. Thus, the +optic nerve may be stimulated by pressure, by cutting, +pricking, thumping, and electricity, and the effect is the +sensation of light; and, in the absence of other sources +of information as to the origin of the sensation, no one +could tell which of these was the originating one. +Every one of them, however, represents some form of +energy spent upon the nerve. What is important to +note about it is this,---the nerve transmits an impulse +it receives, quite indifferent as to its source, and is +interpreted as a definite sensation, quite independent +of its origin. The latter is only an inference, and is, +therefore, liable to be \DPtypo{eroneous}{erroneous}. + +But there are several other kinds of nerves, each +with some different function from the rest. Thus there +are nerves running to muscles, causing them to contract, +called motor, or efferent, nerves; secretory nerves, +to glands that cause secretions; vascular nerves, that +cause contraction or dilatation of the walls of blood-vessels;\DPnote{** Only instance,} +inhibitory nerves, that affect other nerves so +as to moderate or entirely stop their action; reflex, or +afferent, nerves, which convey disturbances to the brain +or other nerve centres, but which cause no sensation; +\DPPageSep{305.png}{290}% +and still others known to exist, but the special functions +of which are unknown. + +To describe the action of any nerve is to describe +the transmission of energy in greater or less amount, +and transmission in all cases requires time. This does +not mean that the energy which does the special work +of moving muscles or the chemical transformations of +foods into tissues is transmitted by the nerves, but +that the transformations of energy already present in +each place where the work is to be done are controlled +by nervous energy in the same way as a local galvanic +circuit is controlled by a relay, or the explosion in a +mine is determined by an electric spark. The energy +available for all the purposes of an animal, including +man, exists in the material of the body. The activity +of protoplasm in the various cells transforms the various +food stuffs into the proper substances needed. The +energy is already present; it is only differently distributed +by protoplasm; and nervous action determines +what changes, if any, shall go on at a given place. + +Temperature determines whether any of the physiological +process shall go on or not. Plants and animals +of a low order, such as snakes, frogs, and fishes, may be +frozen without injury. Some of the minuter forms of +life can withstand arctic winters, for there is an abundance +of insect life in those regions. On the other +hand, a temperature of~$140°$ is destructive to the life of +everything except the seeds and spores of a few microscopic +beings. Some of these have been known to +survive a temperature of~$200°$, continued for an hour +or more; but nothing has been found that can withstand +\DPPageSep{306.png}{291}% +\index{Matter, living}% +\index{Toepler-Holtz electrical machine}% +the boiling temperature of~$212°$. The retarding +influence of cold upon vital processes can be understood +by considering that special chemical compounds require +special temperatures to form; and, if energy has to be +supplied to maintain the proper temperature, so much +the less will be at disposal for other processes. If life +processes were other than physical, it might be expected +that they would not be quite so rigidly conditioned by +physical surroundings. + +There is a distinction between a living plant or animal +and the seed or spore or egg out of which they +grow. Both are commonly spoken of as living things, +but the processes that constitute life in the one are not +present in the other in any degree; thus, for example, +growing corn and the grain of corn from which the +plant started. The grain of corn may be kept in a +suitable dry place for several years without any apparent +change, unless it be some loss in weight due to +evaporation from it. How long it may exist thus and +still be able to grow if planted is not known. Grains +of wheat found with Egyptian mummies buried three +thousand years ago have been said to grow, but there +is much doubt about it, and botanists do not credit +the story. A few years' keeping in moister climates +destroys their ability to grow, and farmers always +choose seed corn from last year's growth, which is an +indication that there is a process of slow deterioration +going on that ends after no long time in utter inability +to grow under any conditions. This ability to remain +for several years in a nearly stable condition is a property +of the seed that does not belong to the plant; for, +\DPPageSep{307.png}{292}% +when growth has once really begun, it must keep on +growing or die: arrest is impossible, which seems to +show that life is a process rather than a condition, and +the grain of corn is simply a combination of materials +where, under suitable conditions, life may begin. + +The constitution of corn is well known; that is, the +elements out of which it is built up, and the proportionate +parts of each. Like other kinds of food, it has +carbon, hydrogen, oxygen, nitrogen, for the chief constituents, +and in addition a little sulphur, phosphorus, +iron, potassium, and a trace of some others. These, +when organized as they are in a grain of corn, form a +very complex body indeed. There are not only molecular +groups of many sorts, but these are segregated +into families, so that bodies of one constitution are all +in one locality, and bodies of other constitutions in +other separate localities, but definitely arranged so as +to be available when the life process begins. Once +formed, it appears to be as inert as a crystal of any +sort, and no change happens to it until such physical +conditions as heat and moisture are provided. These +it absorbs and transforms; a sprout appears, then a +root, each with different functions, one for absorbing +ether waves, the other for absorbing water. The +energy of ether waves is utilized in digesting carbonic +acid and building up the structure, and the +growth is simply the addition of materials gathered +in this way and elaborated into similar protoplasmic +form and structure. Growth implies transformation +of one substance into the material of another, and is +effected by means of energy from external sources. +\DPPageSep{308.png}{293}% +\index{Atoms, life associated with}% +\index{Foster, Dr.\ Michael, quoted}% +The energy of a stalk of corn may be found by using +it as fuel and finding its heat units per pound. It has +about the same value as wood. The corn itself has +somewhat higher value, which shows it to have a more +complex molecular structure, and is correspondingly +less stable. + +In like manner an egg, say that of a hen, possesses a +degree of stability that does not belong to it after it +has begun to grow. It may be kept with some care +for a few months and retain its ability to develop into +a chick; yet it ultimately wholly loses its possibility, +which shows that slow changes of the nature of disintegration +are going on that cannot be arrested. The +physical condition necessary to initiate the growth of +the egg is simply one of temperature. One hundred +and four degrees continued for three weeks completes +the process. When one reflects upon the nature of +heat,---that it is but vibratory motion,---he can at once +see that energy has been supplied to a complex mass +of matter and it has been chemically transformed. +There are new chemical products and new properties +produced; and however wonderful the completed product +may be, the factors at work to produce it have been +absolutely physical from beginning to end. After +growth has once begun the process must continue, at +the peril of quick degeneration on stopping; so that an +egg, like the grain of corn, seems to be a material +structure where life may begin, rather than a living +thing itself. Such a distinction has not, however, +been made in the literature of the development of living +things. It has, perhaps, only a philosophical importance; +\DPPageSep{309.png}{294}% +but, if there are any who would still hold that +life is a something \textit{sui generis}, that may be considered +apart from some material structure and not as a transformation +process, it will be well for such to inquire +what can become of such life as a grain of corn or an +egg has when either of them is cooked, or when either +of them is left for months or years and they rot. At +first it is in the grain of corn or egg. If it be an entity +of any sort it must be somewhere else after leaving +either the one or the other. On the other supposition +the question does not arise at all, for it is plain that +disintegration destroys the molecular arrangement, and +with the destruction of that the properties of such +organizations of matter must go also; for the properties +of a mass of matter are, by general agreement, the +result of the arrangements of the matter. Woody fibre +and starch are of precisely the same chemical composition, +but the properties of the two are far from being +identical. + +What, then, is the distinction between what is called +living and dead matter? One is able to transform +energy for its maintenance, and the other seems to be +wholly inert; yet, if analyzed, both may be reduced to +precisely the same amount of elements. + +An analogy may make the distinction plainer. A +maker of physical instruments may make what is called +a Toepler-Holtz electrical machine. It is composed of +wood and glass and brass and tinsel and tin foil, and +possibly of other materials. Each one of these is got +at a different place from the rest, and all are assembled +in the shop of the maker. The individual parts are +\DPPageSep{310.png}{295}% +\index{Fields, physical}% +\index{Fields, thermal}% +\index{Physical fields}% +shaped in particular ways, and these are at last fixed in +their appropriate places. The machine is done; but it +has never generated an electric spark, and one could +discover no electricity about it. Indeed, there is none, +any more than when the material was unshapen and +lying upon his bench. If the proper kind of energy is +spent upon it, however, it at once becomes electrified, +and electrical energy may now be got from it in indefinite +quantity, dependent wholly upon the proper turning +of the crank. If that be turned the wrong way, or +if it be stopped, the electricity soon quite disappears. +Now, it is the function of such a machine to transform +mechanical energy into electrical, and it does this so +long as energy is furnished for transformation and the +integrity of the machine is maintained. If one weighs +the machine before it has been worked, and also while +it is electrified, he will find no difference. If the brass +buttons get off or displaced, if the belt gets broken or +the glass cracked, the machine will weigh just as much +as it did when they were in place; but the property of +the machine to transform energy will be destroyed, and +it may be as useless for the purpose as a coffee-mill +would be. One might speak of the whole machine as +an organism,---its wood and glass and brass as its molecular +composition, its function depending upon each +of these being in its appropriate place, and nothing +more. It can only exercise that function when energy +of the proper sort is turned into it. If its molecular +composition is deranged in any of a dozen different +ways, no one is surprised that it no longer responds to +the turning of the crank. If the complete and perfect +\DPPageSep{311.png}{296}% +machine be called living, then the one with its +parts disarranged so it can no longer perform its functions +might be called a dead machine. + +The egg may be likened to the machine. So long as +its molecular arrangement is intact, so long it is competent +to transform the heat supplied to it and exhibit +new properties. When the molecular arrangement is +interfered with, whether from within or without, its +function as transformer ceases, and we call it dead. + +It may be said, and often has been, that every living +thing has an ancestry of living things; and in human +experience it is true. It is sometimes said that one +cannot get out of a mass of matter what is not in it, +which, in this case, might imply that matter itself is +alive, as suggested a few pages back, though I have +never heard any one so conclude. If one would apply +this dictum, let him settle with himself before turning +a new electrical machine whether the electricity he is +to get from it is or is not in the machine, and how, if it +be in the machine, he can get an infinite amount from +it by simply turning the crank. He may reach the conclusion +that what can be got out of a mass of matter +depends upon its composition and structure. + +In conclusion, one perhaps can do no better than to +quote the words of Dr.\ Michael Foster, Professor of +Physiology, University of Cambridge, England, as to +the properties of protoplasm. ``The more these molecular +problems of physiology are studied, the stronger +becomes the conviction that the consideration of what +we call structure and composition must, in harmony +with the modern teachings of physics, be approached +\DPPageSep{312.png}{297}% +\index{Electrical field}% +\index{Fields, electrical}% +under the dominant conception of modes of motion. +The physicists have been led to consider the qualities +of things as expressions of internal movements; even +more imperative does it seem to us that the biologist +should regard the qualities of protoplasm (including +structure and composition) as in like manner the expressions +of internal movements. He may speak of +protoplasm as a complex substance, but he must strive +to realize that what he means by that is a complex +whirl, an intricate dance, of which what he calls chemical +composition, histological structure, and gross configuration +are, so to speak, the figures; to him the +renewal of protoplasm is but the continuance of the +dance, its functions and actions the transferences of +the figures\ldots. It seems to us necessary, for a satisfactory +study of the problems, to keep clearly before +the mind the conception that the phenomena in question +are the result, not of properties of kinds of matter, +but of kinds of motion.'' + +If such be the case, it is clear that the solution of +every ultimate question in biology is to be found only +in physics, for it is the province of physics to discover +the antecedents as well as the consequents of all modes +of motion. +%\DPPageSep{313.png}{298}% + + +\Chapter{XII}{Physical Fields}{298} + +\Section{I.---THE THERMAL FIELD} + +\First{When} a mass of matter of any kind possesses +energy of such a kind as to be able to impart some or +all of it to the medium about it, whether that medium +be the air or the ether, which transmits or distributes +it outwards with a velocity which depends solely upon +the ability of the medium to transmit energy, and not +upon the source of it, the energy so distributed is +called radiant energy. + +The term was first applied to the energy radiated by +a hot or luminous body, from which the heat was said +to be radiated away, the motions of the molecules of +the hot body being transformed into wave motions in +the ether. The wave motion thus set up is known to +be competent to set other masses of matter upon +which it falls into vibratory molecular motions, similar +to those that originated the waves. In other words, +they are capable of heating other matter. The space +within which such effects can be produced will evidently +be limited only by the distance to which the +wave motion is transmitted, and this in turn depends +upon the special medium concerned---in this case the +ether---and the uniformity of its distribution. As has +\DPPageSep{314.png}{299}% +\index{Inductive action}% +been already pointed out, the ether transmits such +wave motions in straight lines, and to an indefinite +distance,---so great at least as to require not less than +five thousand years to cross the space accessible to our +observations. As such waves of all wave lengths +travel with equal velocities, and as all known bodies +of matter are continually radiating waves of many +wave lengths, it follows that in reality every molecule +of matter sets the whole visible and invisible physical +universe in a tremor. The magnitude of this effect is +not now under consideration. + +The space external to a body within which the body +can act in this physical way upon other bodies, so as to +bring them into a condition similar to its own, is called +its \emph{field}. The heat or thermal field of a mass of +matter of any size and of any temperature must, +therefore, be as extensive as the universe, unless the +ether absorbs the energy to some extent and becomes +itself heated. At present there is no evidence that +such an effect is produced. Some astronomers have +inferred that absorption takes place, else the whole +surface of the sky would be bright with the multitude +of stars that occupy it. On the other hand, if absorption +did take place in a manner at all comparable +with gaseous absorption, it would be selective in some +degree, and the more distant stars would have a color +different from those closer to us; and the colors of all +stars would depend upon their distance from us. If +such a condition had been observed, it would be conclusive +evidence of absorption in the ether, but it has +not been observed. +\DPPageSep{315.png}{300}% +\index{Earth, a magnet}% +\index{Electrical waves}% +\index{Magnetic field}% +\index{Waves, electric}% + +Furthermore, the perception of light implies a definite +though a small amount of energy; and, as the +energy of ether waves from a given point upon a +surface varies inversely as the square of the distance +from the point, it follows that there must be some +distance from it where the energy upon the retina +must be too slight to affect it; and hence the inability +of the eye to perceive the light could not be +used as an argument against the existence of the waves +altogether. At the rate of $186,000$ miles per second +light travels $5,800000,000000$ (nearly six millions of +millions of miles) a year, and in five thousand years, +which is the distance of some of the more remote +stars, $29000,000000,000000$ (twenty-nine thousand +millions of millions) of miles. This, therefore, is the +known length of the radius of the thermal or light +field of a heated or luminous body; and, as such heat-producing +waves are radiated in every direction about +the body, the sphere having such a radius represents +the space within which any or every atom of matter +can affect other atoms to heat them. + + +\Section{II.---THE ELECTRICAL FIELD.} + +The phenomenon called electrical induction, by +which one body becomes electrified by simply being +in proximity to another body which is electrified, is +another illustration of both a \emph{field} and its property, +depending altogether upon its origin. But an electric +field differs in a marked way from a thermal field. + +Imagine a sphere---say a cannon-ball---to be electrified, +and be isolated a long way from any other body. +\DPPageSep{316.png}{301}% +Its effect upon the ether about it would be equal in +every direction. Practically, it would be distributed as +the thermal field would be; and, if the strength of the +field should be measured in any way, it would be found +to vary inversely as the square of the distance from +the body that produced the field. When such an electrified +body is adjacent to other bodies, as is necessarily +the case with every electrified body upon the +earth, the strength of the field at a given point is +found to depend upon the size, the nearness, and the +quality of the adjacent body. Suppose the adjacent +body were a similar cannon-ball, and its distance from +the former one foot. Then the strength of the field +would be found to be greatest between them, and to be +very weak in the space equidistant and on the opposite +side. One may get a mechanical idea of the condition +of things by imagining straight lines drawn from the +electrified body when out in space as if they were rays +of light, evenly distributed in space. When, as in the +second case, another ball is near to it, these rays crowd +around the second one and apparently are absorbed by +it; and these may now be represented by the same +lines, starting at the same places as before, but sweeping +in curves to the second, with only here and there +one to escape into the unoccupied space. The nearer +the two are together the more closely are these lines +crowded together in the space between; and, as the +number of these lines in a given area represent the +strength of the electric field, it is plain the field is +strongest where the lines are most crowded. On the +other hand, if the second ball had been made of glass, +\DPPageSep{317.png}{302}% +\index{Chemical field}% +\index{Fields, chemical}% +the field would have been changed but little, for glass +is a substance having but little absorptive power for +electric rays; that is, it is not much affected by an +electric field. When such an electrified ball is suspended +in an ordinary large room, these lines, representing +the field, are distributed about the room in a +manner that depends altogether upon the kind of +material there is in the room. The metallic objects, +such as a stove, a steam-radiator, a gas-pipe, and the +like, will divide the field between them, not equally, +for the nearer ones will have the most, and other parts +of the space in the room will have but a trace of it. +The great distinction between the electrical and the +thermal field will be apparent when one reflects upon +what the latter would be for the same cannon-ball made +hot and suspended, in the same manner, in the room. +The rays go straight in every direction, and are not +deflected by proximity to other bodies. The one is +uniform in every direction about it; the other is warped +by the presence of other bodies. + +An electric field, which is merely the ether in a +condition of stress, electrifies the bodies upon which it +acts; that is to say, it produces in them a condition +similar to that of the body that produced the field. It +does not heat them: it electrifies them. The process +is ordinarily called induction. If one would follow +mentally the mechanical conditions and changes that +take place when this process of induction takes place, +let him imagine the two cannon-balls suspended in +a room a few feet apart, and one of them to be +suddenly electrified artificially in any kind of a way, +\DPPageSep{318.png}{303}% +\index{Crystallization}% +as by connecting it to a charged electrical machine for +an instant. The re-action upon the ether will at once +begin. The stress into which it will be thrown will be +propagated outwards as a wave, with the velocity of +light, and equally in every direction about it too, until +the advancing wave reaches the second ball, when the +absorption so reduces the stress that other parts of +the field can move towards it, thus distorting it; for +at the outset every part of the wave moved in a radial +line. This must be the case unless the field acted +intelligently instead of mechanically, and knew where +it was to go beforehand. Of course no one would +suppose that, but the remark is made to emphasize +the necessity for the mechanical steps in order to have +clear ideas of what has happened. The whole would +happen in so small a fraction of a second that it would +be exceedingly difficult to measure it, but the rate at +which a thing is done does not necessarily modify the +way of doing it. + +\Section{III.----THE MAGNETIC FIELD.} % + +The distribution of iron filings about a magnet gives +one a very definite mechanical conception of the shape +and properties of a magnetic field. It has before been +remarked that the shape of the field depended upon +the form of the magnet, and when this was altered the +field changed its form. That it too represents a condition +of the ether seems unquestionable. That it is produced +by the arrangement of the molecules of the magnet +is also certain; but that presumes that the atoms +themselves are magnets, each having its own field. +\DPPageSep{319.png}{304}% +\index{Mechanical field}% +When these atoms are either in disorder or so arranged +as to mutually cancel each other's field, there is no field +observable. When they are made to all face one way, +their individual fields will conspire to produce a resultant +field, which will be strong in proportion to the +number of such individual fields that make it up. The +nature of this magnetic field is probably a kind of +whirl or spiral movement in the ether between the +two poles of the magnet; but, as two similar adjacent +whirls or lines are mutually repulsive, they spread out +into space indefinitely, and are almost always curved. +The earth as a great magnet has such a field, the lines +reaching from the north polar regions upwards and +southwards, re-entering the earth by similar downward +sweeps in the south polar regions. How far away +from the earth some of them may extend no one +knows, but there seems to be no reason why they +should not extend as far as any ray of light. There is +good reason for thinking that the other members of the +solar system are magnets, especially as iron and nickel +are so abundant in the sun and in the meteorites that +reach us from space. If that be the case, they are all +moving in each other's magnetic fields. As the movement +of a conductor in a magnetic field produces an +electric current in the conductor, and as what are known +as earth currents, apparently due to some extra terrestrial +source, are well known, their origin is accounted +for. But, when there is iron in a magnetic field, the latter +acts upon it so as to compel it to produce a field of +its own. In other words, it makes a magnet of the iron. +The process is called magnetic induction. Like the +\DPPageSep{320.png}{305}% +other cases, it is a two-step process. There is, first, the +magnet with its molecular arrangement; second, the +action of the magnet upon the surrounding ether; and, +third, the re-action of the ether upon the second body, +making it a magnet. The heat field heats a body, the +electric field electrifies a body, the magnet field magnetizes +a body; and each of these fields may exist separately +or simultaneously, and each do its own characteristic +work, quite independent of either of the +others: so the same body may become magnetized, electrified, +and heated at the same time by the same medium, +acted upon by three different sources. The magnetic +field is more selective in its action than either of +the other two. A heat field will heat any kind of matter +in it if it be solid or liquid; an electric field will +electrify all bodies to some degree, but solid conducting +bodies to the highest degree; while the magnetic field +magnetizes only iron, nickel, and cobalt appreciably, +and the two latter but to a very small extent. The +point of chief importance here is the function of the +field itself to produce, in a certain kind of elementary +solid matter, a molecular disposition and arrangement +similar to that of the body which produced the field. + +\Section{IV.--THE CHEMICAL FIELD.} % + +The phenomena attendant upon the combination of +atoms into molecules, and molecules in cohering together +to form larger masses, make it certain that each +atom has a peculiar field, which, for a name, may be +called its chemical field, within which it acts upon the +\DPPageSep{321.png}{306}% +\index{Attraction, gravitative}% +\index{Gravitation}% +ether about it, and which extends to a distance from it +many times the diameter of any atom or molecule. + +Chemists have concluded that there is really no distinction +between what has been called chemical attraction +and cohesive attraction; such, for instance, as enables +a drop of water to adhere to a surface, or glue to +hold wood surfaces together. + +Crystals are built up of similar cohering molecules +arranged in a definite order. And these molecules exist +as independent bodies while in the solution before +being crystallized, and consequently each molecule must +have some degree of attraction for others; and this is +about the same as saying that there is an ether stress +about each one that depends upon its temperature, for +crystallization cannot take place in a solution above a +definite temperature. But one of the best evidences of +a chemical field of the sort is found in the fact that a +solution of a given crystallizable salt has its process +easily initiated by putting in a small crystal of the same +kind of a substance. Moreover, the mere presence of +certain kinds of molecules among others is sufficient to +bring about chemical changes which otherwise would +not occur; while the catalytic body, as it is called, is not +changed. This is the case with starch, which is converted +into sugar by the mere presence of sulphuric +acid, which undergoes no change. This is apparently +inexplicable, unless it is admitted that molecules of all +sorts have fields which, in one degree or another, control +chemical combinations. This has been treated of +at some length in the chapter on chemism. Its signification +here is to point out again that the field of similar +\DPPageSep{322.png}{307}% +\index{Growth}% +molecules is of such a sort as to compel within it an arrangement +of atoms into similar molecules, and molecules +into similar positions, as exhibited by crystals of +any sort. It is, therefore, another example of the property +of a physical field to bring about in a mass of matter +within it the same kind of physical phenomena as +that which induced the field. + +\Section{V.--THE MECHANICAL FIELD.} % + +A sounding body sets up air waves that travel outwards +radially from it in every direction to an indefinite +distance. Such periodic waves are capable of making +other bodies vibrate at the same rate as the original +body. When the second body has the same specific +rate, absorption takes place, the amplitude of vibration +increases, and the case is known as one of sympathetic +vibration. When the specific rate is different from +that of the recurring waves, there is more or less interference, +and this case is called forced vibration. In all +cases, however, the second body is made to vibrate by +the sound waves that fall upon it, whether the medium +be the air or any other substance, solid or liquid. And +the space within which such effects are produced is the +field of the first or sounding body. If one considers +simply the air as the medium of the field, it will be +perceived that sound waves travel in every direction in +it, and to distances unlimited except by the presence of +the air itself. Of course, the farther the distribution +goes on the less energy there will be to any cubic inch +or any other dimension, and there must be some limit +\DPPageSep{323.png}{308}% +\index{Thought transference}% +where the energy is too small to affect the organs of +hearing; but such a limit ought not to be considered +the actual limit of sound vibrations or the field of the +sounding body. There is no reason for doubting that +every sound vibration of every kind and degree is distributed +throughout the whole earth and its atmosphere, +and more than that: as the impact of molecules in +sound vibrations results in heating them to a higher +temperature, increased radiation into space follows, and +the consequent energy in this form must affect in some +degree every particle of matter in the universe upon +which it falls. It is plain how far-reaching almost every +act and movement of every kind must be. + +A sound vibration, being a to-and-fro movement of a +mass of matter, may easily be great enough to be seen, +as in the case of a tuning-fork or a piano string; and, +therefore, it is treated as being mechanical as distinguished +from molecular: but even where the sound +vibration is too slight to be seen as an actual displacement, +it can give to another body a large amount of +visible motion, as when a suspended marble is held +against a sounding tuning-fork, or as when a paper +windmill is held over a sounding Chladni plate. + +The motion of a sounding body being mechanical, +the field it produces may be called the mechanical field, +because the effect of it upon other bodies is similar in +kind to that which produced the field. There are, therefore, +five well-defined modes of physical action,---heat, +electricity, magnetism, chemism, and sound,---which, in +the past, have often been called physical forces, each +one of which affects the medium about it, producing +\DPPageSep{324.png}{309}% +\index{Hair-cloth loom}% +\index{Machines}% +either a stress or a motion, or both---conditions that +travel outwards into space indefinitely, and constitute as +many different physical fields. They may all co-exist in +the same space without interference, and each one produces +upon other bodies of matter within it the same +physical condition of motion, position, or arrangement as +that which initiated the field itself. So the established +relation deserves to be called a law better than many +relations that are called laws, but are such only within +rather narrow limits (as, for instance, the law of Charles +and \DPtypo{Boyles}{Boyle's} Law), inasmuch as this law of physical fields +is as universal as gravitation. + +What is called gravitation might be included in this +list, for every particle of matter attracts every other +particle near or far; so every atom has a gravitative +field as extensive as the universe, and there is no more +interference between it and the other fields than there +is between any of them. The chief distinction between +the gravitation field and all of the others is that +they are all artificially\DPtypo{,}{} variable while gravitation is not +known to be, though some phenomena indicate the +possibility of it. + +It follows, from the foregoing, that every object large +or small is continually affecting the space about it in +several different ways,---through its temperature, electric +and magnetic conditions, as well as by its various +movements; and it also follows that the shape of a body +as well as its molecular arrangement determines whether +the field shall be symmetrical or otherwise. A crystal +certainly has a symmetrical field, but it cannot be +turned over in the hand without affecting in some degree +everything outside of it. +\DPPageSep{325.png}{310}% + +If it be true for certain collocations of matter that +external form and molecular arrangement determine +the existence of its field, it is difficult to imagine why +it should not hold true for all cases,---a cell structure +for instance, in which case the organization of a similar +cell in adjoining space where the proper material for +construction exists would only be in accordance with +the physical properties of fields in general; and the +phenomenon of growth would be as definitely understood +as the growth of a crystal. This is not demonstrative; +but it is in accordance with everything else we +know, and is what would be predicted by one who knew +the properties of physical fields, though he had no +knowledge of cell growths. + +To take one step more, yet not to go beyond the domain +of physics: It is as certain as any physical fact +can be that every movement of an individual---change +of attitude, gesture, or expression of countenance---must +produce a corresponding change in his field, and +tend to bring about in others similar movements; and, +even if such phenomena are not observed in every one, +it is no more of an argument against the existence of +the operative conditions than is the failure to perceive +through the sense of feeling the sound vibrations produced +by a speaker's voice, when it is certain the whole +body is in a state of tremor; and the effect of sympathetic +speech is more largely physical than has been supposed. +Strong emotions, or the physical semblance of +them by skilful actors, re-act in the same physical way. +This is not saying there may not be other factors, but +the purely physical ones are present and act in the way +\DPPageSep{326.png}{311}% +\index{Motion, transformations of}% +described. The term ``sympathetic action'' was applied +to physical phenomena when it was discovered to be a +mode of action quite analogous to mental phenomena +between individuals in which similar mental states are +induced. + +Lastly, so far as mental action depends upon brain +structure, any changes in the latter must produce corresponding +changes in the brain field, and there must +be a brain field if there be any truth in the foregoing; +the conclusion is inevitable. Other similar structures +must be affected in some degree by them, and whether +such induced changes be able to induce similar brain +changes with the accompanying mental phenomena or +not must evidently depend upon the possibility of +synchronous action. + +This is not to be understood as asserting that such +thought transference as is implied in the foregoing actually +occurs. All that is asserted is that the physical +conditions necessary for such transference actually +exist, and one who was acquainted with the properties +of physical fields would certainly predict the possibility +of thought transference in certain cases. +%\DPPageSep{327.png}{312}% + + +\Chapter{XIII}{On Machines.---Mechanism}{312} + +\index{Push and pull}% + +The common notion of a machine is that it is an implement +designed for doing this or that: as, for instance, +a loom is a machine for weaving cloth or carpets; a +steam-engine is a machine for driving machinery; a +water-wheel, for utilizing the power of water; and so on. +Some of these structures, built for specific purposes, are +highly complex, and many of their parts stand in curious +relation to each other, and altogether they may be able +to produce results that seem but little short of intelligent +action. Looms weave out beautiful fabrics with +artistic designs in colors, when furnished with only the +bare threads. The hair-cloth loom draws with iron fingers +a single hair from a large bundle of hairs. If it +fails to grasp one, another and another attempt is made +until one is seized, and meanwhile the rest of the machinery +waits. If it seizes more than one, as sometimes +happens, it drops both and tries again, the rest of the +apparatus waiting as before, exhibiting a kind of deliberativeness +and consciousness of what it is about that +one hardly looks for through any combination of wheels, +ratchets, levers, and the like, such as make up a complex +machine. Every one knows that by far the larger +number of things in common use which were formerly +\DPPageSep{328.png}{313}% +made by hand tools are now made by machinery more +rapidly and oftentimes more perfect than they could be +made by hand. The parts of clocks and watches are +so made; papers are printed, folded, and directed at +the rate of ten thousand in an hour by one machine; +grass is mown, grain is cut, threshed, and winnowed by +one machine as fast as it can be driven through the +field; shoes, toys, and beautiful pictures are thus made +by the million, and there is no department of human +effort but is dependent upon mechanism of some kind. +In many cases the entire work is thus done automatically, +as when pins and needles are made from the wire, +sharpened, polished, counted, arranged in papers, and +folded ready for the market. There is no field independent +of such aids. Even music is absolutely dependent +upon it, and all that is called sentiment and feeling +in it are resolvable into degrees and directions of movements +for the production of sounds; and there are no +movements of muscles but may be duplicated by automatic +mechanism. If the effects produced by mechanism +to-day are not the effects wanted, it only shows +that the mechanism has not been perfected, not that it +cannot be done. + +If one considers the almost infinite number of processes +needed for the maintenance, conveniences, comforts, +and tastes of what is called civilized life, it might +seem as if an almost unlimited number of physical conditions +would be necessary; but let such an one recall +the fact that all kinds of motions are reducible to not +more than three fundamental kinds,---translatory, vibratory, +and rotary,---and he will be prepared to trace +\DPPageSep{329.png}{314}% +\index{Lever}% +\index{Pulley}% +the most complicated movements to these elementary +forms. + +In the chapter on motion, only the kinds of motion +were considered; but here it is proposed to point out +the conditions under which motion is transferred from +one place to another, and how these elementary forms +are transformed into each other. For convenience, the +term ``mechanical motion'' will be employed for all having +visible magnitude, but simply on the ground of visibility, +not because there is any other distinction between +such motions and those of a molecular or atomic kind. + +When one pushes against a paper-weight on the table +and it moves in consequence, no one is surprised, for +the movement is expected. If the weight were free to +move and it did not move, no matter how strong the +push, one would have reason to be surprised, because +such a phenomenon is not in accordance with the +experience of mankind. If one billiard-ball in contact +with another one received a push in direction toward +the latter, the latter would be moved in the same direction, +and the motion of the second one would be explained +by saying it was due to the push of the first +upon it. Suppose there were ten or a hundred such +balls in a line. If the end one was pushed towards the +rest of them, they would all move, the farthest one as +much as the first, as the movement imparted by push +to the first would be handed on step by step to the last. +If the balls were glued together at their points of contact, +that would make no difference in this transfer of +motion by contact; and, if there were a thousand or a million, +or any other number, there would be no difference. +\DPPageSep{330.png}{315}% +\index{Work, measure of}% +Neither would there be any difference if the separate +balls were no bigger than molecules. A rod of wood +or metal is entirely made up of a great number of cohering +particles, and, when a push is applied to one end, +every particle is pushed as much as the end particles. +If there was a row of thin rubber balls and the end one +was thus pushed, the side would be flattened somewhat, +and the opposite side in contact with the next adjacent +ball would push against its neighbor and each be flattened, +and so on, till the last one was reached, which +would be pressed on one side but not on the other, and +would, therefore, be like a single ball pressed upon one +side. The intermediate balls would act as transferrers of +pressure from one end to the other. The rubber balls +so flattened by pressure will recover their form when +the pressure is removed, and the same may be said of +a rod of any material, the difference in this particular +being only one of degree. The same process takes +place when one pulls upon a rod. It is to be remembered, +however, that in either case the transmission of +the pull is not instantaneous for any distance, however +short. Time is requisite, and hence there is a rate of +propagation of such motion in all bodies, which depends +upon the degree of elasticity and the density of the +material; and this rate cannot be exceeded, no matter +how great the initial push or pull. This rate is about +sixteen thousand feet per second for steel and the most +elastic woods, and is about eleven hundred feet per +second for air. If one inquires what the condition is +that initiates motion in any given body, it will be found +to be a push or a pull, and either of them may be measured +\DPPageSep{331.png}{316}% +in pounds. The chief distinction between a push +and a pull lies in the relative position of the moving +power and the body being moved by it. In the push, +the body being moved leads in the line of movement; +in the pull, the moving power leads. When a locomotive +goes ahead of the train, it pulls; if the train goes +ahead, it pushes. A stiff rod or bar may be used for +either a push or a pull, but a rope can be used only for +a pull, for when pressure is applied to it longitudinally +it bends at right angles to the direction of the pressure, +and so fails to act in the right direction. A rod can +transmit a push or pull only in the direction of its +length, while a rope may rest on a pulley and the pull +may act upon any other body in the same plane the +pulley turns in. If a pressure of ten pounds be applied +as a push at one end of a rod or bar, the whole of that +pressure may be transmitted to the other end. The +same may be said of the pull either with a rod or rope, +but neither rod nor rope can possibly transmit and give +up at the one end more than is applied at the other. +For this reason, a rope hanging over a pulley will hold +equal weights on its two ends. If a ten-pound weight +be tied to one end, the pull transmitted will be ten +pounds, which may be balanced by a pull either by +weight or in any other way on the other leg of the rope. +The function of a pulley is to change the direction of +the pull: it does not alter its amount. + +\Section{MECHANICAL MACHINES.} + +In the older treatises on natural philosophy, there +were described several machines which were called the +\DPPageSep{332.png}{317}% +mechanical powers, because their principles were embodied +in mechanical devices for transmitting pressure +or pulls. The \emph{lever} stood first among them. It consists +of a stiff rod or bar resting upon a point of support +for it called a fulcrum, and this fulcrum may be +placed anywhere between the ends of the bar. The +advantage or disadvantage of this machine depends +upon how near the fulcrum is to the body to be moved. +A stiff rod four feet long supported at its middle would +be balanced if it were of uniform dimensions. If a +weight of ten pounds was hung at one end, an equal +weight or pull would be needed at the other end to +balance it. If one weight fell one foot, it would do ten +foot-pounds of work in raising the other ten pounds +one foot. In any case the work done, measured in +foot-pounds, will be the same at both ends of the bar or +lever. + +The lever changes the direction of motion or the +amount of pressure, but does not change the amount +of work measured in foot-pounds. + +The simple \emph{pulley} is a device for changing the direction +of a pull, as seen in the apparatus for raising merchandise +to higher levels in buildings; but by far the +most extensive use of it is in the transfer of a continuous +pull from one place to another through the agency +of belts of leather or other pliable material. + +This combination of pulley and belt is adaptable to +many places and purposes, as well as permitting great +ranges in speeds of rotation by simply making the diameters +of the pulleys proportional to the differences in +rotation wanted. It is the chief agency in machine-% +\DPPageSep{333.png}{318}% +\index{Transformations of motion}% +shops, factories, etc., for distributing the power to the +various machines. By crossing the belt the second +pulley can be made to turn in the opposite direction. + +In all the ways in which it is serviceable, it is plain +that it cannot deliver more of a push or a pull than is +given to it any more than can a lever. There is no +gain of energy or work by its use, but always some loss, +because friction uses up some of the working-power in +other than useful ways. The \emph{wedge}, the \emph{inclined plane}, +and the \emph{screw} are but simple devices for utilizing push +or pull; but there are other means also employed for the +same purpose; for instance, the pressure of the air or +other gas, and steam. Windmills are made to turn by +the pressure of the wind upon the inclined blades, and, +by forcing air into pipes, an increased pressure may be +transmitted for long distances and then used. The +reason this method of using air is not in more general +use is that when the air is compressed it heats. The +heat it loses soon if conveyed in pipes very far, and as a +consequence its pressure is very much reduced, so it is +not an economical thing to do. Water-wheels utilize +the pressure of water, and the amount of work it can do +is definite and easily calculated. If at a waterfall a +hundred pounds of water falls ten feet, then it can do +$100 \times 10 = 1,000$ foot-pounds of work; that is, it can +raise $1,000$ pounds a foot high, and so on for any other +amount. A perfect water-wheel that did not let slip +by any water without its doing its work would give up +practically $1,000$ foot-pounds. Really, the best water-wheels +give but about ninety per cent of \DPtypo{the-working-power}{the working-power} +of the water. So-called water-motors are but properly +\DPPageSep{334.png}{319}% +constructed wheels enclosed in the pipe through +which water is made to flow with considerable pressure. +In the cases of air, steam, and water power there is the +condition we call a push, which may be measured in +pounds; and a push measured in pounds multiplied by +the distance in feet through which it is maintained is +the measure of work. + +In each of the cases, the air, or steam, or water, +as it moves on and does its work, gives up the motion +it has; and the substance itself, being no longer of use, +is allowed to escape as a waste product. Such bodies +have been sometimes called \emph{prime-movers}. + +So far has been considered only the apparatus in +common use for transferring motion of one body to +other bodies, but frequently it is important to have the +\emph{form} of the motion changed from the kind it may +chance to have at the outset to one better adapted to +the special end desired. + +In a sewing-machine, for instance, the particular +movement of the needle must be vibratory. The +treadle has a similar movement, but not rapid enough; +so there is arranged between them a series of movable +parts, which not only \emph{transfers} a certain amount of +motion, but the latter is \emph{transformed} into appropriate +forms. The vibratory motion of the treadle is transformed +into the rotary motion of the balance-wheel, +this into swifter rotation of the pulley by means of a +belt; then by lever and cam the needle receives its +proper kind of motion, the shuttle a similar one at +right angles to that of the needle, and the other moving +parts such forms of motion, and rates of motion, as +\DPPageSep{335.png}{320}% +are needful for their special kinds of work. In a steam-engine +the constant pressure of the steam is made to +act upon the alternate sides of a piston, giving it a +vibratory motion, which must be transformed for most +purposes into rotary; and this is effected by means of a +crank, which is, therefore, a device for transforming vibratory +motion into rotary, or \textit{vice versa}. When the +driving-wheels of a locomotive are made to rotate, their +adherence to the track carries the whole structure forward; +that is, the rotary motion is transformed into +translatory. In the stationary engine the rotary motion +of the balance-wheel is transferred to a pulley by a +belt, and the shafting transfers this through its whole +length to other pulleys. If the reader will follow back +to its antecedents any particular motion he may think +of, he will see that the function of each movable part of +a machine of any sort is to transfer push or pull, or +transform one kind of motion into another kind. However +complex a machine may be, it does no more. + +It is to be noted that \emph{what} a given thing will or may +do depends altogether upon what kind or form of +motion it has, not upon how much motion or energy +it has. For instance, a bullet might spin on some axis +on the table before one, and have great rotary velocity +and energy, yet be perfectly harmless; whereas, if it +had the same amount of energy with the motion translatory, +it might be destructive to anything it struck. + +\Section{MOLECULAR MACHINES.} + +If one of the functions of a machine be to transform +the kind of motion it is supplied with into some other +\DPPageSep{336.png}{321}% +kind of motion,---translatory into rotary or vibratory, +any one into either of the others,---one may be prepared +to follow mechanical processes from masses of +visible magnitude into molecular magnitudes, and thus +note the antecedents of the new phenomena that +appear. + +When a gas is condensed by pressure the individual +molecules have less free space to move in, and they +consequently collide with each other more frequently. +Being elastic, their average amplitude of vibration is +increased proportionally, and a greater number of them +will strike with greater velocity upon the walls of the +containing vessel per second than before. Thus the +temperature and the pressure of the gas are increased. +We say that mechanical energy has been converted +into heat energy, or sometimes simply into heat, +though what has really happened has been the transformation +of external translational motion into internal +vibratory motion, which the elasticity and mobility +of the molecules permit. When by friction or percussion +a body is heated, the same thing precisely +has happened: translatory motion has been transformed +into vibratory, through the agency of the +molecules, which have, therefore, acted as machines for +transformation. + +In like manner the reverse transformation may take +place in several ways. When the increased vibratory +motion of the molecules produces an increased pressure +upon the movable head of a piston in an engine, the +piston as a whole may move and do work. Also, when +the molecules strike harder upon one side of a surface +\DPPageSep{337.png}{322}% +than upon the other side, the surface moves toward +the side of less pressure, as with the radiometer; so +that both engine and radiometer are machines for +\index{Machines}% +transforming vibratory molecular motions into translatory +mechanical motion. + +When the temperature of steam is raised to about +$5,000°$~F., the amplitude of vibration is so great that the +atoms can no longer cohere in the molecules, and they +become separated into the gases hydrogen and oxygen; +and again vibratory motion is transformed into translatory, +which in gases is called free-path. + +Heat is also largely derived from the chemical properties +of coal, wood, oils, gas, and other substances +called fuel. As the heat is derived from some antecedent +condition which is not heat, it follows that the +stove or furnace is a machine for transforming into +heat motions those motions which constitute and are +the measure of chemism. + +When heat is applied in any way to the face of a +thermo-pile, electricity may appear which may be made +to do work in many ways. The vibratory motion disappears +as such,---that is, it is annihilated,---while an +electric current appears as its substitute. The thermo-pile +is, therefore, a machine for the transformation of +heat into electric current. If heat be a kind of molecular +motion, then an electric current must be some +other kind of motion! + +When the armature of a dynamo is turned and an +electrical current is developed, the latter is the representative +of the mechanical movement of the armature. +It takes more power to make it move at a given +\DPPageSep{338.png}{323}% +speed when it is producing a current than when it is +not. The current represents the difference. It is mechanical +motion that goes into the dynamo, and an +electrical current comes out of it; and hence a dynamo +is a machine for the transformation of mechanical into +electrical motion. One is visible, the other molecular, +as is the case when friction develops heat. + +An ordinary static electrical machine possesses a +similar function. + +On the other hand, a galvanic battery transforms +chemical into electrical motions; and, in every case +where electricity is developed, there is some sort of +apparatus which receives one kind of motion for transformation. +That one kind of machine will transform +mechanical motion, a second heat, a third chemical, all +into the same kind of a product, helps one to see that +the antecedents, which at first seem to be so unlike, +are really but varieties of the same condition, namely, +motion, which, when transformed by suitable machines, +might be expected to appear as a similar product of +each. + +An electrical current always heats the conductor +through which it passes. It is, therefore, an antecedent +for the production of heat in the same sense as mechanical +motion is an antecedent in condensation, percussion, +and friction; and the conductor is the agency for +the transformation into the vibratory molecular form. + +So far as the production of light by electricity is concerned, +whether by the incandescent or the arc system, +the function of the current is to raise the temperature +of the conductor to the proper degree for luminousness. +\DPPageSep{339.png}{324}% +The light comes from the hot molecules, not from the +electricity; but here, as in the simpler case of heating +the conductor, the conductor itself, whether it be a filament +of carbon or the tips of the carbon rods, acts as a +transformer of electrical into heat motions, and thence +to ether waves. + +Ether waves may be transformed in two different +ways. First, by falling on molecules of matter; the +latter absorb them, and are heated in consequence, +which is the converse of the production of ether waves +by heated molecules. Second, by their own interferences +plane, elliptical, and spiral waves may be produced, +which resultant waves are capable of affecting matter +in different ways. One of these consequences is of so +much theoretic importance it will be well to allude +to it. + +Given a flexible section of a spiral ether wave, no +matter what its origin. If its ends were to come together, +there is good reason for thinking they would +close and weld together, forming a ring, which would +then be practically a vortex ring. The ends of vortex +rings formed in the air will do thus, so if the atoms of +matter are really vortex rings, as has been supposed, +the above suggests how they may originate, or how +matter is created. + +All the different kinds of phenomena which are generally +attributed to different forces one may readily +trace to these antecedents; namely, matter, ether, and +motion of various forms. The condition necessary for +a new phenomenon to appear is that the present forms +of motion in either matter or ether needs to be transformed. +\DPPageSep{340.png}{325}% +Atoms and molecules, as well as large masses +of them, which we call bodies of visible magnitude, act +as machines for the transferrence and the transformation +of motion; and one might define a machine as a \emph{collocation +of matter having for its function the transferrence or +the transformation of motion, or both}. An atom and a +molecule, then, are as much machines as a steam-engine +or a dynamo; and every molecule in the universe, +whether near or remote, is constantly receiving and +transforming energy through its individual motions. +What the particular phenomenon will be in a given +case depends upon the form of the motion received by +the mechanism and the new form which the latter has +made it to assume. As before remarked, what a given +mass of matter will do depends upon the kind of motion +it has. + +So far nothing has been said about the relation of +these mechanical principles to living things,---animals +and plants; but it will be obvious to every thinking +person that unless, when matter assumes the forms exhibited +by such living things, it surrenders its mechanical +properties and relations, then such transformations +must be going on constantly in all living things. Mechanical +motions, chemical re-actions, heat, and so on, +ought to be expected from such complex machines as +animals. Foods, as fuel, air, and water, are physical +factors which imply metamorphosis; and the forms into +which the factors will be changed depend upon the +special mechanism provided. Hence, an animal is a +complex machine for the transformation of motions of +various sorts, the sum of them being what are called +the phenomena of life. +\DPPageSep{341.png}{326}% +\index{Solar system}% + +The foregoing analysis shows that what have heretofore +been considered as forces in nature are non-existent;\DPnote{** Only instance.} +that all phenomena in the different fields of +physics are simply and plainly mechanical; and that +an application of the laws of motion, as presented by +Sir Isaac Newton, supplemented by the laws of ether +action, is sufficient to account for all kinds of phenomena: +and therefore the supposition of particular forces +of any kind is entirely unnecessary. What have been +called forces are but various forms of motion, of matter, +or of the ether, each embodying energy; the particular +phenomenon a given body may produce depending +upon its size and the particular quality of motions it +chances to have. Granting this, one may at once perceive +that expressions implying higher and lower forms +of force are misleading. No one is higher in dignity or +importance than any other one. Let one ask the question, +Which is higher, vibratory or translatory motion? +and he will see the absurdity of the language. + +If one will bear these principles in mind, they will be +helpful in unravelling phenomena which otherwise may +appear to be very puzzling. For instance, one may frequently +come across the statement that one cannot get +out of a machine what is not in it or put into it. Is it +so? Coal is put into the furnace, and heat comes out. +Mechanical motion is put into a dynamo, and electricity +comes out. A current of electricity is turned into an +arc lamp, and light comes out. The character of the +product thus depends upon the form of the machine +and its relation to some antecedent factor. The physical +\DPPageSep{342.png}{327}% +\index{Physical universe a machine}% +knowledge we have enables us in most cases to +trace and understand the metamorphosis. In some +cases the molecular changes are not so completely +known in detail, yet the quantitative relations between +what goes in and what comes out of the machine are so +definite that one is warranted in asserting that no other +factors are present than the one considered. In one +sense the product of any machine is like its antecedent, +if both be but kinds of motion, or forms of energy as +some prefer to say; but if one assumes that these +various forms of energy differ in any way from forms +of motion, or that they have distinct individualities, +then one can get out of a machine what he does not put +into it. What seem to be more unlike than the mechanical +movements of a steam-engine and the electricity +of the dynamo? One is simplicity itself; the +nature of the other, its product, has been the despair of +philosophers for generations. The subject is of fundamental +importance chiefly because some philosophers +have evolved their schemes without duly considering +these obvious relations. + +However much a given phenomenon may differ in +character from its known antecedents, no good reason +can be assigned for thinking that, when properly analyzed, +it would be found resolvable into other factors +than matter, ether, and motion. Furthermore, there is +no evidence that any one of the physical forms of +motion is or was necessarily prior to any other. As +there is no hierarchy among them, no one of them can +be called primal. A linear arrangement does not +\DPPageSep{343.png}{328}% +\index{Matter, as modes of motion}% +properly represent their mutual relations. They are +more like a closed ring of interrelations thus:--- +%[Illustration: ] +\begin{center} + \Graphic{2.5in}{343a} + \Figlabel{35} + + {\scriptsize Diag.\ 35.---Forms of Energy.} +\end{center} + +The visible universe may be considered as a vast +machine, within which motions are being exchanged +by contact and by radiation. It is not the absolute +amount of energy a body may have which determines +whether it shall give or receive, but it is the degree +it has of a given kind of energy. Thus it is the temperature +of a body that determines for it whether it +shall gain or lose heat in the presence of other bodies. +The whole tendency is towards equalization of conditions, +and for this reason some philosophers think they +foresee the end of this act in the drama of the solar +system. The possibility of the variety of phenomena +that gives interest to existence depends upon the fact +that at present matter is in an unstable condition, and, +when uniformity of condition is reached, there will be +an end to changing phenomena. Astronomers have +figured out that in five or ten millions of years the sun +\DPPageSep{344.png}{329}% +\index{Cohesion, in solids and liquids}% +\index{Matter, states of}% +will have radiated away so much of his energy that the +earth will no longer be habitable. Perhaps so; but it +is certain that the whole solar system is drifting in space +somewhere at the rate of seven hundred millions of +miles a year, and in one million of years it may reach a +region in space where the present rate of loss might be +greatly reduced. In that time it will have travelled +three times the distance to the nearest of the fixed +stars. It could hardly be where its expenditure would +be greater than now. If it should drift into one of the +great hydrogen regions such as are numerous in the +heavens, not only would the supply of energy be renewed +indefinitely, but the earth would become uninhabitable +in an hour. At any rate, there is no guarantee +in nature for permanent stability, supposing that stability +should be attained; for simple mechanical impact +between the sun and any of the millions of stars would +not only annihilate the earth as such, but would so +reduce to a nebulous mass the matter that now composes +the solar system that the whole process of world +formation would have to be gone through with again. +The sudden blazing out of stars here and there in the +heavens shows that similar physical processes are taking +place elsewhere in the universe. Such an end is +quite as probable as the refrigerating one referred to; +for there is implied in the latter not only that the present +conditions in the solar system will continue, but +that the environment of the solar system will remain +for so many millions of years what it is. The matter +is not alluded to here on account of its humanitarian +\DPPageSep{345.png}{330}% +\index{Cohesion, destroyed}% +\index{Gas, motion in}% +interest, but to point out that in either case the results +will be due to purely physical conditions. What mankind +would contemplate as a dreadful catastrophe would +be but the interaction of huge machines, where energy +was transformed on a grand scale, and no particle of +matter omitted for an instant to conform to the three +laws of motion. +%\DPPageSep{346.png}{331}% + + +\Chapter{XIV}{Properties of Matter as Modes of Motion}{331} + +\index{Gas, free path in}% +\index{Gas, pressure in}% + +In the first chapter of the book only the most +obvious qualities of matter are considered, such as +magnitude, density, inertia, and so on, the properties +which are exhibited by masses of matter of visible +magnitude and form, from which the common notions +concerning its nature and possibilities have been derived. +If one stops his inquiries concerning the properties +of matter with these, and imagines that they are +the ultimate properties, and may rightly be assumed +and asserted of the individual atoms, he will be greatly +in error; for it is not difficult to show that nearly +every property of masses cannot be true of atoms, and +that nearly if not quite all material properties of what +we call matter, are derived from antecedent conditions, +and are resolvable into them or into mere relations +which are not inherent, and may be absent. It is, +then, worth the while to study the real significance +of some of the physical terms in common use, in +order the better to eliminate from the mind unessential +qualities when thinking of the inherent qualities +of matter. + +During the past ten years laboratory facilities for +physical investigations have greatly aided inquirers, +\DPPageSep{347.png}{332}% +\index{Heat, effects}% +and added much to real knowledge in this field. Some +of this knowledge is of such a character as will presently +make it needful for every one to reconstruct +his notions and explanations of physical phenomena, +in order to prevent hopeless confusion in his own +thinking. + +\Section{THE STATES OF MATTER.} + +Under the conditions of ordinary observations matter +is found in the solid, liquid, and gaseous states; +the solid state being that in which the molecules +cohere so strongly as not to be easily separated from +each other nor from the relative positions they have +assumed with reference to other molecules. Thus, a +piece of granite, as the type of a solid, may have its +molecules cohering to each other in certain positions, +so strongly as to require a ton's weight to pull apart +a section of one square inch. + +The granite is made up of small crystals of quartz, +mica, and feldspar, each having a definite chemical +composition. The individual crystals retain their relative +places for an indefinite time, and the atoms of the +individual molecules retain their relative positions for +a like indefinitely long time, else the crystalline structure +would be lost, for crystalline structure implies +definite atomic arrangement as well as molecular +arrangement. So in solids the adjacent molecules +are in what are called stable positions, and are not +easily separated. + +In a liquid there is little cohesion among the molecules, +and no stable arrangement at all. The individual +molecules move among each other without +\DPPageSep{348.png}{333}% +\index{Absolute zero}% +\index{Charles, Law of}% +\index{Chemism and heat}% +\index{Chemical reactions depend on temperature}% +\index{Gas, pressure in}% +\index{Gas, destroyed}% +\index{Matter, effect of temperature upon}% +apparent friction, and the slightest force acting upon +them makes them to turn on any axis; and there is +good reason for thinking that in a liquid like water, +the individual molecules are continuously rolling and +tossing about with perfect freedom to move in every +direction. The phenomena of diffusion exemplifies +this. There is also good reason for thinking that the +individual atoms in the water are continuously changing +partners at a rapid rate, so if there were some +means for identifying the atoms of hydrogen and oxygen +in a given molecule, they might be seen presently +all separated and forming temporary constituents of +other molecules a relatively long remove from the first +position where they were observed. When the water +is frozen, that is has become a crystalline solid, this +freedom of atomic change and molecular rotations is +no longer recognized as a property. Molecular cohesion +is now exhibited where before there was none. +There are also new qualities called crystalline, hardness, +density, and so on, which before this change did +not belong to it. The new qualities which seem to +have been developed are produced by lowering the temperature +of the water, that is, reducing the amount +of kinetic energy the molecules had; and by again +imparting a like amount to the ice \emph{both crystallization +and cohesion are destroyed}. + +A gas is a body of molecules in which the individuals +are free to move in every direction unconstrained by +any degree of cohesion, and where they are in frequent +collisions, bounding away in new directions through +distances usually many times the diameter of the molecules +\DPPageSep{349.png}{334}% +themselves. Thus, in air the ordinary average +distance between impacts is nearly two hundred times +the diameter of the individual particles which, as before +stated, is in the neighborhood of one fifty-millionth of +an inch. Their continuous bumping against each other +and the walls of the containing vessel, produces what +is called the gaseous pressure. Increasing the temperature +of the gas increases the velocity of movement +in the free path, and, consequently, the momentum and +the pressure. It has been customary to say that heat +increases the elasticity of a gas, that a gas occupies +the whole space which encloses it, that a gas has a +tendency to indefinite expansion, and that the properties +of a gas are due to repulsive force among the +molecules. In a loose sense such expressions may be +allowed, but they are not to be understood as correctly +specifying the qualities of the gaseous matter. It is +not repulsion that makes a ball move which has been +struck by a bat, but impact; and that it should continue +to move on until it strikes another body, follows +from the first law of motion, as true for a molecule of +a gas as for a baseball. The direction the ball takes +depends upon where it is hit, as well as upon how hard +it is hit; the velocity it has depends upon how hard it +is hit, and there is nothing peculiar to a gaseous particle +requiring the affirmation of different properties. + +Some years ago improved methods of making a +vacuum were adopted, by which one could reduce the +amount of gas in a tube to even the hundred millionth +of its ordinary amount, so that a particle might have a +relatively long free path measurable in feet instead of +\DPPageSep{350.png}{335}% +\index{Diamond, hardness of}% +\index{Hardness not atomic property}% +hundred thousandths of an inch, and the phenomena +of such rarefied gases were so new and surprising that +it was at first conjectured that a new state of matter +had been discovered, and it was called the fourth or +ultra gaseous state to distinguish it from the others; +but it was soon perceived that it was still only rarefied +gas, and that no new qualities had been developed, and +the same phenomena witnessed in the rarefied gas were +present in the denser, only disguised by the greater +number of molecules which took part. So what was +called for a short time the fourth state has been +practically abandoned. + +The three states already considered are known to +depend upon temperature. Thus, if ice or iron or +many other solids be heated they become liquid; if +heated still more they become gaseous. Some solids, +like wood, when heated do not assume the liquid intermediate +form, but are at once converted into a gas; +but different substances have different temperatures at +which they change from one form to the other. Thus, +water becomes a solid at $32°$~Fah., and a gas at $212°$~Fah. +Iron becomes fluid at~$2,800°$ and gaseous at~$6,000°$. So +far, then, it appears one might as properly speak of +iron as a liquid or a gas, as of water as either, if they +both may exist in the three conditions, and no temperature +is specified. We do not do that, because when +speaking thus ordinary temperatures are implied, but +seldom or never thought of. If one had been brought +up in the sun it is probable he would never have seen +a solid, and if at the moon, he would know of neither +liquid nor gas. +\DPPageSep{351.png}{336}% +\index{Color, nature of}% + +But the pressure of a gas is caused by the impact of +its molecules, and is proportionate to the temperature. +The law of Charles states what has been found to be +true within the limits of experiment; namely, that the +volume of a gas is proportionate to its absolute temperature; +that is, temperature measured from an absolute +zero, in which case, it is plainly to be seen, at +absolute zero the \emph{gaseous} volume would be nothing. +It does not imply that the matter of the gas would be +annihilated, but that the matter no longer existed in +its gaseous form; the individual molecules would no +longer have any free path motion, but would fall to +the floor of the containing vessel, and thus remain +quiescent, like so much dust. \emph{At absolute zero there +would be no gas.} + +Again, in the chapter on Chemism it is shown how +chemical reactions are determined by temperature, and +cannot take place in the absence of heat. The late +experiments of Pictet and Dewar show that as temperature +is lowered chemical reactions become weaker +and weaker, until some of the elements that have very +strong affinities at ordinary temperatures, and so combine +with energy, are incapable of combining, and +appear inert at such low temperatures as can now +be artificially made without great difficulty. Their +experiments confirm the conclusions given on \Pageref{page}{242}; +namely, that at absolute zero chemical affinity +does not exist. Molecules would not only fall apart, +but their individual atoms would no longer exhibit +any cohesive quality; and this, it will be perceived, +would render the existence of such a thing as either +\DPPageSep{352.png}{337}% +\index{Impenetrability}% +a liquid or a solid quite impossible, for each requires +chemical action for both molecular formations and +cohesion in any degree. Every kind of a structure +would crumble to atoms in a literal sense. Book, +tower, mountain, ocean, as well as every living organism, +would completely disintegrate, and lose every characteristic +property which had belonged to it. Hence, +such qualities of matter as would be absolutely emptied +out of it by simply reducing its temperature, cannot +be considered as essential qualities. Yet when the +atoms were thus deprived of what seems to us as all +their useful qualities, there is reason for thinking they +would still have definite form, mass, gravitation, magnetic +and electric qualities which, however, by themselves +could not make the mass of matter we call the +earth a habitable place, nor give to life a material +habitat as it now has. + +It is then plainly evident that what we call solids, +liquids, and gases, with all the laws that belong to each +of them, are simply the relations of heat energy to +groups of atoms, not the properties or laws that may +be asserted of the atoms as such, and do not need to +be considered by one who is inquiring for the essential +endowments of matter. + +There remains, therefore, an examination of the +other so called qualities to see if, perchance, they +too may not, in a similar manner, be resolvable into +energy relations, which, in turn, may be absent. +\DPPageSep{353.png}{338}% +\index{Elasticity}% +\index{Elasticity due to motion}% + +\Section{MOLECULAR AND ATOMIC QUALITIES.} +\Subsection{(HARDNESS.)} + +Substances vary greatly in what is called hardness, +and this properly serves, in many cases, to distinguish +one mineral from another. The mineralogist employs +a scale of ten, differing in degree from talc which is +the softest, to diamond which is the hardest, and with +these all other minerals are compared. But the mineralogist +tells us that this scale does not represent hardness +in any proportional way, because diamond is as +much as ten times harder than the ruby which stands +next to it in the scale; also that some diamonds are so +much harder than others, that no means has yet been +discovered for grinding and polishing them. + +The diamond, however, is crystallized carbon, yet carbon +exists in another crystalline form called graphite, +or plumbago, which is soft, and may be whittled with +a knife, while coke, charcoal, and lampblack are forms +of precisely the same element, and these vary through +the whole range in hardness. What, then, does hardness +mean? Evidently it signifies the resistance +offered to the separation of molecules from each other. +It is the measure of their cohesion, and could have no +existence in a single molecule of carbon. Furthermore, +as has been pointed out, as molecular structure +can have no existence at absolute zero for lack of +energy needed for maintaining cohesion, \emph{hardness cannot +be a property of atoms at all}. +\DPPageSep{354.png}{339}% + +\Subsection{COLOR.} + +Color, either simple or compound, is exhibited by all +masses of matter---for white is but a mixture of wave +lengths, and no object is so black as to be invisible. +Gold is yellow, copper red, lead is bluish. The petals +of flowers, the feathers of birds, the gorgeous dyes of +the chemist, seem to impress us with an assurance that +color is a real quality of some kinds of matter, and can +be affirmed of it without any qualifications. Bodies +become visible either by their own luminousness as +when they are hot or phosphorescent, or by the light +reflected by them from some other source, as is most +commonly the case. When sunlight falls upon a rose +it is to be remembered that the sunlight is what we +call white light; it is made up of all wave lengths which +we can see. The rose petals absorb some of these +waves,---the blue, the green, and the yellow, but not +the red; these are rejected by the surface, and they +therefore are reflected away, and testify to the selective +power of the petals, \emph{not their color}, as can be found +by holding the same rose in yellow or blue light, when +it will appear black, that is, will absorb all offered to it +and reflect little or none. Again, when a body is self-luminous, +as, for example, a piece of burning sodium +which gives out a yellow light, it is to be kept in mind +that the yellow rays are produced by certain vibratory +rates which the atoms are compelled for the time +being to make, but which the atoms will not make +except on compulsion, that is, the high temperature +which the heat energy gives to it, and therefore does +\DPPageSep{355.png}{340}% +not represent what can be called the color of the body---only +an artificial state of vibration. Lastly, if all +substances whatever were at absolute zero in temperature, +they would be setting up no ether waves of any +length, and could not effect any organ of vision, and, +consequently, would not only show no color, but would +be absolutely invisible. \emph{Hence color cannot be affirmed +of atoms.} + +\Subsection{IMPENETRABILITY.} + +It has seemed to nearly every one who has given +thought to the subject that what is called impenetrability +must be a fundamental property of matter; +that it was axiomatic, if anything could be, that two +masses of matter could not occupy the same space +at the same time. This has been believed to be +true, not because it was demonstrable, but because +it seemed to be reasonable. Maxwell, however, calls +it a vulgar opinion. He further takes the pains to +say, If hydrogen and oxygen combine to form water, +we have no experimental evidence that the molecule +of oxygen is not in the very same place with the two +molecules of hydrogen.\footnote + {See Art. Atom.\quad Encyc. Brit., 9th ed.} + +When it is possible to make one, a mechanical model +is often of great assistance in helping one to conceive +of conditions which are more or less difficult to describe +in mere words; and a mechanical model that +embodies this possibility of the coexistence of two +atoms in precisely the same space may easily be made. +Roll up a length of wire into a loose helix or spiral of +any convenient length---say two feet long. Cut it in +\DPPageSep{356.png}{341}% +\index{Hertz waves}% +\index{Magnetic waves}% +\index{Tesla ether waves}% +two parts of equal length, and bend the ends of each +round until they touch, and fasten them thus, so as to +have two rings made of spirals of wire. Each one may +be taken as representing an atom of matter somewhat +similar to a vortex ring, which has been assumed as +\index{Vortex ring model}% +the probable form of the atoms of matter. Each has +form, size, and various other qualities, but if one of +them be pressed down upon the other it will be found +they will make room for each other, so that \emph{as rings +they both occupy precisely the same space}. This is not +given here as anything more than as, possibly, a +helpful suggestion as to how a seemingly impossible +condition may be true. Evidently in this case the +difficulty lies in the assumption that an atom of matter +is a hard, impenetrable, geometrical solid, and, as Maxwell +says, there is no proof that such is the fact. +\emph{Impenetrability is an unwarrantable assumption.} + +\Subsection{ELASTICITY.} + +Elasticity has been assumed to be a fundamental +property of atoms, and so not derivable from physical +conditions underlying it; but Lord Kelvin has shown +good reason for thinking that elasticity is a derived +quality, for it is possible to construct models which +exhibit the phenomenon in a high degree while they +are in motion, and not at all while they are at rest. A +number of gyroscopic disks set whirling on a circular +axis, shows this in a remarkable way, and suggests on +inspection, that something like such an arrangement +may be the complete explanation of the quality as +exhibited by atoms. A vortex ring may be considered +\DPPageSep{357.png}{342}% +\index{Inertia}% +\index{Mass}% +as a large number of revolving disks on a circular +\Pagelabel{342}% [** PP: Best guess at page anchor] +axis, which will give to the ring not only rigidity, but +stability of form, any departure from which will be +resisted by the mechanical structure, and it will return +to its original form after the deforming stress has +ceased, with a rate depending upon the rate of rotation +of the constituent +%[Illustration: ] +\begin{wrapfigure}[15]{l}{1.375in} + \Graphic{1.375in}{357a} + \Caption{36}{Diag.\ 36.} +\end{wrapfigure} +parts of the ring. On \Pageref{page}{40} +reference is made to the behavior of a rotating disk, +and how it simulates this property of elasticity. The +common gyroscope may be cited as exhibiting it in a +\index{Gyroscope}% +manner that depends upon the +way in which the disk is mechanically +mounted. + +An ordinary whirling disk can +be freely moved only in its plane +of rotation, or planes parallel to +that. Any attempt to change +the angle of the axis is mechanically +resisted. This may be understood +by reference to diagram +where $a$~$b$ is a disk capable of +rotation on axis $c$~$d$. While rotating, +it can move freely in the +plane $a$~$b$, but any attempt to tip +the axis in any direction will be +resisted by it. Imagine, then, a large number of similar +disks, mounted on a circular axis, as in diagram~36, +each one rotating. It is plain that any attempt to tip +the ring in one direction or the other, or to change +the form of the ring itself, supposing it to be flexible, +will necessarily change the plane of some of the revolving +\DPPageSep{358.png}{343}% +disks, and will be resisted as a whole, for the +same reason that one of its parts will do the same. It +will be seen that if all these disks be rotating in the +same direction the movements will be like those of a +vortex ring. If additional disks could be inserted +upon the axis, so as to form a continuous body quite +round the circular axis, it would constitute a ring; +and if the proper rotation were set up, it would possess +all the qualities of a vortex ring, and elasticity +would be a prominent quality, as stated on \Pageref{page}{39}. It +is no longer necessary, if it ever was, to assume elasticity +as a fiat quality, imposed upon atoms which +might have existed without it; \emph{for the laws of motion, +acting in a properly constructed mechanism, are quite +sufficient to produce it}. + +\Subsection{MAGNETISM.} + +On \Pageref{page}{205} the statement is made that magnetic +phenomena have led to the belief that all atoms of +all kinds of matter are magnetic, and are only obscured +in ordinary matter by the molecular arrangements +which tend to neutralize the magnetic fields of the +individual atoms. Attention is again invited to the +diagrams on \Pageref{page}{105}, with the accompanying description, +in order to freshly bring to mind how vortex +motion necessarily produces what is called polarity---the +two sides of the ring have different qualities. +On one side the movements are all inwards, on the +other outwards, and from these the phenomena of +apparent attraction and repulsion necessarily follow. +But beyond this, once\DPnote{** PP: Missing "we"?} assume that individual atoms +\DPPageSep{359.png}{344}% +\index{Gravitation}% +are magnets by virtue of their constitution, and that +every magnet has a magnetic field infinite in extent, +within which it can affect other atoms, one can see +at once that every atom in creation has a magnetic +hold upon every other atom, because every one is +in the magnetic field of every other one. This effect +is not necessarily one of attraction or repulsion tending +to move one mass towards or away from another; +but, on the other hand, it tends to rotate each on an +axis so both shall face the same way. So long as +there is no change in position or in \emph{form} of such a +magnet, the magnetic field will be uniform; but if the +form be changed in any way the whole field has to +change in conformity with it, as described on \Pageref{page}{252}, +and such vibrations as constitute the heat of an atom +are really the change in form of the atom, and this, +therefore, changes necessarily the whole magnetic +field of the vibrating body. These changes in the +field, which originate in this way, are what are called +ether waves. When the waves are produced slowly, +by an alternating dynamo current, or more swiftly by +some of the methods so ingeniously devised by Hertz +and Tesla, they are called electro-magnetic waves. +When produced so swiftly as to have a wave length +only the one thirty-thousandth of an inch, they have +been called heat waves; and when the waves are so +short as to be capable of affecting the retina of the +eye, they are called light waves, though there is no +distinction between any of them except in their length. +The vibrations of the atomic magnet are rapid because +it is small; the waves it produces are changes in +\DPPageSep{360.png}{345}% +\index{Gravity follows from structure}% +its magnetic field in the ether, so one may trace +back in this manner the phenomena of light, of heat, +and electricity, to the mechanical structure of atoms; +and it is mechanically intelligible too, and, like the +preceding accounts of properties, it appears \emph{that magnetic +and electric qualities are due to the peculiar kinds +of motion embodied in the atoms}, and cannot be considered +as particular endowments of a something called +matter, which it might have been without. + +\Subsection{INERTIA.} + +The inertness of matter has been touched upon on +\Pageref{page}{70}, and here may be added the consideration of +what interpretation could be put upon such phenomena +as are exhibited by such a device as is represented by +diagram 36, supposing it were enclosed in a box so one +could not see the mechanism? The box enclosing it +would exhibit a new quality of the nature of inertia, +by virtue of the motions within it, which it would lose +as the friction diminished the rate of motion, and +when this stopped altogether the property would no +longer be present. \emph{Hence, inertia, too, must be looked +upon as probably due to motion.} + +\Subsection{MASS.} + +Mass, as a property of matter, is generally defined +as the amount of matter considered, and is measured +by what is called acceleration, that is, the velocity +it acquires in a second when acted on by a constant +force or push. Amount of matter is a very indefinite +expression, but is often convenient, and seldom misleading +\DPPageSep{361.png}{346}% +\index{Atoms, as vortex rings}% +when one is considering a given weight of a +substance. + +One may speak of a pound of iron or of hydrogen +as a mass of iron or of hydrogen, meaning a definite +weight made up of a very large number of molecules +of one or the other element; but if one will think of +the atoms of these, and endeavor to form an idea of +what can be the physical meaning of mass, when applied +to one of them, he will at once see that the term +carries with it no conception whatever of the physical +difference between atoms of different kinds. An +atom of iron is said to contain fifty-six times the mass +of an atom of hydrogen, while an atom of gold has +a hundred and ninety-six times the mass of the hydrogen +atom, and all the elements differ in mass in the +ratio of their atomic weights. Can any one suppose +for an instant, that an atom of gold is a hundred and +ninety-six times larger than an atom of hydrogen? +There is some evidence that atoms differ somewhat +in magnitude from each other, but none of any such +difference as is represented by their atomic weights. +Furthermore, this would imply that atoms were blocks +of some primeval stuff of uniform quality, and that +atoms of a given element were but uniform volumes +of it; and it hardly needs to be said that such a view +is negatived by all we know, for the properties of the +various elements do not vary simply with their weights, +as would be the case if they were thus constituted. +Hence, mass as applied to atoms cannot be thus conceived. +It is possible to form a conception of the +physical meaning of mass as applied to atoms or +\DPPageSep{362.png}{347}% +molecules, by recalling the phenomenon of rigidity +in position, which is the outcome of rotations, as described +on pages \Pageref{}{40}~and~\Pageref{}{342}, for the amount of effort +needed to move such a rotating body depends not +simply upon the amount of rotating material, but its +velocity of rotation; so a small amount of material +with a high speed may offer as great a resistance to +movement from its position as another much larger +amount of material with corresponding slower rate, +but otherwise the two would necessarily have great +differences in their other properties; thus their rates +of vibration would be very different, because their +degrees of elasticity would be different. + +One may then assume that such differences between +\emph{the atoms of the elements as are called their masses, +are due to the relative rates of rotation}. This, of +course, on the fundamental assumption that the atoms +themselves are vortex rings such as we have argued as +being highly probable. + +\Subsection{GRAVITY.} + +There now remains to be considered one more +general property of atoms and all combinations of +them; namely, their gravitative property. If one be +content to say that not enough is known about it +to warrant even a tentative opinion, and, therefore, +refuses to draw any inferences from what is known +as to what gravitative property is, or is like, one +need to have no quarrel with such an one; but if, +on the other hand, one is interested in fundamental +questions, and thinks that whatever be the truth +\DPPageSep{363.png}{348}% +\index{Hertz waves}% +\index{Materialists}% +about gravitation or any other unsolved problem, when +it is known, it will be seen to be in harmony with +every other physical truth, and will, therefore, be a +consistent part of the body of physical knowledge +which we now possess, such an one will perceive that +with the banishment of the old notions concerning the +structure of matter, with its endowments of sundry +properties which might have been otherwise, or that +the matter we know might have had entirely different +properties, must also go the notion of quality endowments +in any such sense as was formerly held. He +will also have good reason for holding it altogether +probable, that if the other properties of matter are +reducible to modes of motion, so the last one in +the list will be found to be reducible to the same +factor. If the others have been interpreted thus, one +after another yielding as molecular phenomena became +better understood, he will conclude that if the problem +of gravitation has not been solved, as the others +have been, it is not because it is insoluble in itself, but +because it is inherently more difficult, or has not received +the degree of attention that has been given to +other problems since conservation has been discovered +and forms a part of every discussion. + +One thing seems certain, if the vortex-ring theory +of matter be true, or anything like it, then gravity +must follow from the structure; for in the absence of +any evidence of the existence of gravitation in the +ether, no one is at liberty to postulate it there for +the sake of finding it in the atoms. It must be looked +for as due to the particular kind of motion that constitutes +\DPPageSep{364.png}{349}% +\index{Ether phenomena not explained}% +the atom, and is constant because that motion +is constant. + +In the chapter on gravitation is given a mechanical +conception of gravitative conditions which, whatever +may be its inadequacy, is consistent with other physical +knowledge. Faraday, as is well known, made +several efforts to discover some relation between +gravitation and electricity, but only negative results +were reached. He was not discouraged by his lack +of success, and had planned still other experiments, +which he was not able to finish. He always worked +on some hypothesis almost always radically different +from the hypotheses of his scientific contemporaries, +and time has vindicated his rather than theirs; and +that there must be some physical relation between +the two classes of phenomena was one of his, and so +it seems to-day; for if gravity be due to the form of +motion in the atom, and if an electric current in a +circuit represents a real vortex ring, having the conductor +for its core, then it seems likely there is some +gravitative effect between such current and the earth; +but it may be so slight with a single circuit as to not +be detectable with present means, and the mutual gravitative +effects between two such circuits would be +obscured by their electro-magnetic effects. + +Lastly, if the atom itself be a vortex ring, as +explained in the chapter on the ether, it follows that +in the absence of such form of motion there would +be no atom---no matter, though the substance out of +which the ring was constituted would exist, but without +any of the characteristics that we assign to matter +\DPPageSep{365.png}{350}% +\index{Laws not compulsory}% +\index{Miracles possible}% +\index{Phenomena, unexplained}% +in any of its forms. If one chooses to call a common +smoke-ring \emph{alpha}, evidently when the ring is dissipated +there is no more ring, there is no alpha, it has been +annihilated as a ring; and in like manner, one may +understand that what constitutes an atom is not so +much the substance it is composed of as the motion +involved in it. Such \emph{an atom is a particular form of +motion of the ether in the ether}, in the same sense +as what is called light is a form of motion of the +ether in the ether. One is an undulation, the other +a vortex. One we call an ether wave, the other we +call matter: both involve energy, and both have properties. +Thus, one after another of the properties of +matter are found to be resolvable into ether motions, +ether being the primal substance, and matter only one +of its manifestations. + +Such a conception of matter as is here presented, +resolving as it does all its physical properties, even +itself, into modes of motion of the ether in the ether, +is not simply a new conception of matter, it is rather +a revolution in fundamental conceptions, and if trustworthy, +necessitates an abandonment of nearly every +notion concerning them which men have entertained +when thinking and discoursing upon the subject. +The mystery of phenomena is not lessened but made +greater by the discovery that everything which affects +our senses in every degree is finally resolvable into a +substance having physical properties so utterly unlike +the properties of what we call matter, that it is a misuse +of terms to call it matter. + +No one in the past has been able to forecast its +\DPPageSep{366.png}{351}% +\index{Electricity, origin of}% +properties. The necessity for such a medium has not +been felt by many philosophers, and though there has +been some expectation on the part of a few, any new +\index{of}% +step has been a source of surprise. For instance, when +Hertz succeeded in producing electro-magnetic waves +in the ether only two or three feet long, it was heralded +as being a demonstration of the existence of the +ether, implying that all the phenomena of induction +and electro-magnetic waves developed by machines +vibrating up to four thousand per second in telephonic +apparatus, could have some other interpretation. The +point here emphasized is that the properties of the +ether and their relations to such physical phenomena +as have been the subjects of research are so little +known, that no one has yet ventured to embody them +in an all embracing philosophy, so as to deduce apparent +phenomena from them. + +The significance of this will be apparent when one +recalls the various attempts of materialistic philosophers +to explain all sorts of phenomena as due to +matter and its properties. Some of them have been +ignorant of the existence of the ether; others have +grouped matter and ether together and called both +matter, and considered both as subject to the same +laws as are found to hold true for matter as defined +in this book. When it is apparent that such physical +views are radically unsound, that one cannot reason +from our perceptual matter to imperceptual ether,---for +it is true that there are no known nerves that +respond directly to ether action,---it will also be apparent +that any scheme of things that ignores this knowledge +\DPPageSep{367.png}{352}% +or fails to make proper distinctions here cannot +be entitled to respectful consideration. Indeed, such +physical materialism is less rational than ever, for it +ignores much knowledge now in our possession which +is as certain as any we possess, and it ignores the +trend of all the physical knowledge we have; for it +cannot be denied that the advance in knowledge which +has been so marked during the past half century has +been in the discovery of the simplicity of relations, +rather than towards ultimate explanation. It may +truly be said that, in a philosophical sense, nothing +has been explained. Familiarity with constant phenomenal +relations induces in us expectations of certain +happenings, and presently they seem obvious. +The car moves because the engine pulls it; the engine +moves because the steam pushes it; the steam +pushes because the heat pushes it; and the heat +pushes because---it is the nature of heat to do work. +In that way, every physical phenomenon runs at last +into an inexplicable, into an ether question; and the +necessity for it follows from nothing we know or can +assume. No one may assume for an instant that the +possibilities of ether phenomena are limited by such +interactions as have hitherto found expression in treatises +on physics. Indeed, there is already a body of +evidence which cannot safely be ignored, that physical +phenomena sometimes take place when all the ordinary +physical antecedents are absent, when bodies move +without touch or electric or magnetic agencies,---movements +which are orderly, and more or less subject to +volition. In addition to this is still other evidence of +\DPPageSep{368.png}{353}% +\index{Postulates of Physical Science}% +\Pagelabel{356}% +competent critical observers that the subject-matter +of thought is directly transferable from one mind to +another. Such things are now well vouched for, and +those who have not chanced to be a witness have no +\textit{a~priori} right from physics or philosophy to deny such +statements. Such facts do not in any way invalidate +physical laws, nor make it needful to modify present +statements concerning energy. Physical laws are not +compulsory; they \emph{rule} nothing; they are but statements +of our more or less uniform experience. If +these things be true, they are of more importance to +philosophy than the whole body of physical knowledge +we now have, and of vast importance to humanity; +for it gives to religion corroborative testimony of the +real existence of possibilities for which it has always +contended. The antecedent improbabilities of such +occurrences as have been called miracles, which were +very great because they were plainly incompatible +with the commonly held theory of matter and its +forces, have been removed, and their antecedent probabilities +greatly strengthened by this new knowledge; +and religion will soon be able to be aggressive with +a new weapon. +%\DPPageSep{369.png}{354}% + + +\Chapter{XV}{Implications of Physical Phenomena}{354} + +\index{Fable, La Fontaine's}% + +A physical phenomenon is a phenomenon which +involves energy. Every change of condition in matter +is brought about by the action of energy upon it in one +way or another. It may be gravitative energy or heat +or light or electric or any other; but every physical +change has a physical antecedent as well as a physical +consequent, and the explanation of any given phenomenon +consists in pointing out the precise antecedents that +brought it about. There is a common saying that like +causes produce like effects, but this is far from being +true in the popular sense. If it were true the development +of science would not be the difficult and painfully +slow process it has proved to be. Electricity may be +produced by turning a crank, by dissolving a metal, by +twisting a wire, by splitting a crystal, and in others +ways. The product is the same, but the antecedents +are so different that no one can tell by examining the +product how it was produced. If it became important +to know what caused the electrical phenomenon, it +would not be sufficient to know that electricity could +be produced in these different ways; one would need +to know the specific apparatus employed. The more +\DPPageSep{370.png}{355}% +complicated the phenomenon the more difficulty there +is in unravelling it. + +So far as experiment and experience have led us, the +antecedents of every physical phenomenon are themselves +physical, and more than that, all reactions are +quantitative, that is, the product is proportional to the +antecedent, and this is sometimes embodied in what is +called the doctrine of the Conservation of Energy +which every one knows about. + +The exchange relations between the different forms +of energy,---mechanical, thermal, chemical, electrical, +etc., which are so well-known, being quantitative, are +therefore mathematical. They have therefore become +a corporate part of the body of knowledge, and are no +longer subject to any questions as to their validity +under any circumstances whatever. One who should +challenge them would no more be deserving of attention +than if he should offer to prove he could square a +circle. + +The fundamental postulates of physical science are +binding upon the one who understands them, for the +same reason that the multiplication table is. There +are no contingencies and no possibilities of hedging. +If any one of them could be overthrown the whole +body of science would go with it. This is said because +there are not a few who appear to think that +what is called physical science may not be so certain +as its advocates think, and that there may be factors +which have not yet been reckoned with that may quite +transform the whole scheme. Science is a consistent +body of relations, not simply a classified body of facts. +\DPPageSep{371.png}{356}% +\index{Blavatsky, Madam, pretensions of}% +\index{Guppy, Mrs.}% +\index{Power, needed for rapid movement in air}% +These relations have been discovered by experiment, +not by deduction. + +Some of them are the following:--- + + 1. Physical changes affect only the condition of +matter, not its quantity. One cannot create or annihilate +it, nor can one element be changed into +another. + + 2. Every atom is continually exchanging energy +with every other atom, the rate of the exchange depending +upon their difference in temperature. + + 3. The different forms of energy are transformable +into each other, but the quantity of energy is not +altered by the transformation. + + 4. Complex organic molecules differ from simpler +inorganic molecules in possessing more energy. The +differences in this respect are definite, may be measured +in foot-pounds, and are practically enormous. + +5. Every physical change has a physical antecedent, +is therefore mechanical, and is conditioned by the laws +of energy. + +These principles are the outcome of modern investigation, +the evidence for them is overwhelming, and +a working knowledge of them needs to be a part of +the mental equipment of every investigator, especially +of the one who takes it as his province to explain +phenomena. + +Science is strong here if it is anywhere; and any +description of any event, any explanation of a genuine +phenomenon that practically ignores these, cannot be +true, and can have no claim to consideration. + +Before any explanation is needed there is always the +\DPPageSep{372.png}{357}% +\index{Sound, origin of}% +\index{Spiritualistic theory}% +\index{Spirit disembodied}% +advisibility of ascertaining that the alleged event really +happened, and whatever is not professedly miraculous +must not be in discordance with the bast knowledge +we have. + +With the above principles in hand one is prepared to +fairly judge as to whether a given statement is credible +or not. It is not necessary, as some seem to suppose, +that one should be able to explain a phenomenon if he +rejects the explanation of another one, or to assert with +emphasis whether a thing is possible, probable, or +impossible. + +In La Fontaine's fable the philosophers were at the +theatre witnessing a play in which Ph{\oe}bus rose in the +air and disappeared overhead. They undertook to explain +the phenomenon. One says Ph{\oe}bus has an +occult quality which carries him up. Another says +he is composed of certain numbers that make him +move upward. Another says Ph{\oe}bus has a longing +for the top of the theatre, and is not easy till he gets +there. Still another says Ph{\oe}bus has not a natural +tendency to fly, but he prefers flying to leaving the +top of the theatre empty. Lastly, a more modern +philosopher thinks that Ph{\oe}bus goes up because he +is pulled up by a weight that goes down behind the +scenes. The last is an explanation. From a physical +standpoint the others are not simply inadequate explanations, +they are absolute nonsense. They make +the antecedents of a phenomenon involving energy, +factors that have no more relation to energy than has +moonshine to metaphysics. Yet there has been a large +number of men in all ages, men able in many ways +\DPPageSep{373.png}{358}% +too, who have ventured to explain phenomena in such +a \emph{non-sequitur} way, and who have spurned the mechanical +philosopher and his explanations. + +In that class of phenomena called spiritualistic there +is a large body of reputed physical phenomena, vouched +for by large numbers of witnesses, such as the movements +of furniture, chairs, tables, books, pianos, etc., +the playing upon musical instruments, guitars, accordions, +pianos, the appearance of lights, of faces, of +full forms clothed, of conversations with materialized +spirits, and so on, in great variety. + +I suppose no one doubts that to move a body of any +magnitude requires the expenditure of energy, and to +do a definite amount of work requires always the same +amount of energy, yet I suspect there are many persons +who give credence to statements of occurrences +which practically deny the above proposition, thinking +it to be probable that spiritual agencies may have +control of powers that mankind knows nothing about. +This may be true enough, but the question is not as to +what this or that agency can do, but whether if spirits +do a certain kind of work it takes less energy than if a +man should do the same thing. + +Whenever a weight or a resistance and a velocity +are given, it is always possible to compute the energy +spent to produce or maintain it. Let us study a case +or two. In olden times it was related that one of the +prophets was carried through the air by the hair of his +head from Babylon to Jerusalem. In later times it +was said that Mrs.\ Guppy was similarly transported +from Edinburgh to London. The distance is about $400$ +\DPPageSep{374.png}{359}% +\index{Séances, phenomena at}% +miles, and if I remember rightly she made the transit +through the air in less than one hour. This makes the +velocity to be about seven miles a minute or $600$ feet +per second, which is three times faster than the highest +tornado velocity. The resistance offered by the air +to the movement of bodies in it is very well known. +Pressure in hurricanes has been observed as high as $90$ +pounds per square foot, and as the pressure increases +with the square of the velocity, it follows that at $600$ +feet per second the pressure per square foot would be +about $800$ pounds; and if the exposed surface of Mrs.\ +Guppy was no more than six square feet, the total air +pressure must have been not less than $4,800$ pounds. +Now, the energy of this is found by multiplying the +pressure by the velocity per second. +\[ +4,800 \times 600 = 2,880,000\text{ foot-pounds,} +\] +and as a horse-power is equal to $550$ foot-pounds per +second, it follows that it took not less than +\[ +\dfrac{2,880,000}{550} = 5,236\text{ horse-power} +\] +to move Mrs.\ Guppy in that way at that rate. + +It was reported when Madam Blavatsky was living +that she was in the habit of receiving letters from +distant correspondents, brought to her by some occult +agency and dropped upon her table. These letters +were said to have been written only a few minutes +before by persons living in the most distant parts of +the earth. + +It takes but a little figuring to discover the amount +of energy necessary to do a work of this kind. Thus, +\DPPageSep{375.png}{360}% +\index{Light, a sensation}% +let the distance be $10,000$ miles, the time ten minutes. +The pressure per square foot due to such a velocity in +the air will be $17,000,000$ pounds, or $118,000$ pounds +per square inch. Assume but one square inch as the +area exposed to such a pressure, then the energy +needed to transport it with the speed of $16.6$ miles +per second, will be +\[ +\dfrac{118,000 \times 5,280 \times 16.6}{550.} = 18,000,000\text{ horse-power.} +\] + +Unless such packages were protected by occult +agencies also, they would be burned up before they +had gone the first mile of their journey. + +The popular idea is that at death the spirit leaves +the body, but that it may, and often does, remain +in the locality, and is frequently in the presence of +its friends, unperceived by them, though occasionally +they may be seen and communed with through the +agency of certain preternaturally gifted persons called +mediums. + +This proposition has so many physical data, and involves +so many physical implications, it will be worth +the while to look squarely at some of them. + +1. A spirit is supposed to be a conscious entity dissociated +from matter, having ability to move at will and +to be more or less interested in what is going on in the +world, and capable of giving information on matters +remote from observation or the knowledge of men. +Suppose then such an entity, a disembodied spirit, +without a corporeal body, but anxious to be in the +neighborhood of its former friends. Seeing that it +\DPPageSep{376.png}{361}% +\index{Light, its nature}% +now has, according to this view, no longer a hold upon +matter, it has ceased to be in any way affected by +gravity and inertia, for these are attributes of matter. +Now the earth has a variety of motions in space; it +turns on its axis, so that a point on the equator is +moving at the rate of a thousand miles an hour. It revolves +about the sun at the rate of nearly seventy thousand +miles an hour, and with the sun and the rest of +the bodies that make up the solar system it is drifting +in space at the speed of sixty thousand miles an hour +or more, so that the actual line drawn in space by any +point upon the earth is a highly complex curve drawn +at the rate of upwards of a hundred and twenty-five +thousand miles in an hour. Now, any object whatever +keeping up with the earth, but without the help of +gravity, must maintain the velocity in space of not less +than a hundred and twenty-five thousand miles an hour, +and that is not all, as the movement is not in a straight +line, any such object wishing to keep in a particular +locality, say a room, would have to be on the alert constantly, +for the earth wabbles\DPnote{** [sic]} for numerous reasons and +what seems to us, who have bodies held by gravitation +to the earth, as so quiet and smooth running that we +are never conscious of the motion for an instant, is so +simply because gravity takes care of us. Once surrender +that and undertake to depend upon some supposed +private source of energy, and one would instantly +discover he had an engineering problem of a high degree +of complexity. If one assumes, as some have +done, that such spirit is composed of, or associated +with, some sort of matter, and that navigation is accomplished +\DPPageSep{377.png}{362}% +\index{Materializations and energy}% +by an act of the will, it will not change the +foregoing factors in the problem at all. + +2. Suppose, as some have done, that disembodied +spirits lose their hold upon matter, and that they do +not remain at the earth. Then, if they remain at the +point where separation from the body took place, in an +hour the earth will have moved forward one hundred +and twenty-five thousand miles. But over the earth +there is certainly a death every minute all the time, +and such are left in the rear by the earth never to return +to them, for the movement of the earth is not a +circuit, but an apparently endless drift. Think of the +dead of the earth for the thousands of years since man +has lived upon it! On this view, the spirits might be +seen like the tail of a comet reaching backwards for +millions on millions of miles,---the trail of the dead. + +In any view, time and space and energy cannot be +ignored or ruled out. + +At \emph{séances} the reported phenomena are mostly of a +physical sort, the trance of the medium being a physico-mental +phenomenon. The phenomenon of sound implies +the expenditure of energy, it is a vibratory motion +of the air or other elastic body, and in order to produce +it some antecedent force must be spent; it may be produced +by mechanical means, or heat, or electricity, or +by the muscles. Its production does not imply any +specific method any more than articulate speech implies +a person, as Faber's talking-machine and the +phonograph prove. + +Let us consider some of the more subtle phenomena +that are reported. First, as to so-called conditions. +\DPPageSep{378.png}{363}% +\index{Organic and inorganic matter, difference between}% +One of the primal ones of these for such phenomena as +the movements of bodies and materializations, is said +to be darkness. This is of so much importance that it +must be fully attended to. To one who has not paid +any attention to what has been done in molecular +science within the past fifteen or twenty years, the +phenomena of light may and probably do seem to be +due to an unique agency, as much as heat or electricity; +and therefore he looks upon light as he looks +upon the others in the hierarchy of the physical +sciences, and expects that in its absence a potent +agency or kind of energy is lacking. That this idea +and conclusion is all wrong will be apparent when it is +recognized that \emph{what we call} light is a particular sensation +in the eye, and that to produce the sensation +\emph{there is no one antecedent that is essential}. Press the +eye with the finger in the darkest night and one will +see a ring of light with great distinctness. An electric +shock, a bump upon the head, will also give one the +sensation of light, and in the absence of other aids to +a judgment no one could tell what was the antecedent +of a given light sensation. + +Radiations from a luminous body, and reflections +from a non-luminous one, were not long ago thought to +consist of three different kinds of rays,---heat, light, and +actinic rays. It has been discovered that there is no +such distinction in fact. What a ray will do depends +upon what it falls upon. The same ray that falls upon +the eye and produces the sensation of light, would heat +another body, or do photographic work. The only +difference in rays is in their longer or shorter wave +\DPPageSep{379.png}{364}% +\index{Immortality}% +lengths, and the energy of a wave does not depend +upon its length. From this it follows that there is no +such thing as light as distinguished among forces or +forms of energy. \emph{Light is a sensation}, and in the absence +of eyes no such distinction could possibly be discovered. +Light, then, as a particular kind of agency +takes no part in phenomena outside of the eye. The +eye of man is adapted to respond to certain wave +lengths, the eyes of other animals are adapted to respond +to other wave lengths; and if our eyes were +adapted to perceive all wave lengths the whole universe +would be always light about us, every object, +whatever its temperature, could always be seen as +easily as we now see when the sun shines. + +These facts make it quite impossible for a physicist +to understand why darkness should be an essential +condition for the occurrence of such phenomena as +are described. Again, every ray of light when traced +back leads to a vibrating molecule or atom. Indeed, +light or ether waves in general all imply vibrating +atoms or molecules; and what is called spectrum analysis +is but a development of this fundamental principle, +and not only the kind of matter, but its physical +condition is revealed. If Moses had had a spectroscope +when he saw the burning bush it might have +told him the nature of that conflagration. + +So when luminous forms appear at a dark \textit{séance}, +there is first the ether waves of such length as to +affect the eye; these traced to their source must +arise from vibrating molecules, that is, matter expending +energy in the production of ether waves; +\DPPageSep{380.png}{365}% +for no matter ever shines without some source of +energy. + +If the matter that gives out the light be ordinary +matter, there is no difficulty in understanding it; for +matter can be made to shine in several ways,---by +impact, by high temperature, by electric vibrations, +by chemical reactions; and no one could tell from +the simple fact that the matter shone, what the origin +was. But it is said that these forms that are seen +and thus affect the eye, that are touched and thus +affect the sense of touch, that are warm and thus +testify to vibrating molecules, that speak and appeal +to the ear through air vibrations, are \emph{materializations}; +meaning by that that the body with its various organs +and their functions is built up \textit{de novo} out of material +at hand, as Adam was said to be made of the dust of +the ground, and as the lion that pawed to free its +hinder parts from the soil out of which it thus grew. +What are the materials that make up a human body? +Ultimately there are carbon, hydrogen, oxygen, nitrogen, +iron, phosphorous, sulphur, potassium, sodium, and +several other ingredients of less importance. From a +hundred to a hundred and fifty or more pounds of these +are needed for one full-grown person. + +Many of the materializations that have been described, +from Samuel the prophet to Katie King, have +appeared to be veritable specimens of humanity even +to avoirdupois and all that is implied in that. If the +matter of such bodies was a creation and not a collocation, +then one of the fundamental principles of +physics is simply not true; for matter can be created +\DPPageSep{381.png}{366}% +\index{Seeing, what is implied in}% +and annihilated by any spirit that knows how to find +a suitable medium. If the material is gathered from +the environment---and this sometimes is asserted---then +the difficulty is nearly as great. + +One must take notice of the difference there is +between inorganic or relatively simple chemical compounds +and those that make up the bodies of living +things,---the bones, the tissues, the muscles, the nerves, +the brain, the blood. For building up a single pound +of such tissue as muscle or of fat requires the expenditure +of energy represented by about sixteen million +foot-pounds; and as in such a body as we are supposing +there could hardly be less than twenty-five or thirty +to be so reckoned, it follows that not less than four +hundred million foot-pounds of energy is necessary, a +quantity equal to upwards of twelve thousand horsepower, +if done in a minute; and if done in half a +minute, then twice that quantity. I cannot but wonder +if those who think they have witnessed such phenomena +could have been conscious of the stupendous +amount of energy which was being evolved before their +eyes. Then dematerialization involves the annihilation +of the same amount; for it is to be remembered that +organic matter differs from inorganic in the amount of +energy absorbed. There has been either the creation +and annihilation of matter or the creation and annihilation +of an enormous amount of energy, without antecedents +and with no residuals. This is not saying that +such events have not taken place, it only points out the +factors of energy which are implied if they do happen. + +One who is unaware of such implications and phenomena +\DPPageSep{382.png}{367}% +\index{Hearing, what is implied in}% +may easily suppose the most improbable things +can take place. Those who are aware of such implications +cannot hear of such events without instantly perceiving +how almost infinitely improbable they are. + +Reports of such phenomena have never come from +any man who understood the relations of phenomena. + +Scientific men have been often told of their incompetency +to investigate so-called psychical phenomena; +but if the latter involve physical phenomena, then who +else can properly investigate them? + +This paper is not to be understood as implying that +there is no relation between the living and the dead, +for the writer does not believe that doctrine; instead +of that he thinks we are very near to a discovery of a +physical basis for immortality that will transform most +all our thinking. If spiritual communication is not +accompanied with physical phenomena in the alleged +way, it does not follow that it may not happen in other +ways that do not do such violence to our fundamental +knowledge as most of the reported cases do. The universe +is large, not much of it has been explored. We +live and move and have our being in an environment +about which our knowledge is most meagre; but our +knowledge of energy we get not only from the earth, +but from the sun and most distant stars and nebulæ, +and it is not probable that any contribution whatever +will materially modify our present knowledge of it. + +Thus far I have considered what is always implied +when physical phenomena are considered, especially +with reference to the antecedents; for instance, when +a steam-engine is run it implies the consumption of +\DPPageSep{383.png}{368}% +\index{Senses}% +fuel, which in turn implies molecular structure, and a +definite amount of energy in what is called its chemical +form. That energy is not created or destroyed by +any physical process, and, therefore, every exhibition of +energy, no matter where or when, is to be explained +solely by reference to the laws of energy which are +now so well known as to have passed out of the region +of conjecture or hypothesis. If there be any knowledge +which man possesses, which for certainty and +accuracy compares with mathematical knowledge, it is +the knowledge of physical relations. I traced out a +few cases in which the alleged phenomena were of +such a physical sort as to be easily handled, and +showed how one must look at their antecedents. That +such phenomena did take place was not denied. It +was simply asserted that when they did happen one +must reckon with the implications, unless he was prepared +to affirm that physical phenomena might happen +when physical laws are ignored and quite counted out. +There are yet some further implications it is well to +consider. They have to do with the objective structure +and qualities of the spiritual beings that are +supposed to bring about the phenomena we are considering, +such as moving objects, playing upon musical +instruments, writing upon slates, and so on. + +As such beings are always addressed as if they were +visible personages, possessing the same organs of hearing, +seeing, and so on, as are possessed by individuals +still having a material body; and as the replies to questions +never contradict such assumptions, but, on the +contrary, are confirmatory of such assumptions, it follows +\DPPageSep{384.png}{369}% +that one may properly consider what really is +implied in the assumption that spirits have eyes and +ears, because they can see and hear. When I say \emph{I +see}, I assert not only the existence of what we call +light, but the existence of an organ called the eye, the +structure of which is adapted to be acted upon by what +we call light. Light is, as we all know, a wave-motion +in the ether. It travels at the great velocity of a hundred +and eighty-six thousand miles in a second, and the +waves are in the neighborhood of only the one fifty-thousandth +of an inch long. The eye is the only +structure in the body that can perceive these waves. +It is a kind of camera, and photographic work goes on +in the retina very much as it does in the process of +photography. Then, there is the optic nerve, which is +an essential part of the apparatus, and conveys to the +seat of consciousness the impress of the molecular +disturbances which have taken place in the eye. No +one is conscious of the phenomenon of light except +through the action of this complex mechanism. Therefore, +when one says he \emph{sees}, he means that a particular +kind of disturbance has taken place in a particular physiological +structure. The term sight is never used in a +different sense from this, except when it is avowedly +used figuratively. In the absence of ether waves there +could no more be what we call sight than if there were +no eyes; both are essential. + +When, then, it is said or admitted that a spirit \emph{sees}, +not in a figurative sense, but in the sense in which we +all use the term, it is implied that a spirit has eyes, a +physiological structure, acted upon by ether waves, and +\DPPageSep{385.png}{370}% +\index{Law, physical}% +\index{Specialists}% +the nervous system behind that. It has what \emph{we} call +eyes. It will not do at all to say that such spirit has +an equivalent sense, for whatever that might be it +would certainly not be \emph{sight}. One may get a very +accurate knowledge of the presence of another person +by the voice, or by the sense of touch, but it +would be a culpable misuse of language to say of such +person that he was \emph{seen}. Sound can no more affect +the eyes than light can affect the ears. This, then, is +the same as saying that a spirit has a physical structure +for seeing similarly constituted to that in man, +and, indeed, in all organizations that \emph{see}. + +When I say \emph{I hear}, I mean that air vibrations have +affected my organs of hearing, the ears with the nervous +structure between the ear and the seat of consciousness. +There is implied in the statement not +only that sound vibrations of a definite sort have been +produced and are acting, but that they are acting upon +a certain physiological structure adapted to be affected +by gaseous vibrations. Vibrations in the ether cannot +affect the organ of hearing. The media are radically +different, and cannot be used as substitutes for each +other; and it is therefore wrong to say \emph{I hear}, unless +what I perceive reaches my consciousness through the +physiological mechanism called the auditory apparatus. +In a figurative sense one may say he hears as he may +say he sees. +\begin{verse} + \small + ``Lo, the poor Indian! whose untutored mind \\ + \PadTo{``}{}Sees God in clouds, or hears him in the wind.'' +\end{verse} + +But real seeing and real hearing imply certain distinct +\DPPageSep{386.png}{371}% +organs adapted to different physical conditions. +One cannot, by talking, affect one's eyes; nor will +light waves, as such, affect one's ears. + +Suppose, then, in a \textit{séance}, when a spirit is addressed +thus: Will the spirit please rap upon the table? and +the answer comes at once,---a rap distinctly heard. The +question was an oral one, and was produced by physical +means, regular sound vibrations, and can be heard +by such beings as are possessed of the proper organs +to be acted upon by air vibrations, that is, ears; and +by ears I \emph{mean} ears, not substitutes of any sort. What +we call \emph{speech} is absolutely impossible in a vacuum, +as much as is sound, for speech is a succession of +sounds. There are numerous substitutes for speech,---signs +made with the fingers or lips that do not appeal +to the ear; but these are not speech. If, then, spirits +\emph{hear}, it is because they have ears, organs that can be +affected by sound vibrations in the same manner as we, +the so-called living beings, can be. Moreover, do not +all testify that they can and do both see and hear? + +In like manner one may treat of the sense of feeling, +or any other sense. All imply a molecular structure, a +nervous organization, indeed, everything that goes to +make up a consciousness of the external world such as +is possessed by living beings governed by physical +laws. + +It is clear that what we call pain is immediately due +to disordered nervous structure, and in the absence of +nerves could never be known. This can be tested in a +minute by any one, by simply pricking one's finger. +Does not the destruction of the nervous tissue in any +\DPPageSep{387.png}{372}% +manner end the possibility of pain? Can a spirit +then suffer physical pain without a nervous organization? +By pain I mean what all mean by the +term, the sensation which, if severe and long-continued, +results fatally to the sufferer, because the +nervous tissue is itself destroyed. + +If some one having read so far, perhaps with impatience, +should say, ``All this may be as you say for living +beings, incorporated in a body of flesh and blood +and a nervous system, but we are not to suppose for +a moment that spirits are thus constituted, and if not, +then they are not to be supposed to be conditioned by +such physical laws as all common matter is conditioned +by. They have their own constitution, different enough +from ours, and one cannot reason from our condition to +theirs.'' To this I would reply, that if one cannot do +this, if a physicist must not carry his terms and conceptions +into this spiritual domain, for precisely the +same reason the spiritualist must not talk about a spirit +\emph{seeing}, \emph{hearing}, \emph{feeling}, and so on, unless he admits he +is talking loosely, and means by those terms only to +symbolize his conceptions, and has to employ such +terms as best convey the idea, which idea cannot be +physically true. Even then it is very difficult to understand +why, if the physical terminology is inappropriate, +any one should at a \textit{séance} ask such a question aloud as, +If John be present will he please rap on the table; for +this is \emph{sound} addressed to an ear---both of which are +purely physical things. + +An Arab may not have any difficulty in imagining a +genie that may be summoned by rubbing a cup, to do +\DPPageSep{388.png}{373}% +wonderful things, and then vanish out of relations to +everything; but no one who has studied deeply into +the significance of physical relations can possibly admit +that affairs in nature go on in such a fast-and-loose +way. + +Thus far I have considered such relations of physical +phenomena as have been found by experience to hold +good in the whole range of physics---such relations as +properly come under the domain of what is called law, +and by law I mean mathematical precision, both in the +antecedents and the results. With the exception of +the original apparition of matter and of physical energy, +there has not been found in the whole field of physics, +by any investigator of any nationality, any kind of a +phenomenon which is believed to be unexplainable on +the basis of the knowledge of physical science we +already possess. Of course, what we call explanation +is merely presenting the antecedent factors of a given +occurrence, both in quality and quantity, and a thing is +fully explained when these are given so fully as to leave +no reasonable doubt as to their sufficiency in the mind +of one who is properly well acquainted with the data; +but the data that enter into a given phenomenon are +the very things most persons know least about; and a +given explanation may be full and adequate, and yet, to +some, seem to be wholly insufficient. + +In these days one often hears about \emph{specialists}---of +their limited knowledge and inadequate preparation for +giving a judgment in other fields than their own. So it +has come to be reckoned that if a man has, by study +and investigation in a given field, made himself a competent +\DPPageSep{389.png}{374}% +judge, so as to be considered an authority in +that field, he is by so much less fitted to be heard in +the settlement of some question foreign to that field; +whereas some other man who is not known to have +done anything in any field, may be called in for judgment, +to the exclusion of the former, lest his increased +knowledge in some one department should disqualify +him elsewhere. + +Do we not hear that biologists are incompetent +judges of mental phenomena, that astronomers are not +competent in biological questions, and so on? If this +distinction be true to the extent generally assumed, +then philosophy itself is impossible; for if a man's +opinion can be good only in a small department of +knowledge, and he cannot adequately master more, how +shall we ever know the relationships that constitute +philosophy? The truth is, this is a one-sided affair +altogether, and holds true from but one standpoint. If +an astronomer propounds a chemical theory of the sun, +will it be needful in any degree that the chemist who +reviews the work shall have even studied astronomy +or paid the slightest attention to telescopes or solar +affairs? If chemical science is involved, it is for the +chemist to say whether what is propounded is adequate +or not. That is to say, the man who concerns himself +with the constitution of the sun must so far be a +chemist, but a man may be a chemist and never concern +himself about the sun. + +Again, if a biologist who is admittedly ignorant of +chemical and physical science makes statements that +plainly contradict the laws of energy as determined in +\DPPageSep{390.png}{375}% +\index{Science, no one independent}% +chemistry and physics, and if a physicist challenges the +statements, shall the latter be silenced by calling him a +specialist who may be competent enough in his own +field, but who knows nothing of biology? Or shall he +be told that physical laws may be rigorous enough in +one mass of matter, but not in another? Is it to be +believed that physical laws thus play fast and loose? +Here the arithmetic holds good, but there all is indefinite, +and would not this be a fine example of dictation +out of one's field? Physiologists tell us that ultimately +every physiological problem reduces itself to one of +chemistry and physics.\footnote + {See Appendix, \Pageref{p.}{400}.} +If this be so, is it not plain +that the one who treats broadly of biological problems +must either be a physicist or submit his work to the +criticism of a physicist? But a man may be a physicist +and never trouble himself about biological questions. + +If a social philosopher presents a scheme for ameliorating +the evils present in society, in which scheme he +plainly ignores the laws of life as determined by biologists,---as +if such laws were not the very determining +factors which must first be reckoned with,---shall not +the biologist condemn such work? and shall he, too, be +told that however much he knows of biology, he is incompetent +in sociology? Plainly, not so. But is this +process a reversible one? Can the sociologist criticise +the biologist's work unless he be himself a biologist, or +the biologist criticise the chemist's or physicist's work +unless he be so far a chemist or physicist? He certainly +cannot; and this shows that there is a certain +relationship among these subjects in which there is an +\DPPageSep{391.png}{376}% +\index{Séances, phenomena at}% +order of dependence. In order to fully understand and +explain a sociological problem, a knowledge of psychology +is essential; a working knowledge of biology, +or the laws of life, and no adequate knowledge of this +can be had without a preparation in chemistry and +physics. + +In this there is nothing new, but it is generally +ignored by most persons who treat on broad questions. +It is plain that every kind of a question is, in the last +analysis, referable to the laws of physical phenomena, +and from these there is no appeal. There are not +many who like this, it is true; but the test for truth +is not what one likes or dislikes, but whether the +proposition is in accordance with the best and most +fundamental knowledge we have. Some of those fundamental +truths discovered within the past fifty years, +and not questioned by any one who can stand an +examination on them, were given on \Pageref{page}{356}; and +whoever sees, or thinks he sees, a phenomenon which +he interprets in a way which plainly contradicts or +ignores those laws, does not so much have a contention +with any man as with science itself. If those laws are +not irrefragably true, then we have no science at all, +no philosophy, knowledge is scrappy, and what we call +the interdependence of phenomena is a myth. + +Some of the phenomena alleged to happen at spiritual +\textit{séances}, such as levitation of human bodies, writing between +closed slates, the moving of matter without contact, +and so forth, are said to be as thoroughly proved +as any of the facts of the fundamental knowledge I +have treated. Such a statement cannot have come +\DPPageSep{392.png}{377}% +from any one who knows how the knowledge I spoke +of was obtained, or how it may be verified by anybody +who cares to take the pains. None of it depends in +any degree upon anybody's dictum. If any one has +doubts as to the constitution of water, he can determine +it himself in half a dozen different ways. If +he doubts that the earth is eight thousand miles in +diameter, he can measure it in several ways. If he +thinks a pound of coal does not have eleven million +foot-pounds of energy, he can himself try it and be satisfied. +Any one can satisfy himself by himself; assistance +of others is only a convenience, not a necessity, +and the fundamental statements are now believed by +so many because so many have tested them, and all +have reached the same conclusion. Furthermore, great +commercial enterprises are founded upon some of them, +as when so much limestone and coal are mixed with a +given ore of iron for its reduction. So if such alleged +facts be true, it cannot be true they are as thoroughly +proved as the ones I stated, and they will not be so +proved until each one can be verified in like manner. + +There is another excellent reason for denying that +they are proved in any scientific sense. All physical +phenomena, so far as they have become a part of physical +science, have been examined and reported upon by +physicists; and both phenomena and their interpretation +have been the subject of remorseless criticism, +and have been adopted, if at all, on \emph{compulsion}; their +acceptance has been a matter of last resort. This is +true in all departments. Why should one believe that +the world turns round unless there is no other possible +\DPPageSep{393.png}{378}% +\index{Growth of crystals}% +way to explain and account for all the facts which must +be reckoned with in any explanation? The theory itself +is so remote from the common experience of mankind +that nobody suspected it for thousands of years, and it +is not at all obvious to one who is not acquainted with +phenomena out of the range of ordinary experience. +The form of the earth, the aberration of light, the +apparent change of latitude, and so forth, have to be +considered even more than the recurrence of day and +night. For most of the purposes of life it does not +matter whether it turns round or not, and most men +have no interest in the question further than that it +accords or not with their other beliefs and feelings. +But the answer to the question, ``Does it turn?'' is +not one that can be settled by submitting it to the vote +of the world. The judgment of one Galileo is worth +more than that of all the rest of the world on that +point. Once admit that no department of science is +independent of other departments, and that no phenomenon +occurs independent of relations which must +be satisfied by any attempted explanation, and it follows +that no explanation of an event should be adopted +and be considered a part of science, unless it is shown +to be in agreement with what is known. Hence, if an +event is reported which appears to be out of relation +with those established relations which there is general +agreement upon, there is the best of reasons for thinking +that either the event did not happen, or that it did +not happen as reported, especially if the one reporting +it is unacquainted with the variety of ways in which it +is possible to do the same thing. If one sees a wheel +\DPPageSep{394.png}{379}% +\index{Physicists, prepossessions}% +turning round but does not see its connections, how can +he tell whether it is turned by muscular action or water-power +or wind-power or gravity or heat or electricity +or magnetism, every one of which is capable of turning +a wheel? Even if he can see the connections, he cannot +always tell what makes the wheel go without further +investigation. Air and steam will make a water motor +go as well as water itself, and the presence of electrical +devices would not insure that the wheel was turned by +electricity, and the absence of such electrical devices +would not insure that it was not driven by electrical +agency. Hence the testimony of witnesses only, even +though they were otherwise competent, would be of +little weight in deciding what made the wheel go. If +the question were one of any importance it could be +determined only by a competent investigator with +proper appliances, and unhindered by restrictions of +any sort. One cannot trust his sense of sight implicitly. +Many persons have lost fingers because the +buzz saw looked as if it was still; and it is easy with +the zoetrope, and in other ways, to produce the impression +of movements that are not taking place; so it +might be that after all the wheel was not turning, or +even that there was no wheel at all. + +Admitting, for the argument's sake, that the alleged +phenomena at \textit{séances} are real occurrences and must +be accounted for, there are certainly three different +possible ways:--- + +1. By more or less skilfully devised tricks, and fraudulent +only in the attempt to make others believe they +are not tricks. To be certain they are not the results +\DPPageSep{395.png}{380}% +of manipulative skill on the part of some one, only a +skilful juggler might be able to find out. It is known +that hundreds have been thus imposed upon; and skilful +jugglers, such as Hermann and Maskaline, who have +investigated many such, declare themselves satisfied +that the whole of it is trickery. + +2. Suppose some of the surprising things done are +not the results of conscious duplicity, then it may be, +as most interested persons contend, the work of disembodied +spirits who, through the agency of mediums, +do apparently the most absurd and irrational things, +but are never willing or able to do the simplest reasonable +thing to satisfy a competent judge; who mutter no +end of maudlin rubbish, add nothing of wisdom or +knowledge to mankind, and justify Professor Huxley +in saying that if such is the state of the dead we have +another good reason against suicide. + +3. There are a small number who think some of the +\emph{phenomena} to be genuine, but who attribute them not +to spirits, but to some obscure physical force not yet +understood, and but little investigated. This is the +attitude of Professor Crookes, and of the Milan experimenters. + +As to the class that is satisfied with the spiritistic +interpretation, it may be remarked that such an explanation +is in accordance with the attempts of the race +to give a rational explanation of all kinds of phenomena. +In the absence of proper knowledge, what +seems simpler or more natural than to assume some intelligent +agency as the cause of any obscure event? +This it was that peopled the mountains, glens, trees, +\DPPageSep{396.png}{381}% +\index{Knowledge, rapid growth of}% +and rivers with unseen beings, watchful and interested +in the affairs of men. The more ignorant, the closer +was the fetich; the more enlightened, the higher these +agencies retreated into the sky, useful now chiefly for +literary and artistic purposes. For some reason it has +always been discreditable to be without some theory +for all sorts of occurrences, and even to-day, in the +most enlightened communities, a man is liable to be +denounced for his stupidity or his cowardice if he says, +about some matters, I don't know. It is said, however, +that some of the phenomena at \textit{séances} bear the marks +of intelligence such as do not belong to natural occurrences, +and that it is a fair inference that other minds +than the witnesses are present. When Kepler discovered +that the planets moved in elliptical orbits +instead of circular ones as had been supposed, he felt +bound to give some reasonable explanation of the facts. +He knew of nothing but intelligence that could maintain +such motions, and he therefore supposed that each +planet must have some guiding spirit. When the law +of gravitation was applied, it was found that a circular +orbit was the only unstable orbit in the system, and +that gravity alone was sufficient to account for the +order, the harmony, and all the variety of motions; so +the spirits were dismissed from further duty. When a +spider has a leg grow to replace one that has been lost, +it has been held to be due to intelligent action superior +to ordinary chemical and physical action. When a +crystal of quartz is seen to replace a part accidentally +lost, so as to complete its symmetry before it begins to +grow elsewhere, it appears as if mind was at work here +\DPPageSep{397.png}{382}% +quite as much as in the other case, only in the latter most +persons are content not to follow the implications, for +they quickly see the philosophical rocks ahead. The +real truth is that the further one pursues the causes +of phenomena the more clearly does it appear unlikely +that disembodied intelligence is behind any particular +phenomena. + +Among all those who make up the great class of +believers in the spiritualistic theory of physical phenomena, +there is not a single physicist; that is, not one +to whom one would go for an explanation of any complicated +physical process. It is assumed that he is no +better qualified to investigate \textit{séance} phenomena than +others who do not know what to expect and look out +for in simpler cases, and that he is unreasonable if he +does not accept the statements of untrained observers +as being as good as his own observations. + +It is true that he has some prepossessions. He does +not believe the multiplication table should be trifled +with. He knows that most things may be done in +many different ways, independent of appearances. He +knows a man may sometimes not perceive what is +plainly before his eyes, simply because he was not +looking for it. He deems it right to exhaust the +possibilities of the known before summoning some +unknown and hypothetical factors in any given case. +He knows it to be well-nigh impossible for a man to +give an entirely accurate account to-day of what occurred +yesterday. He knows that a photograph is a +better witness of an event, and that a stenographic +report of statements made is more reliable than any +\DPPageSep{398.png}{383}% +\index{Miracle defined}% +man's memory. He knows that the interpretations of +events by mankind have never been true interpretations, +and that the general beliefs of mankind have +never been confirmed by science in any particular, and +that, so far as anything has been settled, it has been +decided against the opinions and judgment of mankind +and its leaders. He is aware that his key has unlocked +every one of the doors in Doubting Castle that have +been unlocked, and therefore he believes that the +implications of physical science as a whole are against +any generally received interpretation of any event that +has not been subjected to its scrutiny. +%\DPPageSep{399.png}{384}% + + +\Chapter[The Relations of Physical and Psychical Phenomena]% +{XVI}{The Relations of Physical and Psychical +Phenomena\protect\footnotemark}{384} + +\footnotetext{Read before the Psychical Congress, Chicago, August, 1893.}% + +% Set manually +\SetRunningHeads{MATTER, ETHER, AND MOTION}{Physical and Psychical Phenomena}% + +\First{Knowledge} has grown apace within the past fifty +years. It is generally admitted that more has been +acquired in this time than in all the preceding centuries. +Furthermore, the knowledge thus acquired has +not been simply an addition to the mental possessions +of former days; it has instead been of such a kind as +to completely overthrow nearly all former notions of +nature and its mode of operations, and the new product +can hardly be allowed to be an outcome of the work of +earlier men. It is in the nature of a catastrophe where +old continents have sunk and new ones have arisen +from old ocean beds. + +This generation lives in a new world, with new environments, +new ideas, new explanations, new philosophy, +new ideals, and new beliefs. We have new astronomy, +new chemistry, new physics, new psychology, new natural +history, and everybody is on the \textit{qui vive} to know +what can possibly come next. This does not mean +that nature goes on in a different way from what it had +hitherto done, but that we have mentally grasped a new +\DPPageSep{400.png}{385}% +\index{Mental processes imply physical conditions}% +and transforming idea. We have reached an elevation +from which it is possible to survey a broader field, and +can interpret phenomena better because their relations +are better perceived, and because of this it is seen that +the old interpretations were all wrong, and, indeed, +were worthless, because not true. While all this is +granted readily by most thoughtful persons, there are +not a few who recognize the changed opinions in the +various sciences and philosophy in general, who are not +at all persuaded but what the present philosophy of +things, which is dubbed evolution, is only a passing +phase and may itself presently give way to some +new and possibly truer conceptions, being content to +be mildly agnostic on such matters, and willing to wait +with patience for more light. There are some who +think the new philosophy does not take account of all +the known factors, if, by chance, there may not be +unknown factors of as much or more importance than +any which have been included, and which a final philosophy +of things will certainly include; and such object +strenuously to the limitations which the current philosophy +seems to set to knowledge and to the ideals +of the race. + +The man of science hears rumors of phenomena +which are said to be as certain as any in his own field, +which he has never investigated, and which cannot +come into his category of related things. Some of +these reported happenings are as marvellous as any +miracles that have been recorded. Persons of undoubted +probity have reported phenomena taking place +in their presence which, if true, give credence to many +\DPPageSep{401.png}{386}% +things for which in the past men and women have been +burned to death as wizards and witches. Thus, I have +an acquaintance, an eminent man not given to romancing, +who assures me he has seen, in undimmed light, a +chair ten feet from any person rise as if some one had +hold of its back and come and set itself down by his +side. Something of the same kind is said to have taken +place in the Milan experiments of last fall. Mr.\ +William Crookes tells us that the weight of a body has +been changed to be more or less according to an effort +of the will of Mr.\ Home, and likewise in Milan the +weight of the medium varied as much as fifty pounds. + +Now, there have been numerous attempts to define a +miracle for the purposes of philosophy, and usually it +is not the thing accomplished so much as the means +adopted for doing it. The antecedents of the event +are supposed to be other than the usual ones which +might do the same thing. Thus, a chair may be moved +by a person who lifts it and carries it to a new place; +but the chair may be pushed by a stick or pulled by a +string to a new place, while no one touched it, and all +who have been to see Hermann, and other magicians, +have seen things move about in a surprising manner +when no one touched them. In such cases it is +believed that none but well-known means are skilfully +used to produce such displacements, and that any one +might learn the art if it were worth his while. In other +words, no one thinks he is looking at a miraculous +event at a magician's show, no matter how surprising +the thing done; but if any person should be able to +make a chair, or an object, move from one place to +\DPPageSep{402.png}{387}% +\index{Consciousness implies energy}% +\index{Mind and energy}% +another without the mechanical adjuncts of some sort +which are needed by others, by an act of will rather +than by the employment of what we call energy, such +a person is able to work what has always been called a +``miracle.'' His method of doing that thing is a super-natural\DPnote{** Only instance.} +method, which is not the gift of every one even +in the slightest degree; for any one can try and satisfy +himself as to whether he can, by any simple act of will, +make the tiniest mote in a sunbeam or the most delicately +poised needle move in the slightest degree. +This is the common experience; and because it has +been found by experience that matter never moves +except when some other body has previously acted +upon it with a push or a pull, it has come about that +we have reduced the experience to the statements +embodied in so-called laws of motion, have found them +to be justified and without any exception so far as +investigation has gone, and this, too, by a multitude of +persons for two hundred years. As modern science +rests upon a mechanical basis, as it is concerned altogether +with the phenomena of matter and the relations +of the phenomena, and as these have been found in +every case that has been fully investigated to conform +to mathematical laws rigorously, not partly or dubiously, +is it not much more probable that any other phenomenon, +no matter what, that involves matter and its +changes, does conform strictly to the general laws, +than that these laws are sometimes inoperative? + +Probably the whole thing resolves itself into this: +Are the fundamental properties of matter variable? +Some of the phenomena alleged to happen at \textit{séances} +\DPPageSep{403.png}{388}% +imply that they are. How strong the case is against +such assumption, I think is not perceived by many persons +who give credence to the happenings, but who are +not well equipped with physical knowledge. Many persons +seem willing enough to admit physical laws and +physical processes in what they take to be the field of +physics, but they hold that there are other fields just as +certain, and among such, mind, that controls matter and +its forces, and to which it is not necessarily subject; +that it is perfectly philosophical to think that mind may +exist independent of matter and its relations, and be +able in this condition to control phenomena. + +Let us examine this. Assume that every physical +process in the world should be suddenly stopped, so +there should be no change. That would mean that all +motions were stopped. There would at once be neither +day nor night, for these are due to the earth's rotation; +no light, for light is a wave motion; there would +be no heat, for heat is a vibratory motion; there +would be no chemical changes, for they depend upon +heat; there would be neither solid nor liquid nor +gas, for each depends upon conditions of temperature, +that is, of heat, which is assumed to be absent; there +would be no sight, for that implies wave motions; nor +sound, for that implies air waves; nor taste, for that +implies chemical action; nor smell, for like reason; nor +touch, for that implies pressure---the result of motion. +The heart would cease to beat, the blood to flow, and +consciousness would be stopped. Every one of the +senses would be obliterated or annihilated; nothing +would happen, because there would be no change anywhere. +\DPPageSep{404.png}{389}% +Every phenomenon in the world of sensation +would be stopped, because every phenomenon in the +physical world had stopped; which is the same as saying +that all we call sensations are absolutely dependent +upon physical changes, going on all the time independent +of our will or choice, and which cannot be controlled +in the slightest degree by anybody. Every +phenomenon of every kind, then, consists in, as well +as is dependent upon, matter and its motion, and there +is in the whole range of experience no example of any +kind of a phenomenon where matter, ordinary matter, +is not the conditioning factor. There is no known case +where force or energy is changed in degree or direction +or kind but through the agency of matter. Every kind +of a change implies matter that has thus acted. What +is called the correlation of forces means that one kind +is convertible into some other kind of energy, as heat +into mechanical energy in the steam engine. But the +engine, a material structure, is essential for the change. +What is called the conservation of energy means that +in all the exchanges energy may undergo, as heat into +light, or work of any kind, the quantity of it does not +vary. The matter, as such, does not add to, or subtract +from it; hence only a material body can possess energy, +and a second material structure is necessary in order +that the energy of the first should be changed into any +other form. So it appears there must be at least two +bodies before anything can possibly happen. + +This all means that what we call energy is embodied +only in matter, and that what we call phenomena is but +the exchange of energy between different masses of +\DPPageSep{405.png}{390}% +\index{Mind and matter}% +matter; also that these exchanges take place with +mathematical precision, else prediction would be impossible, +and computation a waste of time. + +Now, assume that the physical structure of an individual +was kept intact, and that every atom and molecule +in the body maintained its relative position after all +motions had ceased. Assume, too, that the mind or +soul, or whatever one chooses to call the conscious +individuality, was present and capable as ever of acting +upon the material structure; can a single atom be +moved in the slightest degree? If any be moved, then +energy has been expended, energy which must have existed +elsewhere or have been created \textit{de novo}. For conscious +perception, whether sight or sound or any other, +motions embodying energy are essential, as pointed out; +and hence, to produce any perception, some motions +would necessarily have to be initiated, and to initiate +them energy from some source must be supplied. +All the energy the matter had has been destroyed +according to the assumption; so, if any movement has +begun, it must have been created or produced from some +other unthinkable condition which was not energy, in +some such sense as matter is supposed to have been +created, in which something is made out of nothing. +The demand is for creative power. Admit for the +argument's sake that it is done, and matter begins to +move in any kind of a way; so far it possesses energy, +physical energy as embodied in matter. Call the +amount of it ``A.'' Now, if the original condition of +things was established, so far as the amount of energy +was concerned, which may be called ``B,'' then the +\DPPageSep{406.png}{391}% +\index{Phenomena, unexplained}% +\index{Psychics}% +whole amount of energy is ``A plus B.'' It will make +no difference in this sum if one supposes that the +original motions and energy were not interrupted; for +if, on account of mind action, any particle moves more +or less than it would have done with its original supply, +then something has been added to the store of energy +in matter, and what is called the conservation of energy +is not true. + +Until all phenomena have been examined, there will be +obscure happenings and things to be explained by some +one who can; but it is no final explanation of anything +to say, ``A man did it,'' or ``An intelligence did it.'' +What kind of changes, that is, what kind of phenomena, +the forms of energy we are now acquainted with are +capable of producing no one can now limit, certainly +not one who has not been to the pains to understand +how the simple ones take place. I have often been +told that things cannot move in certain ways, or certain +things cannot be done except by intelligent action +or guidance; but it may be remembered that Kepler +thought guiding spirits were needful for making the +planets move in their elliptical orbits. If one must +explain an obscure phenomenon, is it not wisest to explain +it in accordance with what we know rather than in +accordance with what we do not know? It is better for +one to acknowledge his ignorance of the cause of it, than +to go romancing for a reason, and repudiate all we really +do know and its implications. A juggler may do the +most surprising things before one's eyes, but if one +cares to inquire into the antecedents of anything done +he will have no difficulty in tracing it as far as the +\DPPageSep{407.png}{392}% +\index{Thought transference}% +breakfast. What is meant is, the juggler does nothing +which does not require energy,---energy of the ordinary +sort, in the same sense as if it had been required +for sawing wood or walking up the street. As for consciousness, +dexterity, and all that is implied in both, I +pointed out a little way back there could be neither in +the absence of those changes which constitute physical +phenomena; and that not only life itself, but consciousness +as we know it, would be impossible without the +exchanges in the energy embodied in the cellular structure +of the brain. In the light of what has been accomplished +in the direction of physiological psychology, it +is entirely unwarrantable to assume that even thinking +can go on in the absence of physical changes of measurable +magnitude; and this is the same as saying that +what we call intelligent action is physical at its basis. + +There is such a formal agreement as well as actual +connection between conscious life and the life of the +brain, that it is not to be supposed any one who has properly +attended to the facts will venture to deny them. +Argue as one will, it is true there is no experimental +knowledge that is a part of science, of consciousness +separable from a material structure called brain, in which +physiological changes take place as the conditions for +thinking as well as for acting. This is the only known +relation of mind and body. However this association of +such apparently different provinces is to be explained, +it is still true that for every phenomenon in consciousness +there is a corresponding phenomenon in matter. +Psychologists have pointed out that the phenomena indicate +an identity at bottom between the activity of +\DPPageSep{408.png}{393}% +consciousness and cerebral activity. To follow this out +into particulars would be interesting and perhaps profitable +to most; but the significance of it here is that even +in the psychological field, where the opportunities for investigation +are right at hand and most is known, there +is no evidence for consciousness apart from a material +structure, or that the law of conservation of energy does +not hold as strictly true here as elsewhere in physics. +So there is no experimental reason for assuming the +existence of incorporeal intelligences. There is no +psychological question that is not at the same time a +physiological question. + +Experimentally it appears that the association of mind +with matter and energy is not of such a nature that one +is at liberty to assume their dissociation, any more than +one is at liberty to assume gravitation or magnetism as +independent existing somethings controlling matter according +to certain laws. So any hypothesis invented to +account for an occurrence that is not yet explained ought +not to be in contradiction to everything else we know, +and ought not to be entertained except as a last resort; +and the hypothesis of disembodied intelligences acting +now in and now out of the field of material things is +such an one. If such phenomena really happen at +\textit{séances} as are alleged, then we have to do with affairs +strictly within the line of physics, whether such phenomena +are so-called mental or so-called physical. It is +useless to affirm that the two are such radically different +phenomena that the methods of the latter are not +appropriate in the former; and the extensive laboratories +for physiological psychology, which are now +\DPPageSep{409.png}{394}% +being established in all the larger institutions of +learning, is a sufficient denial of the proposition. + +The term psychics is intended to denote something +different from the phenomena of psychology as manifested +in a given organism. It is supposed to relate to +the sympathetic relation of one mind to that of another +quite apart from the ordinary physical relations, that is, +from the senses. As for the mind-reading as exhibited +some years ago by Brown and others, I believe it is now +agreed that it is due to the sense of touch, and cannot +be done without contact. In hypnotic work there has +to be ``suggestion,'' and most of the very remarkable +cases, such as those in France last winter, have been +shown to be gross frauds. But let it be granted that +some of it is genuine, that it is possible in some cases +to impart information and discover the thoughts of +another without the common resources, it does not +then follow that the method is extra-physical. If only +here and there is to be found an individual called a +psychic, who is thus sensitive, and it is not a race +endowment, one no more need to summon a mysterious +supernormal agency to account for it, than such is +needed for the work of Newton or Mozart. Because a +phenomenon has not been explained, and no one knows +how to explain it, is no reason at all for supposing there +is anything mysterious about it. There are any number +of phenomena throughout nature that have not +been explained, and no one knows how to explain on +the basis of what is known. Such, for instance, is the +whirlwind that crosses the field, raising dust and leaves +into the air. No one has explained the soaring of birds, +\DPPageSep{410.png}{395}% +no one knows what goes on in an active nerve, or why +atoms are selective in their associates. Ignorance is +not a proper basis for speculation; and if one must have +a theory, let it be one having some obvious continuity +with our best physical knowledge. + +What is here given is not intended to be a denial that +such phenomena as thought-transference, or even the +most surprising things such as those described in the +Milan experiments, take place. It is only intended to +emphasize the probability that whatever happens has a +physical basis, and is therefore explained only when +these physical relations are known. +\DPPageSep{411.png}{unnumbered}% +%[Blank Page] + + +\Appendix +\DPPageSep{412.png}{397}% + +\Note{Note to \Pageref{Page}{57}.} +\Pagelabel{400}% + +\First{As} to whether it is considered as known that the sum of +the interior angles of a plane triangle are exactly equal to +one hundred and eighty degrees: ``Suppose that three points +are taken in space, distant from one another as far as the +sun is from $\alpha$~Centauri; and that the shortest distance between +these points is drawn so as to form a triangle. And suppose +the angles of this triangle to be very accurately measured +and added together; this can at present be done so accurately +that the error shall certainly be less than one minute, +less therefore than the five-thousandth part of a right angle. +Then I do not know that this sum would differ at all from +two right angles; but I also \emph{do not know that the difference +would be less than ten degrees}, and I have reasons for not +knowing.'' +\AppendixCite{W.~K. Clifford:}{Aims and Instruments of Scientific Thought.} + +``If the Euclidian\DPnote{** [sic]} assumptions are true, the constitution +of parts of space at an infinite distance is as well known as +the geometry of any portion of this room. So that here we +have real knowledge of something at least that concerns the +cosmos; something that is true throughout the immensities +and the eternities. That something Lobotchewski\DPnote{** [sic]} and his +successors have taken away.'' +\AppendixCite{W.~K. Clifford:}{Philosophy of the Pure Sciences.} +\DPPageSep{413.png}{398}% + +``In this case the universe as known becomes a valid conception, +for the extent of space is a finite number of cubic +miles. If you were to start in any direction whatever, and +move in a perfectly straight line according to the definition +of Liebnitz,\DPnote{** [sic]} after travelling a most prodigious distance \ldots +you would arrive at---this place.'' +\AppendixRef{\textsc{Ibid.}} + +``It must remain an open question whether, if we had +large enough triangles, the sum of the three angles would +still be two right angles.'' +\AppendixRef{\textit{Enc.\ Brit.\ 9th~ed., Art.\ Measurement.}} + +``It is true that according to the axioms of geometry, the +sum of the three angles of a triangle are precisely one hundred +and eighty degrees; but these axioms are now exploded, +and geometers confess that they, as geometers, know not the +slightest reason for supposing them to be precisely true. +That they are exactly that amount is what nobody can be +justified in concluding.'' +\AppendixCitePage{C.~S. Peirce:}{Monist,}{vol.~i.\ No.~2, p.~174.} + +``All that we need do is to call the attention of those who +busy themselves with mental philosophy to this generalization +of geometry as one of the results of modern mathematical +research which they cannot afford to overlook.'' +\AppendixCite{George Chrystal,}{in Enc.\ Brit., Art.\ Parallels.} + +Such as care to look into the matter further will find +the subject treated in an untechnical way in the works of +W.~K.~Clifford, in the chapters on the ``Theories of the +Physical Forces,'' ``Aims and Instruments of Scientific +Thought,'' and especially the ``Philosophy of the Pure Sciences.'' +There is much on it in the \textit{American Journal of +Mathematics}, vols. \i.~and~ii., also in the ``Proceedings of the +Royal Society,'' Edinburgh, vol.~x., 1879, and in article +``Measurement,'' \textit{Enc.~Brit.} +\DPPageSep{414.png}{399}% + +\Note{Note to \Pageref{Page}{208}.} +\Pagelabel{402a}% + +In 1881 the author discovered how electric ether waves +could be produced and identified, where the vibratory rates +were as high as $4000$ or more per second, by employing +static telephones detached and removed many feet from +the inducing electric current. These gave a wave length +of $\frac{186000}{4000} = 46+$ miles long. Hertz, Tesla, and others have +since then described methods of producing them so short +as to be but a few feet long. When they have thus been +mechanically shortened so as to be but the one forty-thousandth +of an inch in length, they will be seen by the eye as +red light. + +\Note{Note to \Pageref{Page}{242}.} +\Pagelabel{402b}% + +See Maxwell's ``Theory of Heat,'' pp.~160, 161. + +\settowidth{\TmpLen}{$\dfrac{H}{S} = \dfrac{h}{T}$.} +\begin{wrapfigure}[2]{l}{\TmpLen+\parindent} +\hfill\smash{$\dfrac{H}{S} = \dfrac{h}{T}$.} +\end{wrapfigure} +\noindent $S$~and~$T$ are the absolute temperatures of the +hot and cold bodies in Carnot's engine. $H$ +and $h$ are the quantities of heat taken up and given out. +When $T = 0°$, $h = 0$, when $h$ is the equivalent of the work +done. As this is $0$ at absolute zero, no work could be done +in changing the volume of a substance at that temperature. +There can be no cohesion among the molecules or atoms, for +this would require that work should be done to separate +them. It is the temperature of \emph{dissociation}. + +This conclusion is one to which chemists and physicists +have been led by their researches. For example, Dr.\ Lothar +Meyer says, ``At the lowest temperature to which we can +attain, the majority of chemical reactions studied under +these conditions have been found to cease or to proceed +very slowly, so that it would appear to be very probable that +at the absolute zero, viz., $273°$, a temperature much below +the lowest yet attained, chemical action would cease altogether +from the absence of any form of heat motion whatsoever; +so without heat there would be no exertion of the +so-called chemical affinity.'' +\AppendixRef{\textit{Modern Theories of Chemistry}, §~211.} +\DPPageSep{415.png}{400}% + +\Note{Note to \Pageref{Page}{277}.} +\Pagelabel{403}% + +The hypothesis of a ``vital principle'' is now as completely +discarded as the hypothesis of phlogiston in chemistry. +No biologist with a reputation to lose would for a +moment think of defending it. +\AppendixCitePage{John Fiske:}{Cosmic Philosophy,}{vol.~i.\ p.~422.} + +``We can demonstrate the infinitely manifold and complicated +physical and chemical properties of the albuminous +bodies to be the real cause of organic or vital phenomena.'' +\AppendixCitePage{Haeckel:}{History of Creation,}{vol.~i.\ p.~330.} + +``The aim of modern physiology is to conceive all organic +processes as physical or chemical.'' +\AppendixCitePage{Höffding:}{Outlines of Psychology,}{p.~57.} + +``Physiologists must expect to meet with an unconditional +conformity to law of the forces of nature in their inquiries +respecting the vital processes. They will have to apply +themselves to the investigation of the physical and chemical +processes going on within the organism.'' +\AppendixCitePage{Helmholtz:}{Scientific Lectures,}{p.~384.} + +``A vital element, i.e., an element peculiar to organisms, +no more exists than does a vital force working independently +of natural and material processes.'' +\AppendixCitePage{Claus \& Sedgwick:}{Zoölogy,}{part~i.\ p.~10.} + +``In Physiology the word life is understood to mean the +chemical and physical activities of the parts of which the +organism consists.'' +\AppendixCitePage{B. Sanderson:}{Nature,}{vol.~xlviii., p.~613.} + +``Modern physiology interprets the phenomena of organic +life by means of physical and chemical laws. An appeal to +`vital force' or to the intervention of mind, it does not +recognize as an explanation of an organic phenomenon.'' +\AppendixCitePage{Höffding:}{Outlines of Psychology,}{p.~10.} +\DPPageSep{416.png}{401}% + +``Physiology thus appears as a branch of applied physics, +its problems being a reduction of vital phenomena to general +physical laws and thus ultimately to the fundamental laws +of mechanics.'' +\AppendixCitePage{Wundt:}{Lehrbuch der Physiologie,}{p.~2.} + +``It must not be supposed that the differences between +living and not living matter are such as to justify the +assumption that the forces at work in the one are different +from those to be met with in the other.'' +\AppendixCitePage{Huxley:}{Art.\ Biology, Enc.\ Brit.,}{p.~681.} + +``Zoölogy, the science which seeks to arrange and discuss +the phenomena of animal life and form as the outcome +of the operation of the laws of physics and chemistry.'' +\AppendixCitePage{Lankester:}{Art.\ Zoölogy, Enc.\ Brit.,}{p.~803.} + +``If corporal functions are mediated by immaterial +agencies, physiological science is impossible.'' +\AppendixCitePage{G.~Stanley Hall:}{Amer.\ Jour.\ Psychology,}{vol.~iii.\ p.~74.} + +``It has not occurred to me that any one now uses the +term `vital force' in any other way than as a convenient +method of expressing the sum total of the physical and +chemical activities of organisms.'' +\AppendixCite{Prof.\ E.~L. Mark,}{Harvard University.} + +``These phenomena of life, though they may not as yet be +physically and chemically explained, are certainly not to be +referred to the working of any special \emph{vital force} peculiar +to organisms\ldots. We have to do here with the same +forces and the same substances that we meet with elsewhere +in nature.'' +\AppendixCitePage{Lang:}{Textbook of Comp.\ Anat.,}{London, 1891, p.~2.} + +``Modern science has allowed the vitalistic theory (\textit{vitalismus}) +to drop; instead of by means of a special vital force, +it explains irritability as a very complex chemico-physical +phenomenon. It is only distinguished from other chemico-physical +\DPPageSep{417.png}{402}% +phenomena of inorganic nature by degree, namely, +that the external stimuli come in contact with a substance +of complicated structure, an organism, and correspondingly +produce in it also a series of complicated processes.'' +\AppendixCitePage{O.~Hertwig:}{Die Zelle und die Gewebe,}{p.~75, 1893.} + +``I know of no authority in recent years which recognizes +a distinct vital force; all students of nature, so far as I am +aware, explain all the phenomena of life by means of physical +and chemical forces.\DPtypo{}{''} +\AppendixCite{Prof.\ J.~S. Kingsley,}{Tufts College.} + +%\DPPageSep{418.png}{403}% +% [** PP: Not small-capping first index entry] + +\normalsize +\clearpage +\fancyhf{} +\cleardoublepage + +\IndexBookmark +\fancyhead[C]{\textsc{INDEX}} +\printindex + +\iffalse +Action at a distance 88 + +Absolute zero 242, 336 + +Affinity, chemical 240 + +Albumen, size of molecule 15 + +Ampère turns 209 + +Arcturus 145 + +Arc light 216 + +Atmosphere, height of 26 + +Atoms 10, 18, 19 + +Atoms, unalterable 21, 22 + +Atoms, life associated with 24, 296 + +Atoms, chemical properties 239 + +Atoms, as vortex rings 349 + +Atoms, vibrations of 243 + +Attraction, gravitative 83, 309 + +Attraction of vibrating fork 87 + +Attraction of disks 94 + +Attraction depends upon distance 85 + +Attraction of vortex rings 95, 244 +% \indexspace + +Blavatsky, Madam, pretensions of 359 + +Bonnenburger's apparatus 40 + +Boiling-point pressure 125 +% \indexspace + +Cause and effect 75 + +Camera 162, 163 + +Catalysis 248 + +Cell structure 280 + +Charles, Law of 336 + +Chemism 238 + +Chemism and heat 241, 336 + +Chemical field 247, 305 + +Chemical effects 218 + +Chemical origin of electricity 177 + +Chemical reactions depend on temperature 336 + +Cohesion, in solids and liquids 332 + +Cohesion, destroyed 333 + +Colors 165 + +Color-blindness 171 + +Color, nature of 339 + +Combustion 103 + +Conductivity, electrical 190, 192 + +Consciousness implies energy 390 + +Corti's fibres 275 + +Corn, life of 291 + +Crookes' tubes 224 + +Crystallization 245, 249, 306 +% \indexspace + +Decomposition of water 218 + +Density 6 + +Diamond, hardness of 338 + +Dissociations 131, 219 + +Dispersion 138 + +Dynamo 213 +% \indexspace + +Ear 274 + +Earth, velocity of, in space 34 + +Earth, diameter of 55 +%\DPPageSep{419.png}{404}% + +Earth, a magnet 303 + +Earth, curvature 69 + +Earth, solidity of 126 + +Egg 291 + +Echo 265 + +Efficiency of machines 213 + +Elasticity 341 + +Elasticity due to motion 39, 341 + +Elements 136 + +Energy, factors of 70, 77 + +Energy in the ether 79, 105 + +Energy. What determines transfer 214 + +Energy, unknown, preface. + +Electricity, origin of 174, 229, 354 + +Electricity, thermal 174 + +Electricity, mechanical origin 180, 230 + +Electricity, magnetic origin 181 + +Electricity, electrical origin 182, 230 + +Electrical antecedents 186 + +Electrical effects 231 + +Electrical effects, reversible 232 + +Electricity, dual 234 + +Electricity, activity 194 + +Electrical field 196, 300 + +Electrical stress 197 + +Electrical waves 198, 303 + +Electro-magnets 81, 210 + +Electric lamps 215 + +Energy of translation 64 + +Energy of vibration 66 + +Energy of rotation 68 + +Ether 26, 32, 34, 80 + +Ether, a non-conductor 191 + +Ether waves 134 + +Ether wave qualities 134 + +Ether phenomena not explained 352 + +Ether waves, their source 135, 207 + +Ether pressure 205 + +Ether rotations 234 + +Explosion products 71 +% \indexspace + +Fable, La Fontaine's 357 + +Falling bodies 60 + +Falling bodies, energy of 60 + +Fibres of Corti 275 + +Fields, physical 298 + +Fields, chemical 247, 305 + +Fields, electrical 196, 300 + +Fields, magnetic 202, 214, 252 + +Fields, mechanical 247 + +Fields, thermal 298 + +Flames 137 + +Foot-pound 60, 62 + +Food 284 + +Foster, Dr.\ Michael, quoted 296 + +Force, vital 279 + +Friction, its effects 23, 34 + +Fuels 103 +% \indexspace + +Galvanic battery 178 + +Gas, motion in 333 + +Gas, free path in 334 + +Gas, pressure in 334, 336 + +Gas, destroyed 336 + +Gaseous absorption 142 + +Geometry 56, 57 % Appendix. + +Geometry@{Appendix.} + +Geissler's tubes 223 + +Goose, work in flying 65 + +Gravitation 82, 90, 309, 347 + +Gravitation, law of 84 + +Gravity, specific 7 + +Gravity follows from structure 348 + +Growth 250, 292, 310 + +Growth of crystals 283, 381 + +Growth of lobster 283 + +Gunpowder 103 + +Guppy, Mrs. 359 + +Gyroscope 342 +% \indexspace + +Hair-cloth loom 312 + +Hardness not atomic property 338 +%\DPPageSep{420.png}{405}% + +Hearing, what is implied in 370 + +Hertz waves 344, 351 + +Helmholtz 35 + +Heat, mechanical origin of 99 + +Heat, chemical origin of 102 + +Heat, electrical origin of 104 + +Heat, radiational origin of 105 + +Heat, mechanical equivalent 109 + +Heat unit 112 + +Heat, effects 123, 254, 335 + +Heat by impact 225 + +Heat of the sun, origin of 119 + +Heat, nature of 115, 118 + +Hypothesis, needful 94 + +Hypothesis, gravitation 90 + +Hydrogen vibrations 116 +% \indexspace + +Impenetrability 340 + +Immortality 24, 367 + +Inertia 70, 345 + +Induction coils 208 + +Inductive action 183, 195, 250, 302 +% \indexspace + +Joule 110 + +Jupiter, temperature of 144 +%[**missing \indexspace] + +Kepler, the guesser 90 + +Kinetics 46 + +Kinematics 46 + +Knowledge, rapid growth of 384 +% \indexspace + +Laws not compulsory 353 + +Law, physical 373 + +Lever 317 + +Life 277 % Appendix. + +Life@{Appendix.} + +Life, definitions of 278 + +Light, a sensation 135, 363 + +Light, energy of 80 + +Light, its velocity 26, 28 + +Light, its nature 27, 80, 134, 364 + +Light waves 207 + +Lightning 185, 223 + +Lighting, electric 214, 222 + +Luminous effects 222 +% \indexspace + +Matter, living 283, 294 + +Matter, characteristic property 4 + +Matter, its definition 4 + +Matter, divisibility of 8 + +Matter, effect of temperature upon 132, 336 + +Matter, as modes of motion 331 + +Matter, states of 332 + +Mass 345 + +Materialists 351 + +Materializations and energy 365 + +Mars, atmosphere of 144 + +Mars, signalling to 217 + +Machines 312, 325 + +Magnetic field 202, 204, 214, 252, 303 + +Magnetic induction 208 + +Magnetic rotation 235 + +Magnetic waves 81, 202, 207, 344 + +Magnet, electro 81 + +Mathematics 89 + +Mechanical field 307 + +Medium, necessity for 29 + +Mental processes imply physical conditions 388 + +Meteors 21, 26, 64 + +Mercury 55 + +Miracles possible 353 + +Miracle defined 386 + +Mind and energy 390 + +Mind, a material habitat for 24 + +Mind and matter 24, 393 + +Mirrors 147 + +Microscope, magnifying powers 15, 149 + +Molecules, size of 13, 18, 46 + +Molecules, loaded 160 + +Molecules, long free path 224 +%\DPPageSep{421.png}{406}% + +Molecules, number of, in universe 124 + +Motion, kinds of 46, 48, 49, 145 + +Motion, velocity of 50 + +Motion, transformations of 314 + +Motion, molecular and atomic 49 + +Motion, laws of 70, 73 + +Motion, antecedent of 72 + +Molecular fatigue 78 + +Molecular stability 281 + +Momentum 74 + +Motor, electric 212 + +Muscles 286 + +Muscular work 67 + +Musical sounds 268 + +Musical ratios 269 + +Musical instruments 271 +% \indexspace + +Newton, Sir Isaac 30, 82, 83, 88 + +Nerves, their functions 288, 290 + +Nebula theory 97 + +Neptune, discovery of 89 + +Noise 269 +% \indexspace + +Ohm's law 189 + +Organic and inorganic matter, difference between 366 +% \indexspace + +Phenomena, nature of 59 + +Phenomena, unexplained 353, 394 + +Phenomena physical, implications + +of 354 + +Photography 156 + +Phosphorescence 226 + +Physical fields 298 + +Physical universe a machine 330 + +Physical processes, reversible 232 + +Physicists, prepossessions 382 + +Pitch 259 + +Plating, electro 221 + +Polarization of molecules 178, 219 + +Postulates of Physical Science 356 + +Power, needed for rapid movement in air 359 + +Potential, electrical 189 + +Principia 31, 70 + +Prism 138 + +Protoplasm 280 + +Psychics 394 + +Pulley 317 + +Purpurine 169 + +Push and pull 315 +% \indexspace + +Radiometer 154 + +Reflection 147 + +Retina, its functions 171 + +Reflex action 172 + +Refraction 138, 147 + +Resistance, electrical 192, 214 + +Rotations in ether 235 +% \indexspace + +Satellite 69 + +Saturn, temperature of 144 + +Science, no one independent 378 + +Senses 161, 371 + +Séances, phenomena at 362, 379 + +Seeing, what is implied in 369 + +Sirius 145 + +Silver salts unstable 159 + +Soap-bubbles 10 + +Sound, origin of 257, 360 + +Sound, characteristics 262 + +Sound, range of 263 + +Sound, velocity of 263 + +Sound, vocal 272 + +Solar system 329 + +Space 58 + +Space, navigation of 154 + +Specialists 373 + +Spiritualistic theory 360 + +Specific gravity 7 + +Specific heat 130 + +Spectroscope 139 + +Spectrum analysis 140 +%\DPPageSep{422.png}{407}% + +Spectrum, solar 138, 142 + +Spark, electric 223 + +Spirit disembodied 360 + +Stress in ether 93 + +Stress in glass 92 + +Stress, electrical 183, 197, 231 + +Stress, magnetic 181 + +Steam-engine 113 + +Steam-engine, efficiency of 114 + +Stars, their number 18 + +Stars, their distance 19, 28 + +Stars, their motions 145 + +Sun, its distance 28, 56 + +Sun, its magnitude 122 + +Sun, its heat 122 + +Sun, its age 122 + +Sun, its structure 143 +% \indexspace + +Temperature 106 + +Temperature, table 108 + +Temperature, maximum 127 + +Terminology, electrical 186 + +Telegraph 211 + +Telephone 211 + +Thermometer 107 + +Tesla ether waves 344 + +Thermometer, air 109 + +Thomson, Sir Wm. 35 + +Thermodynamics 112 + +Thermopile 176 + +Thermodynamics, electric 174 + +Thought transference 395, 311 + +Toepler-Holtz electrical machine 294 + +Top, sleep of 72 + +Transparency 146 + +Transformations of motion 321 +% \indexspace + +Universe, its size 28 + +Universe, atoms in 20 +% \indexspace + +Vacuum, a non-conductor 223 + +Vacuum 47 + +Venus 55 + +Velocities 50, 54, 56 + +Vibrations per second 52, 53 + +Vibrations, gaseous 116 + +Vibrations, sympathetic 249, 267 + +Vibrations, forced 267 + +Vital force 279 % Appendix. + +Vital force@{Appendix.} + +Vision, phenomena of 164 + +Vision, hallucinations of 166 + +Vision, energy needed for 166 + +Vision of animals 168 + +Vision, theory of 168 + +Voice 272 + +Vortex ring theory of matter 94 + +Vortex ring model 342 + +Vortex rings in air 35 + +Vortex rings, properties of 37, 72 + +Volcanoes 127 +% \indexspace + +Wave lengths of sound 265 + +Waves, electric 303 + +Water decomposition 218 + +Weight 61 + +Weights, standards of 60 + +Welding, electric 210 + +Work, standard of 60 + +Work, measure of 62, 64, 318 + +Work, muscular 67 +\fi + +\cleardoublepage +\phantomsection +\pdfbookmark[0]{Catalog}{Catalog} + +%\DPPageSep{423.png}{I}% +\renewcommand{\headrulewidth}{0.5pt} +\fancyhead[C]{\textit{Books Upon Various Subjects}} +\thispagestyle{empty} + +\begin{center} +\textsf{\Large LEE AND SHEPARD}\\[12pt] +\textsf{\large 10~MILK STREET BOSTON}\\[8pt] +\tb\\[12pt] +{\Large List of Books upon Various Subjects}\\[8pt] +\tb +\end{center} + +\Entry{QUABBIN} + +\Subentry +Sketches in a Small Town \quad With Outlooks upon Puritan Life \quad By \Au{Francis~H. +Underwood}~LL.D. author of ``Handbooks of English Literature'' +``Man Proposes'' ``Lord of Himself'' etc. Fully illustrated +Cloth \$1.75 + +\begin{Descrip} +This work purports to give an account of the progress of a small New England town; +but it is of wider and deeper import; namely, a view of the development of the narrow +and sombre Puritan into the variously gifted and accomplished ``Yankee'' of to-day. It +concerns the state of literature and art in the early part of the present century, and shows +how the fairer conditions of modern times came into being. + +In plan it is wholly unlike any modern book. It is not a town history, nor an historical +essay, nor a collection of reminiscences. Its chapters are mostly picturesque descriptions +of the old times, and show the ``rude forefathers'' at home, at church, at town-meetings, at +road-making, and in other scenes of their daily life. There are sketches of the successive +ministers, the schools, the quiltings, sleigh-rides, and other rustic gatherings,---of the +homely speech and manners, and of the complexities of Yankee character. + +It is believed that these graphic, tender, and humorous pictures will appeal to the hearts +and memories of New England people, and to their descendants along the line of migration +westward to the Mississippi and beyond. + +The illustrations are from photographs taken from beautiful scenes in ``Quabbin.'' +\end{Descrip} + +\clearpage +\Entry{UNIVERSAL PHONOGRAPHY or Short-hand by the ``Allen +Method''} + +\Subentry +A self-instructor, whereby more speed than long-hand writing is gained at +the first lesson, and additional speed at each subsequent lesson \quad By \Au{G.~G. +Allen}, Principal of the Allen Stenographic Institute Boston \quad 50~cents + +\begin{Descrip} +There is scarcely any requirement so helpful to the student, scholar, scientist, or professional +man as short-hand writing. Heretofore all methods have required so long a +time before one could become so proficient as to make it of any advantage, that men in +middle life, or busy men, have not been able to give the time to learn it; but by the ``Allen +Method'' one can almost in ``the idle moments of a busy life,'' certainly in an hour a day +for two or three months, become so expert as to report a lecture \textit{verbatim}. +\end{Descrip} +%\DPPageSep{424.png}{II}% +%Font size changes on this page +\Entry{MATTER, ETHER, AND MOTION} + +\Subentry +The Factors and Relations of Physical Science \quad By \Au{Prof.\ A.~E. Dolbear} +Tufts College author of ``The Telephone'' ``The Art of Projecting'' +etc. \quad Cloth~\$2.00 + +\begin{Descrip} +``Matter, Ether, and Motion,'' the Factors and Relations of Physical Science, by A.~E. +Dolbear,~Ph.D\@. The author in this treatise presents to his readers the principles of physical +science. The chapters are arranged as Matter, Ether, Motion, Energy, Gravitation, +Heat, Ether Waves, Electricity, Chemism, Sound, Life, Physical Fields, Machines and +Mechanism. This is a tolerably comprehensive table, and introduces the student to the +principles on which, so far as at present known, the action of the universe seems to +depend. + +Altogether this little treatise gives an insight into matters outside the common range of +serious study, and yet places the subject within reach of the student seeking for knowledge. +Although dealing with abstruse scientific topics, the style is lucid, and the matter intelligible +to ordinary thinkers and readers in search of information.---\textit{New York Commercial +Advertiser}. +\end{Descrip} + + +\Entry{THE TELEPHONE} + +\Subentry +An account of the phenomena of electricity, magnetism, and sound as involved +in its action; with directions for making a speaking telephone \quad +By \Au{Prof.\ A.~E. Dolbear} of Tufts College \quad 50~cents + +\begin{Descrip} +An interesting little book upon this most fascinating subject, which is treated in a very +clear and methodical way. First we have a thorough review of the discoveries in electricity, +then of magnetism, then of those in the study of sound,---pitch, velocity, timbre, tone, +resonance, sympathetic vibrations, etc. From these the telephone is reached, and by them +in a measure explained.---\textit{Hartford Courant}. +\end{Descrip} + + +\Entry{THE ART OF PROJECTING} + +\Subentry +By \textsc{Prof.\ A.~E. Dolbear}~Ph.D. (Tufts College) \quad New Edition revised +with additions \quad $125$~illustrations \quad Cloth~\$2.00 + +\begin{Descrip} +A Manual of Experimentation in Physics, Chemistry, and Natural History with the Porte +Lumière and the Magic Lantern; also with Electric Lights and Lamps and the Production +and Phenomena of Vortex Rings. +\end{Descrip} + + +\Entry{WHAT IS TO BE DONE--(Emergency Handbook)} + +\Subentry +A Handbook for the Nursery with Useful Hints for Children and Adults \quad +By \Au{Robert~B. Dixon}~M.D. Surgeon of the Fifth Massachusetts Infantry, +Physician to the Boston Dispensary \quad Cloth 50~cents; paper 30~cents + +\begin{Descrip} +Dr.\ Dixon, in this little ``Emergency Handbook,'' gives simple directions what to do +in a number of the most common cases that arise, either in home treatment of slight accidents, +or indispositions, or in the case of patients in more serious cases, until the arrival of +the physician. The book is worth its weight in gold, and ought to have a place in every +family library.---\textit{Providence Press}. +\end{Descrip} + + +%%%%%%%%%%%%%%%%%%%%%%%%% GUTENBERG LICENSE %%%%%%%%%%%%%%%%%%%%%%%%%% + +\clearpage +\fancyhf{} +\renewcommand{\headrulewidth}{0pt} +\cleardoublepage + +\backmatter +\phantomsection +\pdfbookmark[-1]{Back Matter}{Back Matter} +\phantomsection +\pdfbookmark[0]{PG License}{Project Gutenberg License} +\renewcommand{\headrulewidth}{0.5pt} +\fancyhead[C]{\textsc{LICENSING}} + +\begin{PGtext} +End of the Project Gutenberg EBook of Matter, Ether, and Motion, Rev. ed., +enl., by Amos Emerson Dolbear + +*** END OF THIS PROJECT GUTENBERG EBOOK MATTER, ETHER, AND MOTION *** + +***** This file should be named 31428-pdf.pdf or 31428-pdf.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/1/4/2/31428/ + +Produced by Andrew D. 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Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..ca669d2 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #31428 (https://www.gutenberg.org/ebooks/31428) |
