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+The Project Gutenberg EBook of The Advance of Science in the Last
+Half-Century, by T.H. (Thomas Henry) Huxley
+
+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: The Advance of Science in the Last Half-Century
+
+Author: T.H. (Thomas Henry) Huxley
+
+Release Date: March 4, 2005 [EBook #15253]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK ADVANCE OF SCIENCE ***
+
+
+
+
+Produced by Digital & Multimedia Center, Michigan State University
+Libraries, Marilynda Fraser-Cunliffe, and the PG Online Distributed
+Proofreading Team.
+
+
+
+
+
+
+THE ADVANCE OF SCIENCE IN THE LAST HALF-CENTURY
+
+BY
+
+T.H. HUXLEY, F.R.S.
+
+NEW YORK
+
+D. APPLETON AND COMPANY
+
+1889
+
+
+
+
+THE ADVANCE OF SCIENCE IN THE LAST HALF-CENTURY
+
+[Sidenote: Recent industrial progress]
+
+The most obvious and the most distinctive features of the History of
+Civilisation, during the last fifty years, is the wonderful increase
+of industrial production by the application of machinery, the
+improvement of old technical processes and the invention of new ones,
+accompanied by an even more remarkable development of old and new
+means of locomotion and intercommunication. By this rapid and vast
+multiplication of the commodities and conveniences of existence, the
+general standard of comfort has been raised, the ravages of pestilence
+and famine have been checked, and the natural obstacles, which time
+and space offer to mutual intercourse, have been reduced in a manner,
+and to an extent, unknown to former ages. The diminution or removal of
+local ignorance and prejudice, the creation of common interests among
+the most widely separated peoples, and the strengthening of the forces
+of the organisation of the commonwealth against those of political or
+social anarchy, thus effected, have exerted an influence on the
+present and future fortunes of mankind the full significance of which
+may be divined, but cannot, as yet, be estimated at its full value.
+
+[Sidenote: caused by the increase of physical science]
+
+This revolution--for it is nothing less--in the political and social
+aspects of modern civilisation has been preceded, accompanied, and in
+great measure caused, by a less obvious, but no less marvellous,
+increase of natural knowledge, and especially of that part of it which
+is known as Physical Science, in consequence of the application of
+scientific method to the investigation of the phenomena of the
+material world. Not that the growth of physical science is an
+exclusive prerogative of the Victorian age. Its present strength and
+volume merely indicate the highest level of a stream which took its
+rise, alongside of the primal founts of Philosophy, Literature, and
+Art, in ancient Greece; and, after being dammed up for a thousand
+years, once more began to flow three centuries ago.
+
+[Sidenote: Greek and medićval science.]
+
+It may be doubted if even-handed justice, as free from fulsome
+panegyric as from captious depreciation, has ever yet been dealt out
+to the sages of antiquity who, for eight centuries, from the time of
+Thales to that of Galen, toiled at the foundations of physical
+science. But, without entering into the discussion of that large
+question, it is certain that the labors of these early workers in the
+field of natural knowledge were brought to a standstill by the decay
+and disruption of the Roman Empire, the consequent disorganisation of
+society, and the diversion of men's thoughts from sublunary matters to
+the problems of the supernatural world suggested by Christian dogma in
+the Middle Ages. And, notwithstanding sporadic attempts to recall men
+to the investigation of nature, here and there, it was not until the
+fifteenth and sixteenth centuries that physical science made a new
+start, founding itself, at first, altogether upon that which had been
+done by the Greeks. Indeed, it must be admitted that the men of the
+Renaissance, though standing on the shoulders of the old philosophers,
+were a long time before they saw as much as their forerunners had
+done.
+
+The first serious attempts to carry further the unfinished work of
+Archimedes, Hipparchus, and Ptolemy, of Aristotle and of Galen,
+naturally enough arose among the astronomers and the physicians. For
+the imperious necessity of seeking some remedy for the physical ills
+of life had insured the preservation of more or less of the wisdom of
+Hippocrates and his successors, and, by a happy conjunction of
+circumstances, the Jewish and the Arabian physicians and philosophers
+escaped many of the influences which, at that time, blighted natural
+knowledge in the Christian world. On the other hand, the superstitious
+hopes and fears which afforded countenance to astrology and to alchemy
+also sheltered astronomy and the germs of chemistry. Whether for this,
+or for some better reason, the founders of the schools of the Middle
+Ages included astronomy, along with geometry, arithmetic, and music,
+as one of the four branches of advanced education; and, in this
+respect, it is only just to them to observe that they were far in
+advance of those who sit in their seats. The school men considered no
+one to be properly educated unless he were acquainted with, at any
+rate, one branch of physical science. We have not, even yet, reached
+that stage of enlightenment.
+
+[Sidenote: Further advance after Renaissance.]
+
+In the early decades of the seventeenth century, the men of the
+Renaissance could show that they had already put out to good interest
+the treasure bequeathed to them by the Greeks. They had produced the
+astronomical system of Copernicus, with Kepler's great additions; the
+astronomical discoveries and the physical investigations of Galileo;
+the mechanics of Stevinus and the 'De Magnete' of Gilbert; the anatomy
+of the great French and Italian schools and the physiology of Harvey.
+In Italy, which had succeeded Greece in the hegemony of the scientific
+world, the Accademia dei Lyncei and sundry other such associations for
+the investigation of nature, the models of all subsequent academies
+and scientific societies, had been founded, while the literary skill
+and biting wit of Galileo had made the great scientific questions of
+the day not only intelligible, but attractive, to the general public.
+
+[Sidenote: Francis Bacon.]
+
+In our own country, Francis Bacon, had essayed to sum up the past of
+physical science, and to indicate the path which it must follow if its
+great destinies were to be fulfilled. And though the attempt was just
+such a magnificent failure as might have been expected from a man of
+great endowments, who was so singularly devoid of scientific insight
+that he could not understand the value of the work already achieved by
+the true instaurators of physical science; yet the majestic eloquence
+and the fervid vaticinations of one who was conspicuous alike by the
+greatness of his rise and the depth of his fall, drew the attention of
+all the world to the 'new birth of Time.'
+
+[Sidenote: The defect of his method.]
+
+But it is not easy to discover satisfactory evidence that the 'Novum
+Organum' had any direct beneficial influence on the advancement of
+natural knowledge. No delusion is greater than the notion that method
+and industry can make up for lack of motherwit, either in science or
+in practical life; and it is strange that, with his knowledge of
+mankind, Bacon should have dreamed that his, or any other, 'via
+inveniendi scientias' would 'level men's wits' and leave little scope
+for that inborn capacity which is called genius. As a matter of fact,
+Bacon's 'via' has proved hopelessly impracticable; while the
+'anticipation of nature' by the invention of hypotheses based on
+incomplete inductions, which he specially condemns, has proved itself
+to be a most efficient, indeed an indispensable, instrument of
+scientific progress. Finally, that transcendental alchemy--the
+superinducement of new forms on matter--which Bacon declares to be the
+supreme aim of science, has been wholly ignored by those who have
+created the physical knowledge of the present day.
+
+Even the eloquent advocacy of the Chancellor brought no unmixed good
+to physical science. It was natural enough that the man who, in his
+better moments, took 'all knowledge for his patrimony,' but, in his
+worse, sold that birthright for the mess of pottage of Court favor and
+professional success, for pomp and show, should be led to attach an
+undue value to the practical advantages which he foresaw, as Roger
+Bacon and, indeed, Seneca had foreseen, long before his time, must
+follow in the train of the advancement of natural knowledge. The
+burden of Bacon's pleadings for science is the gathering of
+fruit'--the importance of winning solid material advantages by the
+investigation of Nature and the desirableness of limiting the
+application of scientific methods of inquiry to that field.
+
+[Sidenote: Hobbes.]
+
+[Sidenote: Descartes.]
+
+Bacon's younger contemporary, Hobbes, casting aside the prudent
+reserve of his predecessor in regard to those matters about which the
+Crown or the Church might have something to say, extended scientific
+methods of inquiry to the phenomena of mind and the problems of social
+organisation; while, at the same time, he indicated the boundary
+between the province of real, and that of imaginary, knowledge. The
+'Principles of Philosophy' and the 'Leviathan' embody a coherent
+system of purely scientific thought in language which is a model of
+clear and vigorous English style. At the same time, in France, a man
+of far greater scientific capacity than either Bacon or Hobbes, René
+Descartes, not only in his immortal 'Discours de la Méthode' and
+elsewhere, went down to the foundations of scientific certainty, but,
+in his 'Principes de Philosophie,' indicated where the goal of
+physical science really lay. However, Descartes was an eminent
+mathematician, and it would seem that the bent of his mind led him to
+overestimate the value of deductive reasoning from general principles,
+as much as Bacon had underestimated it. The progress of physical
+science has been effected neither by Baconians nor by Cartesians, as
+such, but by men like Galileo and Harvey, Boyle and Newton, who would
+have done their work just as well if neither Bacon nor Descartes had
+ever propounded their views respecting the manner in which scientific
+investigation should be pursued.
+
+[Sidenote: For a time the progress without fruits.]
+
+The progress of science, during the first century after Bacon's death,
+by means verified his sanguine prediction of the fruits which it would
+yield. For, though the revived and renewed study of nature had spread
+and grown to an extent which surpassed reasonable expectation, the
+practical results--the 'good to men's estate'--were, at first, by no
+means apparent. Sixty years after Bacon's death, Newton had crowned
+the long labors of the astronomers and the physicists, by coordinating
+the phenomena of solar motion throughout the visible universe into one
+vast system; but the 'Principia' helped no man to either wealth or
+comfort. Descartes, Newton, and Leibnitz had opened up new worlds to
+the mathematician, but the acquisitions of their genius enriched only
+man's ideal estate. Descartes had laid the foundations of rational
+cosmogony and of physiological psychology; Boyle had produced models
+of experimentation in various branches of physics and chemistry;
+Pascal and Torricelli had weighed the air; Malpighi and Grew, Ray and
+Willoughby had done work of no less importance in the biological
+sciences; but weaving and spinning were carried on with the old
+appliances; nobody could travel faster by sea or by land than at any
+previous time in the world's history, and King George could send a
+message from London to York no faster than King John might have done.
+Metals were worked from their ores by immemorial rule of thumb, and
+the centre of the iron trade of these islands was still among the oak
+forests of Sussex. The utmost skill of our mechanicians did not get
+beyond the production of a coarse watch.
+
+The middle of the eighteenth century is illustrated by a host of great
+names in science--English, French, German, and Italian--especially in
+the fields of chemistry, geology, and biology; but this deepening and
+broadening of natural knowledge produced next to no immediate
+practical benefits. Even if, at this time, Francis Bacon could have
+returned to the scene of his greatness and of his littleness, he must
+have regarded the philosophic world which praised and disregarded his
+precepts with great disfavor. If ghosts are consistent, he would have
+said, 'These people are all wasting their time, just as Gilbert and
+Kepler and Galileo and my worthy physician Harvey did in my day. Where
+are the fruits of the restoration of science which I promised? This
+accumulation of bare knowledge is all very well, but _cui bono_? Not
+one of these people is doing what I told him specially to do, and
+seeking that secret of the cause of forms which will enable men to
+deal, at will, with matter, and superinduce new natures upon the old
+foundations.'
+
+[Sidenote: Its recent effect on life.]
+
+But, a little later, that growth of knowledge beyond imaginable
+utilitarian ends, which is the condition precedent of its practical
+utility, began to produce some effect upon practical life; and the
+operation of that part of nature we call human upon the rest began to
+create, not 'new natures,' in Bacon's sense, but a new Nature, the
+existence of which is dependent upon men's efforts, which is
+subservient to their wants, and which would disappear if man's
+shaping and guiding hand were withdrawn. Every mechanical artifice,
+every chemically pure substance employed in manufacture, every
+abnormally fertile race of plants, or rapidly growing and fattening
+breed of animals, is a part of the new Nature created by science.
+Without it, the most densely populated regions of modern Europe and
+America must retain their primitive, sparsely inhabited, agricultural
+or pastoral condition; it is the foundation of our wealth and the
+condition of our safety from submergence by another flood of barbarous
+hordes; it is the bond which unites into a solid political whole,
+regions larger than any empire of antiquity; it secures us from the
+recurrence of the pestilences and famines of former times; it is the
+source of endless comforts and conveniences, which are not mere
+luxuries, but conduce to physical and moral well-being. During the
+last fifty years, this new birth of time, this new Nature begotten by
+science upon fact, has pressed itself daily and hourly upon our
+attention, and has worked miracles which have modified the whole
+fashion of our lives.
+
+[Sidenote: These results often too much regarded;]
+
+What wonder, then, if these astonishing fruits of the tree of
+knowledge are too often regarded by both friends and enemies as the
+be-all and end-all of science? What wonder if some eulogise, and
+others revile, the new philosophy for its utilitarian ends and its
+merely material triumphs?
+
+[Sidenote: for scientific research rarely directed to practical ends]
+
+In truth, the new philosophy deserves neither the praise of its
+eulogists, nor the blame of its slanderers. As I have pointed out, its
+disciples were guided by no search after practical fruits, during the
+great period of its growth, and it reached adolescence without being
+stimulated by any rewards of that nature. The bare enumeration of the
+names of the men who were the great lights of science in the latter
+part of the eighteenth and the first decade of the nineteenth
+century, of Herschel, of Laplace, of Young, of Fresnel, of Oersted, of
+Cavendish, of Lavoisier, of Davy, of Lamarck, of Cuvier, of Jussieu,
+of Decandolle, of Werner and of Hutton, suffices to indicate the
+strength of physical science in the age immediately preceding that of
+which I have to treat. But of which of these great men can it be said
+that their labors were directed to practical ends? I do not call to
+mind even an invention of practical utility which we owe to any of
+them, except the safety lamp of Davy. Werner certainly paid attention
+to mining, and I have not forgotten James Watt. But, though some of
+the most important of the improvements by which Watt converted the
+steam-engine, invented long before his time, into the obedient slave
+of man, were suggested and guided by his acquaintance with scientific
+principles, his skill as a practical mechanician, and the efficiency
+of Bolton's workmen had quite as much to do with the realisation of
+his projects.
+
+[Sidenote: but instigated by love of knowledge]
+
+In fact, the history of physical science teaches (and we cannot too
+carefully take the lesson to heart) that the practical advantages,
+attainable through its agency, never have been, and never will be,
+sufficiently attractive to men inspired by the inborn genius of the
+interpreter of nature, to give them courage to undergo the toils and
+make the sacrifices which that calling requires from its votaries.
+That which stirs their pulses is the love of knowledge and the joy of
+the discovery of the causes of things sung by the old poets--the
+supreme delight of extending the realm of law and order ever farther
+towards the unattainable goals of the infinitely great and the
+infinitely small, between which our little race of life is run. In the
+course of this work, the physical philosopher, sometimes
+intentionally, much more often unintentionally, lights upon something
+which proves to be of practical value. Great is the rejoicing of those
+who are benefited thereby; and, for the moment, science is the Diana
+of all the craftsmen. But, even while the cries of jubilation resound
+and this floatsam and jetsam of the tide of investigation is being
+turned into the wages of workmen and the wealth of capitalists, the
+crest of the wave of scientific investigation is far away on its
+course over the illimitable ocean of the unknown.
+
+[Sidenote: It is in its turn assisted by industrial improvements.]
+
+Far be it from me to depreciate the value of the gifts of science to
+practical life, or to cast a doubt upon the propriety of the course of
+action of those who follow science in the hope of finding wealth
+alongside truth, or even wealth alone. Such a profession is as
+respectable as any other. And quite as little do I desire to ignore
+the fact that, if industry owes a heavy debt to science, it has
+largely repaid the loan by the important aid which it has, in its
+turn, rendered to the advancement of science. In considering the
+causes which hindered the progress of physical knowledge in the
+schools of Athens and of Alexandria, it has often struck me[A] that
+where the Greeks did wonders was in just those branches of science,
+such as geometry, astronomy, and anatomy, which are susceptible of
+very considerable development without any, or any but the simplest,
+appliances. It is a curious speculation to think what would have
+become of modern physical science if glass and alcohol had not been
+easily obtainable; and if the gradual perfection of mechanical skill
+for industrial ends had not enabled investigators to obtain, at
+comparatively little cost, microscopes, telescopes, and all the
+exquisitely delicate apparatus for determining weight and measure and
+for estimating the lapse of time with exactness, which they now
+command. If science has rendered the colossal development of modern
+industry possible, beyond a doubt industry has done no less for modern
+physics and chemistry, and for a great deal of modern biology. And as
+the captains of industry have, at last, begun to be aware that the
+condition of success in that warfare, under the forms of peace, which
+is known as industrial competition lies in the discipline of the
+troops and the use of arms of precision, just as much as it does in
+the warfare which is called war, their demand for that discipline,
+which is technical education, is reacting upon science in a manner
+which will, assuredly, stimulate its future growth to an incalculable
+extent. It has become obvious that the interests of science and of
+industry are identical, that science cannot make a step forward
+without, sooner or later, opening up new channels for industry, and,
+on the other hand, that every advance of industry facilitates those
+experimental investigations, upon which the growth of science depends.
+We may hope that, at last, the weary misunderstanding between the
+practical men who professed to despise science, and the high and dry
+philosophers who professed to despise practical results, is at an end.
+
+Nevertheless, that which is true of the infancy of physical science in
+the Greek world, that which is true of its adolescence in the
+seventeenth and eighteenth centuries, remains true of its riper age in
+these latter days of the nineteenth century. The great steps in its
+progress have been made, are made, and will be made, by men who seek
+knowledge simply because they crave for it. They have their
+weaknesses, their follies, their vanities, and their rivalries, like
+the rest of the world; but whatever by-ends may mar their dignity and
+impede their usefulness, this chief end redeems them.[B] Nothing great
+in science has ever been done by men, whatever their powers, in whom
+the divine afflatus of the truth-seeker was wanting. Men of moderate
+capacity have done great things because it animated them; and men of
+great natural gifts have failed, absolutely or relatively, because
+they lacked this one thing needful.
+
+[Sidenote: True aim and method of research.]
+
+To anyone who knows the business of investigation practically, Bacon's
+notion of establishing a company of investigators to work for
+'fruits,' as if the pursuit of knowledge were a kind of mining
+operation and only required well-directed picks and shovels, seems
+very strange.[C] In science, as in art, and, as I believe, in every
+other sphere of human activity, there may be wisdom in a multitude of
+counsellors, but it is only in one or two of them. And, in scientific
+inquiry, at any rate, it is to that one or two that we must look for
+light and guidance. Newton said that he made his discoveries by
+'intending' his mind on the subject; no doubt truly. But to equal his
+success one must have the mind which he 'intended.' Forty lesser men
+might have intended their minds till they cracked, without any like
+result. It would be idle either to affirm or to deny that the last
+half-century has produced men of science of the calibre of Newton. It
+is sufficient that it can show a few capacities of the first rank,
+competent not only to deal profitably with the inheritance bequeathed
+by their scientific forefathers, but to pass on to their successors
+physical truths of a higher order than any yet reached by the human
+race. And if they have succeeded as Newton succeeded, it is because
+they have sought truth as he sought it, with no other object than the
+finding it.
+
+       *       *       *       *       *
+
+[Sidenote: Progress from 1837 to 1887.]
+
+I am conscious that in undertaking to progress give even the briefest
+sketch of the progress of physical science, in all its branches,
+during the last half-century, I may be thought to have exhibited more
+courage than discretion, and perhaps more presumption than either. So
+far as physical science is concerned, the days of Admirable Crichtons
+have long been over, and the most indefatigable of hard workers may
+think he has done well if he has mastered one of its minor
+subdivisions. Nevertheless, it is possible for anyone, who has
+familiarised himself with the operations of science in one department,
+to comprehend the significance, and even to form a general estimate of
+the value, of the achievements of specialists in other departments.
+
+Nor is their any lack either of guidance, or of aids to ignorance. By
+a happy chance, the first edition of Whewell's 'History of the
+Inductive Sciences' was published in 1837, and it affords a very
+useful view of the state of things at the commencement of the
+Victorian epoch. As to subsequent events, there are numerous
+excellent summaries of the progress of various branches of science,
+especially up to 1881, which was the jubilee year of the British
+Association.[D] And, with respect to the biological sciences, with
+some parts of which my studies have familiarised me, my personal
+experience nearly coincides with the preceding half-century. I may
+hope, therefore, that my chance of escaping serious errors is as good
+as that of anyone else, who might have been persuaded to undertake the
+somewhat perilous enterprise in which I find myself engaged.
+
+There is yet another prefatory remark which it seems desirable I
+should make. It is that I think it proper to confine myself to the
+work done, without saying anything about the doers of it. Meddling
+with questions of merit and priority is a thorny business at the best
+of times, and unless in case of necessity, altogether undesirable when
+one is dealing with contemporaries. No such necessity lies upon me,
+and I shall, therefore, mention no names of living men, lest,
+perchance, I should incur the reproof which the Israelites, who
+struggled with one another in the field, addressed to Moses--'Who made
+thee a prince and a judge over us.'
+
+[Sidenote: The aim of physical science]
+
+Physical science is one and indivisible. Although, for practical
+purposes, it is convenient to mark it out into the primary regions of
+Physics, Chemistry, and Biology, and to subdivide these into
+subordinate provinces, yet the method of investigation and the
+ultimate object of the physical inquirer are everywhere the same.
+
+[Sidenote: the discovery of the rational order of the universe]
+
+The object is the discovery of the rational order which pervades the
+universe, the method consists of observation and experiment (which is
+observation under artificial conditions) for the determination of the
+facts of nature, of inductive and deductive reasoning for the
+discovery of their mutual relations and connection. The various
+branches of physical science differ in the extent to which at any
+given moment of their history, observation on the one hand, or
+ratiocination on the other, is their more obvious feature, but in no
+other way, and nothing can be more incorrect than the assumption one
+sometimes meets with, that physics has one method, chemistry another,
+and biology a third.
+
+[Sidenote: It is based on postulates]
+
+All physical science starts from certain postulates. One of them is
+the objective existence of a material world. It is assumed that the
+phenomena which are comprehended under this name have a 'substratum'
+of extended, impenetrable, mobile substance, which exhibits the
+quality known as inertia, and is termed matter.[E] Another postulate
+is the universality of the law of causation; that nothing happens
+without a cause (that is, a necessary precedent condition), and that
+the state of the physical universe, at any given moment, is the
+consequence of its state at any preceding moment. Another is that any
+of the rules, or so-called 'laws of nature,' by which the relation of
+phenomena is truly defined, is true for all time. The validity of
+these postulates is a problem of metaphysics; they are neither
+self-evident nor are they, strictly speaking, demonstrable. The
+justification of their employment, as axioms of physical philosophy,
+lies in the circumstance that expectations logically based upon them
+are verified, or, at any rate, not contradicted, whenever they can be
+tested by experience.
+
+[Sidenote: and uses hypotheses.]
+
+Physical science therefore rests on verified or uncontradicted
+hypotheses; and, such being the case, it is not surprising that a
+great condition of its progress has been the invention of verifiable
+hypotheses. It is a favorite popular delusion that the scientific
+inquirer is under a sort of moral obligation to abstain from going
+beyond that generalisation of observed facts which is absurdly called
+'Baconian' induction. But anyone who is practically acquainted with
+scientific work is aware that those who refuse to go beyond fact,
+rarely get as far as fact; and anyone who has studied the history of
+science knows that almost every great step therein has been made by
+the 'anticipation of Nature,' that is, by the invention of hypotheses,
+which, though verifiable, often had very little foundation to start
+with; and, not unfrequently, in spite of a long career of usefulness,
+turned out to be wholly erroneous in the long run.
+
+[Sidenote: Fruitful use of an hypothesis even when wrong.]
+
+The geocentric system of astronomy, with its eccentrics and its
+epicycles, was an hypothesis utterly at variance with fact, which
+nevertheless did great things for the advancement of astronomical
+knowledge. Kepler was the wildest of guessers. Newton's corpuscular
+theory of light was of much temporary use in optics, though nobody now
+believes in it; and the undulatory theory, which has superseded the
+corpuscular theory and has proved one of the most fertile of
+instruments of research, is based on the hypothesis of the existence
+of an 'ether,' the properties of which are defined in propositions,
+some of which, to ordinary apprehension, seem physical antinomies.
+
+It sounds paradoxical to say that the attainment of scientific truth
+has been effected, to a great extent, by the help of scientific
+errors. But the subject-matter of physical science is furnished by
+observation, which cannot extend beyond the limits of our faculties;
+while, even within those limits, we cannot be certain that any
+observation is absolutely exact and exhaustive. Hence it follows that
+any given generalisation from observation may be true, within the
+limits of our powers of observation at a given time, and yet turn out
+to be untrue, when those powers of observation are directly or
+indirectly enlarged. Or, to put the matter in another way, a doctrine
+which is untrue absolutely, may, to a very great extent, be
+susceptible of an interpretation in accordance with the truth. At a
+certain period in the history of astronomical science, the assumption
+that the planets move in circles was true enough to serve the purpose
+of correlating such observations as were then possible; after Kepler,
+the assumption that they move in ellipses became true enough in regard
+to the state of observational astronomy at that time. We say still
+that the orbits of the planets are ellipses, because, for all ordinary
+purposes, that is a sufficiently near approximation to the truth; but,
+as a matter of fact, the centre of gravity of a planet describes
+neither an ellipse or any other simple curve, but an immensely
+complicated undulating line. It may fairly be doubted whether any
+generalisation, or hypothesis, based upon physical data is absolutely
+true, in the sense that a mathematical proposition is so; but, if its
+errors can become apparent only outside the limits of practicable
+observation, it may be just as usefully adopted for one of the symbols
+of that algebra by which we interpret nature, as if it were absolutely
+true.
+
+The development of every branch of physical knowledge presents three
+stages which, in their logical relation, are successive. The first is
+the determination of the sensible character and order of the
+phenomena. This is _Natural History_, in the original sense of the
+term, and here nothing but observation and experiment avail us. The
+second is the determination of the constant relations of the phenomena
+thus defined, and their expression in rules or laws. The third is the
+explication of these particular laws by deduction from the most
+general laws of matter and motion. The last two stages constitute
+_Natural Philosophy_ in its original sense. In this region, the
+invention of verifiable hypotheses is not only permissible, but is one
+of the conditions of progress.
+
+[Sidenote: and mutual assistance of observation, experiment, and
+speculation.]
+
+Historically, no branch of science has followed this order of growth;
+but, from the dawn of exact knowledge to the present day, observation,
+experiment, and speculation have gone hand in hand; and, whenever
+science has halted or strayed from the right path, it has been, either
+because its votaries have been content with mere unverified or
+unverifiable speculation (and this is the commonest case, because
+observation and experiment are hard work, while speculation is
+amusing); or it has been, because the accumulation of details of
+observation has for a time excluded speculation.
+
+[Sidenote: Recognition of these truths in recent times, and consequent
+progress.]
+
+The progress of physical science, since the revival of learning, is
+largely due to the fact that men have gradually learned to lay aside
+the consideration of unverifiable hypotheses; to guide observation
+and experiment by verifiable hypotheses; and to consider the latter,
+not as ideal truths, the real entities of an intelligible world behind
+phenomena, but as a symbolical language, by the aid of which nature
+can be interpreted in terms apprehensible by our intellects. And if
+physical science, during the last fifty years, has attained dimensions
+beyond all former precedent, and can exhibit achievements of greater
+importance than any former such period can show, it is because able
+men, animated by the true scientific spirit, carefully trained in the
+method of science, and having at their disposal immensely improved
+appliances, have devoted themselves to the enlargement of the
+boundaries of natural knowledge in greater number than during any
+previous half-century of the world's history.
+
+[Sidenote: The three great achievements. Doctrines of (1) molecular
+constitution of matter, (2) conservation of energy, (3) evolution.]
+
+I have said that our epoch can produce achievements in physical
+science of greater moment than any other has to show, advisedly; and
+I think that there are three great products of our time which justify
+the assertion. One of these is that doctrine concerning the
+constitution of matter which, for want of a better name, I will call
+'molecular;' the second is the doctrine of conservation of energy; the
+third is the doctrine of evolution. Each of these was foreshadowed,
+more or less distinctly, in former periods of the history of science;
+and, so far is either from being the outcome of purely inductive
+reasoning, that it would be hard to overrate the influence of
+metaphysical, and even of theological, considerations upon the
+development of all three. The peculiar merit of our epoch is that it
+has shown how these hypotheses connect a vast number of seemingly
+independent partial generalisations; that it has given them that
+precision of expression which is necessary for their exact
+verification; and that it has practically proved their value as
+guides to the discovery of new truth. All three doctrines are
+intimately connected, and each is applicable to the whole physical
+cosmos. But, as might have been expected from the nature of the case,
+the first two grew, mainly, out of the consideration of
+physico-chemical phenomena; while the third, in great measure, owes
+its rehabilitation, if not its origin, to the study of biological
+phenomena.
+
+[Sidenote: (1) Molecular constitution of matter.]
+
+In the early decades of this century, a number of important truths
+applicable, in part, to matter in general, and, in part, to particular
+forms of matter, had been ascertained by the physicists and chemists.
+
+The laws of motion of visible and tangible, or _molar_, matter had
+been worked out to a great degree of refinement and embodied in the
+branches of science known as Mechanics, Hydrostatics, and Pneumatics.
+These laws had been shown to hold good, so far as they could be
+checked by observation and experiment, throughout the universe, on the
+assumption that all such masses of matter possessed inertia and were
+susceptible of acquiring motion, in two ways, firstly by impact, or
+impulse from without; and, secondly, by the operation of certain
+hypothetical causes of motion termed 'forces,' which were usually
+supposed to be resident in the particles of the masses themselves, and
+to operate at a distance, in such a way as to tend to draw any two
+such masses together, or to separate them more widely.
+
+[Sidenote: The two theories as to matter.]
+
+With respect to the ultimate constitution of these masses, the same
+two antagonistic opinions which had existed since the time of
+Democritus and of Aristotle were still face to face. According to the
+one, matter was discontinuous and consisted of minute indivisible
+particles or atoms, separated by a universal vacuum; according to the
+other, it was continuous, and the finest distinguishable, or
+imaginable, particles were scattered through the attenuated general
+substance of the plenum. A rough analogy to the latter case would be
+afforded by granules of ice diffused through water; to the former,
+such granules diffused through absolutely empty space.
+
+[Sidenote: Reassertion by Dalton of atomic theory.]
+
+In the latter part of the eighteenth century, the chemists had arrived
+at several very important generalisations respecting those properties
+of matter with which they were especially concerned. However plainly
+ponderable matter seemed to be originated and destroyed in their
+operations, they proved that, as mass or body, it remained
+indestructible and ingenerable; and that, so far, it varied only in
+its perceptibility by our senses. The course of investigation further
+proved that a certain number of the chemically separable kinds of
+matter were unalterable by any known means (except in so far as they
+might be made to change their state from solid to fluid, or _vice
+versâ_), unless they were brought into contact with other kinds of
+matter, and that the properties of these several kinds of matter were
+always the same, whatever their origin. All other bodies were found to
+consist of two or more of these, which thus took the place of the four
+'elements' of the ancient philosophers. Further, it was proved that,
+in forming chemical compounds, bodies always unite in a definite
+proportion by weight, or in simple multiples of that proportion, and
+that, if any one body were taken as a standard, every other could have
+a number assigned to it as its proportional combining weight. It was
+on this foundation of fact that Dalton based his re-establishment of
+the old atomic hypothesis on a new empirical foundation. It is
+obvious, that if elementary matter consists of indestructible and
+indivisible particles, each of which constantly preserves the same
+weight relatively to all the others, compounds formed by the
+aggregation of two, three, four, or more such particles must exemplify
+the rule of combination in definite proportions deduced from
+observation.
+
+In the meanwhile, the gradual reception of the undulatory theory of
+light necessitated the assumption of the existence of an 'ether'
+filling all space. But whether this ether was to be regarded as a
+strictly material and continuous substance was an undecided point, and
+hence the revived atomism, escaped strangling in its birth. For it is
+clear, that if the ether is admitted to be a continuous material
+substance, Democritic atomism is at an end and Cartesian continuity
+takes its place.
+
+[Sidenote: The real value of hypothesis; it predicates the existence
+of units of matter.]
+
+The real value of the new atomic hypothesis, however, did not lie in
+the two points which Democritus and his followers would have
+considered essential--namely, the indivisibility of the 'atoms' and
+the presence of an interatomic vacuum--but in the assumption that, to
+the extent to which our means of analysis take us, material bodies
+consist of definite minute masses, each of which, so far as physical
+and chemical processes of division go, may be regarded as a
+unit--having a practically permanent individuality. Just as a man is
+the unit of sociology, without reference to the actual fact of his
+divisibility, so such a minute mass is the unit of physico-chemical
+science--that smallest material particle which under any given
+circumstances acts as a whole.[F]
+
+The doctrine of specific heat originated in the eighteenth century.
+It means that the same mass of a body, under the same circumstances,
+always requires the same quantity of heat to raise it to a given
+temperature, but that equal masses of different bodies require
+different quantities. Ultimately, it was found that the quantities of
+heat required to raise equal masses of the more perfect gases, through
+equal ranges of temperature, were inversely proportional to their
+combining weights. Thus a definite relation was established between
+the hypothetical units and heat. The phenomena of electrolytic
+decomposition showed that there was a like close relation between
+these units and electricity. The quantity of electricity generated by
+the combination of any two units is sufficient to separate any other
+two which are susceptible of such decomposition. The phenomena of
+isomorphism showed a relation between the units and crystalline forms;
+certain units are thus able to replace others in a crystalline body
+without altering its form, and others are not.
+
+Again, the laws of the effect of pressure and heat on gaseous bodies,
+the fact that they combine in definite proportions by volume, and that
+such proportion bears a simple relation to their combining weights,
+all harmonised with the Daltonian hypothesis, and led to the bold
+speculation known as the law of Avogadro--that all gaseous bodies,
+under the same physical conditions, contain the same number of units.
+In the form in which it was first enunciated, this hypothesis was
+incorrect--perhaps it is not exactly true in any form; but it is
+hardly too much to say that chemistry and molecular physics would
+never have advanced to their present condition unless it had been
+assumed to be true. Another immense service rendered by Dalton, as a
+corollary of the new atomic doctrine, was the creation of a system of
+symbolic notation, which not only made the nature of chemical
+compounds and processes easily intelligible and easy of recollection,
+but, by its very form, suggested new lines of inquiry. The atomic
+notation was as serviceable to chemistry as the binomial nomenclature
+and the classificatory schematism of Linnćus were to zoölogy and
+botany.
+
+[Sidenote: In biology a like theory of molecularstructure.]
+
+Side by side with these advances arose in another, which also has a
+close parallel in the history of biological science. If the unit of a
+compound is made up by the aggregation of elementary units, the notion
+that these must have some sort of definite arrangement inevitably
+suggests itself; and such phenomena as double decomposition pointed,
+not only to the existence of a molecular architecture, but to the
+possibility of modifying a molecular fabric without destroying it, by
+taking out some of the component units and replacing them by others.
+The class of neutral salts, for example, includes a great number of
+bodies in many ways similar, in which the basic molecules, or the acid
+molecules, may be replaced by other basic and other acid molecules
+without altering the neutrality of the salt; just as a cube of bricks
+remains a cube, so long as any brick that is taken out is replaced by
+another of the same shape and dimensions, whatever its weight or other
+properties may be. Facts of this kind gave rise to the conception of
+'types' of molecular structure, just as the recognition of the unity
+in diversity of the structure of the species of plants and animals
+gave rise to the notion of biological 'types.' The notation of
+chemistry enabled these ideas to be represented with precision; and
+they acquired an immense importance, when the improvement of methods
+of analysis, which took place about the beginning of our period,
+enabled the composition of the so-called 'organic' bodies to be
+determined with, rapidity and precision.[G] A large proportion of
+these compounds contain not more than three or four elements, of which
+carbon is the chief; but their number is very great, and the diversity
+of their physical and chemical properties is astonishing. The
+ascertainment of the proportion of each element in these compounds
+affords little or no help towards accounting for their diversities;
+widely different bodies being often very similar, or even identical,
+in that respect. And, in the last case, that of _isomeric_ compounds,
+the appeal to diversity of arrangement of the identical component
+units was the only obvious way out of the difficulty. Here, again,
+hypothesis proved to be of great value; not only was the search for
+evidence of diversity of molecular structure successful, but the study
+of the process of taking to pieces led to the discovery of the way to
+put together; and vast numbers of compounds, some of them previously
+known only as products of the living economy, have thus been
+artificially constructed. Chemical work, at the present day, is, to a
+large extent, synthetic or creative--that is to say, the chemist
+determines, theoretically, that certain non-existent compounds ought
+to be producible, and he proceeds to produce them.
+
+It is largely because the chemical theory and practice of our epoch
+have passed into this deductive and synthetic stage, that they are
+entitled to the name of the 'New Chemistry' which they commonly
+receive. But this new chemistry has grown up by the help of
+hypotheses, such as those of Dalton and of Avogadro, and that
+singular conception of 'bonds' invented to colligate the facts of
+'valency' or 'atomicity,' the first of which took some time to make
+its way; while the second fell into oblivion, for many years after it
+was propounded, for lack of empirical justification. As for the third,
+it may be doubted if anyone regards it as more than a temporary
+contrivance.
+
+But some of these hypotheses have done yet further service. Combining
+them with the mechanical theory of heat and the doctrine of the
+conservation of energy, which are also products of our time,
+physicists have arrived at an entirely new conception of the nature of
+gaseous bodies and of the relation of the physico-chemical units of
+matter to the different forms of energy. The conduct of gases under
+varying pressure and temperature, their diffusibility, their relation
+to radiant heat and to light, the evolution of heat when bodies
+combine, the absorption of heat when they are dissociated, and a host
+of other molecular phenomena, have been shown to be deducible from the
+dynamical and statical principles which apply to molar motion and
+rest; and the tendency of physico-chemical science is clearly towards
+the reduction of the problems of the world of the infinitely little,
+as it already has reduced those of the infinitely great world, to
+questions of mechanics.[H]
+
+In the meanwhile, the primitive atomic theory, which has served as the
+scaffolding for the edifice of modern physics and chemistry, has been
+quietly dismissed. I cannot discover that any contemporary physicist
+or chemist believes in the real indivisibility of atoms, or in an
+interatomic matterless vacuum. 'Atoms' appear to be used as mere
+names for physico-chemical units which have not yet been subdivided,
+and 'molecules' for physico-chemical units which are aggregates of the
+former. And these individualised particles are supposed to move in an
+endless ocean of a vastly more subtle matter--the ether. If this ether
+is a continuous substance, therefore, we have got back from the
+hypothesis of Dalton to that of Descartes. But there is much reason to
+believe that science is going to make a still further journey, and, in
+form, if not altogether in substance, to return to the point of view
+of Aristotle.
+
+[Sidenote: Elementary bodies]
+
+The greater number of the so-called 'elementary' bodies, now known,
+had been discovered before the commencement of our epoch; and it had
+become apparent that they were by no means equally similar or
+dissimilar, but that some of them, at any rate, constituted groups,
+the several members of which were as much like one another as they
+were unlike the rest. Chlorine, iodine, bromine, and fluorine thus
+formed a very distinct group; sulphur and selenium another; boron and
+silicon another; potassium, sodium, and lithium another; and so on. In
+some cases, the atomic weights of such allied bodies were nearly the
+same, or could be arranged in series, with like differences between
+the several terms. In fact, the elements afforded indications that
+they were susceptible of a classification in natural groups, such as
+those into which animals and plants fall.
+
+[Sidenote: fall into different series.]
+
+Recently this subject has been taken up afresh, with a result which
+may be stated roughly in the following terms: If the sixty-five or
+sixty-eight recognised 'elements' are arranged in the order of their
+atomic weights--from hydrogen, the lightest, as unity, to uranium, the
+heaviest, as 240--the series does not exhibit one continuous
+progressive modification in the physical and chemical characters of
+its several terms, but breaks up into a number of sections, in each of
+which the several terms present analogies with the corresponding terms
+of the other series.
+
+Thus the whole series does not run:
+
+_a, b, d, e, f, g, h, i, k,_ &c.,
+
+but
+
+_a, b, c, d_, A, B, C, D, alpha, beta, gamma, delta, &c.;
+
+so that it is said to express a _periodic law_ of recurrent
+similarities. Or the relation may be expressed in another way. In each
+section of the series, the atomic weight is greater than in the
+preceding section, so that if _w_ is the atomic weight of any element
+in the first segment, _w+x_ will represent the atomic weight of any
+element in the next, and _w+x+y_ the atomic weight of any element in
+the next, and so on. Therefore the sections may be represented as
+parallel series, the corresponding terms of which have analogous
+properties; each successive series starting with a body the atomic
+weight of which is greater than that of any in the preceding series,
+in the following fashion:
+
+_d_       D         delta
+_c_       C         gamma
+_b_       B          beta
+_a_       A         alpha
+ -      -----     ---------
+_w_    _w + x_   _w + x + y_
+
+[Sidenote: The possibility of a primary form of matter.]
+
+This is a conception with, which biologists are very familiar, animal
+and plant groups constantly appearing as series of parallel
+modifications of similar and yet different primary forms. In the
+living world, facts of this kind are now understood to mean evolution
+from a common prototype. It is difficult to imagine that in the
+not-living world they are devoid of significance. Is it not possible,
+nay probable that they may mean the evolution of our 'elements' from a
+primary undifferentiated form of matter? Fifty years ago, such a
+suggestion would have been scouted as a revival of the dreams of the
+alchemists. At present, it may be said to be the burning question of
+physico-chemical science.
+
+In fact, the so-called 'vortex-ring' hypothesis is a very serious and
+remarkable attempt to deal with material units from a point of view
+which is consistent with the doctrine of evolution. It supposes the
+ether to be a uniform substance, and that the 'elementary' units are,
+broadly speaking, permanent whirlpools, or vortices, of this ether,
+the properties of which depend on their actual and potential modes of
+motion. It is curious and highly interesting to remark that this
+hypothesis reminds us not only of the speculations of Descartes, but
+of those of Aristotle. The resemblance of the 'vortex-rings' to the
+'tourbillons' of Descartes is little more than nominal; but the
+correspondence between the modern and the ancient notion of a
+distinction between primary and derivative matter is, to a certain
+extent, real. For this ethereal 'Urstoff' of the modern corresponds
+very closely with the prhôtę hylę of Aristotle, the _materia prima_ of
+his medićval followers; while matter, differentiated into our
+elements, is the equivalent of the first stage of progress towards the
+heschhatę hylę, or finished matter, of the ancient philosophy.
+
+If the material units of the existing order of nature are specialised
+portions of a relatively homogeneous _materia prima_--which were
+originated under conditions that have long ceased to exist and which
+remain unchanged and unchangeable under all conditions, whether
+natural or artificial, hitherto known to us--it follows that the
+speculation that they may be indefinitely altered, or that new units
+may be generated under conditions yet to be discovered, is perfectly
+legitimate. Theoretically, at any rate, the transmutability of the
+elements is a verifiable scientific hypothesis; and such inquiries as
+those which have been set afoot, into the possible dissociative action
+of the great heat of the sun upon our elements, are not only
+legitimate, but are likely to yield results which, whether affirmative
+or negative, will be of great importance. The idea that atoms are
+absolutely ingenerable and immutable 'manufactured articles' stands on
+the same sort of foundation as the idea that biological species are
+'manufactured articles' stood thirty years ago; and the supposed
+constancy of the elementary atoms, during the enormous lapse of time
+measured by the existence of our universe, is of no more weight
+against the possibility of change in them, in the infinity of
+antecedent time, than the constancy of species in Egypt, since the
+days of Rameses or Cheops, is evidence of their immutability during
+all past epochs of the earth's history. It seems safe to prophesy
+that the hypothesis of the evolution of the elements from a primitive
+matter will, in future, play no less a part in the history of science
+than the atomic hypothesis, which, to begin with, had no greater, if
+so great, an empirical foundation.
+
+[Sidenote: The old and the new atomic theory.]
+
+It may perhaps occur to the reader that the boasted progress of
+physical science does not come to much, if our present conceptions of
+the fundamental nature of matter are expressible in terms employed,
+more than two thousand years ago, by the old 'master of those that
+know.' Such a criticism, however, would involve forgetfulness of the
+fact, that the connotation of these terms, in the mind of the modern,
+is almost infinitely different from that which they possessed in the
+mind of the ancient, philosopher. In antiquity, they meant little more
+than vague speculation; at the present day, they indicate definite
+physical conceptions, susceptible of mathematical treatment, and
+giving rise to innumerable deductions, the value of which can be
+experimentally tested. The old notions produced little more than
+floods of dialectics; the new are powerful aids towards the increase
+of solid knowledge.
+
+[Sidenote: (2) Conservation of energy.]
+
+Everyday observation shows that, of the bodies which compose the
+material world, some are in motion and some are, or appear to be, at
+rest. Of the bodies in motion, some, like the sun and stars, exhibit a
+constant movement, regular in amount and direction, for which no
+external cause appears. Others, as stones and smoke, seem also to move
+of themselves when external impediments are taken away. But these
+appear to tend to move in opposite directions: the bodies we call
+heavy, such as stones, downwards, and the bodies we call light, at
+least such as smoke and steam, upwards. And, as we further notice
+that the earth, below our feet, is made up of heavy matter, while the
+air, above our heads, is extremely light matter, it is easy to regard
+this fact as evidence that the lower region is the place to which
+heavy things tend--their proper place, in short--while the upper
+region is the proper place of light things; and to generalise the
+facts observed by saying that bodies, which are free to move, tend
+towards their proper places. All these seem to be natural motions,
+dependent on the inherent faculties, or tendencies, of bodies
+themselves. But there are other motions which are artificial or
+violent, as when a stone is thrown from the hand, or is knocked by
+another stone in motion. In such cases as these, for example, when a
+stone is cast from the hand, the distance travelled by the stone
+appears to depend partly on its weight and partly upon the exertion
+of the thrower. So that, the weight of the stone remaining the same,
+it looks as if the motive power communicated to it were measured by
+the distance to which the stone travels--as if, in other words, the
+power needed to send it a hundred yards was twice as great as that
+needed to send it fifty yards. These, apparently obvious, conclusions
+from the everyday appearances of rest and motion fairly represent the
+state of opinion upon the subject which prevailed among the ancient
+Greeks, and remained dominant until the age of Galileo. The
+publication of the 'Principia' of Newton, in 1686-7, marks the epoch
+at which the progress of mechanical physics had effected a complete
+revolution of thought on these subjects. By this time, it had been
+made clear that the old generalisations were either incomplete or
+totally erroneous; that a body, once set in motion, will continue to
+move in a straight line for any conceivable time or distance, unless
+it is interfered with; that any change of motion is proportional to
+the 'force' which causes it, and takes place in the direction in which
+that 'force' is exerted; and that, when a body in motion acts as a
+cause of motion on another, the latter gains as much as the former
+loses, and _vice versâ_. It is to be noted, however, that while, in
+contradistinction to the ancient idea of the inherent tendency to
+motion of bodies, the absence of any such spontaneous power of motion
+was accepted as a physical axiom by the moderns, the old conception
+virtually maintained itself is a new shape. For, in spite of Newton's
+well-known warning against the 'absurdity' of supposing that one body
+can act on another at a distance through a vacuum, the ultimate
+particles of matter were generally assumed to be the seats of
+perennial causes of motion termed 'attractive and repulsive forces,'
+in virtue of which, any two such particles, without any external
+impression of motion, or intermediate material agent, were supposed to
+tend to approach or remove from one another; and this view of the
+duality of the causes of motion is very widely held at the present
+day.
+
+Another important result of investigation, attained in the seventeenth
+century, was the proof and quantitative estimation of physical
+inertia. In the old philosophy, a curious conjunction of ethical and
+physical prejudices had led to the notion that there was something
+ethically bad and physically obstructive about matter. Aristotle
+attributes all irregularities and apparent dysteleologies in nature to
+the disobedience, or sluggish yielding, of matter to the shaping and
+guiding influence of those reasons and causes which were hypostatised
+in his ideal 'Forms.' In modern science, the conception of the
+inertia, or resistance to change, of matter is complex. In part, it
+contains a corollary from the law of causation: A body cannot change
+its state in respect of rest or motion without a sufficient cause.
+But, in part, it contains generalisations from experience. One of
+these is that there is no such sufficient cause resident in any body,
+and that therefore it will rest, or continue in motion, so long as no
+external cause of change acts upon it. The other is that the effect
+which the impact of a body in motion produces upon the body on which
+it impinges depends, other things being alike, on the relation of a
+certain quality of each which is called 'mass.' Given a cause of
+motion of a certain value, the amount of motion, measured by distance
+travelled in a certain time, which it will produce in a given quantity
+of matter, say a cubic inch, is not always the same, but depends on
+what that matter is--a cubic inch of iron will go faster than a cubic
+inch of gold. Hence, it appears, that since equal amounts of motion
+have, _ex hypothesi_, been produced, the amount of motion in a body
+does not depend on its speed alone, but on some property of the body.
+To this the name of 'mass' has been given. And since it seems
+reasonable to suppose that a large quantity of matter, moving slowly,
+possesses as much motion as a small quantity moving faster, 'mass' has
+been held to express 'quantity of matter.' It is further demonstrable
+that, at any given time and place, the relative mass of any two bodies
+is expressed by the ratio of their weights.
+
+[Sidenote: Mechanical theory of heat.]
+
+When all these great truths respecting molar motion, or the movements
+of visible and tangible masses, had been shown to hold good not only
+of terrestrial bodies, but of all those which constitute the visible
+universe, and the movements of the macrocosm had thus been expressed
+by a general mechanical theory, there remained a vast number of
+phenomena, such as those of light, heat, electricity, magnetism, and
+those of the physical and chemical changes, which do not involve molar
+motion. Newton's corpuscular theory of light was an attempt to deal
+with one great series of these phenomena on mechanical principles, and
+it maintained its ground until, at the beginning of the nineteenth
+century, the undulatory theory proved itself to be a much better
+working hypothesis. Heat, up to that time, and indeed much later, was
+regarded as an imponderable substance, _caloric_; as a thing which was
+absorbed by bodies when they were wanned, and was given out as they
+cooled; and which, moreover, was capable of entering into a sort of
+chemical combination with them, and so becoming latent. Rumford and
+Davy had given a great blow to this view of heat by proving that the
+quantity of heat which two portions of the same body could be made to
+give out, by rubbing them together, was practically illimitable. This
+result brought philosophers face to face with the contradiction of
+supposing that a finite body could contain an infinite quantity of
+another body; but it was not until 1843, that clear and unquestionable
+experimental proof was given of the fact that there is a definite
+relation between mechanical work and heat; that so much work always
+gives rise, under the same conditions, to so much heat, and so much
+heat to so much mechanical work. Thus originated the mechanical theory
+of heat, which became the starting-point of the modern doctrine of the
+conservation of energy. Molar motion had appeared to be destroyed by
+friction. It was proved that no destruction took place, but that an
+exact equivalent of the energy of the lost molar motion appears as
+that of the _molecular_ motion, or motion of the smallest particles of
+a body, which constitutes heat. The loss of the masses is the gain of
+their particles.
+
+[Sidenote: Earlier approaches towards doctrine of conservation.]
+
+Before 1843, however, the doctrine of conservation of energy had been
+approached Bacon's chief contribution to positive science is the happy
+guess (for the context shows that it was little more) that heat may be
+a mode of motion; Descartes affirmed the quantity of motion in the
+world to be constant; Newton nearly gave expression to the complete
+theorem; while Rumford's and Davy's experiments suggested, though they
+did not prove, the equivalency of mechanical and thermal energy.
+Again, the discovery of voltaic electricity, and the marvellous
+development of knowledge, in that field, effected by such men as Davy,
+Faraday, Oersted, Ampčre, and Melloni, had brought to light a number
+of facts which tended to show that the so-called 'forces' at work in
+light, heat, electricity, and magnetism, in chemical and in mechanical
+operations, were intimately, and, in various cases, quantitatively
+related. It was demonstrated that any one could be obtained at the
+expense of any other; and apparatus was devised which exhibited the
+evolution of all these kinds of action from one source of energy.
+Hence the idea of the 'correlation of forces' which was the immediate
+forerunner of the doctrine of the conservation of energy.
+
+It is a remarkable evidence of the greatness of the progress in this
+direction which has been effected in our time, that even the second
+edition of the 'History of the Inductive Sciences,' which was
+published in 1846, contains no allusion either to the general view of
+the 'Correlation of Forces' published in England in 1842, or to the
+publication in 1843 of the first of the series of experiments by which
+the mechanical equivalent of heat was correctly ascertained.[I] Such a
+failure on the part of a contemporary, of great acquirements and
+remarkable intellectual powers, to read the signs of the times, is a
+lesson and a warning worthy of being deeply pondered by anyone who
+attempts to prognosticate the course of scientific progress.
+
+[Sidenote: What this doctrine is.]
+
+I have pointed out that the growth of clear and definite views
+respecting the constitution of matter has led to the conclusion that,
+so far as natural agencies are concerned, it is ingenerable and
+indestructible. In so far as matter may be conceived to exist in a
+purely passive state, it is, imaginably, older than motion. But, as it
+must be assumed to be susceptible of motion, a particle of bare matter
+at rest must be endowed with the potentiality of motion. Such a
+particle, however, by the supposition, can have no energy, for there
+is no cause why it should move. Suppose now that it receives an
+impulse, it will begin to move with a velocity inversely proportional
+to its mass, on the one hand, and directly proportional to the
+strength of the impulse, on the other, and will possess _kinetic
+energy_, in virtue of which it will not only continue to move for ever
+if unimpeded, but if it impinges on another such particle, it will
+impart more or less of its motion, to the latter. Let it be conceived
+that the particle acquires a tendency to move, and that nevertheless
+it does not move. It is then in a condition totally different from
+that in which it was at first. A cause competent to produce motion is
+operating upon it, but, for some reason or other, is unable to give
+rise to motion. If the obstacle is removed, the energy which was
+there, but could not manifest itself, at once gives rise to motion.
+While the restraint lasts, the energy of the particle is merely
+potential; and the case supposed illustrates what is meant by
+_potential energy_. In this contrast of the potential with the actual,
+modern physics is turning to account the most familiar of Aristotelian
+distinctions--that between dunamis and energeia.
+
+That kinetic energy appears to be imparted by impact is a fact of
+daily and hourly experience: we see bodies set in motion by bodies,
+already in motion, which seem to come in contact with them. It is a
+truth which could have been learned by nothing but experience, and
+which cannot be explained, but must be taken as an ultimate fact
+about which, explicable or inexplicable, there can be no doubt.
+Strictly speaking, we have no direct apprehension of any other cause
+of motion. But experience furnishes innumerable examples of the
+production of kinetic energy in a body previously at rest, when no
+impact is discernible as the cause of that energy. In all such cases,
+the presence of a second body is a necessary condition; and the amount
+of kinetic energy, which its presence enables the first to gain, is
+strictly dependent on the relative positions of the two. Hence the
+phrase _energy of position_, which is frequently used as equivalent to
+potential energy. If a stone is picked up and held, say, six feet
+above the ground, it has _potential energy_, because, if let go, it
+will immediately begin to move towards the earth; and this energy may
+be said to be _energy of position_, because it depends upon the
+relative position of the earth and the stone. The stone is solicited
+to move but cannot, so long as the muscular strength of the holder
+prevents the solicitation from taking effect. The stone, therefore,
+has potential energy, which becomes kinetic if it is let go, and the
+amount of that kinetic energy which will be developed before it
+strikes the earth depends on its position--on the fact that it is,
+say, six feet off the earth, neither more nor less. Moreover, it can
+be proved that the raiser of the stone had to exert as much energy in
+order to place it in its position, as it will develop in falling.
+Hence the energy which was exerted, and apparently exhausted, in
+raising the stone, is potentially in the stone, in its raised
+position, and will manifest itself when the stone is set free. Thus
+the energy, withdrawn from the general stock to raise the stone, is
+returned when it falls, and there is no change in the total amount.
+Energy, as a whole, is conserved.
+
+Taking this as a very broad and general statement of the essential
+facts of the case, the raising of the stone is intelligible enough, as
+a case of the communication of motion from one body to another. But
+the potential energy of the raised stone is not so easily
+intelligible. To all appearance, there is nothing either pushing or
+pulling it towards the earth, or the earth towards it; and yet it is
+quite certain that the stone tends to move towards the earth and the
+earth towards the stone, in the way defined by the law of gravitation.
+
+In the currently accepted language of science, the cause of motion, in
+all such cases as this, when bodies tend to move towards or away from
+one or another, without any discernible impact of other bodies, is
+termed a 'force,' which is called 'attractive' in the one case, and
+'repulsive' in the other. And such attractive or repulsive forces are
+often spoken of as if they were real things, capable of exerting a
+pull, or a push, upon the particles of matter concerned. Thus the
+potential energy of the stone is commonly said to be due to the
+'force' of gravity which is continually operating upon it.
+
+Another illustration may make the case plainer. The bob of a pendulum
+swings first to one side and then to the other of the centre of the
+arc which it describes. Suppose it to have just reached the summit of
+its right-hand half-swing. It is said that the 'attractive forces' of
+the bob for the earth, and of the earth for the bob, set the former in
+motion; and as these 'forces' are continually in operation, they
+confer an accelerated velocity on the bob; until, when it reaches the
+centre of its swing, it is, so to speak, fully charged with kinetic
+energy. If, at this moment, the whole material universe, except the
+bob, were abolished, it would move for ever in the direction of a
+tangent to the middle of the arc described. As a matter of fact, it
+is compelled to travel through its left-hand half-swing, and thus
+virtually to go up hill. Consequently, the 'attractive forces' of the
+bob and the earth are now acting against it, and constitute a
+resistance which the charge of kinetic energy has to overcome. But, as
+this charge represents the operation of the attractive forces during
+the passage of the bob through the right-hand half-swing down to the
+centre of the arc, so it must needs be used up by the passage of the
+bob upwards from the centre of the arc to the summit of the left-hand
+half-swing. Hence, at this point, the bob comes to a momentary rest.
+The last fraction of kinetic energy is just neutralised by the action
+of the attractive forces, and the bob has only potential energy equal
+to that with which it started. So that the sum of the phenomena may be
+stated thus: At the summit of either half-arc of its swing, the bob
+has a certain amount of potential energy; as it descends it gradually
+exchanges this for kinetic energy, until at the centre it possesses an
+equivalent amount of kinetic energy; from this point onwards, it
+gradually loses kinetic energy as it ascends, until, at the summit of
+the other half-arc, it has acquired an exactly similar amount of
+potential energy. Thus, on the whole transaction, nothing is either
+lost or gained; the quantity of energy is always the same, but it
+passes from one form into the other.
+
+To all appearance, the phenomena exhibited by the pendulum are not to
+be accounted for by impact: in fact, it is usually assumed that
+corresponding phenomena would take place if the earth and the pendulum
+were situated in an absolute vacuum, and at any conceivable distance
+from, one another. If this be so, it follows that there must be two
+totally different kinds of causes of motion: the one impact--a _vera
+causa_, of which, to all appearance, we have constant experience; the
+other, attractive or repulsive 'force'--a metaphysical entity which is
+physically inconceivable. Newton expressly repudiated the notion of
+the existence of attractive forces, in the sense in which that term is
+ordinarily understood; and he refused to put forward any hypothesis as
+to the physical cause of the so-called 'attraction of gravitation.' As
+a general rule, his successors have been content to accept the
+doctrine of attractive and repulsive forces, without troubling
+themselves about the philosophical difficulties which it involves. But
+this has not always been the case; and the attempt of Le Sage, in the
+last century, to show that the phenomena of attraction and repulsion
+are susceptible of explanation by his hypothesis of bombardment by
+ultra-mundane particles, whether tenable or not, has the great merit
+of being an attempt to get rid of the dual conception of the causes
+of motion which has hitherto prevailed. On this hypothesis, the
+hammering of the ultra-mundane corpuscles on the bob confers its
+kinetic energy, on the one hand, and takes it away on the other; and
+the state of potential energy means the condition of the bob during
+the instant at which the energy, conferred by the hammering during the
+one half-arc, has just been exhausted by the hammering during the
+other half-arc. It seems safe to look forward to the time when the
+conception of attractive and repulsive forces, having served its
+purpose as a useful piece of scientific scaffolding, will be replaced
+by the deduction of the phenomena known as attraction and repulsion,
+from the general laws of motion.
+
+The doctrine of the conservation of energy which I have endeavored to
+illustrate is thus defined by the late Clerk Maxwell:
+
+'The total energy of any body or system of bodies is a quantity which
+can neither be increased nor diminished by any mutual action of such
+bodies, though it may be transformed into any one of the forms of
+which energy is susceptible.' It follows that energy, like matter, is
+indestructible and ingenerable in nature. The phenomenal world, so far
+as it is material, expresses the evolution and involution of energy,
+its passage from the kinetic to the potential condition and back
+again. Wherever motion of matter takes place, that motion is effected
+at the expense of part of the total store of energy.
+
+Hence, as the phenomena exhibited by living beings, in so far as they
+are material, are all molar or molecular motions, these are included
+under the general law. A living body is a machine by which energy is
+transformed in the same sense as a steam-engine is so, and all its
+movements, molar and molecular, are to be accounted for by the energy
+which is supplied to it. The phenomena of consciousness which arise,
+along with certain transformations of energy, cannot be interpolated
+in the series of these transformations, inasmuch as they are not
+motions to which the doctrine of the conservation of energy applies.
+And, for the same reason, they do not necessitate the using up of
+energy; a sensation has no mass and cannot be conceived to be
+susceptible of movement. That a particular molecular motion does give
+rise to a state of consciousness is experimentally certain; but the
+how and why of the process are just as inexplicable as in the case of
+the communication of kinetic energy by impact.
+
+When dealing with the doctrine of the ultimate constitution of matter,
+we found a certain resemblance between the oldest speculations and the
+newest doctrines of physical philosophers. But there is no such
+resemblance between the ancient and modern views of motion and its
+causes, except in so far as the conception of attractive and repulsive
+forces may be regarded as the modified descendant of the Aristotelian
+conception of forms. In fact, it is hardly too much to say that the
+essential and fundamental difference between ancient and modern
+physical science lies in the ascertainment of the true laws of statics
+and dynamics in the course of the last three centuries; and in the
+invention of mathematical methods of dealing with all the consequences
+of these laws. The ultimate aim of modern physical science is the
+deduction of the phenomena exhibited by material bodies from
+physico-mathematical first principles. Whether the human intellect is
+strong enough to attain the goal set before it may be a question, but
+thither will it surely strive.
+
+[Sidenote: (3) Evolution.]
+
+The third great scientific event of our time, the rehabilitation of
+the doctrine of evolution, is part of the same tendency of increasing
+knowledge to unify itself, which has led to the doctrine of the
+conservation of energy. And this tendency, again, is mainly a product
+of the increasing strength conferred by physical investigation on the
+belief in the universal validity of that orderly relation of facts,
+which we express by the so-called 'Laws of Nature.'
+
+[Sidenote: Early stages of this theory]
+
+The growth of a plant from its seed, of an animal from its egg, the
+apparent origin of innumerable living things from mud, or from the
+putrefying remains of former organisms, had furnished the earlier
+scientific thinkers with abundant analogies suggestive of the
+conception of a corresponding method of cosmic evolution from a
+formless 'chaos' to an ordered world which might either continue for
+ever or undergo dissolution into its elements before starting on a new
+course of evolution. It is therefore no wonder that, from the days of
+the Ionian school onwards, the view that the universe was the result
+of such a process should have maintained itself as a leading dogma of
+philosophy. The emanistic theories which played so great a part in
+Neoplatonic philosophy and Gnostic theology are forms of evolution. In
+the seventeenth century, Descartes propounded a scheme of evolution,
+as an hypothesis of what might have been the mode of origin of the
+world, while professing to accept the ecclesiastical scheme of
+creation, as an account of that which actually was its manner of
+coming into existence. In the eighteenth century, Kant put forth a
+remarkable speculation as to the origin of the solar system, closely
+similar to that subsequently adopted by Laplace and destined to become
+famous under the title of the 'nebular hypothesis.'
+
+The careful observations and the acute reasonings of the Italian
+geologists of the seventeenth and eighteenth centuries; the
+speculations of Leibnitz in the 'Protogaea' and of Buffon in his
+'Théorie de la Terre;' the sober and profound reasonings of Hutton, in
+the latter part of the eighteenth century; all these tended to show
+that the fabric of the earth itself implied the continuance of
+processes of natural causation for a period of time as great, in
+relation to human history, as the distances of the heavenly bodies
+from us are, in relation to terrestrial standards of measurement. The
+abyss of time began to loom as large as the abyss of space. And this
+revelation to sight and touch, of a link here and a link there of a
+practically infinite chain of natural causes and effects, prepared the
+way, as perhaps nothing else has done, for the modern form of the
+ancient theory of evolution.
+
+In the beginning of the eighteenth century, De Maillet made the first
+serious attempt to apply the doctrine to the living world. In the
+latter part of it, Erasmus Darwin, Goethe, Treviranus, and Lamarck
+took up the work more vigorously and with better qualifications. The
+question of special creation, or evolution, lay at the bottom of the
+fierce disputes which broke out in the French Academy between Cuvier
+and St.-Hilaire; and, for a time, the supporters of biological
+evolution were silenced, if not answered, by the alliance of the
+greatest naturalist of the age with their ecclesiastical opponents.
+Catastrophism, a short-sighted teleology, and a still more
+short-sighted orthodoxy, joined forces to crush evolution.
+
+Lyell and Poulett Scrope, in this country, resumed the work of the
+Italians and of Hutton; and the former, aided by a marvellous power of
+clear exposition, placed upon an irrefragable basis the truth that
+natural causes are competent to account for all events, which can be
+proved to have occurred, in the course of the secular changes which
+have taken place during the deposition of the stratified rocks. The
+publication of 'The Principles of Geology,' in 1830, constituted an
+epoch in geological science. But it also constituted an epoch in the
+modern history of the doctrines of evolution, by raising in the mind
+of every intelligent reader this question: If natural causation is
+competent to account for the not-living part of our globe, why should
+it not account for the living part?
+
+By keeping this question before the public for some thirty years,
+Lyell, though the keenest and most formidable of the opponents of the
+transmutation theory, as it was formulated by Lamarck, was of the
+greatest possible service in facilitating the reception of the sounder
+doctrines of a later day. And, in like fashion, another vehement
+opponent of the transmutation of species, the elder Agassiz, was
+doomed to help the cause he hated. Agassiz not only maintained the
+fact of the progressive advance in organisation of the inhabitants of
+the earth at each successive geological epoch, but he insisted upon
+the analogy of the steps of this progression with those by which the
+embryo advances to the adult condition, among the highest forms of
+each group. In fact, in endeavoring to support these views he went a
+good way beyond the limits of any cautious interpretation of the facts
+then known.
+
+[Sidenote: Darwin]
+
+Although little acquainted with biological science, Whewell seems to
+have taken particular pains with that part of his work which deals
+with the history of geological and biological speculation; and several
+chapters of his seventeenth and eighteenth books, which comprise the
+history of physiology, of comparative anatomy and of the
+palćtiological sciences, vividly reproduce the controversies of the
+early days of the Victorian epoch. But here, as in the case of the
+doctrine of the conservation of energy, the historian of the inductive
+sciences has no prophetic insight; not even a suspicion of that which
+the near future was to bring forth. And those who still repeat the
+once favorite objection that Darwin's 'Origin of Species' is nothing
+but a new version of the 'Philosophie zoologique' will find that, so
+late as 1844, Whewell had not the slightest suspicion of Darwin's main
+theorem, even as a logical possibility. In fact, the publication of
+that theorem by Darwin and Wallace, in 1859, took all the biological
+world by surprise. Neither those who were inclined towards the
+'progressive transmutation' or 'development' doctrine, as it was then
+called, nor those who were opposed to it, had the slightest suspicion
+that the tendency to variation in living beings, which all admitted as
+a matter of fact; the selective influence of conditions, which no one
+could deny to be a matter of fact, when his attention was drawn to the
+evidence; and the occurrence of great geological changes which also
+was matter of fact; could be used as the only necessary postulates of
+a theory of the evolution of plants and animals which, even if not at
+once, competent to explain all the known facts of biological science,
+could not be shown to be inconsistent with any. So far as biology is
+concerned, the publication of the 'Origin of Species,' for the first
+time, put the doctrine of evolution, in its application to living
+things, upon a sound scientific foundation. It became an instrument of
+investigation, and in no hands did it prove more brilliantly
+profitable than in those of Darwin himself. His publications on the
+effects of domestication in plants and animals, on the influence of
+cross-fertilisation, on flowers as organs for effecting such
+fertilisation, on insectivorous plants, on the motions of plants,
+pointed out the routes of exploration which have since been followed
+by hosts of inquirers, to the great profit of science.
+
+Darwin found the biological world a more than sufficient field for
+even his great powers, and left the cosmical part of the doctrine to
+others. Not much has been added to the nebular hypothesis, since the
+time of Laplace, except that the attempt to show (against that
+hypothesis) that all nebulć are star clusters, has been met by the
+spectroscopic proof of the gaseous condition of some of them.
+Moreover, physicists of the present generation appear now to accept
+the secular cooling of the earth, which is one of the corollaries of
+that hypothesis. In fact, attempts have been made, by the help of
+deductions from the data of physics, to lay down an approximate limit
+to the number of millions of years which have elapsed since the earth
+was habitable by living beings. If the conclusions thus reached should
+stand the test of further investigation, they will undoubtedly be very
+valuable. But, whether true or false, they can have no influence upon
+the doctrine of evolution in its application to living organisms. The
+occurrence of successive forms of life upon our globe is an historical
+fact, which cannot be disputed; and the relation of these successive
+forms, as stages of evolution of the same type, is established in
+various cases. The biologist has no means of determining the time over
+which the process of evolution has extended, but accepts the
+computation of the physical geologist and the physicist, whatever that
+may be.
+
+[Sidenote: and philosophy]
+
+Evolution as a philosophical doctrine applicable to all phenomena,
+whether physical or mental, whether manifested by material atoms or by
+men in society, has been dealt with systematically in the 'Synthetic
+Philosophy' of Mr. Herbert Spencer. Comment on that great undertaking
+would not be in place here. I mention it because, so far as I know, it
+is the first attempt to deal, on scientific principles, with modern
+scientific facts and speculations. For the 'Philosophic positive' of
+M. Comte, with which Mr. Spencer's system of philosophy is sometimes
+compared, though it professes a similar object, is unfortunately
+permeated by a thoroughly unscientific spirit, and its author had no
+adequate acquaintance with the physical sciences even of his own time.
+
+       *       *       *       *       *
+
+The doctrine of evolution, so far as the present physical cosmos is
+concerned, postulates the fixity of the rules of operation of the
+causes of motion in the material universe. If all kinds of matter are
+modifications of one kind, and if all modes of motion are derived from
+the same energy, the orderly evolution of physical nature out of one
+substratum and one energy implies that the rules of action of that
+energy should be fixed and definite. In the past history of the
+universe, back to that point, there can be no room for chance or
+disorder. But it is possible to raise the question whether this
+universe of simplest matter and definitely operating energy, which
+forms our hypothetical starting point, may not itself be a product of
+evolution from a universe of such matter, in which the manifestations
+of energy were not definite--in which, for example, our laws of motion
+held good for some units and not for others, or for the same units at
+one time and not at another--and which would therefore be a real
+epicurean chance-world?
+
+For myself, I must confess that I find the air of this region of
+speculation too rarefied for my constitution, and I am disposed to
+take refuge in 'ignoramus et ignorabimus.'
+
+[Sidenote: Other achievements in physical science.]
+
+The execution of my further task, the indication of the most important
+achievements in the several branches of physical science during the
+last fifty years, is embarrassed by the abundance of the objects of
+choice; and by the difficulty which everyone, but a specialist in each
+department, must find in drawing a due distinction between discoveries
+which strike the imagination by their novelty, or by their practical
+influence, and those unobtrusive but pregnant observations and
+experiments in which the germs of the great things of the future
+really lie. Moreover, my limits restrict me to little more than a bare
+chronicle of the events which I have to notice.
+
+[Sidenote: Physics and chemistry.]
+
+In physics and chemistry, the old boundaries of which sciences are
+rapidly becoming effaced, one can hardly go wrong in ascribing a
+primary value to the investigations into the relation between the
+solid, liquid, and gaseous states of matter on the one hand, and
+degrees of pressure and of heat on the other. Almost all, even the
+most refractory, solids have been vaporised by the intense heat of the
+electric arc; and the most refractory gases have been forced to assume
+the liquid, and even the solid, forms by the combination of high
+pressure with intense cold. It has further been shown that there is no
+discontinuity between these states--that a gas passes into the liquid
+state through a condition which is neither one nor the other, and that
+a liquid body becomes solid, or a solid liquid, by the intermediation
+of a condition in which it is neither truly solid nor truly liquid.
+
+Theoretical and experimental investigations have concurred in the
+establishment of the view that a gas is a body, the particles of which
+are in incessant rectilinear motion at high velocities, colliding with
+one another and bounding back when they strike the walls of the
+containing vessel; and, on this theory, the already ascertained
+relations of gaseous bodies to heat and pressure have been shown to be
+deducible from mechanical principles. Immense improvements have been
+effected, in the means of exhausting a given space of its gaseous
+contents; and experimentation on the phenomena which attend the
+electric discharge and the action of radiant heat, within the
+extremely rarefied media thus produced, has yielded a great number of
+remarkable results, some of which have been made familiar to the
+public by the Gieseler tubes and the radiometer. Already, these
+investigations have afforded an unexpected insight into the
+constitution of matter and its relations with thermal and electric
+energy, and they open up a vast field for future inquiry into some of
+the deepest problems of physics. Other important steps, in the same
+direction, have been effected by investigations into the absorption of
+radiant heat proceeding from different sources by solid, fluid, and
+gaseous bodies. And it is a curious example of the interconnection of
+the various branches of physical science, that some of the results
+thus obtained have proved of great importance in meteorology.
+
+[Sidenote: The spectroscope.]
+
+The existence of numerous dark lines, constant in their number and
+position in the various regions of the solar spectrum, was made out by
+Fraunhofer in the early part of the present century, but more than
+forty years elapsed before their causes were ascertained and their
+importance recognised. Spectroscopy, which then took its rise, is
+probably that employment of physical knowledge, already won, as a
+means of further acquisition, which most impresses the imagination.
+For it has suddenly and immensely enlarged our power of overcoming the
+obstacles which almost infinite minuteness on the one hand, and almost
+infinite distance on the other, have hitherto opposed to the
+recognition of the presence and the condition of matter. One
+eighteen-millionth of a grain of sodium in the flame of a spirit-lamp
+may be detected by this instrument; and, at the same time, it gives
+trust-worthy indications of the material constitution not only of the
+sun, but of the farthest of those fixed stars and nebulć which afford
+sufficient light to affect the eye, or the photographic plate, of the
+inquirer.
+
+[Sidenote: Electricity.]
+
+The mathematical and experimental elucidation of the phenomena of
+electricity, and the study of the relations of this form of energy
+with chemical and thermal action, had made extensive progress before
+1837. But the determination of the influence of magnetism on light,
+the discovery of diamagnetism, of the influence of crystalline
+structure on magnetism, and the completion of the mathematical theory
+of electricity, all belong to the present epoch. To it also appertain
+the practical execution and the working out of the results of the
+great international system of observations on terrestrial magnetism,
+suggested by Humboldt in 1836; and the invention of instruments of
+infinite delicacy and precision for the quantitative determination of
+electrical phenomena. The voltaic battery has received vast
+improvements; while the invention of magneto-electric engines and of
+improved means of producing ordinary electricity has provided sources
+of electrical energy vastly superior to any before extant in power,
+and far more convenient for use.
+
+It is perhaps this branch of physical science which may claim the palm
+for its practical fruits, no less than for the aid which it has
+furnished to the investigation of other parts of the field of physical
+science. The idea of the practicability of establishing a
+communication between distant points, by means of electricity, could
+hardly fail to have simmered in the minds of ingenious men since,
+well nigh a century ago, experimental proof was given that electric
+disturbances could be propagated through a wire twelve thousand feet
+long. Various methods of carrying the suggestion into practice had
+been carried out with some degree of success; but the system of
+electric telegraphy, which, at the present time, brings all parts of
+the civilised world within a few minutes of one another, originated
+only about the commencement of the epoch under consideration. In its
+influence on the course of human affairs, this invention takes its
+place beside that of gunpowder, which tended to abolish the physical
+inequalities of fighting men; of printing, which tended to destroy the
+effect of inequalities in wealth among learning men; of steam
+transport, which has done the like for travelling men. All these gifts
+of science are aids in the process of levelling up; of removing the
+ignorant and baneful prejudices of nation against nation, province
+against province, and class against class; of assuring that social
+order which is the foundation of progress, which has redeemed Europe
+from barbarism, and against which one is glad to think that those who,
+in our time, are employing themselves in fanning the embers of ancient
+wrong, in setting class against class, and in trying to tear asunder
+the existing bonds of unity, are undertaking a futile struggle. The
+telephone is only second in practical importance to the electric
+telegraph. Invented, as it were, only the other day, it has already
+taken its place as an appliance of daily life. Sixty years ago, the
+extraction of metals from their solutions, by the electric current,
+was simply a highly interesting scientific fact. At the present day,
+the galvano-plastic art is a great industry; and, in combination with
+photography, promises to be of endless service in the arts. Electric
+lighting is another great gift of science to civilisation, the
+practical effects of which have not yet been fully developed, largely
+on account of its cost. But those whose memories go back to the
+tinder-box period, and recollect the cost of the first lucifer
+matches, will not despair of the results of the application of science
+and ingenuity to the cheap production of anything for which there is a
+large demand.
+
+The influence of the progress of electrical knowledge and invention
+upon that of investigation in other fields of science is highly
+remarkable. The combination of electrical with mechanical contrivances
+has produced instruments by which, not only may extremely small
+intervals of time be exactly measured, but the varying rapidity of
+movements, which take place in such intervals and appear to the
+ordinary sense instantaneous, is recorded. The duration of the winking
+of an eye is a proverbial expression for an instantaneous action;
+but, by the help of the revolving cylinder and the electrical
+marking-apparatus, it is possible to obtain a graphic record of such
+an action, in which, if it endures a second, that second shall be
+subdivided into a hundred, or a thousand, equal parts, and the state
+of the action at each hundredth, or thousandth, of a second exhibited.
+In fact, these instruments may be said to be time-microscopes. Such
+appliances have not only effected a revolution in physiology, by the
+power of analysing the phenomena of muscular and nervous activity
+which they have conferred, but they have furnished new methods of
+measuring the rate of movement of projectiles to the artillerist.
+Again, the microphone, which renders the minutest movements audible,
+and which enables a listener to hear the footfall of a fly, has
+equipped the sense of hearing with the means of entering almost as
+deeply into the penetralia of nature, as does the sense of sight.
+
+[Sidenote: Photography as an instrument of science.]
+
+That light exerts a remarkable influence in bringing about certain
+chemical combinations and decompositions was well known fifty years
+ago, and various more or less successful attempts to produce permanent
+pictures, by the help of that knowledge, had already been made. It was
+not till 1839, however, that practical success was obtained; but the
+'daguerreotypes' were both cumbrous and costly, and photography would
+never have attained its present important development had not the
+progress of invention substituted paper and glass for the silvered
+plates then in use. It is not my affair to dwell upon the practical
+application of the photography of the present day, but it is germane
+to my purpose to remark that it has furnished a most valuable
+accessory to the methods of recording motions and lapse of time
+already in existence. In the hands of the astronomer and the
+meteorologist, it has yielded means of registering terrestrial, solar,
+planetary, and stellar phenomena, independent of the sources of error
+attendant on ordinary observation; in the hands of the physicist, not
+only does it record spectroscopic phenomena with unsurpassable ease
+and precision, but it has revealed the existence of rays having
+powerful chemical energy, or beyond the visible limits of either end
+of the spectrum; while, to the naturalist, it furnishes the means by
+which the forms of many highly complicated objects may be represented,
+without that possibility of error which is inherent in the work of the
+draughtsman. In fact, in many cases, the stern impartiality of
+photography is an objection to its employment: it makes no distinction
+between the important and the unimportant; and hence photographs of
+dissections, for example, are rarely so useful as the work of a
+draughtsman who is at once accurate and intelligent.
+
+[Sidenote: Astronomy,]
+
+The determination of the existence of a new planet, Neptune, far
+beyond the previously known bounds of the solar system, by
+mathematical deduction from the facts of perturbation; and the
+immediate confirmation of that determination, in the year 1846, by
+observers who turned their telescopes into the part of the heavens
+indicated as its place, constitute a remarkable testimony of nature to
+the validity of the principles of the astronomy of our time. In
+addition, so many new asteroids have been added to those which were
+already known to circulate in the place which theoretically should be
+occupied by a planet, between Mars and Jupiter, that their number now
+amounts to between two and three hundred. I have already alluded to
+the extension of our knowledge of the nature of the heavenly bodies by
+the employment of spectroscopy. It has not only thrown wonderful
+light upon the physical and chemical constitution of the sun, fixed
+stars, and nebulć, and comets, but it holds out a prospect of
+obtaining definite evidence as to the nature of our so-called
+elementary bodies.
+
+[Sidenote: its relation to geology.]
+
+The application of the generalisations of thermotics to the problem of
+the duration of the earth, and of deductions from tidal phenomena to
+the determination of the length of the day and of the time of
+revolution of the moon, in past epochs of the history of the universe;
+and the demonstration of the competency of the great secular changes,
+known under the general name of the precession of the equinoxes, to
+cause corresponding modifications in the climate of the two
+hemispheres of our globe, have brought astronomy into intimate
+relation with geology. Geology, in fact, proves that, in the course of
+the past history of the earth, the climatic conditions of the same
+region have been widely different, and seeks the explanation of this
+important truth from the sister sciences. The facts that, in the
+middle of the Tertiary epoch, evergreen trees abounded within the
+arctic circle; and that, in the long subsequent Quaternary epoch, an
+arctic climate, with its accompaniment of gigantic glaciers, obtained
+in the northern hemisphere, as far south as Switzerland and Central
+France, are as well established as any truths of science. But, whether
+the explanation of these extreme variations in the mean temperature of
+a great part of the northern hemisphere is to be sought in the
+concomitant changes in the distribution of land and water surfaces of
+which geology affords evidence, or in astronomical conditions, such as
+those to which I have referred, is a question which must await its
+answer from the science of the future.
+
+[Sidenote: Biological sciences.]
+
+[Sidenote: The 'cell theory.']
+
+Turning now to the great steps in that progress which the biological
+sciences have made since 1837, we are met, on the threshold of our
+epoch, with perhaps the greatest of all--namely, the promulgation by
+Schwann, in 1839, of the generalisation known as the 'cell theory,'
+the application and extension of which by a host of subsequent
+investigators has revolutionised morphology, development, and
+physiology. Thanks to the immense series of labors thus inaugurated,
+the following fundamental truths have been established.
+
+[Sidenote: Fundamental truths established.]
+
+All living bodies contain substances of closely similar physical and
+chemical composition, which constitute the physical basis of life,
+known as protoplasm. So far as our present knowledge goes, this takes
+its origin only from pre-existing protoplasm.
+
+All complex living bodies consist, at one period of their existence,
+of an aggregate of minute portions of such substance, of similar
+structure, called cells, each cell having its own life independent of
+the others, though influenced by them.
+
+All the morphological characters of animals and plants are the results
+of the mode of multiplication, growth, and structural metamorphosis of
+these cells, considered as morphological units.
+
+All the physiological activities of animals and plants--assimilation,
+secretion, excretion, motion, generation--are the expression of the
+activities of the cells considered as physiological units. Each
+individual, among the higher animals and plants, is a synthesis of
+millions of subordinate individualities. Its individuality, therefore,
+is that of a 'civitas' in the ancient sense, or that of the Leviathan
+of Hobbes.
+
+There is no absolute line of demarcation between animals and plants.
+The intimate structure, and the modes of change, in the cells of the
+two are fundamentally the same. Moreover, the higher forms are
+evolved from lower, in the course of their development, by analogous
+processes of differentiation, coalescence, and reduction in both the
+vegetable and the animal worlds.
+
+At the present time, the cell theory, in consequence of recent
+investigations into the structure and metamorphosis of the 'nucleus,'
+is undergoing a new development of great significance, which, among
+other things, foreshadows the possibility of the establishment of a
+physical theory of heredity, on a safer foundation than those which
+Buffon and Darwin have devised.
+
+[Sidenote: Spontaneous generation disproved.]
+
+The popular belief in abiogenesis, or the so-called 'spontaneous'
+generation of the lower forms of life, which was accepted by all the
+philosophers of antiquity, held its ground down to the middle of the
+seventeenth century. Notwithstanding the frequent citation of the
+phrase, wrongfully attributed to Harvey, 'Omne vivum ex ovo,' that
+great physiologist believed in spontaneous generation as firmly as
+Aristotle did. And it was only in the latter part of the seventeenth
+century, that Redi, by simple and well-devised experiments,
+demonstrated that, in a great number of cases of supposed spontaneous
+generation, the animals which made their appearance owed their origin
+to the ordinary process of reproduction, and thus shook the ancient
+doctrine to its foundations. In the middle of the eighteenth century,
+it was revived, in a new form, by Needham and Buffon; but the
+experiments of Spallanzani enforced the conclusions of Redi, and
+compelled the advocates of the occurrence of spontaneous generation to
+seek evidence for their hypothesis only among the parasites and the
+lowest and minutest organisms. It is just fifty years since Schwann
+and others proved that, even with respect to them, the supposed
+evidence of abiogenesis was untrustworthy.
+
+During the present epoch, the question, whether living matter can be
+produced in any other way than by the physiological activity of other
+living matter, has been discussed afresh with great vigor; and the
+problem has been investigated by experimental methods of a precision
+and refinement unknown to previous investigators. The result is that
+the evidence in favor of abiogenesis has utterly broken down, in every
+case which has been properly tested. So far as the lowest and minutest
+organisms are concerned, it has been proved that they never make their
+appearance, if those precautions by which their germs are certainly
+excluded are taken. And, in regard to parasites, every case which
+seemed to make for their generation from the substance of the animal,
+or plant, which they infest has been proved to have a totally
+different significance. Whether not-living matter may pass, or ever
+has, under any conditions, passed into living matter, without the
+agency of pre-existing living matter, necessarily remains an open
+question; all that can be said is that it does not undergo this
+metamorphosis under any known conditions. Those who take a monistic
+view of the physical world may fairly hold abiogenesis as a pious
+opinion, supported by analogy and defended by our ignorance. But, as
+matters stand, it is equally justifiable to regard the physical world
+as a sort of dual monarchy. The kingdoms of living matter and of
+not-living matter are under one system of laws, and there is a perfect
+freedom of exchange and transit from one to the other. But no claim to
+biological nationality is valid except birth.
+
+[Sidenote: Morphology.]
+
+In the department of anatomy and development, a host of accurate and
+patient inquirers, aided by novel methods of preparation, which
+enable the anatomist to exhaust the details of visible structure and
+to reproduce them with geometrical precision, have investigated every
+important group of living animals and plants, no less than the fossil
+relics of former faunć and florć. An enormous addition has thus been
+made to our knowledge, especially of the lower forms of life, and it
+may be said that morphology, however inexhaustible in detail, is
+complete in its broad features. Classification, which is merely a
+convenient summary expression of morphological facts, has undergone a
+corresponding improvement. The breaks which formerly separated our
+groups from one another, as animals from plants, vertebrates from
+invertebrates, cryptogams from phanerogams, have either been filled
+up, or shown to have no theoretical significance. The question of the
+position of man, as an animal, has given rise to much disputation,
+with the result of proving that there is no anatomical or
+developmental character by which he is more widely distinguished from
+the group of animals most nearly allied to him, than they are from one
+another. In fact, in this particular, the classification of Linnćus
+has been proved to be more in accordance with the facts than those of
+most of his successors.
+
+[Sidenote: Anthropology.]
+
+The study of man, as a genus and species of the animal world,
+conducted with reference to no other considerations than those which
+would be admitted by the investigator of any other form of animal
+life, has given rise to a special branch of biology, known, as
+Anthropology, which has grown with great rapidity. Numerous societies
+devoted to this portion of science have sprung up, and the energy of
+its devotees has produced a copious literature. The physical
+characters of the various races of men have been studied with a
+minuteness and accuracy heretofore unknown; and demonstrative
+evidence of the existence of human contemporaries of the extinct
+animals of the latest geological epoch has been obtained, physical
+science has thus been brought into the closest relation with history
+and with archćology; and the striking investigations which, during our
+time, have put beyond doubt the vast antiquity of Babylonian and
+Egyptian civilisation, are in perfect harmony with the conclusions of
+anthropology as to the antiquity of the human species.
+
+Classification is a logical process which consists in putting together
+those things which are like and keeping asunder those which are
+unlike; and a morphological classification, of course, takes notes
+only of morphological likeness and unlikeness. So long, therefore, as
+our morphological knowledge was almost wholly confined to anatomy, the
+characters of groups were solely anatomical; but as the phenomena of
+embryology were explored, the likeness and unlikeness of individual
+development had to be taken into account; and, at present, the study
+of ancestral evolution introduces a new element of likeness and
+unlikeness which is not only eminently deserving of recognition, but
+must ultimately predominate over all others. A classification which
+shall represent the process of ancestral evolution is, in fact, the
+end which the labors of the philosophical taxonomist must keep in
+view. But it is an end which cannot be attained until the progress of
+palćontology has given us far more insight than we yet possess, into
+the historical facts of the case. Much of the speculative 'phylogeny,'
+which abounds among my present contemporaries, reminds me very
+forcibly of the speculative morphology, unchecked by a knowledge of
+development, which was rife in my youth. As hypothesis, suggesting
+inquiry in this or that direction, it is often extremely useful; but,
+when the product of such speculation is placed on a level with those
+generalisations of morphological truths which are represented by the
+definitions of natural groups, it tends to confuse fancy with fact and
+to create mere confusion. We are in danger of drifting into a new
+'Natur-Philosophie' worse than the old, because there is less excuse
+for it. Boyle did great service to science by his 'Sceptical Chemist,'
+and I am inclined to think that, at the present day, a 'Sceptical
+Biologist' might exert an equally beneficent influence.
+
+[Sidenote: Physiology.]
+
+Whoso wishes to gain a clear conception of the progress of physiology,
+since 1837, will do well to compare Müller's 'Physiology,' which
+appeared in 1835, and Drapiez's edition of Richard's 'Nouveaux
+Eléments de Botanique,' published in 1837, with any of the present
+handbooks of animals and vegetable physiology. Müller's work was a
+masterpiece, unsurpassed since the time of Haller, and Richard's book
+enjoyed a great reputation at the time; but their successors transport
+one into a new world. That which characterises the new physiology is
+that it is permeated by, and indeed based upon, conceptions which,
+though not wholly absent, are but dawning on the minds of the older
+writers.
+
+Modern physiology sets forth as its chief ends: Firstly, the
+ascertainment of the facts and conditions of cell-life in general.
+Secondly, in composite organisms, the analysis of the functions of
+organs into those of the cells of which they are composed. Thirdly,
+the explication of the processes by which this local cell-life is
+directly, or indirectly, controlled and brought into relation with the
+life of the rest of the cells which compose the organism. Fourthly,
+the investigation of the phenomena of life in general, on the
+assumption that the physical and chemical processes which take place
+in the living body are of the same order as those which take place out
+of it; and that whatever energy is exerted in producing such phenomena
+is derived from the common stock of energy in the universe. In the
+fifth place, modern physiology investigates the relation between
+physical and psychical phenomena, on the assumption that molecular
+changes in definite portions of nervous matter stand in the relation
+of necessary antecedents to definite mental states and operations. The
+work which has been done in each of the directions here indicated is
+vast, and the accumulation of solid knowledge, which has been
+effected, is correspondingly great. For the first time in the history
+of science, physiologists are now in the position to say that they
+have arrived at clear and distinct, though by no means complete,
+conceptions of the manner in which the great functions of
+assimilation, respiration, secretion, distribution of nutriment,
+removal of waste products, motion, sensation, and reproduction are
+performed; while the operation of the nervous system, as a regulative
+apparatus, which influences the origination and the transmission of
+manifestations of activity, either within itself or in other organs,
+has been largely elucidated.
+
+[Sidenote: Practical value of physiological discovery.]
+
+I have pointed out, in an earlier part of this chapter, that the
+history of all branches of science proves that they must attain a
+considerable stage of development before they yield practical
+'fruits;' and this is eminently true of physiology. It is only within
+the present epoch, that physiology and chemistry have reached the
+point at which they could offer a scientific foundation to
+agriculture; and it is only within the present epoch, that zoology and
+physiology have yielded any very great aid to pathology and hygiene.
+But within that time, they have already rendered highly important
+services by the exploration of the phenomena of parasitism. Not only
+have the history of the animal parasites, such as the tapeworms and
+the trichina, which infest men and animals, with deadly results, been
+cleared up by means of experimental investigations, and efficient
+modes of prevention deduced from the data so obtained; but the
+terrible agency of the parasitic fungi and of the infinitesimally
+minute microbes, which work far greater havoc among plants and
+animals, has been brought to light. The 'particulate' or 'germ' theory
+of disease, as it is called, long since suggested, has obtained a firm
+foundation, in so far as it has been proved to be true in respect of
+sundry epidemic disorders. Moreover, it has theoretically justified
+prophylactic measures, such as vaccination, which formerly rested on a
+merely empirical basis; and it has been extended to other diseases
+with excellent results. Further, just as the discovery of the cause of
+scabies proved the absurdity of many of the old prescriptions for the
+prevention and treatment of that disease; so the discovery of the
+cause of splenic fever, and other such maladies, has given a new
+direction to prophylactic and curative measures against the worst
+scourges of humanity. Unless the fanaticism of philozoic sentiment
+overpowers the voice of philanthropy, and the love of dogs and cats
+supersedes that of one's neighbor, the progress of experimental
+physiology and pathology will, indubitably, in course of time, place
+medicine and hygiene upon a rational basis. Two centuries ago England
+was devastated by the plague; cleanliness and common sense were enough
+to free us from its ravages. One century since, small-pox was almost
+as great a scourge; science, though working empirically, and almost in
+the dark, has reduced that evil to relative insignificance. At the
+present time, science, working in the light of clear knowledge, has
+attacked splenic fever and has beaten it; it is attacking hydrophobia
+with no mean promise of success; sooner or later it will deal, in the
+same way, with diphtheria, typhoid and scarlet fever. To one who has
+seen half a street swept clear of its children, or has lost his own by
+these horrible pestilences, passing one's offspring through the fire
+to Moloch seems humanity, compared with the proposal to deprive them
+of half their chances of health and life because of the discomfort to
+dogs and cats, rabbits and frogs, which may be involved in the search
+for means of guarding them.
+
+[Sidenote: Scientific exploration.]
+
+An immense extension has been effected in our knowledge of the
+distribution of plants and animals; and the elucidation of the causes
+which have brought about that distribution has been greatly advanced.
+The establishment of meteorological observations by all civilised
+nations, has furnished a solid foundation to climatology; while a
+growing sense of the importance of the influence of the 'struggle for
+existence' affords a wholesome check to the tendency to overrate the
+influence of climate on distribution. Expeditions, such as that of the
+Challenger,' equipped, not for geographical exploration and discovery,
+but for the purpose of throwing light on problems of physical and
+biological science, have been sent out by our own and other
+Governments, and have obtained stores of information of the greatest
+value. For the first time, we are in possession of something like
+precise knowledge of the physical features of the deep seas, and of
+the living population of the floor of the ocean. The careful and
+exhaustive study of the phenomena presented by the accumulations of
+snow and ice, in polar and mountainous regions, which has taken place
+in our time, has not only revealed to the geologist an agent of
+denudation and transport, which has slowly and quietly produced
+effects, formerly confidently referred to diluvial catastrophes, but
+it has suggested new methods of accounting for various puzzling facts
+of distribution.
+
+[Sidenote: Palćontology.]
+
+Palćontology, which treats of the extinct forms of life and their
+succession and distribution upon our globe, a branch of science which
+could hardly be said to exist a century ago, has undergone a wonderful
+development in our epoch. In some groups of animals and plants, the
+extinct representatives, already known, are more numerous and
+important than the living. There can be no doubt that the existing
+Fauna and Flora is but the last term of a long series of equally
+numerous contemporary species, which have succeeded one another, by
+the slow and gradual substitution of species for species, in the vast
+interval of time which has elapsed between the deposition of the
+earliest fossiliferous strata and the present day. There is no
+reasonable ground for believing that the oldest remains yet obtained
+carry us even near the beginnings of life. The impressive warnings of
+Lyell against hasty speculations, based upon negative evidence, have
+been fully justified; time after time, highly organised types have
+been discovered in formations of an age in which the existence of such
+forms of life had been confidently declared to be impossible. The
+western territories of the United States alone have yielded a world of
+extinct animal forms, undreamed of fifty years ago. And, wherever
+sufficiently numerous series of the remains of any given group, which
+has endured for a long space of time, are carefully examined, their
+morphological relations are never in discordance with the requirements
+of the doctrine of evolution, and often afford convincing evidence of
+it. At the same time, it has been shown that certain forms persist
+with very little change, from the oldest to the newest fossiliferous
+formations; and thus show that progressive development is a
+contingent, and not a necessary result, of the nature of living
+matter.
+
+[Sidenote: Geology.]
+
+Geology is, as it were, the biology of our planet as a whole. In so
+far as it comprises the surface configuration and the inner structure
+of the earth, it answers to morphology; in so far as it studies
+changes of condition and their causes, it corresponds with physiology;
+in so far as it deals with the causes which have effected the progress
+of the earth from its earliest to its present state, it forms part of
+the general doctrine of evolution. An interesting contrast between the
+geology of the present day and that of half a century ago, is
+presented by the complete emancipation of the modern geologist from
+the controlling and perverting influence of theology, all-powerful at
+the earlier date. As the geologist of my young days wrote, he had one
+eye upon fact, and the other on Genesis; at present, he wisely keeps
+both eyes on fact, and ignores the pentateuchal mythology altogether.
+The publication of the 'Principles of Geology' brought upon its
+illustrious author a period of social ostracism; the instruction given
+to our children is based upon those principles. Whewell had the
+courage to attack Lyell's fundamental assumption (which surely is a
+dictate of common sense) that we ought to exhaust known causes before
+seeking for the explanation of geological phenomena in causes of which
+we have no experience. But geology has advanced to its present state
+by working from Lyell's[J] axiom; and, to this day, the record of the
+stratified rocks affords no proof that the intensity or the rapidity
+of the causes of change has ever varied, between wider limits, than
+those between which the operations of nature have taken place in the
+youngest geological epochs.
+
+An incalculable benefit has accrued to geological science from the
+accurate and detailed surveys, which have now been executed by skilled
+geologists employed by the Governments of all parts of the civilised
+world. In geology, the study of large maps is as important as it is
+said to be in politics; and sections, on a true scale, are even more
+important, in so far as they are essential to the apprehension of the
+extraordinary insignificance of geological perturbations in relation
+to the whole mass of our planet. It should never be forgotten that
+what we call 'catastrophes,' are, in relation to the earth, changes,
+the equivalents of which would be well represented by the development
+of a few pimples, or the scratch of a pin, on a man's head. Vast
+regions of the earth's surface remain geologically unknown; but the
+area already fairly explored is many times greater than it was in
+1837; and, in many parts of Europe and the United States, the
+structure of the superficial crust of the earth has been investigated
+with great minuteness.
+
+The parallel between Biology and Geology, which I have drawn, is
+further illustrated by the modern growth of that branch of the science
+known as Petrology, which answers to Histology, and has made the
+microscope as essential an instrument to the geological as to the
+biological investigator.
+
+The evidence of the importance of causes now in operation has been
+wonderfully enlarged by the study of glacial phenomena; by that of
+earthquakes and volcanoes; and by that of the efficacy of heat and
+cold, wind, rain, and rivers as agents of denudation and transport. On
+the other hand, the exploration of coral reefs and of the deposits now
+taking place at the bottom of the great oceans, has proved that, in
+animal and plant life, we have agents of reconstruction of a potency
+hitherto unsuspected.
+
+There is no study better fitted than that of geology to impress upon
+men of general culture that conviction of the unbroken sequence of the
+order of natural phenomena, throughout the duration of the universe,
+which is the great, and perhaps the most important, effect of the
+increase of natural knowledge.
+
+
+THE END.
+
+FOOTNOTES:
+
+     [A] There are excellent remarks to the same effect in
+     Zeller's _Philosophie der Griechen_, Theil II. Abth. ii p.
+     407, and in Eucken's _Die Methode der Aristotelischen,
+     Forschung_, pp. 136 _et seq_.
+
+     [B] Fresnel, after a brilliant career of discovery in some
+     of the most difficult regions of physico-mathematical
+     science, died at thirty-nine years of age. The following
+     passage of a letter from him to Young (written in November
+     1824), quoted by Whewell, so aptly illustrates the spirit
+     which animates the scientific inquirer that I may cite it:
+
+          'For a long time that sensibility, or that vanity,
+          which people call love of glory is munch blunted
+          in me. I labor much less to catch the suffrages of
+          the public than to obtain an inward approval which
+          has always been the mental reward of my efforts.
+          Without doubt I have often wanted the spur of
+          vanity to excite me to pursue my researches in
+          moments of disgust and discouragement. But all the
+          compliments which I have received from M.M. Arago,
+          De Laplace, or Biot, never gave me so much
+          pleasure as the discovery of a theoretical truth
+          or the confirmation of a calculation by
+          experiment.'
+
+     [C] 'Mémorable exemple de l'impuissance des recherches
+     collectives appliquées ŕ la découverte des vérités
+     nouvelles!' says one of the most distinguished of living
+     French _savants_ of the corporate chemical work of the old
+     Académie des Sciences. (See Berthelot, _Science et
+     Philosophie_, p. 201.)
+
+     [D] I am particularly indebted to my friend and colleague
+     Professor Rücker, F.R.S., for the many acute criticisms and
+     suggestions on my remarks respecting the ultimate problems
+     of physics, with which he has favored me, and by which I
+     have greatly profited.
+
+     [E] I am aware that this proposition may be challenged. It
+     may be said, for example, that, on the hypothesis of
+     Boscovich, matter has no extension, being reduced to
+     mathematical points serving as centres of 'forces.' But as
+     the 'forces' of the various centres are conceived to limit
+     one another's action in such a manner that an area around
+     each centre has an individuality of its own extension comes
+     back in the form of that area. Again, a very eminent
+     mathematician and physicist--the late Clerk Maxwell--has
+     declared that impenetrability is not essential to our
+     notions of matter, and that two atoms may conceivably occupy
+     the same space. I am loth to dispute any dictum of a
+     philosopher as remarkable for the subtlety of his intellect
+     as for his vast knowledge; but the assertion that one and
+     the same point or area of space can have different
+     (conceivably opposite) attributes appears to me to violate
+     the principle of contradiction, which is the foundation not
+     only of physical science, but of logic in general. It means
+     that A can be not-A.
+
+     [F] 'Molecule' would be the more appropriate name for such a
+     particle. Unfortunately, chemists employ this term in a
+     special sense, as a name for an aggregation of their
+     smallest particles, for which they retain the designation of
+     'atoms.'
+
+     [G] 'At present more organic analyses are made in a single
+     day than were accomplished before Liebig's time in a whole
+     year.'--Hofmann, _Faraday Lecture_, p. 46.
+
+     [H] In the preface to his _Mécanique Chimique_ M. Berthelot
+     declares his object to be 'ramener la chimie tout entirčre
+     ... aux męmes principes mécaniques qui régissent déjŕ les
+     diverses branches de la physique.'
+
+     [I] This is the more curious, as Ampčre's hypothesis that
+     vibrations of molecules, causing and caused by vibrations of
+     the ether, constitute heat, is discussed. See vol. ii. p.
+     587, 2nd ed. In the _Philosophy of the Inductive Sciences_,
+     2nd ed., 1847, p. 239, Whewell remarks, _ŕ propos_ of
+     Bacon's definition of heat, 'that it is an expansive,
+     restrained motion, modified in certain ways, and exerted in
+     the smaller particles of the body;' that 'although the exact
+     nature of heat is still an obscure and controverted matter,
+     the science of heat now consists of many important truths;
+     and that to none of these truths is there any approximation
+     in Bacon's essay.' In point of fact, Bacon's statement,
+     however much open to criticism, does contain a distinct
+     approximation to the most important of all the truths
+     respecting heat which had been discovered when Whewell
+     wrote.
+
+     [J] Perhaps I ought rather to say Button's axiom. For that
+     great naturalist and writer embodied the principles of sound
+     geology in a pithy phrase of the _Théoris de la Terre_:
+     'Pour juger de ce qui est arrivé, et męme de ce qui
+     arrivera, nous n'avons qu'ŕ examiner ce qui arrive.'
+
+
+
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+LIGHT AND ELECTRICITY.
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+     With an Appendix and numerous Illustrations. Cloth, $1.50.
+
+ADDRESS delivered before the British Association, assembled at
+Belfast. Revised with Additions.
+     12mo. Paper, 50 cents.
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+Question of Diamagnetic Polarity. With Ten Plates.
+     12mo, cloth. Price, $1.50.
+
+
+
+
+CHARLES DARWIN'S WORKS.
+
+
+ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, OR THE PRESERVATION
+OF FAVORED RACES IN THE STRUGGLE FOR LIFE. From sixth and last London
+edition.
+     2 vols., 12mo. Cloth, $4.00.
+
+DESCENT OF MAN, AND SELECTION IN RELATION TO SEX. With many
+Illustrations. A new edition.
+     12mo. Cloth, $3.00.
+
+JOURNAL OF RESEARCHES INTO THE NATURAL HISTORY AND GEOLOGY OF
+COUNTRIES VISITED DURING THE VOYAGE OF H.M.S. BEAGLE ROUND THE WORLD.
+New edition.
+     12mo. Cloth, $2.00.
+
+EMOTIONAL EXPRESSIONS OF MAN AND THE LOWER ANIMALS.
+     12mo. Cloth, $3.50.
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+THE VARIATIONS OF ANIMALS AND PLANTS UNDER DOMESTICATION. With a
+Preface, by Professor ASA GRAY.
+     2 vols. Illustrated. Cloth, $5.00.
+
+INSECTIVOROUS PLANTS.
+     12mo. Cloth, $2.00.
+
+MOVEMENTS AND HABITS OF CLIMBING PLANTS.
+     With Illustrations. 12mo. Cloth, $1.25.
+
+THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILIZED BY INSECTS.
+     Revised edition, with Illustrations. 12mo. Cloth, $1.75.
+
+THE EFFECTS OF CROSS AND SELF FERTILIZATION IN THE VEGETABLE
+KINGDOM.
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+DIFFERENT FORMS OF FLOWERS ON PLANTS OF THE SAME SPECIES. With
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+     12mo. Cloth, $1.50.
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+THE POWER OF MOVEMENT IN PLANTS. By CHARLES DARWIN, LL.D., F.R.S.,
+assisted by FRANCIS DARWIN.
+     With Illustrations. 12mo. Cloth, $2.00.
+
+THE FORMATION OF VEGETABLE MOULD THROUGH THE ACTION OF WORMS. With
+Observations on their Habits.
+     With Illustrations. 12mo. Cloth, $1.50.
+
+
+
+
+ALEXANDER BAIN'S WORKS.
+
+
+THE SENSES AND THE INTELLECT. By ALEXANDER BAIN. LL.D., Professor of
+Logic in the University of Aberdeen.
+     8vo. Cloth, $5.00.
+     The object of this treatise is to give a full and systematic
+     account of two principal divisions of the science of mind--the
+     senses and the intellect. The value of the third edition of the
+     work is greatly enhanced by an account of the psychology of
+     Aristotle, which has been contributed by Mr. Grote.
+
+THE EMOTIONS AND THE WILL. By ALEXANDER BAIN, LL.D.
+     8vo. Cloth, $5.00.
+     The present publication la a sequel to the former one on "The
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+
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+Philosophy. Designed as a Text-book for High-Schools and Colleges. By
+ALEXANDER BAIN, LL.D.
+     12mo. Cloth, leather back, $1.50.
+     This present volume is an abstract of two voluminous works, "The
+     Senses and the intellect" and "The Emotions and the Will," and
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+     the Moral Faculty. The second division--on the Ethical
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+MIND AND BODY. Theories of their Relations. By ALEXANDER BAIN, LL.D.
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+     "A forcible statement of the connection between mind and body,
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+     Revised edition, 12mo. Cloth, leather back, $2.00.
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+The Project Gutenberg EBook of The Advance of Science in the Last
+Half-Century, by T.H. (Thomas Henry) Huxley
+
+This eBook is for the use of anyone anywhere at no cost and with
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+Title: The Advance of Science in the Last Half-Century
+
+Author: T.H. (Thomas Henry) Huxley
+
+Release Date: March 4, 2005 [EBook #15253]
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+*** START OF THIS PROJECT GUTENBERG EBOOK ADVANCE OF SCIENCE ***
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+
+
+
+<h1>THE ADVANCE OF SCIENCE</h1>
+<h1>IN THE LAST HALF-CENTURY</h1>
+
+<h3>BY</h3>
+
+<h2>T.H. HUXLEY, F.R.S.</h2>
+
+<p class="center">NEW YORK</p>
+
+<p class="center">D. APPLETON AND COMPANY</p>
+
+<p class="center">1889</p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="THE_ADVANCE_OF_SCIENCE_IN_THE_LAST_HALF_CENTURY" id="THE_ADVANCE_OF_SCIENCE_IN_THE_LAST_HALF_CENTURY" />THE ADVANCE OF SCIENCE IN THE LAST HALF-CENTURY</h2>
+
+<div class="sidenote">Recent industrial progress</div>
+
+<p>The most obvious and the most distinctive features of the History of
+Civilisation, during the last fifty years, is the wonderful increase
+of industrial production by the application of machinery, the
+improvement of old technical processes and the invention of new ones,
+accompanied by an even more remarkable development of old and new
+means of locomotion and intercommunication. By this rapid and vast
+multiplication of the commodities and conveniences of existence, the
+general standard of comfort has been raised, the ravages of pestilence
+and famine have been checked, and the natural obstacles, which time
+and space offer to mutual intercourse, have been reduced in a manner,
+and to an extent, unknown to former ages. The diminution or removal of
+local ignorance and prejudice, the creation of common interests among
+the most widely separated peoples, and the strengthening of the forces
+of the organisation of the commonwealth against those of political or
+social anarchy, thus effected, have exerted an influence on the
+present and future fortunes of mankind the full significance of which
+may be divined, but cannot, as yet, be estimated at its full value.</p>
+
+<div class="sidenote">caused by the increase of physical science</div>
+
+<p>This revolution&mdash;for it is nothing less&mdash;in the political and social
+aspects of modern civilisation has been preceded, accompanied, and in
+great measure caused, by a less obvious, but no less marvellous,
+increase of natural knowledge, and especially of that part of it which
+is known as Physical Science, in consequence of the application of
+scientific method to the investigation of the phenomena of the
+material world. Not that the growth of physical science is an
+exclusive prerogative of the Victorian age. Its present strength and
+volume merely indicate the highest level of a stream which took its
+rise, alongside of the primal founts of Philosophy, Literature, and
+Art, in ancient Greece; and, after being dammed up for a thousand
+years, once more began to flow three centuries ago.</p>
+
+<div class="sidenote">Greek and medi&aelig;val science.</div>
+
+<p>It may be doubted if even-handed justice, as free from fulsome
+panegyric as from captious depreciation, has ever yet been dealt out
+to the sages of antiquity who, for eight centuries, from the time of
+Thales to that of Galen, toiled at the foundations of physical
+science. But, without entering into the discussion of that large
+question, it is certain that the labors of these early workers in the
+field of natural knowledge were brought to a standstill by the decay
+and disruption of the Roman Empire, the consequent disorganisation of
+society, and the diversion of men's thoughts from sublunary matters to
+the problems of the supernatural world suggested by Christian dogma in
+the Middle Ages. And, notwithstanding sporadic attempts to recall men
+to the investigation of nature, here and there, it was not until the
+fifteenth and sixteenth centuries that physical science made a new
+start, founding itself, at first, altogether upon that which had been
+done by the Greeks. Indeed, it must be admitted that the men of the
+Renaissance, though standing on the shoulders of the old philosophers,
+were a long time before they saw as much as their forerunners had
+done.</p>
+
+<p>The first serious attempts to carry further the unfinished work of
+Archimedes, Hipparchus, and Ptolemy, of Aristotle and of Galen,
+naturally enough arose among the astronomers and the physicians. For
+the imperious necessity of seeking some remedy for the physical ills
+of life had insured the preservation of more or less of the wisdom of
+Hippocrates and his successors, and, by a happy conjunction of
+circumstances, the Jewish and the Arabian physicians and philosophers
+escaped many of the influences which, at that time, blighted natural
+knowledge in the Christian world. On the other hand, the superstitious
+hopes and fears which afforded countenance to astrology and to alchemy
+also sheltered astronomy and the germs of chemistry. Whether for this,
+or for some better reason, the founders of the schools of the Middle
+Ages included astronomy, along with geometry, arithmetic, and music,
+as one of the four branches of advanced education; and, in this
+respect, it is only just to them to observe that they were far in
+advance of those who sit in their seats. The school men considered no
+one to be properly educated unless he were acquainted with, at any
+rate, one branch of physical science. We have not, even yet, reached
+that stage of enlightenment.</p>
+
+<div class="sidenote">Further advance after Renaissance.</div>
+
+<p>In the early decades of the seventeenth century, the men of the
+Renaissance could show that they had already put out to good interest
+the treasure bequeathed to them by the Greeks. They had produced the
+astronomical system of Copernicus, with Kepler's great additions; the
+astronomical discoveries and the physical investigations of Galileo;
+the mechanics of Stevinus and the 'De Magnete' of Gilbert; the anatomy
+of the great French and Italian schools and the physiology of Harvey.
+In Italy, which had succeeded Greece in the hegemony of the scientific
+world, the Accademia dei Lyncei and sundry other such associations for
+the investigation of nature, the models of all subsequent academies
+and scientific societies, had been founded, while the literary skill
+and biting wit of Galileo had made the great scientific questions of
+the day not only intelligible, but attractive, to the general public.</p>
+
+<div class="sidenote">Francis Bacon.</div>
+
+<p>In our own country, Francis Bacon, had essayed to sum up the past of
+physical science, and to indicate the path which it must follow if its
+great destinies were to be fulfilled. And though the attempt was just
+such a magnificent failure as might have been expected from a man of
+great endowments, who was so singularly devoid of scientific insight
+that he could not understand the value of the work already achieved by
+the true instaurators of physical science; yet the majestic eloquence
+and the fervid vaticinations of one who was conspicuous alike by the
+greatness of his rise and the depth of his fall, drew the attention of
+all the world to the 'new birth of Time.'</p>
+
+<div class="sidenote">The defect of his method.</div>
+
+<p>But it is not easy to discover satisfactory evidence that the 'Novum
+Organum' had any direct beneficial influence on the advancement of
+natural knowledge. No delusion is greater than the notion that method
+and industry can make up for lack of motherwit, either in science or
+in practical life; and it is strange that, with his knowledge of
+mankind, Bacon should have dreamed that his, or any other, 'via
+inveniendi scientias' would 'level men's wits' and leave little scope
+for that inborn capacity which is called genius. As a matter of fact,
+Bacon's 'via' has proved hopelessly impracticable; while the
+'anticipation of nature' by the invention of hypotheses based on
+incomplete inductions, which he specially condemns, has proved itself
+to be a most efficient, indeed an indispensable, instrument of
+scientific progress. Finally, that transcendental alchemy&mdash;the
+superinducement of new forms on matter&mdash;which Bacon declares to be the
+supreme aim of science, has been wholly ignored by those who have
+created the physical knowledge of the present day.</p>
+
+<p>Even the eloquent advocacy of the Chancellor brought no unmixed good
+to physical science. It was natural enough that the man who, in his
+better moments, took 'all knowledge for his patrimony,' but, in his
+worse, sold that birthright for the mess of pottage of Court favor and
+professional success, for pomp and show, should be led to attach an
+undue value to the practical advantages which he foresaw, as Roger
+Bacon and, indeed, Seneca had foreseen, long before his time, must
+follow in the train of the advancement of natural knowledge. The
+burden of Bacon's pleadings for science is the gathering of
+fruit'&mdash;the importance of winning solid material advantages by the
+investigation of Nature and the desirableness of limiting the
+application of scientific methods of inquiry to that field.</p>
+
+<div class="sidenote">Hobbes.</div>
+
+<div class="sidenote">Descartes.</div>
+
+<p>Bacon's younger contemporary, Hobbes, casting aside the prudent
+reserve of his predecessor in regard to those matters about which the
+Crown or the Church might have something to say, extended scientific
+methods of inquiry to the phenomena of mind and the problems of social
+organisation; while, at the same time, he indicated the boundary
+between the province of real, and that of imaginary, knowledge. The
+'Principles of Philosophy' and the 'Leviathan' embody a coherent
+system of purely scientific thought in language which is a model of
+clear and vigorous English style. At the same time, in France, a man
+of far greater scientific capacity than either Bacon or Hobbes, Ren&eacute;
+Descartes, not only in his immortal 'Discours de la M&eacute;thode' and
+elsewhere, went down to the foundations of scientific certainty, but,
+in his 'Principes de Philosophie,' indicated where the goal of
+physical science really lay. However, Descartes was an eminent
+mathematician, and it would seem that the bent of his mind led him to
+overestimate the value of deductive reasoning from general principles,
+as much as Bacon had underestimated it. The progress of physical
+science has been effected neither by Baconians nor by Cartesians, as
+such, but by men like Galileo and Harvey, Boyle and Newton, who would
+have done their work just as well if neither Bacon nor Descartes had
+ever propounded their views respecting the manner in which scientific
+investigation should be pursued.</p>
+
+<div class="sidenote">For a time the progress without fruits.</div>
+
+<p>The progress of science, during the first century after Bacon's death,
+by means verified his sanguine prediction of the fruits which it would
+yield. For, though the revived and renewed study of nature had spread
+and grown to an extent which surpassed reasonable expectation, the
+practical results&mdash;the 'good to men's estate'&mdash;were, at first, by no
+means apparent. Sixty years after Bacon's death, Newton had crowned
+the long labors of the astronomers and the physicists, by coordinating
+the phenomena of solar motion throughout the visible universe into one
+vast system; but the 'Principia' helped no man to either wealth or
+comfort. Descartes, Newton, and Leibnitz had opened up new worlds to
+the mathematician, but the acquisitions of their genius enriched only
+man's ideal estate. Descartes had laid the foundations of rational
+cosmogony and of physiological psychology; Boyle had produced models
+of experimentation in various branches of physics and chemistry;
+Pascal and Torricelli had weighed the air; Malpighi and Grew, Ray and
+Willoughby had done work of no less importance in the biological
+sciences; but weaving and spinning were carried on with the old
+appliances; nobody could travel faster by sea or by land than at any
+previous time in the world's history, and King George could send a
+message from London to York no faster than King John might have done.
+Metals were worked from their ores by immemorial rule of thumb, and
+the centre of the iron trade of these islands was still among the oak
+forests of Sussex. The utmost skill of our mechanicians did not get
+beyond the production of a coarse watch.</p>
+
+<p>The middle of the eighteenth century is illustrated by a host of great
+names in science&mdash;English, French, German, and Italian&mdash;especially in
+the fields of chemistry, geology, and biology; but this deepening and
+broadening of natural knowledge produced next to no immediate
+practical benefits. Even if, at this time, Francis Bacon could have
+returned to the scene of his greatness and of his littleness, he must
+have regarded the philosophic world which praised and disregarded his
+precepts with great disfavor. If ghosts are consistent, he would have
+said, 'These people are all wasting their time, just as Gilbert and
+Kepler and Galileo and my worthy physician Harvey did in my day. Where
+are the fruits of the restoration of science which I promised? This
+accumulation of bare knowledge is all very well, but <i>cui bono</i>? Not
+one of these people is doing what I told him specially to do, and
+seeking that secret of the cause of forms which will enable men to
+deal, at will, with matter, and superinduce new natures upon the old
+foundations.'</p>
+
+<div class="sidenote">Its recent effect on life.</div>
+
+<p>But, a little later, that growth of knowledge beyond imaginable
+utilitarian ends, which is the condition precedent of its practical
+utility, began to produce some effect upon practical life; and the
+operation of that part of nature we call human upon the rest began to
+create, not 'new natures,' in Bacon's sense, but a new Nature, the
+existence of which is dependent upon men's efforts, which is
+subservient to their wants, and which would disappear if man's
+shaping and guiding hand were withdrawn. Every mechanical artifice,
+every chemically pure substance employed in manufacture, every
+abnormally fertile race of plants, or rapidly growing and fattening
+breed of animals, is a part of the new Nature created by science.
+Without it, the most densely populated regions of modern Europe and
+America must retain their primitive, sparsely inhabited, agricultural
+or pastoral condition; it is the foundation of our wealth and the
+condition of our safety from submergence by another flood of barbarous
+hordes; it is the bond which unites into a solid political whole,
+regions larger than any empire of antiquity; it secures us from the
+recurrence of the pestilences and famines of former times; it is the
+source of endless comforts and conveniences, which are not mere
+luxuries, but conduce to physical and moral well-being. During the
+last fifty years, this new birth of time, this new Nature begotten by
+science upon fact, has pressed itself daily and hourly upon our
+attention, and has worked miracles which have modified the whole
+fashion of our lives.</p>
+
+<div class="sidenote">These results often too much regarded;</div>
+
+<p>What wonder, then, if these astonishing fruits of the tree of
+knowledge are too often regarded by both friends and enemies as the
+be-all and end-all of science? What wonder if some eulogise, and
+others revile, the new philosophy for its utilitarian ends and its
+merely material triumphs?</p>
+
+<div class="sidenote">for scientific research rarely directed to practical ends</div>
+
+<p>In truth, the new philosophy deserves neither the praise of its
+eulogists, nor the blame of its slanderers. As I have pointed out, its
+disciples were guided by no search after practical fruits, during the
+great period of its growth, and it reached adolescence without being
+stimulated by any rewards of that nature. The bare enumeration of the
+names of the men who were the great lights of science in the latter
+part of the eighteenth and the first decade of the nineteenth
+century, of Herschel, of Laplace, of Young, of Fresnel, of Oersted, of
+Cavendish, of Lavoisier, of Davy, of Lamarck, of Cuvier, of Jussieu,
+of Decandolle, of Werner and of Hutton, suffices to indicate the
+strength of physical science in the age immediately preceding that of
+which I have to treat. But of which of these great men can it be said
+that their labors were directed to practical ends? I do not call to
+mind even an invention of practical utility which we owe to any of
+them, except the safety lamp of Davy. Werner certainly paid attention
+to mining, and I have not forgotten James Watt. But, though some of
+the most important of the improvements by which Watt converted the
+steam-engine, invented long before his time, into the obedient slave
+of man, were suggested and guided by his acquaintance with scientific
+principles, his skill as a practical mechanician, and the efficiency
+of Bolton's workmen had quite as much to do with the realisation of
+his projects.</p>
+
+<div class="sidenote">but instigated by love of knowledge</div>
+
+<p>In fact, the history of physical science teaches (and we cannot too
+carefully take the lesson to heart) that the practical advantages,
+attainable through its agency, never have been, and never will be,
+sufficiently attractive to men inspired by the inborn genius of the
+interpreter of nature, to give them courage to undergo the toils and
+make the sacrifices which that calling requires from its votaries.
+That which stirs their pulses is the love of knowledge and the joy of
+the discovery of the causes of things sung by the old poets&mdash;the
+supreme delight of extending the realm of law and order ever farther
+towards the unattainable goals of the infinitely great and the
+infinitely small, between which our little race of life is run. In the
+course of this work, the physical philosopher, sometimes
+intentionally, much more often unintentionally, lights upon something
+which proves to be of practical value. Great is the rejoicing of those
+who are benefited thereby; and, for the moment, science is the Diana
+of all the craftsmen. But, even while the cries of jubilation resound
+and this floatsam and jetsam of the tide of investigation is being
+turned into the wages of workmen and the wealth of capitalists, the
+crest of the wave of scientific investigation is far away on its
+course over the illimitable ocean of the unknown.</p>
+
+<div class="sidenote">It is in its turn assisted by industrial improvements.</div>
+
+<p>Far be it from me to depreciate the value of the gifts of science to
+practical life, or to cast a doubt upon the propriety of the course of
+action of those who follow science in the hope of finding wealth
+alongside truth, or even wealth alone. Such a profession is as
+respectable as any other. And quite as little do I desire to ignore
+the fact that, if industry owes a heavy debt to science, it has
+largely repaid the loan by the important aid which it has, in its
+turn, rendered to the advancement of science. In considering the
+causes which hindered the progress of physical knowledge in the
+schools of Athens and of Alexandria, it has often struck me<a name="FNanchor_A_1" id="FNanchor_A_1" /><a href="#Footnote_A_1" class="fnanchor">[A]</a> that
+where the Greeks did wonders was in just those branches of science,
+such as geometry, astronomy, and anatomy, which are susceptible of
+very considerable development without any, or any but the simplest,
+appliances. It is a curious speculation to think what would have
+become of modern physical science if glass and alcohol had not been
+easily obtainable; and if the gradual perfection of mechanical skill
+for industrial ends had not enabled investigators to obtain, at
+comparatively little cost, microscopes, telescopes, and all the
+exquisitely delicate apparatus for determining weight and measure and
+for estimating the lapse of time with exactness, which they now
+command. If science has rendered the colossal development of modern
+industry possible, beyond a doubt industry has done no less for modern
+physics and chemistry, and for a great deal of modern biology. And as
+the captains of industry have, at last, begun to be aware that the
+condition of success in that warfare, under the forms of peace, which
+is known as industrial competition lies in the discipline of the
+troops and the use of arms of precision, just as much as it does in
+the warfare which is called war, their demand for that discipline,
+which is technical education, is reacting upon science in a manner
+which will, assuredly, stimulate its future growth to an incalculable
+extent. It has become obvious that the interests of science and of
+industry are identical, that science cannot make a step forward
+without, sooner or later, opening up new channels for industry, and,
+on the other hand, that every advance of industry facilitates those
+experimental investigations, upon which the growth of science depends.
+We may hope that, at last, the weary misunderstanding between the
+practical men who professed to despise science, and the high and dry
+philosophers who professed to despise practical results, is at an end.</p>
+
+<p>Nevertheless, that which is true of the infancy of physical science in
+the Greek world, that which is true of its adolescence in the
+seventeenth and eighteenth centuries, remains true of its riper age in
+these latter days of the nineteenth century. The great steps in its
+progress have been made, are made, and will be made, by men who seek
+knowledge simply because they crave for it. They have their
+weaknesses, their follies, their vanities, and their rivalries, like
+the rest of the world; but whatever by-ends may mar their dignity and
+impede their usefulness, this chief end redeems them.<a name="FNanchor_B_2" id="FNanchor_B_2" /><a href="#Footnote_B_2" class="fnanchor">[B]</a> Nothing great
+in science has ever been done by men, whatever their powers, in whom
+the divine afflatus of the truth-seeker was wanting. Men of moderate
+capacity have done great things because it animated them; and men of
+great natural gifts have failed, absolutely or relatively, because
+they lacked this one thing needful.</p>
+
+<div class="sidenote">True aim and method of research.</div>
+
+<p>To anyone who knows the business of investigation practically, Bacon's
+notion of establishing a company of investigators to work for
+'fruits,' as if the pursuit of knowledge were a kind of mining
+operation and only required well-directed picks and shovels, seems
+very strange.<a name="FNanchor_C_3" id="FNanchor_C_3" /><a href="#Footnote_C_3" class="fnanchor">[C]</a> In science, as in art, and, as I believe, in every
+other sphere of human activity, there may be wisdom in a multitude of
+counsellors, but it is only in one or two of them. And, in scientific
+inquiry, at any rate, it is to that one or two that we must look for
+light and guidance. Newton said that he made his discoveries by
+'intending' his mind on the subject; no doubt truly. But to equal his
+success one must have the mind which he 'intended.' Forty lesser men
+might have intended their minds till they cracked, without any like
+result. It would be idle either to affirm or to deny that the last
+half-century has produced men of science of the calibre of Newton. It
+is sufficient that it can show a few capacities of the first rank,
+competent not only to deal profitably with the inheritance bequeathed
+by their scientific forefathers, but to pass on to their successors
+physical truths of a higher order than any yet reached by the human
+race. And if they have succeeded as Newton succeeded, it is because
+they have sought truth as he sought it, with no other object than the
+finding it.</p>
+
+<hr style='width: 45%;' />
+
+<div class="sidenote">Progress from 1837 to 1887.</div>
+
+<p>I am conscious that in undertaking to progress give even the briefest
+sketch of the progress of physical science, in all its branches,
+during the last half-century, I may be thought to have exhibited more
+courage than discretion, and perhaps more presumption than either. So
+far as physical science is concerned, the days of Admirable Crichtons
+have long been over, and the most indefatigable of hard workers may
+think he has done well if he has mastered one of its minor
+subdivisions. Nevertheless, it is possible for anyone, who has
+familiarised himself with the operations of science in one department,
+to comprehend the significance, and even to form a general estimate of
+the value, of the achievements of specialists in other departments.</p>
+
+<p>Nor is their any lack either of guidance, or of aids to ignorance. By
+a happy chance, the first edition of Whewell's 'History of the
+Inductive Sciences' was published in 1837, and it affords a very
+useful view of the state of things at the commencement of the
+Victorian epoch. As to subsequent events, there are numerous
+excellent summaries of the progress of various branches of science,
+especially up to 1881, which was the jubilee year of the British
+Association.<a name="FNanchor_D_4" id="FNanchor_D_4" /><a href="#Footnote_D_4" class="fnanchor">[D]</a> And, with respect to the biological sciences, with
+some parts of which my studies have familiarised me, my personal
+experience nearly coincides with the preceding half-century. I may
+hope, therefore, that my chance of escaping serious errors is as good
+as that of anyone else, who might have been persuaded to undertake the
+somewhat perilous enterprise in which I find myself engaged.</p>
+
+<p>There is yet another prefatory remark which it seems desirable I
+should make. It is that I think it proper to confine myself to the
+work done, without saying anything about the doers of it. Meddling
+with questions of merit and priority is a thorny business at the best
+of times, and unless in case of necessity, altogether undesirable when
+one is dealing with contemporaries. No such necessity lies upon me,
+and I shall, therefore, mention no names of living men, lest,
+perchance, I should incur the reproof which the Israelites, who
+struggled with one another in the field, addressed to Moses&mdash;'Who made
+thee a prince and a judge over us.'</p>
+
+<div class="sidenote">The aim of physical science</div>
+
+<p>Physical science is one and indivisible. Although, for practical
+purposes, it is convenient to mark it out into the primary regions of
+Physics, Chemistry, and Biology, and to subdivide these into
+subordinate provinces, yet the method of investigation and the
+ultimate object of the physical inquirer are everywhere the same.</p>
+
+<div class="sidenote">the discovery of the rational order of the universe</div>
+
+<p>The object is the discovery of the rational order which pervades the
+universe, the method consists of observation and experiment (which is
+observation under artificial conditions) for the determination of the
+facts of nature, of inductive and deductive reasoning for the
+discovery of their mutual relations and connection. The various
+branches of physical science differ in the extent to which at any
+given moment of their history, observation on the one hand, or
+ratiocination on the other, is their more obvious feature, but in no
+other way, and nothing can be more incorrect than the assumption one
+sometimes meets with, that physics has one method, chemistry another,
+and biology a third.</p>
+
+<div class="sidenote">It is based on postulates</div>
+
+<p>All physical science starts from certain postulates. One of them is
+the objective existence of a material world. It is assumed that the
+phenomena which are comprehended under this name have a 'substratum'
+of extended, impenetrable, mobile substance, which exhibits the
+quality known as inertia, and is termed matter.<a name="FNanchor_E_5" id="FNanchor_E_5" /><a href="#Footnote_E_5" class="fnanchor">[E]</a> Another postulate
+is the universality of the law of causation; that nothing happens
+without a cause (that is, a necessary precedent condition), and that
+the state of the physical universe, at any given moment, is the
+consequence of its state at any preceding moment. Another is that any
+of the rules, or so-called 'laws of nature,' by which the relation of
+phenomena is truly defined, is true for all time. The validity of
+these postulates is a problem of metaphysics; they are neither
+self-evident nor are they, strictly speaking, demonstrable. The
+justification of their employment, as axioms of physical philosophy,
+lies in the circumstance that expectations logically based upon them
+are verified, or, at any rate, not contradicted, whenever they can be
+tested by experience.</p>
+
+<div class="sidenote">and uses hypotheses.</div>
+
+<p>Physical science therefore rests on verified or uncontradicted
+hypotheses; and, such being the case, it is not surprising that a
+great condition of its progress has been the invention of verifiable
+hypotheses. It is a favorite popular delusion that the scientific
+inquirer is under a sort of moral obligation to abstain from going
+beyond that generalisation of observed facts which is absurdly called
+'Baconian' induction. But anyone who is practically acquainted with
+scientific work is aware that those who refuse to go beyond fact,
+rarely get as far as fact; and anyone who has studied the history of
+science knows that almost every great step therein has been made by
+the 'anticipation of Nature,' that is, by the invention of hypotheses,
+which, though verifiable, often had very little foundation to start
+with; and, not unfrequently, in spite of a long career of usefulness,
+turned out to be wholly erroneous in the long run.</p>
+
+<div class="sidenote">Fruitful use of an hypothesis even when wrong.</div>
+
+<p>The geocentric system of astronomy, with its eccentrics and its
+epicycles, was an hypothesis utterly at variance with fact, which
+nevertheless did great things for the advancement of astronomical
+knowledge. Kepler was the wildest of guessers. Newton's corpuscular
+theory of light was of much temporary use in optics, though nobody now
+believes in it; and the undulatory theory, which has superseded the
+corpuscular theory and has proved one of the most fertile of
+instruments of research, is based on the hypothesis of the existence
+of an 'ether,' the properties of which are defined in propositions,
+some of which, to ordinary apprehension, seem physical antinomies.</p>
+
+<p>It sounds paradoxical to say that the attainment of scientific truth
+has been effected, to a great extent, by the help of scientific
+errors. But the subject-matter of physical science is furnished by
+observation, which cannot extend beyond the limits of our faculties;
+while, even within those limits, we cannot be certain that any
+observation is absolutely exact and exhaustive. Hence it follows that
+any given generalisation from observation may be true, within the
+limits of our powers of observation at a given time, and yet turn out
+to be untrue, when those powers of observation are directly or
+indirectly enlarged. Or, to put the matter in another way, a doctrine
+which is untrue absolutely, may, to a very great extent, be
+susceptible of an interpretation in accordance with the truth. At a
+certain period in the history of astronomical science, the assumption
+that the planets move in circles was true enough to serve the purpose
+of correlating such observations as were then possible; after Kepler,
+the assumption that they move in ellipses became true enough in regard
+to the state of observational astronomy at that time. We say still
+that the orbits of the planets are ellipses, because, for all ordinary
+purposes, that is a sufficiently near approximation to the truth; but,
+as a matter of fact, the centre of gravity of a planet describes
+neither an ellipse or any other simple curve, but an immensely
+complicated undulating line. It may fairly be doubted whether any
+generalisation, or hypothesis, based upon physical data is absolutely
+true, in the sense that a mathematical proposition is so; but, if its
+errors can become apparent only outside the limits of practicable
+observation, it may be just as usefully adopted for one of the symbols
+of that algebra by which we interpret nature, as if it were absolutely
+true.</p>
+
+<p>The development of every branch of physical knowledge presents three
+stages which, in their logical relation, are successive. The first is
+the determination of the sensible character and order of the
+phenomena. This is <i>Natural History</i>, in the original sense of the
+term, and here nothing but observation and experiment avail us. The
+second is the determination of the constant relations of the phenomena
+thus defined, and their expression in rules or laws. The third is the
+explication of these particular laws by deduction from the most
+general laws of matter and motion. The last two stages constitute
+<i>Natural Philosophy</i> in its original sense. In this region, the
+invention of verifiable hypotheses is not only permissible, but is one
+of the conditions of progress.</p>
+
+<div class="sidenote">and mutual assistance of observation, experiment, and
+speculation.</div>
+
+<p>Historically, no branch of science has followed this order of growth;
+but, from the dawn of exact knowledge to the present day, observation,
+experiment, and speculation have gone hand in hand; and, whenever
+science has halted or strayed from the right path, it has been, either
+because its votaries have been content with mere unverified or
+unverifiable speculation (and this is the commonest case, because
+observation and experiment are hard work, while speculation is
+amusing); or it has been, because the accumulation of details of
+observation has for a time excluded speculation.</p>
+
+<div class="sidenote">Recognition of these truths in recent times, and consequent
+progress.</div>
+
+<p>The progress of physical science, since the revival of learning, is
+largely due to the fact that men have gradually learned to lay aside
+the consideration of unverifiable hypotheses; to guide observation
+and experiment by verifiable hypotheses; and to consider the latter,
+not as ideal truths, the real entities of an intelligible world behind
+phenomena, but as a symbolical language, by the aid of which nature
+can be interpreted in terms apprehensible by our intellects. And if
+physical science, during the last fifty years, has attained dimensions
+beyond all former precedent, and can exhibit achievements of greater
+importance than any former such period can show, it is because able
+men, animated by the true scientific spirit, carefully trained in the
+method of science, and having at their disposal immensely improved
+appliances, have devoted themselves to the enlargement of the
+boundaries of natural knowledge in greater number than during any
+previous half-century of the world's history.</p>
+
+<div class="sidenote">The three great achievements. Doctrines of (1) molecular
+constitution of matter, (2) conservation of energy, (3) evolution.</div>
+
+<p>I have said that our epoch can produce achievements in physical
+science of greater moment than any other has to show, advisedly; and
+I think that there are three great products of our time which justify
+the assertion. One of these is that doctrine concerning the
+constitution of matter which, for want of a better name, I will call
+'molecular;' the second is the doctrine of conservation of energy; the
+third is the doctrine of evolution. Each of these was foreshadowed,
+more or less distinctly, in former periods of the history of science;
+and, so far is either from being the outcome of purely inductive
+reasoning, that it would be hard to overrate the influence of
+metaphysical, and even of theological, considerations upon the
+development of all three. The peculiar merit of our epoch is that it
+has shown how these hypotheses connect a vast number of seemingly
+independent partial generalisations; that it has given them that
+precision of expression which is necessary for their exact
+verification; and that it has practically proved their value as
+guides to the discovery of new truth. All three doctrines are
+intimately connected, and each is applicable to the whole physical
+cosmos. But, as might have been expected from the nature of the case,
+the first two grew, mainly, out of the consideration of
+physico-chemical phenomena; while the third, in great measure, owes
+its rehabilitation, if not its origin, to the study of biological
+phenomena.</p>
+
+<div class="sidenote">(1) Molecular constitution of matter.</div>
+
+<p>In the early decades of this century, a number of important truths
+applicable, in part, to matter in general, and, in part, to particular
+forms of matter, had been ascertained by the physicists and chemists.</p>
+
+<p>The laws of motion of visible and tangible, or <i>molar</i>, matter had
+been worked out to a great degree of refinement and embodied in the
+branches of science known as Mechanics, Hydrostatics, and Pneumatics.
+These laws had been shown to hold good, so far as they could be
+checked by observation and experiment, throughout the universe, on the
+assumption that all such masses of matter possessed inertia and were
+susceptible of acquiring motion, in two ways, firstly by impact, or
+impulse from without; and, secondly, by the operation of certain
+hypothetical causes of motion termed 'forces,' which were usually
+supposed to be resident in the particles of the masses themselves, and
+to operate at a distance, in such a way as to tend to draw any two
+such masses together, or to separate them more widely.</p>
+
+<div class="sidenote">The two theories as to matter.</div>
+
+<p>With respect to the ultimate constitution of these masses, the same
+two antagonistic opinions which had existed since the time of
+Democritus and of Aristotle were still face to face. According to the
+one, matter was discontinuous and consisted of minute indivisible
+particles or atoms, separated by a universal vacuum; according to the
+other, it was continuous, and the finest distinguishable, or
+imaginable, particles were scattered through the attenuated general
+substance of the plenum. A rough analogy to the latter case would be
+afforded by granules of ice diffused through water; to the former,
+such granules diffused through absolutely empty space.</p>
+
+<div class="sidenote">Reassertion by Dalton of atomic theory.</div>
+
+<p>In the latter part of the eighteenth century, the chemists had arrived
+at several very important generalisations respecting those properties
+of matter with which they were especially concerned. However plainly
+ponderable matter seemed to be originated and destroyed in their
+operations, they proved that, as mass or body, it remained
+indestructible and ingenerable; and that, so far, it varied only in
+its perceptibility by our senses. The course of investigation further
+proved that a certain number of the chemically separable kinds of
+matter were unalterable by any known means (except in so far as they
+might be made to change their state from solid to fluid, or <i>vice
+vers&acirc;</i>), unless they were brought into contact with other kinds of
+matter, and that the properties of these several kinds of matter were
+always the same, whatever their origin. All other bodies were found to
+consist of two or more of these, which thus took the place of the four
+'elements' of the ancient philosophers. Further, it was proved that,
+in forming chemical compounds, bodies always unite in a definite
+proportion by weight, or in simple multiples of that proportion, and
+that, if any one body were taken as a standard, every other could have
+a number assigned to it as its proportional combining weight. It was
+on this foundation of fact that Dalton based his re-establishment of
+the old atomic hypothesis on a new empirical foundation. It is
+obvious, that if elementary matter consists of indestructible and
+indivisible particles, each of which constantly preserves the same
+weight relatively to all the others, compounds formed by the
+aggregation of two, three, four, or more such particles must exemplify
+the rule of combination in definite proportions deduced from
+observation.</p>
+
+<p>In the meanwhile, the gradual reception of the undulatory theory of
+light necessitated the assumption of the existence of an 'ether'
+filling all space. But whether this ether was to be regarded as a
+strictly material and continuous substance was an undecided point, and
+hence the revived atomism, escaped strangling in its birth. For it is
+clear, that if the ether is admitted to be a continuous material
+substance, Democritic atomism is at an end and Cartesian continuity
+takes its place.</p>
+
+<div class="sidenote">The real value of hypothesis; it predicates the existence
+of units of matter.</div>
+
+<p>The real value of the new atomic hypothesis, however, did not lie in
+the two points which Democritus and his followers would have
+considered essential&mdash;namely, the indivisibility of the 'atoms' and
+the presence of an interatomic vacuum&mdash;but in the assumption that, to
+the extent to which our means of analysis take us, material bodies
+consist of definite minute masses, each of which, so far as physical
+and chemical processes of division go, may be regarded as a
+unit&mdash;having a practically permanent individuality. Just as a man is
+the unit of sociology, without reference to the actual fact of his
+divisibility, so such a minute mass is the unit of physico-chemical
+science&mdash;that smallest material particle which under any given
+circumstances acts as a whole.<a name="FNanchor_F_6" id="FNanchor_F_6" /><a href="#Footnote_F_6" class="fnanchor">[F]</a></p>
+
+<p>The doctrine of specific heat originated in the eighteenth century.
+It means that the same mass of a body, under the same circumstances,
+always requires the same quantity of heat to raise it to a given
+temperature, but that equal masses of different bodies require
+different quantities. Ultimately, it was found that the quantities of
+heat required to raise equal masses of the more perfect gases, through
+equal ranges of temperature, were inversely proportional to their
+combining weights. Thus a definite relation was established between
+the hypothetical units and heat. The phenomena of electrolytic
+decomposition showed that there was a like close relation between
+these units and electricity. The quantity of electricity generated by
+the combination of any two units is sufficient to separate any other
+two which are susceptible of such decomposition. The phenomena of
+isomorphism showed a relation between the units and crystalline forms;
+certain units are thus able to replace others in a crystalline body
+without altering its form, and others are not.</p>
+
+<p>Again, the laws of the effect of pressure and heat on gaseous bodies,
+the fact that they combine in definite proportions by volume, and that
+such proportion bears a simple relation to their combining weights,
+all harmonised with the Daltonian hypothesis, and led to the bold
+speculation known as the law of Avogadro&mdash;that all gaseous bodies,
+under the same physical conditions, contain the same number of units.
+In the form in which it was first enunciated, this hypothesis was
+incorrect&mdash;perhaps it is not exactly true in any form; but it is
+hardly too much to say that chemistry and molecular physics would
+never have advanced to their present condition unless it had been
+assumed to be true. Another immense service rendered by Dalton, as a
+corollary of the new atomic doctrine, was the creation of a system of
+symbolic notation, which not only made the nature of chemical
+compounds and processes easily intelligible and easy of recollection,
+but, by its very form, suggested new lines of inquiry. The atomic
+notation was as serviceable to chemistry as the binomial nomenclature
+and the classificatory schematism of Linn&aelig;us were to zo&ouml;logy and
+botany.</p>
+
+<div class="sidenote">In biology a like theory of molecularstructure.</div>
+
+<p>Side by side with these advances arose in another, which also has a
+close parallel in the history of biological science. If the unit of a
+compound is made up by the aggregation of elementary units, the notion
+that these must have some sort of definite arrangement inevitably
+suggests itself; and such phenomena as double decomposition pointed,
+not only to the existence of a molecular architecture, but to the
+possibility of modifying a molecular fabric without destroying it, by
+taking out some of the component units and replacing them by others.
+The class of neutral salts, for example, includes a great number of
+bodies in many ways similar, in which the basic molecules, or the acid
+molecules, may be replaced by other basic and other acid molecules
+without altering the neutrality of the salt; just as a cube of bricks
+remains a cube, so long as any brick that is taken out is replaced by
+another of the same shape and dimensions, whatever its weight or other
+properties may be. Facts of this kind gave rise to the conception of
+'types' of molecular structure, just as the recognition of the unity
+in diversity of the structure of the species of plants and animals
+gave rise to the notion of biological 'types.' The notation of
+chemistry enabled these ideas to be represented with precision; and
+they acquired an immense importance, when the improvement of methods
+of analysis, which took place about the beginning of our period,
+enabled the composition of the so-called 'organic' bodies to be
+determined with, rapidity and precision.<a name="FNanchor_G_7" id="FNanchor_G_7" /><a href="#Footnote_G_7" class="fnanchor">[G]</a> A large proportion of
+these compounds contain not more than three or four elements, of which
+carbon is the chief; but their number is very great, and the diversity
+of their physical and chemical properties is astonishing. The
+ascertainment of the proportion of each element in these compounds
+affords little or no help towards accounting for their diversities;
+widely different bodies being often very similar, or even identical,
+in that respect. And, in the last case, that of <i>isomeric</i> compounds,
+the appeal to diversity of arrangement of the identical component
+units was the only obvious way out of the difficulty. Here, again,
+hypothesis proved to be of great value; not only was the search for
+evidence of diversity of molecular structure successful, but the study
+of the process of taking to pieces led to the discovery of the way to
+put together; and vast numbers of compounds, some of them previously
+known only as products of the living economy, have thus been
+artificially constructed. Chemical work, at the present day, is, to a
+large extent, synthetic or creative&mdash;that is to say, the chemist
+determines, theoretically, that certain non-existent compounds ought
+to be producible, and he proceeds to produce them.</p>
+
+<p>It is largely because the chemical theory and practice of our epoch
+have passed into this deductive and synthetic stage, that they are
+entitled to the name of the 'New Chemistry' which they commonly
+receive. But this new chemistry has grown up by the help of
+hypotheses, such as those of Dalton and of Avogadro, and that
+singular conception of 'bonds' invented to colligate the facts of
+'valency' or 'atomicity,' the first of which took some time to make
+its way; while the second fell into oblivion, for many years after it
+was propounded, for lack of empirical justification. As for the third,
+it may be doubted if anyone regards it as more than a temporary
+contrivance.</p>
+
+<p>But some of these hypotheses have done yet further service. Combining
+them with the mechanical theory of heat and the doctrine of the
+conservation of energy, which are also products of our time,
+physicists have arrived at an entirely new conception of the nature of
+gaseous bodies and of the relation of the physico-chemical units of
+matter to the different forms of energy. The conduct of gases under
+varying pressure and temperature, their diffusibility, their relation
+to radiant heat and to light, the evolution of heat when bodies
+combine, the absorption of heat when they are dissociated, and a host
+of other molecular phenomena, have been shown to be deducible from the
+dynamical and statical principles which apply to molar motion and
+rest; and the tendency of physico-chemical science is clearly towards
+the reduction of the problems of the world of the infinitely little,
+as it already has reduced those of the infinitely great world, to
+questions of mechanics.<a name="FNanchor_H_8" id="FNanchor_H_8" /><a href="#Footnote_H_8" class="fnanchor">[H]</a></p>
+
+<p>In the meanwhile, the primitive atomic theory, which has served as the
+scaffolding for the edifice of modern physics and chemistry, has been
+quietly dismissed. I cannot discover that any contemporary physicist
+or chemist believes in the real indivisibility of atoms, or in an
+interatomic matterless vacuum. 'Atoms' appear to be used as mere
+names for physico-chemical units which have not yet been subdivided,
+and 'molecules' for physico-chemical units which are aggregates of the
+former. And these individualised particles are supposed to move in an
+endless ocean of a vastly more subtle matter&mdash;the ether. If this ether
+is a continuous substance, therefore, we have got back from the
+hypothesis of Dalton to that of Descartes. But there is much reason to
+believe that science is going to make a still further journey, and, in
+form, if not altogether in substance, to return to the point of view
+of Aristotle.</p>
+
+<div class="sidenote">Elementary bodies</div>
+
+<p>The greater number of the so-called 'elementary' bodies, now known,
+had been discovered before the commencement of our epoch; and it had
+become apparent that they were by no means equally similar or
+dissimilar, but that some of them, at any rate, constituted groups,
+the several members of which were as much like one another as they
+were unlike the rest. Chlorine, iodine, bromine, and fluorine thus
+formed a very distinct group; sulphur and selenium another; boron and
+silicon another; potassium, sodium, and lithium another; and so on. In
+some cases, the atomic weights of such allied bodies were nearly the
+same, or could be arranged in series, with like differences between
+the several terms. In fact, the elements afforded indications that
+they were susceptible of a classification in natural groups, such as
+those into which animals and plants fall.</p>
+
+<div class="sidenote">fall into different series.</div>
+
+<p>Recently this subject has been taken up afresh, with a result which
+may be stated roughly in the following terms: If the sixty-five or
+sixty-eight recognised 'elements' are arranged in the order of their
+atomic weights&mdash;from hydrogen, the lightest, as unity, to uranium, the
+heaviest, as 240&mdash;the series does not exhibit one continuous
+progressive modification in the physical and chemical characters of
+its several terms, but breaks up into a number of sections, in each of
+which the several terms present analogies with the corresponding terms
+of the other series.</p>
+
+<p>Thus the whole series does not run:</p>
+
+<p><i>a, b, d, e, f, g, h, i, k,</i> &amp;c.,</p>
+
+<p>but</p>
+
+<p><i>a, b, c, d,</i> A, B, C, D, &#945;, &#946;, &#947;, &#948;, &amp;c.;</p>
+
+<p>so that it is said to express a <i>periodic law</i> of recurrent
+similarities. Or the relation may be expressed in another way. In each
+section of the series, the atomic weight is greater than in the
+preceding section, so that if <i>w</i> is the atomic weight of any element
+in the first segment, <i>w+x</i> will represent the atomic weight of any
+element in the next, and <i>w+x+y</i> the atomic weight of any element in
+the next, and so on. Therefore the sections may be represented as
+parallel series, the corresponding terms of which have analogous
+properties; each successive series starting with a body the atomic
+weight of which is greater than that of any in the preceding series,
+in the following fashion:</p>
+
+<p>
+<i>d</i> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; D &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &#948;<br />
+<i>c</i> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; C &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &#947;<br />
+<i>b</i> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; B &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &#946;<br />
+<span class="u"><i>a</i></span> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span class="u">&nbsp; A &nbsp;</span> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span class="u">&nbsp; &nbsp; &#945; &nbsp; &nbsp; </span><br />
+<i>w</i> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <i>w + x</i> &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <i>w + x + y</i><br />
+</p>
+
+<div class="sidenote">The possibility of a primary form of matter.</div>
+
+<p>This is a conception with, which biologists are very familiar, animal
+and plant groups constantly appearing as series of parallel
+modifications of similar and yet different primary forms. In the
+living world, facts of this kind are now understood to mean evolution
+from a common prototype. It is difficult to imagine that in the
+not-living world they are devoid of significance. Is it not possible,
+nay probable that they may mean the evolution of our 'elements' from a
+primary undifferentiated form of matter? Fifty years ago, such a
+suggestion would have been scouted as a revival of the dreams of the
+alchemists. At present, it may be said to be the burning question of
+physico-chemical science.</p>
+
+<p>In fact, the so-called 'vortex-ring' hypothesis is a very serious and
+remarkable attempt to deal with material units from a point of view
+which is consistent with the doctrine of evolution. It supposes the
+ether to be a uniform substance, and that the 'elementary' units are,
+broadly speaking, permanent whirlpools, or vortices, of this ether,
+the properties of which depend on their actual and potential modes of
+motion. It is curious and highly interesting to remark that this
+hypothesis reminds us not only of the speculations of Descartes, but
+of those of Aristotle. The resemblance of the 'vortex-rings' to the
+'tourbillons' of Descartes is little more than nominal; but the
+correspondence between the modern and the ancient notion of a
+distinction between primary and derivative matter is, to a certain
+extent, real. For this ethereal 'Urstoff' of the modern corresponds
+very closely with the &#960;&#961;&#969;&#964;&#951; &#965;&#955;&#951; of Aristotle, the <i>materia prima</i> of
+his medi&aelig;val followers; while matter, differentiated into our
+elements, is the equivalent of the first stage of progress towards the
+&#949;&#963;&#967;&#945;&#964;&#951; &#965;&#955;&#951;, or finished matter, of the ancient philosophy.</p>
+
+<p>If the material units of the existing order of nature are specialised
+portions of a relatively homogeneous <i>materia prima</i>&mdash;which were
+originated under conditions that have long ceased to exist and which
+remain unchanged and unchangeable under all conditions, whether
+natural or artificial, hitherto known to us&mdash;it follows that the
+speculation that they may be indefinitely altered, or that new units
+may be generated under conditions yet to be discovered, is perfectly
+legitimate. Theoretically, at any rate, the transmutability of the
+elements is a verifiable scientific hypothesis; and such inquiries as
+those which have been set afoot, into the possible dissociative action
+of the great heat of the sun upon our elements, are not only
+legitimate, but are likely to yield results which, whether affirmative
+or negative, will be of great importance. The idea that atoms are
+absolutely ingenerable and immutable 'manufactured articles' stands on
+the same sort of foundation as the idea that biological species are
+'manufactured articles' stood thirty years ago; and the supposed
+constancy of the elementary atoms, during the enormous lapse of time
+measured by the existence of our universe, is of no more weight
+against the possibility of change in them, in the infinity of
+antecedent time, than the constancy of species in Egypt, since the
+days of Rameses or Cheops, is evidence of their immutability during
+all past epochs of the earth's history. It seems safe to prophesy
+that the hypothesis of the evolution of the elements from a primitive
+matter will, in future, play no less a part in the history of science
+than the atomic hypothesis, which, to begin with, had no greater, if
+so great, an empirical foundation.</p>
+
+<div class="sidenote">The old and the new atomic theory.</div>
+
+<p>It may perhaps occur to the reader that the boasted progress of
+physical science does not come to much, if our present conceptions of
+the fundamental nature of matter are expressible in terms employed,
+more than two thousand years ago, by the old 'master of those that
+know.' Such a criticism, however, would involve forgetfulness of the
+fact, that the connotation of these terms, in the mind of the modern,
+is almost infinitely different from that which they possessed in the
+mind of the ancient, philosopher. In antiquity, they meant little more
+than vague speculation; at the present day, they indicate definite
+physical conceptions, susceptible of mathematical treatment, and
+giving rise to innumerable deductions, the value of which can be
+experimentally tested. The old notions produced little more than
+floods of dialectics; the new are powerful aids towards the increase
+of solid knowledge.</p>
+
+<div class="sidenote">(2) Conservation of energy.</div>
+
+<p>Everyday observation shows that, of the bodies which compose the
+material world, some are in motion and some are, or appear to be, at
+rest. Of the bodies in motion, some, like the sun and stars, exhibit a
+constant movement, regular in amount and direction, for which no
+external cause appears. Others, as stones and smoke, seem also to move
+of themselves when external impediments are taken away. But these
+appear to tend to move in opposite directions: the bodies we call
+heavy, such as stones, downwards, and the bodies we call light, at
+least such as smoke and steam, upwards. And, as we further notice
+that the earth, below our feet, is made up of heavy matter, while the
+air, above our heads, is extremely light matter, it is easy to regard
+this fact as evidence that the lower region is the place to which
+heavy things tend&mdash;their proper place, in short&mdash;while the upper
+region is the proper place of light things; and to generalise the
+facts observed by saying that bodies, which are free to move, tend
+towards their proper places. All these seem to be natural motions,
+dependent on the inherent faculties, or tendencies, of bodies
+themselves. But there are other motions which are artificial or
+violent, as when a stone is thrown from the hand, or is knocked by
+another stone in motion. In such cases as these, for example, when a
+stone is cast from the hand, the distance travelled by the stone
+appears to depend partly on its weight and partly upon the exertion
+of the thrower. So that, the weight of the stone remaining the same,
+it looks as if the motive power communicated to it were measured by
+the distance to which the stone travels&mdash;as if, in other words, the
+power needed to send it a hundred yards was twice as great as that
+needed to send it fifty yards. These, apparently obvious, conclusions
+from the everyday appearances of rest and motion fairly represent the
+state of opinion upon the subject which prevailed among the ancient
+Greeks, and remained dominant until the age of Galileo. The
+publication of the 'Principia' of Newton, in 1686-7, marks the epoch
+at which the progress of mechanical physics had effected a complete
+revolution of thought on these subjects. By this time, it had been
+made clear that the old generalisations were either incomplete or
+totally erroneous; that a body, once set in motion, will continue to
+move in a straight line for any conceivable time or distance, unless
+it is interfered with; that any change of motion is proportional to
+the 'force' which causes it, and takes place in the direction in which
+that 'force' is exerted; and that, when a body in motion acts as a
+cause of motion on another, the latter gains as much as the former
+loses, and <i>vice vers&acirc;</i>. It is to be noted, however, that while, in
+contradistinction to the ancient idea of the inherent tendency to
+motion of bodies, the absence of any such spontaneous power of motion
+was accepted as a physical axiom by the moderns, the old conception
+virtually maintained itself is a new shape. For, in spite of Newton's
+well-known warning against the 'absurdity' of supposing that one body
+can act on another at a distance through a vacuum, the ultimate
+particles of matter were generally assumed to be the seats of
+perennial causes of motion termed 'attractive and repulsive forces,'
+in virtue of which, any two such particles, without any external
+impression of motion, or intermediate material agent, were supposed to
+tend to approach or remove from one another; and this view of the
+duality of the causes of motion is very widely held at the present
+day.</p>
+
+<p>Another important result of investigation, attained in the seventeenth
+century, was the proof and quantitative estimation of physical
+inertia. In the old philosophy, a curious conjunction of ethical and
+physical prejudices had led to the notion that there was something
+ethically bad and physically obstructive about matter. Aristotle
+attributes all irregularities and apparent dysteleologies in nature to
+the disobedience, or sluggish yielding, of matter to the shaping and
+guiding influence of those reasons and causes which were hypostatised
+in his ideal 'Forms.' In modern science, the conception of the
+inertia, or resistance to change, of matter is complex. In part, it
+contains a corollary from the law of causation: A body cannot change
+its state in respect of rest or motion without a sufficient cause.
+But, in part, it contains generalisations from experience. One of
+these is that there is no such sufficient cause resident in any body,
+and that therefore it will rest, or continue in motion, so long as no
+external cause of change acts upon it. The other is that the effect
+which the impact of a body in motion produces upon the body on which
+it impinges depends, other things being alike, on the relation of a
+certain quality of each which is called 'mass.' Given a cause of
+motion of a certain value, the amount of motion, measured by distance
+travelled in a certain time, which it will produce in a given quantity
+of matter, say a cubic inch, is not always the same, but depends on
+what that matter is&mdash;a cubic inch of iron will go faster than a cubic
+inch of gold. Hence, it appears, that since equal amounts of motion
+have, <i>ex hypothesi</i>, been produced, the amount of motion in a body
+does not depend on its speed alone, but on some property of the body.
+To this the name of 'mass' has been given. And since it seems
+reasonable to suppose that a large quantity of matter, moving slowly,
+possesses as much motion as a small quantity moving faster, 'mass' has
+been held to express 'quantity of matter.' It is further demonstrable
+that, at any given time and place, the relative mass of any two bodies
+is expressed by the ratio of their weights.</p>
+
+<div class="sidenote">Mechanical theory of heat.</div>
+
+<p>When all these great truths respecting molar motion, or the movements
+of visible and tangible masses, had been shown to hold good not only
+of terrestrial bodies, but of all those which constitute the visible
+universe, and the movements of the macrocosm had thus been expressed
+by a general mechanical theory, there remained a vast number of
+phenomena, such as those of light, heat, electricity, magnetism, and
+those of the physical and chemical changes, which do not involve molar
+motion. Newton's corpuscular theory of light was an attempt to deal
+with one great series of these phenomena on mechanical principles, and
+it maintained its ground until, at the beginning of the nineteenth
+century, the undulatory theory proved itself to be a much better
+working hypothesis. Heat, up to that time, and indeed much later, was
+regarded as an imponderable substance, <i>caloric</i>; as a thing which was
+absorbed by bodies when they were wanned, and was given out as they
+cooled; and which, moreover, was capable of entering into a sort of
+chemical combination with them, and so becoming latent. Rumford and
+Davy had given a great blow to this view of heat by proving that the
+quantity of heat which two portions of the same body could be made to
+give out, by rubbing them together, was practically illimitable. This
+result brought philosophers face to face with the contradiction of
+supposing that a finite body could contain an infinite quantity of
+another body; but it was not until 1843, that clear and unquestionable
+experimental proof was given of the fact that there is a definite
+relation between mechanical work and heat; that so much work always
+gives rise, under the same conditions, to so much heat, and so much
+heat to so much mechanical work. Thus originated the mechanical theory
+of heat, which became the starting-point of the modern doctrine of the
+conservation of energy. Molar motion had appeared to be destroyed by
+friction. It was proved that no destruction took place, but that an
+exact equivalent of the energy of the lost molar motion appears as
+that of the <i>molecular</i> motion, or motion of the smallest particles of
+a body, which constitutes heat. The loss of the masses is the gain of
+their particles.</p>
+
+<div class="sidenote">Earlier approaches towards doctrine of conservation.</div>
+
+<p>Before 1843, however, the doctrine of conservation of energy had been
+approached Bacon's chief contribution to positive science is the happy
+guess (for the context shows that it was little more) that heat may be
+a mode of motion; Descartes affirmed the quantity of motion in the
+world to be constant; Newton nearly gave expression to the complete
+theorem; while Rumford's and Davy's experiments suggested, though they
+did not prove, the equivalency of mechanical and thermal energy.
+Again, the discovery of voltaic electricity, and the marvellous
+development of knowledge, in that field, effected by such men as Davy,
+Faraday, Oersted, Amp&egrave;re, and Melloni, had brought to light a number
+of facts which tended to show that the so-called 'forces' at work in
+light, heat, electricity, and magnetism, in chemical and in mechanical
+operations, were intimately, and, in various cases, quantitatively
+related. It was demonstrated that any one could be obtained at the
+expense of any other; and apparatus was devised which exhibited the
+evolution of all these kinds of action from one source of energy.
+Hence the idea of the 'correlation of forces' which was the immediate
+forerunner of the doctrine of the conservation of energy.</p>
+
+<p>It is a remarkable evidence of the greatness of the progress in this
+direction which has been effected in our time, that even the second
+edition of the 'History of the Inductive Sciences,' which was
+published in 1846, contains no allusion either to the general view of
+the 'Correlation of Forces' published in England in 1842, or to the
+publication in 1843 of the first of the series of experiments by which
+the mechanical equivalent of heat was correctly ascertained.<a name="FNanchor_I_9" id="FNanchor_I_9" /><a href="#Footnote_I_9" class="fnanchor">[I]</a> Such a
+failure on the part of a contemporary, of great acquirements and
+remarkable intellectual powers, to read the signs of the times, is a
+lesson and a warning worthy of being deeply pondered by anyone who
+attempts to prognosticate the course of scientific progress.</p>
+
+<div class="sidenote">What this doctrine is.</div>
+
+<p>I have pointed out that the growth of clear and definite views
+respecting the constitution of matter has led to the conclusion that,
+so far as natural agencies are concerned, it is ingenerable and
+indestructible. In so far as matter may be conceived to exist in a
+purely passive state, it is, imaginably, older than motion. But, as it
+must be assumed to be susceptible of motion, a particle of bare matter
+at rest must be endowed with the potentiality of motion. Such a
+particle, however, by the supposition, can have no energy, for there
+is no cause why it should move. Suppose now that it receives an
+impulse, it will begin to move with a velocity inversely proportional
+to its mass, on the one hand, and directly proportional to the
+strength of the impulse, on the other, and will possess <i>kinetic
+energy</i>, in virtue of which it will not only continue to move for ever
+if unimpeded, but if it impinges on another such particle, it will
+impart more or less of its motion, to the latter. Let it be conceived
+that the particle acquires a tendency to move, and that nevertheless
+it does not move. It is then in a condition totally different from
+that in which it was at first. A cause competent to produce motion is
+operating upon it, but, for some reason or other, is unable to give
+rise to motion. If the obstacle is removed, the energy which was
+there, but could not manifest itself, at once gives rise to motion.
+While the restraint lasts, the energy of the particle is merely
+potential; and the case supposed illustrates what is meant by
+<i>potential energy</i>. In this contrast of the potential with the actual,
+modern physics is turning to account the most familiar of Aristotelian
+distinctions&mdash;that between &#948;&#965;&#957;&#945;&#956;&#953;&#987; and &#949;&#957;&#949;&#961;&#947;&#949;&#953;&#945;.</p>
+
+<p>That kinetic energy appears to be imparted by impact is a fact of
+daily and hourly experience: we see bodies set in motion by bodies,
+already in motion, which seem to come in contact with them. It is a
+truth which could have been learned by nothing but experience, and
+which cannot be explained, but must be taken as an ultimate fact
+about which, explicable or inexplicable, there can be no doubt.
+Strictly speaking, we have no direct apprehension of any other cause
+of motion. But experience furnishes innumerable examples of the
+production of kinetic energy in a body previously at rest, when no
+impact is discernible as the cause of that energy. In all such cases,
+the presence of a second body is a necessary condition; and the amount
+of kinetic energy, which its presence enables the first to gain, is
+strictly dependent on the relative positions of the two. Hence the
+phrase <i>energy of position</i>, which is frequently used as equivalent to
+potential energy. If a stone is picked up and held, say, six feet
+above the ground, it has <i>potential energy</i>, because, if let go, it
+will immediately begin to move towards the earth; and this energy may
+be said to be <i>energy of position</i>, because it depends upon the
+relative position of the earth and the stone. The stone is solicited
+to move but cannot, so long as the muscular strength of the holder
+prevents the solicitation from taking effect. The stone, therefore,
+has potential energy, which becomes kinetic if it is let go, and the
+amount of that kinetic energy which will be developed before it
+strikes the earth depends on its position&mdash;on the fact that it is,
+say, six feet off the earth, neither more nor less. Moreover, it can
+be proved that the raiser of the stone had to exert as much energy in
+order to place it in its position, as it will develop in falling.
+Hence the energy which was exerted, and apparently exhausted, in
+raising the stone, is potentially in the stone, in its raised
+position, and will manifest itself when the stone is set free. Thus
+the energy, withdrawn from the general stock to raise the stone, is
+returned when it falls, and there is no change in the total amount.
+Energy, as a whole, is conserved.</p>
+
+<p>Taking this as a very broad and general statement of the essential
+facts of the case, the raising of the stone is intelligible enough, as
+a case of the communication of motion from one body to another. But
+the potential energy of the raised stone is not so easily
+intelligible. To all appearance, there is nothing either pushing or
+pulling it towards the earth, or the earth towards it; and yet it is
+quite certain that the stone tends to move towards the earth and the
+earth towards the stone, in the way defined by the law of gravitation.</p>
+
+<p>In the currently accepted language of science, the cause of motion, in
+all such cases as this, when bodies tend to move towards or away from
+one or another, without any discernible impact of other bodies, is
+termed a 'force,' which is called 'attractive' in the one case, and
+'repulsive' in the other. And such attractive or repulsive forces are
+often spoken of as if they were real things, capable of exerting a
+pull, or a push, upon the particles of matter concerned. Thus the
+potential energy of the stone is commonly said to be due to the
+'force' of gravity which is continually operating upon it.</p>
+
+<p>Another illustration may make the case plainer. The bob of a pendulum
+swings first to one side and then to the other of the centre of the
+arc which it describes. Suppose it to have just reached the summit of
+its right-hand half-swing. It is said that the 'attractive forces' of
+the bob for the earth, and of the earth for the bob, set the former in
+motion; and as these 'forces' are continually in operation, they
+confer an accelerated velocity on the bob; until, when it reaches the
+centre of its swing, it is, so to speak, fully charged with kinetic
+energy. If, at this moment, the whole material universe, except the
+bob, were abolished, it would move for ever in the direction of a
+tangent to the middle of the arc described. As a matter of fact, it
+is compelled to travel through its left-hand half-swing, and thus
+virtually to go up hill. Consequently, the 'attractive forces' of the
+bob and the earth are now acting against it, and constitute a
+resistance which the charge of kinetic energy has to overcome. But, as
+this charge represents the operation of the attractive forces during
+the passage of the bob through the right-hand half-swing down to the
+centre of the arc, so it must needs be used up by the passage of the
+bob upwards from the centre of the arc to the summit of the left-hand
+half-swing. Hence, at this point, the bob comes to a momentary rest.
+The last fraction of kinetic energy is just neutralised by the action
+of the attractive forces, and the bob has only potential energy equal
+to that with which it started. So that the sum of the phenomena may be
+stated thus: At the summit of either half-arc of its swing, the bob
+has a certain amount of potential energy; as it descends it gradually
+exchanges this for kinetic energy, until at the centre it possesses an
+equivalent amount of kinetic energy; from this point onwards, it
+gradually loses kinetic energy as it ascends, until, at the summit of
+the other half-arc, it has acquired an exactly similar amount of
+potential energy. Thus, on the whole transaction, nothing is either
+lost or gained; the quantity of energy is always the same, but it
+passes from one form into the other.</p>
+
+<p>To all appearance, the phenomena exhibited by the pendulum are not to
+be accounted for by impact: in fact, it is usually assumed that
+corresponding phenomena would take place if the earth and the pendulum
+were situated in an absolute vacuum, and at any conceivable distance
+from, one another. If this be so, it follows that there must be two
+totally different kinds of causes of motion: the one impact&mdash;a <i>vera
+causa</i>, of which, to all appearance, we have constant experience; the
+other, attractive or repulsive 'force'&mdash;a metaphysical entity which is
+physically inconceivable. Newton expressly repudiated the notion of
+the existence of attractive forces, in the sense in which that term is
+ordinarily understood; and he refused to put forward any hypothesis as
+to the physical cause of the so-called 'attraction of gravitation.' As
+a general rule, his successors have been content to accept the
+doctrine of attractive and repulsive forces, without troubling
+themselves about the philosophical difficulties which it involves. But
+this has not always been the case; and the attempt of Le Sage, in the
+last century, to show that the phenomena of attraction and repulsion
+are susceptible of explanation by his hypothesis of bombardment by
+ultra-mundane particles, whether tenable or not, has the great merit
+of being an attempt to get rid of the dual conception of the causes
+of motion which has hitherto prevailed. On this hypothesis, the
+hammering of the ultra-mundane corpuscles on the bob confers its
+kinetic energy, on the one hand, and takes it away on the other; and
+the state of potential energy means the condition of the bob during
+the instant at which the energy, conferred by the hammering during the
+one half-arc, has just been exhausted by the hammering during the
+other half-arc. It seems safe to look forward to the time when the
+conception of attractive and repulsive forces, having served its
+purpose as a useful piece of scientific scaffolding, will be replaced
+by the deduction of the phenomena known as attraction and repulsion,
+from the general laws of motion.</p>
+
+<p>The doctrine of the conservation of energy which I have endeavored to
+illustrate is thus defined by the late Clerk Maxwell:</p>
+
+<p>'The total energy of any body or system of bodies is a quantity which
+can neither be increased nor diminished by any mutual action of such
+bodies, though it may be transformed into any one of the forms of
+which energy is susceptible.' It follows that energy, like matter, is
+indestructible and ingenerable in nature. The phenomenal world, so far
+as it is material, expresses the evolution and involution of energy,
+its passage from the kinetic to the potential condition and back
+again. Wherever motion of matter takes place, that motion is effected
+at the expense of part of the total store of energy.</p>
+
+<p>Hence, as the phenomena exhibited by living beings, in so far as they
+are material, are all molar or molecular motions, these are included
+under the general law. A living body is a machine by which energy is
+transformed in the same sense as a steam-engine is so, and all its
+movements, molar and molecular, are to be accounted for by the energy
+which is supplied to it. The phenomena of consciousness which arise,
+along with certain transformations of energy, cannot be interpolated
+in the series of these transformations, inasmuch as they are not
+motions to which the doctrine of the conservation of energy applies.
+And, for the same reason, they do not necessitate the using up of
+energy; a sensation has no mass and cannot be conceived to be
+susceptible of movement. That a particular molecular motion does give
+rise to a state of consciousness is experimentally certain; but the
+how and why of the process are just as inexplicable as in the case of
+the communication of kinetic energy by impact.</p>
+
+<p>When dealing with the doctrine of the ultimate constitution of matter,
+we found a certain resemblance between the oldest speculations and the
+newest doctrines of physical philosophers. But there is no such
+resemblance between the ancient and modern views of motion and its
+causes, except in so far as the conception of attractive and repulsive
+forces may be regarded as the modified descendant of the Aristotelian
+conception of forms. In fact, it is hardly too much to say that the
+essential and fundamental difference between ancient and modern
+physical science lies in the ascertainment of the true laws of statics
+and dynamics in the course of the last three centuries; and in the
+invention of mathematical methods of dealing with all the consequences
+of these laws. The ultimate aim of modern physical science is the
+deduction of the phenomena exhibited by material bodies from
+physico-mathematical first principles. Whether the human intellect is
+strong enough to attain the goal set before it may be a question, but
+thither will it surely strive.</p>
+
+<div class="sidenote">(3) Evolution.</div>
+
+<p>The third great scientific event of our time, the rehabilitation of
+the doctrine of evolution, is part of the same tendency of increasing
+knowledge to unify itself, which has led to the doctrine of the
+conservation of energy. And this tendency, again, is mainly a product
+of the increasing strength conferred by physical investigation on the
+belief in the universal validity of that orderly relation of facts,
+which we express by the so-called 'Laws of Nature.'</p>
+
+<div class="sidenote">Early stages of this theory</div>
+
+<p>The growth of a plant from its seed, of an animal from its egg, the
+apparent origin of innumerable living things from mud, or from the
+putrefying remains of former organisms, had furnished the earlier
+scientific thinkers with abundant analogies suggestive of the
+conception of a corresponding method of cosmic evolution from a
+formless 'chaos' to an ordered world which might either continue for
+ever or undergo dissolution into its elements before starting on a new
+course of evolution. It is therefore no wonder that, from the days of
+the Ionian school onwards, the view that the universe was the result
+of such a process should have maintained itself as a leading dogma of
+philosophy. The emanistic theories which played so great a part in
+Neoplatonic philosophy and Gnostic theology are forms of evolution. In
+the seventeenth century, Descartes propounded a scheme of evolution,
+as an hypothesis of what might have been the mode of origin of the
+world, while professing to accept the ecclesiastical scheme of
+creation, as an account of that which actually was its manner of
+coming into existence. In the eighteenth century, Kant put forth a
+remarkable speculation as to the origin of the solar system, closely
+similar to that subsequently adopted by Laplace and destined to become
+famous under the title of the 'nebular hypothesis.'</p>
+
+<p>The careful observations and the acute reasonings of the Italian
+geologists of the seventeenth and eighteenth centuries; the
+speculations of Leibnitz in the 'Protogaea' and of Buffon in his
+'Th&eacute;orie de la Terre;' the sober and profound reasonings of Hutton, in
+the latter part of the eighteenth century; all these tended to show
+that the fabric of the earth itself implied the continuance of
+processes of natural causation for a period of time as great, in
+relation to human history, as the distances of the heavenly bodies
+from us are, in relation to terrestrial standards of measurement. The
+abyss of time began to loom as large as the abyss of space. And this
+revelation to sight and touch, of a link here and a link there of a
+practically infinite chain of natural causes and effects, prepared the
+way, as perhaps nothing else has done, for the modern form of the
+ancient theory of evolution.</p>
+
+<p>In the beginning of the eighteenth century, De Maillet made the first
+serious attempt to apply the doctrine to the living world. In the
+latter part of it, Erasmus Darwin, Goethe, Treviranus, and Lamarck
+took up the work more vigorously and with better qualifications. The
+question of special creation, or evolution, lay at the bottom of the
+fierce disputes which broke out in the French Academy between Cuvier
+and St.-Hilaire; and, for a time, the supporters of biological
+evolution were silenced, if not answered, by the alliance of the
+greatest naturalist of the age with their ecclesiastical opponents.
+Catastrophism, a short-sighted teleology, and a still more
+short-sighted orthodoxy, joined forces to crush evolution.</p>
+
+<p>Lyell and Poulett Scrope, in this country, resumed the work of the
+Italians and of Hutton; and the former, aided by a marvellous power of
+clear exposition, placed upon an irrefragable basis the truth that
+natural causes are competent to account for all events, which can be
+proved to have occurred, in the course of the secular changes which
+have taken place during the deposition of the stratified rocks. The
+publication of 'The Principles of Geology,' in 1830, constituted an
+epoch in geological science. But it also constituted an epoch in the
+modern history of the doctrines of evolution, by raising in the mind
+of every intelligent reader this question: If natural causation is
+competent to account for the not-living part of our globe, why should
+it not account for the living part?</p>
+
+<p>By keeping this question before the public for some thirty years,
+Lyell, though the keenest and most formidable of the opponents of the
+transmutation theory, as it was formulated by Lamarck, was of the
+greatest possible service in facilitating the reception of the sounder
+doctrines of a later day. And, in like fashion, another vehement
+opponent of the transmutation of species, the elder Agassiz, was
+doomed to help the cause he hated. Agassiz not only maintained the
+fact of the progressive advance in organisation of the inhabitants of
+the earth at each successive geological epoch, but he insisted upon
+the analogy of the steps of this progression with those by which the
+embryo advances to the adult condition, among the highest forms of
+each group. In fact, in endeavoring to support these views he went a
+good way beyond the limits of any cautious interpretation of the facts
+then known.</p>
+
+<div class="sidenote">Darwin</div>
+
+<p>Although little acquainted with biological science, Whewell seems to
+have taken particular pains with that part of his work which deals
+with the history of geological and biological speculation; and several
+chapters of his seventeenth and eighteenth books, which comprise the
+history of physiology, of comparative anatomy and of the
+pal&aelig;tiological sciences, vividly reproduce the controversies of the
+early days of the Victorian epoch. But here, as in the case of the
+doctrine of the conservation of energy, the historian of the inductive
+sciences has no prophetic insight; not even a suspicion of that which
+the near future was to bring forth. And those who still repeat the
+once favorite objection that Darwin's 'Origin of Species' is nothing
+but a new version of the 'Philosophie zoologique' will find that, so
+late as 1844, Whewell had not the slightest suspicion of Darwin's main
+theorem, even as a logical possibility. In fact, the publication of
+that theorem by Darwin and Wallace, in 1859, took all the biological
+world by surprise. Neither those who were inclined towards the
+'progressive transmutation' or 'development' doctrine, as it was then
+called, nor those who were opposed to it, had the slightest suspicion
+that the tendency to variation in living beings, which all admitted as
+a matter of fact; the selective influence of conditions, which no one
+could deny to be a matter of fact, when his attention was drawn to the
+evidence; and the occurrence of great geological changes which also
+was matter of fact; could be used as the only necessary postulates of
+a theory of the evolution of plants and animals which, even if not at
+once, competent to explain all the known facts of biological science,
+could not be shown to be inconsistent with any. So far as biology is
+concerned, the publication of the 'Origin of Species,' for the first
+time, put the doctrine of evolution, in its application to living
+things, upon a sound scientific foundation. It became an instrument of
+investigation, and in no hands did it prove more brilliantly
+profitable than in those of Darwin himself. His publications on the
+effects of domestication in plants and animals, on the influence of
+cross-fertilisation, on flowers as organs for effecting such
+fertilisation, on insectivorous plants, on the motions of plants,
+pointed out the routes of exploration which have since been followed
+by hosts of inquirers, to the great profit of science.</p>
+
+<p>Darwin found the biological world a more than sufficient field for
+even his great powers, and left the cosmical part of the doctrine to
+others. Not much has been added to the nebular hypothesis, since the
+time of Laplace, except that the attempt to show (against that
+hypothesis) that all nebul&aelig; are star clusters, has been met by the
+spectroscopic proof of the gaseous condition of some of them.
+Moreover, physicists of the present generation appear now to accept
+the secular cooling of the earth, which is one of the corollaries of
+that hypothesis. In fact, attempts have been made, by the help of
+deductions from the data of physics, to lay down an approximate limit
+to the number of millions of years which have elapsed since the earth
+was habitable by living beings. If the conclusions thus reached should
+stand the test of further investigation, they will undoubtedly be very
+valuable. But, whether true or false, they can have no influence upon
+the doctrine of evolution in its application to living organisms. The
+occurrence of successive forms of life upon our globe is an historical
+fact, which cannot be disputed; and the relation of these successive
+forms, as stages of evolution of the same type, is established in
+various cases. The biologist has no means of determining the time over
+which the process of evolution has extended, but accepts the
+computation of the physical geologist and the physicist, whatever that
+may be.</p>
+
+<div class="sidenote">and philosophy</div>
+
+<p>Evolution as a philosophical doctrine applicable to all phenomena,
+whether physical or mental, whether manifested by material atoms or by
+men in society, has been dealt with systematically in the 'Synthetic
+Philosophy' of Mr. Herbert Spencer. Comment on that great undertaking
+would not be in place here. I mention it because, so far as I know, it
+is the first attempt to deal, on scientific principles, with modern
+scientific facts and speculations. For the 'Philosophic positive' of
+M. Comte, with which Mr. Spencer's system of philosophy is sometimes
+compared, though it professes a similar object, is unfortunately
+permeated by a thoroughly unscientific spirit, and its author had no
+adequate acquaintance with the physical sciences even of his own time.</p>
+
+<hr style='width: 45%;' />
+
+<p>The doctrine of evolution, so far as the present physical cosmos is
+concerned, postulates the fixity of the rules of operation of the
+causes of motion in the material universe. If all kinds of matter are
+modifications of one kind, and if all modes of motion are derived from
+the same energy, the orderly evolution of physical nature out of one
+substratum and one energy implies that the rules of action of that
+energy should be fixed and definite. In the past history of the
+universe, back to that point, there can be no room for chance or
+disorder. But it is possible to raise the question whether this
+universe of simplest matter and definitely operating energy, which
+forms our hypothetical starting point, may not itself be a product of
+evolution from a universe of such matter, in which the manifestations
+of energy were not definite&mdash;in which, for example, our laws of motion
+held good for some units and not for others, or for the same units at
+one time and not at another&mdash;and which would therefore be a real
+epicurean chance-world?</p>
+
+<p>For myself, I must confess that I find the air of this region of
+speculation too rarefied for my constitution, and I am disposed to
+take refuge in 'ignoramus et ignorabimus.'</p>
+
+<div class="sidenote">Other achievements in physical science.</div>
+
+<p>The execution of my further task, the indication of the most important
+achievements in the several branches of physical science during the
+last fifty years, is embarrassed by the abundance of the objects of
+choice; and by the difficulty which everyone, but a specialist in each
+department, must find in drawing a due distinction between discoveries
+which strike the imagination by their novelty, or by their practical
+influence, and those unobtrusive but pregnant observations and
+experiments in which the germs of the great things of the future
+really lie. Moreover, my limits restrict me to little more than a bare
+chronicle of the events which I have to notice.</p>
+
+<div class="sidenote">Physics and chemistry.</div>
+
+<p>In physics and chemistry, the old boundaries of which sciences are
+rapidly becoming effaced, one can hardly go wrong in ascribing a
+primary value to the investigations into the relation between the
+solid, liquid, and gaseous states of matter on the one hand, and
+degrees of pressure and of heat on the other. Almost all, even the
+most refractory, solids have been vaporised by the intense heat of the
+electric arc; and the most refractory gases have been forced to assume
+the liquid, and even the solid, forms by the combination of high
+pressure with intense cold. It has further been shown that there is no
+discontinuity between these states&mdash;that a gas passes into the liquid
+state through a condition which is neither one nor the other, and that
+a liquid body becomes solid, or a solid liquid, by the intermediation
+of a condition in which it is neither truly solid nor truly liquid.</p>
+
+<p>Theoretical and experimental investigations have concurred in the
+establishment of the view that a gas is a body, the particles of which
+are in incessant rectilinear motion at high velocities, colliding with
+one another and bounding back when they strike the walls of the
+containing vessel; and, on this theory, the already ascertained
+relations of gaseous bodies to heat and pressure have been shown to be
+deducible from mechanical principles. Immense improvements have been
+effected, in the means of exhausting a given space of its gaseous
+contents; and experimentation on the phenomena which attend the
+electric discharge and the action of radiant heat, within the
+extremely rarefied media thus produced, has yielded a great number of
+remarkable results, some of which have been made familiar to the
+public by the Gieseler tubes and the radiometer. Already, these
+investigations have afforded an unexpected insight into the
+constitution of matter and its relations with thermal and electric
+energy, and they open up a vast field for future inquiry into some of
+the deepest problems of physics. Other important steps, in the same
+direction, have been effected by investigations into the absorption of
+radiant heat proceeding from different sources by solid, fluid, and
+gaseous bodies. And it is a curious example of the interconnection of
+the various branches of physical science, that some of the results
+thus obtained have proved of great importance in meteorology.</p>
+
+<div class="sidenote">The spectroscope.</div>
+
+<p>The existence of numerous dark lines, constant in their number and
+position in the various regions of the solar spectrum, was made out by
+Fraunhofer in the early part of the present century, but more than
+forty years elapsed before their causes were ascertained and their
+importance recognised. Spectroscopy, which then took its rise, is
+probably that employment of physical knowledge, already won, as a
+means of further acquisition, which most impresses the imagination.
+For it has suddenly and immensely enlarged our power of overcoming the
+obstacles which almost infinite minuteness on the one hand, and almost
+infinite distance on the other, have hitherto opposed to the
+recognition of the presence and the condition of matter. One
+eighteen-millionth of a grain of sodium in the flame of a spirit-lamp
+may be detected by this instrument; and, at the same time, it gives
+trust-worthy indications of the material constitution not only of the
+sun, but of the farthest of those fixed stars and nebul&aelig; which afford
+sufficient light to affect the eye, or the photographic plate, of the
+inquirer.</p>
+
+<div class="sidenote">Electricity.</div>
+
+<p>The mathematical and experimental elucidation of the phenomena of
+electricity, and the study of the relations of this form of energy
+with chemical and thermal action, had made extensive progress before
+1837. But the determination of the influence of magnetism on light,
+the discovery of diamagnetism, of the influence of crystalline
+structure on magnetism, and the completion of the mathematical theory
+of electricity, all belong to the present epoch. To it also appertain
+the practical execution and the working out of the results of the
+great international system of observations on terrestrial magnetism,
+suggested by Humboldt in 1836; and the invention of instruments of
+infinite delicacy and precision for the quantitative determination of
+electrical phenomena. The voltaic battery has received vast
+improvements; while the invention of magneto-electric engines and of
+improved means of producing ordinary electricity has provided sources
+of electrical energy vastly superior to any before extant in power,
+and far more convenient for use.</p>
+
+<p>It is perhaps this branch of physical science which may claim the palm
+for its practical fruits, no less than for the aid which it has
+furnished to the investigation of other parts of the field of physical
+science. The idea of the practicability of establishing a
+communication between distant points, by means of electricity, could
+hardly fail to have simmered in the minds of ingenious men since,
+well nigh a century ago, experimental proof was given that electric
+disturbances could be propagated through a wire twelve thousand feet
+long. Various methods of carrying the suggestion into practice had
+been carried out with some degree of success; but the system of
+electric telegraphy, which, at the present time, brings all parts of
+the civilised world within a few minutes of one another, originated
+only about the commencement of the epoch under consideration. In its
+influence on the course of human affairs, this invention takes its
+place beside that of gunpowder, which tended to abolish the physical
+inequalities of fighting men; of printing, which tended to destroy the
+effect of inequalities in wealth among learning men; of steam
+transport, which has done the like for travelling men. All these gifts
+of science are aids in the process of levelling up; of removing the
+ignorant and baneful prejudices of nation against nation, province
+against province, and class against class; of assuring that social
+order which is the foundation of progress, which has redeemed Europe
+from barbarism, and against which one is glad to think that those who,
+in our time, are employing themselves in fanning the embers of ancient
+wrong, in setting class against class, and in trying to tear asunder
+the existing bonds of unity, are undertaking a futile struggle. The
+telephone is only second in practical importance to the electric
+telegraph. Invented, as it were, only the other day, it has already
+taken its place as an appliance of daily life. Sixty years ago, the
+extraction of metals from their solutions, by the electric current,
+was simply a highly interesting scientific fact. At the present day,
+the galvano-plastic art is a great industry; and, in combination with
+photography, promises to be of endless service in the arts. Electric
+lighting is another great gift of science to civilisation, the
+practical effects of which have not yet been fully developed, largely
+on account of its cost. But those whose memories go back to the
+tinder-box period, and recollect the cost of the first lucifer
+matches, will not despair of the results of the application of science
+and ingenuity to the cheap production of anything for which there is a
+large demand.</p>
+
+<p>The influence of the progress of electrical knowledge and invention
+upon that of investigation in other fields of science is highly
+remarkable. The combination of electrical with mechanical contrivances
+has produced instruments by which, not only may extremely small
+intervals of time be exactly measured, but the varying rapidity of
+movements, which take place in such intervals and appear to the
+ordinary sense instantaneous, is recorded. The duration of the winking
+of an eye is a proverbial expression for an instantaneous action;
+but, by the help of the revolving cylinder and the electrical
+marking-apparatus, it is possible to obtain a graphic record of such
+an action, in which, if it endures a second, that second shall be
+subdivided into a hundred, or a thousand, equal parts, and the state
+of the action at each hundredth, or thousandth, of a second exhibited.
+In fact, these instruments may be said to be time-microscopes. Such
+appliances have not only effected a revolution in physiology, by the
+power of analysing the phenomena of muscular and nervous activity
+which they have conferred, but they have furnished new methods of
+measuring the rate of movement of projectiles to the artillerist.
+Again, the microphone, which renders the minutest movements audible,
+and which enables a listener to hear the footfall of a fly, has
+equipped the sense of hearing with the means of entering almost as
+deeply into the penetralia of nature, as does the sense of sight.</p>
+
+<div class="sidenote">Photography as an instrument of science.</div>
+
+<p>That light exerts a remarkable influence in bringing about certain
+chemical combinations and decompositions was well known fifty years
+ago, and various more or less successful attempts to produce permanent
+pictures, by the help of that knowledge, had already been made. It was
+not till 1839, however, that practical success was obtained; but the
+'daguerreotypes' were both cumbrous and costly, and photography would
+never have attained its present important development had not the
+progress of invention substituted paper and glass for the silvered
+plates then in use. It is not my affair to dwell upon the practical
+application of the photography of the present day, but it is germane
+to my purpose to remark that it has furnished a most valuable
+accessory to the methods of recording motions and lapse of time
+already in existence. In the hands of the astronomer and the
+meteorologist, it has yielded means of registering terrestrial, solar,
+planetary, and stellar phenomena, independent of the sources of error
+attendant on ordinary observation; in the hands of the physicist, not
+only does it record spectroscopic phenomena with unsurpassable ease
+and precision, but it has revealed the existence of rays having
+powerful chemical energy, or beyond the visible limits of either end
+of the spectrum; while, to the naturalist, it furnishes the means by
+which the forms of many highly complicated objects may be represented,
+without that possibility of error which is inherent in the work of the
+draughtsman. In fact, in many cases, the stern impartiality of
+photography is an objection to its employment: it makes no distinction
+between the important and the unimportant; and hence photographs of
+dissections, for example, are rarely so useful as the work of a
+draughtsman who is at once accurate and intelligent.</p>
+
+<div class="sidenote">Astronomy,</div>
+
+<p>The determination of the existence of a new planet, Neptune, far
+beyond the previously known bounds of the solar system, by
+mathematical deduction from the facts of perturbation; and the
+immediate confirmation of that determination, in the year 1846, by
+observers who turned their telescopes into the part of the heavens
+indicated as its place, constitute a remarkable testimony of nature to
+the validity of the principles of the astronomy of our time. In
+addition, so many new asteroids have been added to those which were
+already known to circulate in the place which theoretically should be
+occupied by a planet, between Mars and Jupiter, that their number now
+amounts to between two and three hundred. I have already alluded to
+the extension of our knowledge of the nature of the heavenly bodies by
+the employment of spectroscopy. It has not only thrown wonderful
+light upon the physical and chemical constitution of the sun, fixed
+stars, and nebul&aelig;, and comets, but it holds out a prospect of
+obtaining definite evidence as to the nature of our so-called
+elementary bodies.</p>
+
+<div class="sidenote">its relation to geology.</div>
+
+<p>The application of the generalisations of thermotics to the problem of
+the duration of the earth, and of deductions from tidal phenomena to
+the determination of the length of the day and of the time of
+revolution of the moon, in past epochs of the history of the universe;
+and the demonstration of the competency of the great secular changes,
+known under the general name of the precession of the equinoxes, to
+cause corresponding modifications in the climate of the two
+hemispheres of our globe, have brought astronomy into intimate
+relation with geology. Geology, in fact, proves that, in the course of
+the past history of the earth, the climatic conditions of the same
+region have been widely different, and seeks the explanation of this
+important truth from the sister sciences. The facts that, in the
+middle of the Tertiary epoch, evergreen trees abounded within the
+arctic circle; and that, in the long subsequent Quaternary epoch, an
+arctic climate, with its accompaniment of gigantic glaciers, obtained
+in the northern hemisphere, as far south as Switzerland and Central
+France, are as well established as any truths of science. But, whether
+the explanation of these extreme variations in the mean temperature of
+a great part of the northern hemisphere is to be sought in the
+concomitant changes in the distribution of land and water surfaces of
+which geology affords evidence, or in astronomical conditions, such as
+those to which I have referred, is a question which must await its
+answer from the science of the future.</p>
+
+<div class="sidenote">Biological sciences.</div>
+
+<div class="sidenote">The 'cell theory.'</div>
+
+<p>Turning now to the great steps in that progress which the biological
+sciences have made since 1837, we are met, on the threshold of our
+epoch, with perhaps the greatest of all&mdash;namely, the promulgation by
+Schwann, in 1839, of the generalisation known as the 'cell theory,'
+the application and extension of which by a host of subsequent
+investigators has revolutionised morphology, development, and
+physiology. Thanks to the immense series of labors thus inaugurated,
+the following fundamental truths have been established.</p>
+
+<div class="sidenote">Fundamental truths established.</div>
+
+<p>All living bodies contain substances of closely similar physical and
+chemical composition, which constitute the physical basis of life,
+known as protoplasm. So far as our present knowledge goes, this takes
+its origin only from pre-existing protoplasm.</p>
+
+<p>All complex living bodies consist, at one period of their existence,
+of an aggregate of minute portions of such substance, of similar
+structure, called cells, each cell having its own life independent of
+the others, though influenced by them.</p>
+
+<p>All the morphological characters of animals and plants are the results
+of the mode of multiplication, growth, and structural metamorphosis of
+these cells, considered as morphological units.</p>
+
+<p>All the physiological activities of animals and plants&mdash;assimilation,
+secretion, excretion, motion, generation&mdash;are the expression of the
+activities of the cells considered as physiological units. Each
+individual, among the higher animals and plants, is a synthesis of
+millions of subordinate individualities. Its individuality, therefore,
+is that of a 'civitas' in the ancient sense, or that of the Leviathan
+of Hobbes.</p>
+
+<p>There is no absolute line of demarcation between animals and plants.
+The intimate structure, and the modes of change, in the cells of the
+two are fundamentally the same. Moreover, the higher forms are
+evolved from lower, in the course of their development, by analogous
+processes of differentiation, coalescence, and reduction in both the
+vegetable and the animal worlds.</p>
+
+<p>At the present time, the cell theory, in consequence of recent
+investigations into the structure and metamorphosis of the 'nucleus,'
+is undergoing a new development of great significance, which, among
+other things, foreshadows the possibility of the establishment of a
+physical theory of heredity, on a safer foundation than those which
+Buffon and Darwin have devised.</p>
+
+<div class="sidenote">Spontaneous generation disproved.</div>
+
+<p>The popular belief in abiogenesis, or the so-called 'spontaneous'
+generation of the lower forms of life, which was accepted by all the
+philosophers of antiquity, held its ground down to the middle of the
+seventeenth century. Notwithstanding the frequent citation of the
+phrase, wrongfully attributed to Harvey, 'Omne vivum ex ovo,' that
+great physiologist believed in spontaneous generation as firmly as
+Aristotle did. And it was only in the latter part of the seventeenth
+century, that Redi, by simple and well-devised experiments,
+demonstrated that, in a great number of cases of supposed spontaneous
+generation, the animals which made their appearance owed their origin
+to the ordinary process of reproduction, and thus shook the ancient
+doctrine to its foundations. In the middle of the eighteenth century,
+it was revived, in a new form, by Needham and Buffon; but the
+experiments of Spallanzani enforced the conclusions of Redi, and
+compelled the advocates of the occurrence of spontaneous generation to
+seek evidence for their hypothesis only among the parasites and the
+lowest and minutest organisms. It is just fifty years since Schwann
+and others proved that, even with respect to them, the supposed
+evidence of abiogenesis was untrustworthy.</p>
+
+<p>During the present epoch, the question, whether living matter can be
+produced in any other way than by the physiological activity of other
+living matter, has been discussed afresh with great vigor; and the
+problem has been investigated by experimental methods of a precision
+and refinement unknown to previous investigators. The result is that
+the evidence in favor of abiogenesis has utterly broken down, in every
+case which has been properly tested. So far as the lowest and minutest
+organisms are concerned, it has been proved that they never make their
+appearance, if those precautions by which their germs are certainly
+excluded are taken. And, in regard to parasites, every case which
+seemed to make for their generation from the substance of the animal,
+or plant, which they infest has been proved to have a totally
+different significance. Whether not-living matter may pass, or ever
+has, under any conditions, passed into living matter, without the
+agency of pre-existing living matter, necessarily remains an open
+question; all that can be said is that it does not undergo this
+metamorphosis under any known conditions. Those who take a monistic
+view of the physical world may fairly hold abiogenesis as a pious
+opinion, supported by analogy and defended by our ignorance. But, as
+matters stand, it is equally justifiable to regard the physical world
+as a sort of dual monarchy. The kingdoms of living matter and of
+not-living matter are under one system of laws, and there is a perfect
+freedom of exchange and transit from one to the other. But no claim to
+biological nationality is valid except birth.</p>
+
+<div class="sidenote">Morphology.</div>
+
+<p>In the department of anatomy and development, a host of accurate and
+patient inquirers, aided by novel methods of preparation, which
+enable the anatomist to exhaust the details of visible structure and
+to reproduce them with geometrical precision, have investigated every
+important group of living animals and plants, no less than the fossil
+relics of former faun&aelig; and flor&aelig;. An enormous addition has thus been
+made to our knowledge, especially of the lower forms of life, and it
+may be said that morphology, however inexhaustible in detail, is
+complete in its broad features. Classification, which is merely a
+convenient summary expression of morphological facts, has undergone a
+corresponding improvement. The breaks which formerly separated our
+groups from one another, as animals from plants, vertebrates from
+invertebrates, cryptogams from phanerogams, have either been filled
+up, or shown to have no theoretical significance. The question of the
+position of man, as an animal, has given rise to much disputation,
+with the result of proving that there is no anatomical or
+developmental character by which he is more widely distinguished from
+the group of animals most nearly allied to him, than they are from one
+another. In fact, in this particular, the classification of Linn&aelig;us
+has been proved to be more in accordance with the facts than those of
+most of his successors.</p>
+
+<div class="sidenote">Anthropology.</div>
+
+<p>The study of man, as a genus and species of the animal world,
+conducted with reference to no other considerations than those which
+would be admitted by the investigator of any other form of animal
+life, has given rise to a special branch of biology, known, as
+Anthropology, which has grown with great rapidity. Numerous societies
+devoted to this portion of science have sprung up, and the energy of
+its devotees has produced a copious literature. The physical
+characters of the various races of men have been studied with a
+minuteness and accuracy heretofore unknown; and demonstrative
+evidence of the existence of human contemporaries of the extinct
+animals of the latest geological epoch has been obtained, physical
+science has thus been brought into the closest relation with history
+and with arch&aelig;ology; and the striking investigations which, during our
+time, have put beyond doubt the vast antiquity of Babylonian and
+Egyptian civilisation, are in perfect harmony with the conclusions of
+anthropology as to the antiquity of the human species.</p>
+
+<p>Classification is a logical process which consists in putting together
+those things which are like and keeping asunder those which are
+unlike; and a morphological classification, of course, takes notes
+only of morphological likeness and unlikeness. So long, therefore, as
+our morphological knowledge was almost wholly confined to anatomy, the
+characters of groups were solely anatomical; but as the phenomena of
+embryology were explored, the likeness and unlikeness of individual
+development had to be taken into account; and, at present, the study
+of ancestral evolution introduces a new element of likeness and
+unlikeness which is not only eminently deserving of recognition, but
+must ultimately predominate over all others. A classification which
+shall represent the process of ancestral evolution is, in fact, the
+end which the labors of the philosophical taxonomist must keep in
+view. But it is an end which cannot be attained until the progress of
+pal&aelig;ontology has given us far more insight than we yet possess, into
+the historical facts of the case. Much of the speculative 'phylogeny,'
+which abounds among my present contemporaries, reminds me very
+forcibly of the speculative morphology, unchecked by a knowledge of
+development, which was rife in my youth. As hypothesis, suggesting
+inquiry in this or that direction, it is often extremely useful; but,
+when the product of such speculation is placed on a level with those
+generalisations of morphological truths which are represented by the
+definitions of natural groups, it tends to confuse fancy with fact and
+to create mere confusion. We are in danger of drifting into a new
+'Natur-Philosophie' worse than the old, because there is less excuse
+for it. Boyle did great service to science by his 'Sceptical Chemist,'
+and I am inclined to think that, at the present day, a 'Sceptical
+Biologist' might exert an equally beneficent influence.</p>
+
+<div class="sidenote">Physiology.</div>
+
+<p>Whoso wishes to gain a clear conception of the progress of physiology,
+since 1837, will do well to compare M&uuml;ller's 'Physiology,' which
+appeared in 1835, and Drapiez's edition of Richard's 'Nouveaux
+El&eacute;ments de Botanique,' published in 1837, with any of the present
+handbooks of animals and vegetable physiology. M&uuml;ller's work was a
+masterpiece, unsurpassed since the time of Haller, and Richard's book
+enjoyed a great reputation at the time; but their successors transport
+one into a new world. That which characterises the new physiology is
+that it is permeated by, and indeed based upon, conceptions which,
+though not wholly absent, are but dawning on the minds of the older
+writers.</p>
+
+<p>Modern physiology sets forth as its chief ends: Firstly, the
+ascertainment of the facts and conditions of cell-life in general.
+Secondly, in composite organisms, the analysis of the functions of
+organs into those of the cells of which they are composed. Thirdly,
+the explication of the processes by which this local cell-life is
+directly, or indirectly, controlled and brought into relation with the
+life of the rest of the cells which compose the organism. Fourthly,
+the investigation of the phenomena of life in general, on the
+assumption that the physical and chemical processes which take place
+in the living body are of the same order as those which take place out
+of it; and that whatever energy is exerted in producing such phenomena
+is derived from the common stock of energy in the universe. In the
+fifth place, modern physiology investigates the relation between
+physical and psychical phenomena, on the assumption that molecular
+changes in definite portions of nervous matter stand in the relation
+of necessary antecedents to definite mental states and operations. The
+work which has been done in each of the directions here indicated is
+vast, and the accumulation of solid knowledge, which has been
+effected, is correspondingly great. For the first time in the history
+of science, physiologists are now in the position to say that they
+have arrived at clear and distinct, though by no means complete,
+conceptions of the manner in which the great functions of
+assimilation, respiration, secretion, distribution of nutriment,
+removal of waste products, motion, sensation, and reproduction are
+performed; while the operation of the nervous system, as a regulative
+apparatus, which influences the origination and the transmission of
+manifestations of activity, either within itself or in other organs,
+has been largely elucidated.</p>
+
+<div class="sidenote">Practical value of physiological discovery.</div>
+
+<p>I have pointed out, in an earlier part of this chapter, that the
+history of all branches of science proves that they must attain a
+considerable stage of development before they yield practical
+'fruits;' and this is eminently true of physiology. It is only within
+the present epoch, that physiology and chemistry have reached the
+point at which they could offer a scientific foundation to
+agriculture; and it is only within the present epoch, that zoology and
+physiology have yielded any very great aid to pathology and hygiene.
+But within that time, they have already rendered highly important
+services by the exploration of the phenomena of parasitism. Not only
+have the history of the animal parasites, such as the tapeworms and
+the trichina, which infest men and animals, with deadly results, been
+cleared up by means of experimental investigations, and efficient
+modes of prevention deduced from the data so obtained; but the
+terrible agency of the parasitic fungi and of the infinitesimally
+minute microbes, which work far greater havoc among plants and
+animals, has been brought to light. The 'particulate' or 'germ' theory
+of disease, as it is called, long since suggested, has obtained a firm
+foundation, in so far as it has been proved to be true in respect of
+sundry epidemic disorders. Moreover, it has theoretically justified
+prophylactic measures, such as vaccination, which formerly rested on a
+merely empirical basis; and it has been extended to other diseases
+with excellent results. Further, just as the discovery of the cause of
+scabies proved the absurdity of many of the old prescriptions for the
+prevention and treatment of that disease; so the discovery of the
+cause of splenic fever, and other such maladies, has given a new
+direction to prophylactic and curative measures against the worst
+scourges of humanity. Unless the fanaticism of philozoic sentiment
+overpowers the voice of philanthropy, and the love of dogs and cats
+supersedes that of one's neighbor, the progress of experimental
+physiology and pathology will, indubitably, in course of time, place
+medicine and hygiene upon a rational basis. Two centuries ago England
+was devastated by the plague; cleanliness and common sense were enough
+to free us from its ravages. One century since, small-pox was almost
+as great a scourge; science, though working empirically, and almost in
+the dark, has reduced that evil to relative insignificance. At the
+present time, science, working in the light of clear knowledge, has
+attacked splenic fever and has beaten it; it is attacking hydrophobia
+with no mean promise of success; sooner or later it will deal, in the
+same way, with diphtheria, typhoid and scarlet fever. To one who has
+seen half a street swept clear of its children, or has lost his own by
+these horrible pestilences, passing one's offspring through the fire
+to Moloch seems humanity, compared with the proposal to deprive them
+of half their chances of health and life because of the discomfort to
+dogs and cats, rabbits and frogs, which may be involved in the search
+for means of guarding them.</p>
+
+<div class="sidenote">Scientific exploration.</div>
+
+<p>An immense extension has been effected in our knowledge of the
+distribution of plants and animals; and the elucidation of the causes
+which have brought about that distribution has been greatly advanced.
+The establishment of meteorological observations by all civilised
+nations, has furnished a solid foundation to climatology; while a
+growing sense of the importance of the influence of the 'struggle for
+existence' affords a wholesome check to the tendency to overrate the
+influence of climate on distribution. Expeditions, such as that of the
+Challenger,' equipped, not for geographical exploration and discovery,
+but for the purpose of throwing light on problems of physical and
+biological science, have been sent out by our own and other
+Governments, and have obtained stores of information of the greatest
+value. For the first time, we are in possession of something like
+precise knowledge of the physical features of the deep seas, and of
+the living population of the floor of the ocean. The careful and
+exhaustive study of the phenomena presented by the accumulations of
+snow and ice, in polar and mountainous regions, which has taken place
+in our time, has not only revealed to the geologist an agent of
+denudation and transport, which has slowly and quietly produced
+effects, formerly confidently referred to diluvial catastrophes, but
+it has suggested new methods of accounting for various puzzling facts
+of distribution.</p>
+
+<div class="sidenote">Pal&aelig;ontology.</div>
+
+<p>Pal&aelig;ontology, which treats of the extinct forms of life and their
+succession and distribution upon our globe, a branch of science which
+could hardly be said to exist a century ago, has undergone a wonderful
+development in our epoch. In some groups of animals and plants, the
+extinct representatives, already known, are more numerous and
+important than the living. There can be no doubt that the existing
+Fauna and Flora is but the last term of a long series of equally
+numerous contemporary species, which have succeeded one another, by
+the slow and gradual substitution of species for species, in the vast
+interval of time which has elapsed between the deposition of the
+earliest fossiliferous strata and the present day. There is no
+reasonable ground for believing that the oldest remains yet obtained
+carry us even near the beginnings of life. The impressive warnings of
+Lyell against hasty speculations, based upon negative evidence, have
+been fully justified; time after time, highly organised types have
+been discovered in formations of an age in which the existence of such
+forms of life had been confidently declared to be impossible. The
+western territories of the United States alone have yielded a world of
+extinct animal forms, undreamed of fifty years ago. And, wherever
+sufficiently numerous series of the remains of any given group, which
+has endured for a long space of time, are carefully examined, their
+morphological relations are never in discordance with the requirements
+of the doctrine of evolution, and often afford convincing evidence of
+it. At the same time, it has been shown that certain forms persist
+with very little change, from the oldest to the newest fossiliferous
+formations; and thus show that progressive development is a
+contingent, and not a necessary result, of the nature of living
+matter.</p>
+
+<div class="sidenote">Geology.</div>
+
+<p>Geology is, as it were, the biology of our planet as a whole. In so
+far as it comprises the surface configuration and the inner structure
+of the earth, it answers to morphology; in so far as it studies
+changes of condition and their causes, it corresponds with physiology;
+in so far as it deals with the causes which have effected the progress
+of the earth from its earliest to its present state, it forms part of
+the general doctrine of evolution. An interesting contrast between the
+geology of the present day and that of half a century ago, is
+presented by the complete emancipation of the modern geologist from
+the controlling and perverting influence of theology, all-powerful at
+the earlier date. As the geologist of my young days wrote, he had one
+eye upon fact, and the other on Genesis; at present, he wisely keeps
+both eyes on fact, and ignores the pentateuchal mythology altogether.
+The publication of the 'Principles of Geology' brought upon its
+illustrious author a period of social ostracism; the instruction given
+to our children is based upon those principles. Whewell had the
+courage to attack Lyell's fundamental assumption (which surely is a
+dictate of common sense) that we ought to exhaust known causes before
+seeking for the explanation of geological phenomena in causes of which
+we have no experience. But geology has advanced to its present state
+by working from Lyell's<a name="FNanchor_J_10" id="FNanchor_J_10" /><a href="#Footnote_J_10" class="fnanchor">[J]</a> axiom; and, to this day, the record of the
+stratified rocks affords no proof that the intensity or the rapidity
+of the causes of change has ever varied, between wider limits, than
+those between which the operations of nature have taken place in the
+youngest geological epochs.</p>
+
+<p>An incalculable benefit has accrued to geological science from the
+accurate and detailed surveys, which have now been executed by skilled
+geologists employed by the Governments of all parts of the civilised
+world. In geology, the study of large maps is as important as it is
+said to be in politics; and sections, on a true scale, are even more
+important, in so far as they are essential to the apprehension of the
+extraordinary insignificance of geological perturbations in relation
+to the whole mass of our planet. It should never be forgotten that
+what we call 'catastrophes,' are, in relation to the earth, changes,
+the equivalents of which would be well represented by the development
+of a few pimples, or the scratch of a pin, on a man's head. Vast
+regions of the earth's surface remain geologically unknown; but the
+area already fairly explored is many times greater than it was in
+1837; and, in many parts of Europe and the United States, the
+structure of the superficial crust of the earth has been investigated
+with great minuteness.</p>
+
+<p>The parallel between Biology and Geology, which I have drawn, is
+further illustrated by the modern growth of that branch of the science
+known as Petrology, which answers to Histology, and has made the
+microscope as essential an instrument to the geological as to the
+biological investigator.</p>
+
+<p>The evidence of the importance of causes now in operation has been
+wonderfully enlarged by the study of glacial phenomena; by that of
+earthquakes and volcanoes; and by that of the efficacy of heat and
+cold, wind, rain, and rivers as agents of denudation and transport. On
+the other hand, the exploration of coral reefs and of the deposits now
+taking place at the bottom of the great oceans, has proved that, in
+animal and plant life, we have agents of reconstruction of a potency
+hitherto unsuspected.</p>
+
+<p>There is no study better fitted than that of geology to impress upon
+men of general culture that conviction of the unbroken sequence of the
+order of natural phenomena, throughout the duration of the universe,
+which is the great, and perhaps the most important, effect of the
+increase of natural knowledge.</p>
+
+
+<p>THE END.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_A_1" id="Footnote_A_1" /><a href="#FNanchor_A_1"><span class="label">[A]</span></a> There are excellent remarks to the same effect in
+Zeller's <i>Philosophie der Griechen</i>, Theil II. Abth. ii p. 407, and in
+Eucken's <i>Die Methode der Aristotelischen, Forschung</i>, pp. 136 <i>et
+seq</i>.</p></div>
+
+<div class="footnote"><p><a name="Footnote_B_2" id="Footnote_B_2" /><a href="#FNanchor_B_2"><span class="label">[B]</span></a> Fresnel, after a brilliant career of discovery in some of
+the most difficult regions of physico-mathematical science, died at
+thirty-nine years of age. The following passage of a letter from him
+to Young (written in November 1824), quoted by Whewell, so aptly
+illustrates the spirit which animates the scientific inquirer that I
+may cite it:</p>
+
+<div class="blockquot"><p>'For a long time that sensibility, or that vanity, which
+     people call love of glory is munch blunted in me. I labor
+     much less to catch the suffrages of the public than to
+     obtain an inward approval which has always been the mental
+     reward of my efforts. Without doubt I have often wanted the
+     spur of vanity to excite me to pursue my researches in
+     moments of disgust and discouragement. But all the
+     compliments which I have received from M.M. Arago, De
+     Laplace, or Biot, never gave me so much pleasure as the
+     discovery of a theoretical truth or the confirmation of a
+     calculation by experiment.'</p></div>
+</div>
+
+<div class="footnote"><p><a name="Footnote_C_3" id="Footnote_C_3" /><a href="#FNanchor_C_3"><span class="label">[C]</span></a> 'M&eacute;morable exemple de l'impuissance des recherches
+collectives appliqu&eacute;es &agrave; la d&eacute;couverte des v&eacute;rit&eacute;s nouvelles!' says
+one of the most distinguished of living French <i>savants</i> of the
+corporate chemical work of the old Acad&eacute;mie des Sciences. (See
+Berthelot, <i>Science et Philosophie</i>, p. 201.)</p></div>
+
+<div class="footnote"><p><a name="Footnote_D_4" id="Footnote_D_4" /><a href="#FNanchor_D_4"><span class="label">[D]</span></a> I am particularly indebted to my friend and colleague
+Professor R&uuml;cker, F.R.S., for the many acute criticisms and
+suggestions on my remarks respecting the ultimate problems of physics,
+with which he has favored me, and by which I have greatly profited.</p></div>
+
+<div class="footnote"><p><a name="Footnote_E_5" id="Footnote_E_5" /><a href="#FNanchor_E_5"><span class="label">[E]</span></a> I am aware that this proposition may be challenged. It
+may be said, for example, that, on the hypothesis of Boscovich, matter
+has no extension, being reduced to mathematical points serving as
+centres of 'forces.' But as the 'forces' of the various centres are
+conceived to limit one another's action in such a manner that an area
+around each centre has an individuality of its own extension comes
+back in the form of that area. Again, a very eminent mathematician and
+physicist&mdash;the late Clerk Maxwell&mdash;has declared that impenetrability
+is not essential to our notions of matter, and that two atoms may
+conceivably occupy the same space. I am loth to dispute any dictum of
+a philosopher as remarkable for the subtlety of his intellect as for
+his vast knowledge; but the assertion that one and the same point or
+area of space can have different (conceivably opposite) attributes
+appears to me to violate the principle of contradiction, which is the
+foundation not only of physical science, but of logic in general. It
+means that A can be not-A.</p></div>
+
+<div class="footnote"><p><a name="Footnote_F_6" id="Footnote_F_6" /><a href="#FNanchor_F_6"><span class="label">[F]</span></a> 'Molecule' would be the more appropriate name for such a
+particle. Unfortunately, chemists employ this term in a special sense,
+as a name for an aggregation of their smallest particles, for which
+they retain the designation of 'atoms.'</p></div>
+
+<div class="footnote"><p><a name="Footnote_G_7" id="Footnote_G_7" /><a href="#FNanchor_G_7"><span class="label">[G]</span></a> 'At present more organic analyses are made in a single
+day than were accomplished before Liebig's time in a whole
+year.'&mdash;Hofmann, <i>Faraday Lecture</i>, p. 46.</p></div>
+
+<div class="footnote"><p><a name="Footnote_H_8" id="Footnote_H_8" /><a href="#FNanchor_H_8"><span class="label">[H]</span></a> In the preface to his <i>M&eacute;canique Chimique</i> M. Berthelot
+declares his object to be 'ramener la chimie tout entir&egrave;re ... aux
+m&ecirc;mes principes m&eacute;caniques qui r&eacute;gissent d&eacute;j&agrave; les diverses branches de
+la physique.'</p></div>
+
+<div class="footnote"><p><a name="Footnote_I_9" id="Footnote_I_9" /><a href="#FNanchor_I_9"><span class="label">[I]</span></a> This is the more curious, as Amp&egrave;re's hypothesis that
+vibrations of molecules, causing and caused by vibrations of the
+ether, constitute heat, is discussed. See vol. ii. p. 587, 2nd ed. In
+the <i>Philosophy of the Inductive Sciences</i>, 2nd ed., 1847, p. 239,
+Whewell remarks, <i>&agrave; propos</i> of Bacon's definition of heat, 'that it is
+an expansive, restrained motion, modified in certain ways, and exerted
+in the smaller particles of the body;' that 'although the exact nature
+of heat is still an obscure and controverted matter, the science of
+heat now consists of many important truths; and that to none of these
+truths is there any approximation in Bacon's essay.' In point of fact,
+Bacon's statement, however much open to criticism, does contain a
+distinct approximation to the most important of all the truths
+respecting heat which had been discovered when Whewell wrote.</p></div>
+
+<div class="footnote"><p><a name="Footnote_J_10" id="Footnote_J_10" /><a href="#FNanchor_J_10"><span class="label">[J]</span></a> Perhaps I ought rather to say Button's axiom. For that
+great naturalist and writer embodied the principles of sound geology
+in a pithy phrase of the <i>Th&eacute;oris de la Terre</i>: 'Pour juger de ce qui
+est arriv&eacute;, et m&ecirc;me de ce qui arrivera, nous n'avons qu'&agrave; examiner ce
+qui arrive.'</p></div>
+</div>
+
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+$1.50.</p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="CHARLES_DARWINS_WORKS" id="CHARLES_DARWINS_WORKS" />CHARLES DARWIN'S WORKS.</h2>
+
+<p>ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, OR THE PRESERVATION
+OF FAVORED RACES IN THE STRUGGLE FOR LIFE. From sixth and last London
+edition. 2 vols., 12mo. Cloth, $4.00.</p>
+
+<p>DESCENT OF MAN, AND SELECTION IN RELATION TO SEX. With many
+Illustrations. A new edition. 12mo. Cloth, $3.00.</p>
+
+<p>JOURNAL OF RESEARCHES INTO THE NATURAL HISTORY AND GEOLOGY OF
+COUNTRIES VISITED DURING THE VOYAGE OF H.M.S. BEAGLE ROUND THE WORLD.
+New edition. 12mo. Cloth, $2.00.</p>
+
+<p>EMOTIONAL EXPRESSIONS OF MAN AND THE LOWER ANIMALS. 12mo. Cloth,
+$3.50.</p>
+
+<p>THE VARIATIONS OF ANIMALS AND PLANTS UNDER DOMESTICATION. With a
+Preface, by Professor ASA GRAY. 2 vols. Illustrated. Cloth, $5.00.</p>
+
+<p>INSECTIVOROUS PLANTS. 12mo. Cloth, $2.00.</p>
+
+<p>MOVEMENTS AND HABITS OF CLIMBING PLANTS. With Illustrations. 12mo.
+Cloth, $1.25.</p>
+
+<p>THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILIZED BY INSECTS.
+Revised edition, with Illustrations. 12mo. Cloth, $1.75.</p>
+
+<p>THE EFFECTS OF CROSS AND SELF FERTILIZATION IN THE VEGETABLE
+KINGDOM. 12mo. Cloth, $2.00.</p>
+
+<p>DIFFERENT FORMS OF FLOWERS ON PLANTS OF THE SAME SPECIES. With
+Illustrations. 12mo. Cloth, $1.50.</p>
+
+<p>THE POWER OF MOVEMENT IN PLANTS. By CHARLES DARWIN, LL.D., F.R.S.,
+assisted by FRANCIS DARWIN. With Illustrations. 12mo. Cloth, $2.00.</p>
+
+<p>THE FORMATION OF VEGETABLE MOULD THROUGH THE ACTION OF WORMS. With
+Observations on their Habits. With Illustrations. 12mo. Cloth, $1.50.</p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="ALEXANDER_BAINS_WORKS" id="ALEXANDER_BAINS_WORKS" />ALEXANDER BAIN'S WORKS.</h2>
+
+<p>THE SENSES AND THE INTELLECT. By ALEXANDER BAIN. LL.D., Professor of
+Logic in the University of Aberdeen. 8vo. Cloth, $5.00.</p>
+<div class="blockquot"><p>The object of this treatise is to give a full and systematic
+     account of two principal divisions of the science of mind&mdash;the
+     senses and the intellect. The value of the third edition of the
+     work is greatly enhanced by an account of the psychology of
+     Aristotle, which has been contributed by Mr. Grote.</p></div>
+
+<p>THE EMOTIONS AND THE WILL. By ALEXANDER BAIN, LL.D. 8vo. Cloth,
+$5.00.</p>
+<div class="blockquot"><p>The present publication la a sequel to the former one on &quot;The
+     Senses and the Intellect,&quot; and completes a systematic exposition
+     of the human mind.</p></div>
+
+<p>MENTAL SCIENCE. A Compendium of Psychology and the History of
+Philosophy. Designed as a Text-book for High-Schools and Colleges. By
+ALEXANDER BAIN, LL.D. 12mo. Cloth, leather back, $1.50.</p>
+<div class="blockquot"><p>This present volume is an abstract of two voluminous works, &quot;The
+     Senses and the intellect&quot; and &quot;The Emotions and the Will,&quot; and
+     presents in a compressed and lucid form the views which are there
+     more extensively elaborated.</p></div>
+
+<p>MORAL SCIENCE. A Compendium of Ethics. By ALEXANDER BAIN, LL.D.
+12mo. Cloth, leather back, $1.50.</p>
+<div class="blockquot"><p>The present dissertation falls under two divisions. The first
+     division entitled The Theory of Ethics, gives an account of the
+     questions or points brought into discussion, and handles at
+     length the two of greatest prominence, the Ethical Standard and
+     the Moral Faculty. The second division&mdash;on the Ethical
+     Systems&mdash;is a full detail of all the systems, ancient and modern.</p></div>
+
+<p>MIND AND BODY. Theories of their Relations. By ALEXANDER BAIN, LL.D.
+12mo. Cloth, $1.50.</p>
+<div class="blockquot"><p>&quot;A forcible statement of the connection between mind and body,
+     studying their subtile interworkings by the light of the most
+     recent physiological investigations.&quot;&mdash;<i>Christian Register</i>.</p></div>
+
+<p>LOGIC, DEDUCTIVE AND INDUCTIVE. By ALEXANDER BAIN, LL.D. Revised
+edition, 12mo. Cloth, leather back, $2.00.</p>
+
+<p>EDUCATION AS A SCIENCE. By ALEXANDER BAIN, LL.D. 12mo. Cloth, $1.75.</p>
+
+<p>ENGLISH COMPOSITION AND RHETORIC. Enlarged edition. Part I.
+Intellectual Elements of Style. By ALEXANDER BAIN, LL.D., Emeritus
+Professor of Logic in the University of Aberdeen. 12mo. Cloth, leather
+back, $1.50.</p>
+
+<p>ON TEACHING ENGLISH. With Detailed Examples and an Inquiry into the
+Definition of Poetry By ALEXANDER BAIN, LL.D. 12mo. Cloth, $1.25.</p>
+
+<p>PRACTICAL ESSAYS. By ALEXANDER BAIN, LL.D. 12mo. Cloth, $1.50.</p>
+
+
+
+<hr style="width: 65%;" />
+<h2><a name="Established_by_EDWARD_L_YOUMANS" id="Established_by_EDWARD_L_YOUMANS" />Established by EDWARD L. YOUMANS.</h2>
+
+<h2>THE POPULAR SCIENCE MONTHLY,</h2>
+
+<p>Edited by W.J. YOUMANS,</p>
+
+<p>Is filled with scientific articles by well-known writers on subjects
+of popular and practical interest. Its range of topics, which is
+widening with the advance of science, comprises:</p>
+
+<div class="blockquot"><p>Domestic and Social Economy. Political Science, or the
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+     of Disease. Art and Architecture in Practical Life. Race
+     Development. Agriculture and Food Products. Natural History;
+     Exploration; Discovery. Etc.</p></div>
+
+<p>In volume XXXII, which begins with the number for November, 1887,
+Professor Joseph Le Conte will discuss the Relations of Evolution and
+Religion, and the Hon. David A. Wells will continue his valuable
+papers on Recent Economic Disturbances. The volume will also contain
+illustrated articles on Astronomy, Geography, Anthropology, Natural
+History, and the Applications of Science; and will be enriched with
+contributions by Professors J.S. Newberry, F.W. Clarke, N.S. Shaler.
+Mr. Grant Allen, Mr. Appleton Morgan, and other distinguished writers.</p>
+
+<p>It contains Illustrated Articles, Biographical Sketches; records and
+advance made in every branch of science; is not technical; and is
+intended for non-scientific as well as scientific readers.</p>
+
+<p>No magazine in the world contains papers of a more instructive and at
+the same time of a more interesting character.</p>
+
+<p>Single number, 50 cents. Yearly subscription, $5.00.</p>
+
+
+
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+</pre>
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+</body>
+</html>
diff --git a/15253.txt b/15253.txt
new file mode 100644
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+The Project Gutenberg EBook of The Advance of Science in the Last
+Half-Century, by T.H. (Thomas Henry) Huxley
+
+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: The Advance of Science in the Last Half-Century
+
+Author: T.H. (Thomas Henry) Huxley
+
+Release Date: March 4, 2005 [EBook #15253]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK ADVANCE OF SCIENCE ***
+
+
+
+
+Produced by Digital & Multimedia Center, Michigan State University
+Libraries, Marilynda Fraser-Cunliffe, and the PG Online Distributed
+Proofreading Team.
+
+
+
+
+
+
+THE ADVANCE OF SCIENCE IN THE LAST HALF-CENTURY
+
+BY
+
+T.H. HUXLEY, F.R.S.
+
+NEW YORK
+
+D. APPLETON AND COMPANY
+
+1889
+
+
+
+
+THE ADVANCE OF SCIENCE IN THE LAST HALF-CENTURY
+
+[Sidenote: Recent industrial progress]
+
+The most obvious and the most distinctive features of the History of
+Civilisation, during the last fifty years, is the wonderful increase
+of industrial production by the application of machinery, the
+improvement of old technical processes and the invention of new ones,
+accompanied by an even more remarkable development of old and new
+means of locomotion and intercommunication. By this rapid and vast
+multiplication of the commodities and conveniences of existence, the
+general standard of comfort has been raised, the ravages of pestilence
+and famine have been checked, and the natural obstacles, which time
+and space offer to mutual intercourse, have been reduced in a manner,
+and to an extent, unknown to former ages. The diminution or removal of
+local ignorance and prejudice, the creation of common interests among
+the most widely separated peoples, and the strengthening of the forces
+of the organisation of the commonwealth against those of political or
+social anarchy, thus effected, have exerted an influence on the
+present and future fortunes of mankind the full significance of which
+may be divined, but cannot, as yet, be estimated at its full value.
+
+[Sidenote: caused by the increase of physical science]
+
+This revolution--for it is nothing less--in the political and social
+aspects of modern civilisation has been preceded, accompanied, and in
+great measure caused, by a less obvious, but no less marvellous,
+increase of natural knowledge, and especially of that part of it which
+is known as Physical Science, in consequence of the application of
+scientific method to the investigation of the phenomena of the
+material world. Not that the growth of physical science is an
+exclusive prerogative of the Victorian age. Its present strength and
+volume merely indicate the highest level of a stream which took its
+rise, alongside of the primal founts of Philosophy, Literature, and
+Art, in ancient Greece; and, after being dammed up for a thousand
+years, once more began to flow three centuries ago.
+
+[Sidenote: Greek and mediaeval science.]
+
+It may be doubted if even-handed justice, as free from fulsome
+panegyric as from captious depreciation, has ever yet been dealt out
+to the sages of antiquity who, for eight centuries, from the time of
+Thales to that of Galen, toiled at the foundations of physical
+science. But, without entering into the discussion of that large
+question, it is certain that the labors of these early workers in the
+field of natural knowledge were brought to a standstill by the decay
+and disruption of the Roman Empire, the consequent disorganisation of
+society, and the diversion of men's thoughts from sublunary matters to
+the problems of the supernatural world suggested by Christian dogma in
+the Middle Ages. And, notwithstanding sporadic attempts to recall men
+to the investigation of nature, here and there, it was not until the
+fifteenth and sixteenth centuries that physical science made a new
+start, founding itself, at first, altogether upon that which had been
+done by the Greeks. Indeed, it must be admitted that the men of the
+Renaissance, though standing on the shoulders of the old philosophers,
+were a long time before they saw as much as their forerunners had
+done.
+
+The first serious attempts to carry further the unfinished work of
+Archimedes, Hipparchus, and Ptolemy, of Aristotle and of Galen,
+naturally enough arose among the astronomers and the physicians. For
+the imperious necessity of seeking some remedy for the physical ills
+of life had insured the preservation of more or less of the wisdom of
+Hippocrates and his successors, and, by a happy conjunction of
+circumstances, the Jewish and the Arabian physicians and philosophers
+escaped many of the influences which, at that time, blighted natural
+knowledge in the Christian world. On the other hand, the superstitious
+hopes and fears which afforded countenance to astrology and to alchemy
+also sheltered astronomy and the germs of chemistry. Whether for this,
+or for some better reason, the founders of the schools of the Middle
+Ages included astronomy, along with geometry, arithmetic, and music,
+as one of the four branches of advanced education; and, in this
+respect, it is only just to them to observe that they were far in
+advance of those who sit in their seats. The school men considered no
+one to be properly educated unless he were acquainted with, at any
+rate, one branch of physical science. We have not, even yet, reached
+that stage of enlightenment.
+
+[Sidenote: Further advance after Renaissance.]
+
+In the early decades of the seventeenth century, the men of the
+Renaissance could show that they had already put out to good interest
+the treasure bequeathed to them by the Greeks. They had produced the
+astronomical system of Copernicus, with Kepler's great additions; the
+astronomical discoveries and the physical investigations of Galileo;
+the mechanics of Stevinus and the 'De Magnete' of Gilbert; the anatomy
+of the great French and Italian schools and the physiology of Harvey.
+In Italy, which had succeeded Greece in the hegemony of the scientific
+world, the Accademia dei Lyncei and sundry other such associations for
+the investigation of nature, the models of all subsequent academies
+and scientific societies, had been founded, while the literary skill
+and biting wit of Galileo had made the great scientific questions of
+the day not only intelligible, but attractive, to the general public.
+
+[Sidenote: Francis Bacon.]
+
+In our own country, Francis Bacon, had essayed to sum up the past of
+physical science, and to indicate the path which it must follow if its
+great destinies were to be fulfilled. And though the attempt was just
+such a magnificent failure as might have been expected from a man of
+great endowments, who was so singularly devoid of scientific insight
+that he could not understand the value of the work already achieved by
+the true instaurators of physical science; yet the majestic eloquence
+and the fervid vaticinations of one who was conspicuous alike by the
+greatness of his rise and the depth of his fall, drew the attention of
+all the world to the 'new birth of Time.'
+
+[Sidenote: The defect of his method.]
+
+But it is not easy to discover satisfactory evidence that the 'Novum
+Organum' had any direct beneficial influence on the advancement of
+natural knowledge. No delusion is greater than the notion that method
+and industry can make up for lack of motherwit, either in science or
+in practical life; and it is strange that, with his knowledge of
+mankind, Bacon should have dreamed that his, or any other, 'via
+inveniendi scientias' would 'level men's wits' and leave little scope
+for that inborn capacity which is called genius. As a matter of fact,
+Bacon's 'via' has proved hopelessly impracticable; while the
+'anticipation of nature' by the invention of hypotheses based on
+incomplete inductions, which he specially condemns, has proved itself
+to be a most efficient, indeed an indispensable, instrument of
+scientific progress. Finally, that transcendental alchemy--the
+superinducement of new forms on matter--which Bacon declares to be the
+supreme aim of science, has been wholly ignored by those who have
+created the physical knowledge of the present day.
+
+Even the eloquent advocacy of the Chancellor brought no unmixed good
+to physical science. It was natural enough that the man who, in his
+better moments, took 'all knowledge for his patrimony,' but, in his
+worse, sold that birthright for the mess of pottage of Court favor and
+professional success, for pomp and show, should be led to attach an
+undue value to the practical advantages which he foresaw, as Roger
+Bacon and, indeed, Seneca had foreseen, long before his time, must
+follow in the train of the advancement of natural knowledge. The
+burden of Bacon's pleadings for science is the gathering of
+fruit'--the importance of winning solid material advantages by the
+investigation of Nature and the desirableness of limiting the
+application of scientific methods of inquiry to that field.
+
+[Sidenote: Hobbes.]
+
+[Sidenote: Descartes.]
+
+Bacon's younger contemporary, Hobbes, casting aside the prudent
+reserve of his predecessor in regard to those matters about which the
+Crown or the Church might have something to say, extended scientific
+methods of inquiry to the phenomena of mind and the problems of social
+organisation; while, at the same time, he indicated the boundary
+between the province of real, and that of imaginary, knowledge. The
+'Principles of Philosophy' and the 'Leviathan' embody a coherent
+system of purely scientific thought in language which is a model of
+clear and vigorous English style. At the same time, in France, a man
+of far greater scientific capacity than either Bacon or Hobbes, Rene
+Descartes, not only in his immortal 'Discours de la Methode' and
+elsewhere, went down to the foundations of scientific certainty, but,
+in his 'Principes de Philosophie,' indicated where the goal of
+physical science really lay. However, Descartes was an eminent
+mathematician, and it would seem that the bent of his mind led him to
+overestimate the value of deductive reasoning from general principles,
+as much as Bacon had underestimated it. The progress of physical
+science has been effected neither by Baconians nor by Cartesians, as
+such, but by men like Galileo and Harvey, Boyle and Newton, who would
+have done their work just as well if neither Bacon nor Descartes had
+ever propounded their views respecting the manner in which scientific
+investigation should be pursued.
+
+[Sidenote: For a time the progress without fruits.]
+
+The progress of science, during the first century after Bacon's death,
+by means verified his sanguine prediction of the fruits which it would
+yield. For, though the revived and renewed study of nature had spread
+and grown to an extent which surpassed reasonable expectation, the
+practical results--the 'good to men's estate'--were, at first, by no
+means apparent. Sixty years after Bacon's death, Newton had crowned
+the long labors of the astronomers and the physicists, by coordinating
+the phenomena of solar motion throughout the visible universe into one
+vast system; but the 'Principia' helped no man to either wealth or
+comfort. Descartes, Newton, and Leibnitz had opened up new worlds to
+the mathematician, but the acquisitions of their genius enriched only
+man's ideal estate. Descartes had laid the foundations of rational
+cosmogony and of physiological psychology; Boyle had produced models
+of experimentation in various branches of physics and chemistry;
+Pascal and Torricelli had weighed the air; Malpighi and Grew, Ray and
+Willoughby had done work of no less importance in the biological
+sciences; but weaving and spinning were carried on with the old
+appliances; nobody could travel faster by sea or by land than at any
+previous time in the world's history, and King George could send a
+message from London to York no faster than King John might have done.
+Metals were worked from their ores by immemorial rule of thumb, and
+the centre of the iron trade of these islands was still among the oak
+forests of Sussex. The utmost skill of our mechanicians did not get
+beyond the production of a coarse watch.
+
+The middle of the eighteenth century is illustrated by a host of great
+names in science--English, French, German, and Italian--especially in
+the fields of chemistry, geology, and biology; but this deepening and
+broadening of natural knowledge produced next to no immediate
+practical benefits. Even if, at this time, Francis Bacon could have
+returned to the scene of his greatness and of his littleness, he must
+have regarded the philosophic world which praised and disregarded his
+precepts with great disfavor. If ghosts are consistent, he would have
+said, 'These people are all wasting their time, just as Gilbert and
+Kepler and Galileo and my worthy physician Harvey did in my day. Where
+are the fruits of the restoration of science which I promised? This
+accumulation of bare knowledge is all very well, but _cui bono_? Not
+one of these people is doing what I told him specially to do, and
+seeking that secret of the cause of forms which will enable men to
+deal, at will, with matter, and superinduce new natures upon the old
+foundations.'
+
+[Sidenote: Its recent effect on life.]
+
+But, a little later, that growth of knowledge beyond imaginable
+utilitarian ends, which is the condition precedent of its practical
+utility, began to produce some effect upon practical life; and the
+operation of that part of nature we call human upon the rest began to
+create, not 'new natures,' in Bacon's sense, but a new Nature, the
+existence of which is dependent upon men's efforts, which is
+subservient to their wants, and which would disappear if man's
+shaping and guiding hand were withdrawn. Every mechanical artifice,
+every chemically pure substance employed in manufacture, every
+abnormally fertile race of plants, or rapidly growing and fattening
+breed of animals, is a part of the new Nature created by science.
+Without it, the most densely populated regions of modern Europe and
+America must retain their primitive, sparsely inhabited, agricultural
+or pastoral condition; it is the foundation of our wealth and the
+condition of our safety from submergence by another flood of barbarous
+hordes; it is the bond which unites into a solid political whole,
+regions larger than any empire of antiquity; it secures us from the
+recurrence of the pestilences and famines of former times; it is the
+source of endless comforts and conveniences, which are not mere
+luxuries, but conduce to physical and moral well-being. During the
+last fifty years, this new birth of time, this new Nature begotten by
+science upon fact, has pressed itself daily and hourly upon our
+attention, and has worked miracles which have modified the whole
+fashion of our lives.
+
+[Sidenote: These results often too much regarded;]
+
+What wonder, then, if these astonishing fruits of the tree of
+knowledge are too often regarded by both friends and enemies as the
+be-all and end-all of science? What wonder if some eulogise, and
+others revile, the new philosophy for its utilitarian ends and its
+merely material triumphs?
+
+[Sidenote: for scientific research rarely directed to practical ends]
+
+In truth, the new philosophy deserves neither the praise of its
+eulogists, nor the blame of its slanderers. As I have pointed out, its
+disciples were guided by no search after practical fruits, during the
+great period of its growth, and it reached adolescence without being
+stimulated by any rewards of that nature. The bare enumeration of the
+names of the men who were the great lights of science in the latter
+part of the eighteenth and the first decade of the nineteenth
+century, of Herschel, of Laplace, of Young, of Fresnel, of Oersted, of
+Cavendish, of Lavoisier, of Davy, of Lamarck, of Cuvier, of Jussieu,
+of Decandolle, of Werner and of Hutton, suffices to indicate the
+strength of physical science in the age immediately preceding that of
+which I have to treat. But of which of these great men can it be said
+that their labors were directed to practical ends? I do not call to
+mind even an invention of practical utility which we owe to any of
+them, except the safety lamp of Davy. Werner certainly paid attention
+to mining, and I have not forgotten James Watt. But, though some of
+the most important of the improvements by which Watt converted the
+steam-engine, invented long before his time, into the obedient slave
+of man, were suggested and guided by his acquaintance with scientific
+principles, his skill as a practical mechanician, and the efficiency
+of Bolton's workmen had quite as much to do with the realisation of
+his projects.
+
+[Sidenote: but instigated by love of knowledge]
+
+In fact, the history of physical science teaches (and we cannot too
+carefully take the lesson to heart) that the practical advantages,
+attainable through its agency, never have been, and never will be,
+sufficiently attractive to men inspired by the inborn genius of the
+interpreter of nature, to give them courage to undergo the toils and
+make the sacrifices which that calling requires from its votaries.
+That which stirs their pulses is the love of knowledge and the joy of
+the discovery of the causes of things sung by the old poets--the
+supreme delight of extending the realm of law and order ever farther
+towards the unattainable goals of the infinitely great and the
+infinitely small, between which our little race of life is run. In the
+course of this work, the physical philosopher, sometimes
+intentionally, much more often unintentionally, lights upon something
+which proves to be of practical value. Great is the rejoicing of those
+who are benefited thereby; and, for the moment, science is the Diana
+of all the craftsmen. But, even while the cries of jubilation resound
+and this floatsam and jetsam of the tide of investigation is being
+turned into the wages of workmen and the wealth of capitalists, the
+crest of the wave of scientific investigation is far away on its
+course over the illimitable ocean of the unknown.
+
+[Sidenote: It is in its turn assisted by industrial improvements.]
+
+Far be it from me to depreciate the value of the gifts of science to
+practical life, or to cast a doubt upon the propriety of the course of
+action of those who follow science in the hope of finding wealth
+alongside truth, or even wealth alone. Such a profession is as
+respectable as any other. And quite as little do I desire to ignore
+the fact that, if industry owes a heavy debt to science, it has
+largely repaid the loan by the important aid which it has, in its
+turn, rendered to the advancement of science. In considering the
+causes which hindered the progress of physical knowledge in the
+schools of Athens and of Alexandria, it has often struck me[A] that
+where the Greeks did wonders was in just those branches of science,
+such as geometry, astronomy, and anatomy, which are susceptible of
+very considerable development without any, or any but the simplest,
+appliances. It is a curious speculation to think what would have
+become of modern physical science if glass and alcohol had not been
+easily obtainable; and if the gradual perfection of mechanical skill
+for industrial ends had not enabled investigators to obtain, at
+comparatively little cost, microscopes, telescopes, and all the
+exquisitely delicate apparatus for determining weight and measure and
+for estimating the lapse of time with exactness, which they now
+command. If science has rendered the colossal development of modern
+industry possible, beyond a doubt industry has done no less for modern
+physics and chemistry, and for a great deal of modern biology. And as
+the captains of industry have, at last, begun to be aware that the
+condition of success in that warfare, under the forms of peace, which
+is known as industrial competition lies in the discipline of the
+troops and the use of arms of precision, just as much as it does in
+the warfare which is called war, their demand for that discipline,
+which is technical education, is reacting upon science in a manner
+which will, assuredly, stimulate its future growth to an incalculable
+extent. It has become obvious that the interests of science and of
+industry are identical, that science cannot make a step forward
+without, sooner or later, opening up new channels for industry, and,
+on the other hand, that every advance of industry facilitates those
+experimental investigations, upon which the growth of science depends.
+We may hope that, at last, the weary misunderstanding between the
+practical men who professed to despise science, and the high and dry
+philosophers who professed to despise practical results, is at an end.
+
+Nevertheless, that which is true of the infancy of physical science in
+the Greek world, that which is true of its adolescence in the
+seventeenth and eighteenth centuries, remains true of its riper age in
+these latter days of the nineteenth century. The great steps in its
+progress have been made, are made, and will be made, by men who seek
+knowledge simply because they crave for it. They have their
+weaknesses, their follies, their vanities, and their rivalries, like
+the rest of the world; but whatever by-ends may mar their dignity and
+impede their usefulness, this chief end redeems them.[B] Nothing great
+in science has ever been done by men, whatever their powers, in whom
+the divine afflatus of the truth-seeker was wanting. Men of moderate
+capacity have done great things because it animated them; and men of
+great natural gifts have failed, absolutely or relatively, because
+they lacked this one thing needful.
+
+[Sidenote: True aim and method of research.]
+
+To anyone who knows the business of investigation practically, Bacon's
+notion of establishing a company of investigators to work for
+'fruits,' as if the pursuit of knowledge were a kind of mining
+operation and only required well-directed picks and shovels, seems
+very strange.[C] In science, as in art, and, as I believe, in every
+other sphere of human activity, there may be wisdom in a multitude of
+counsellors, but it is only in one or two of them. And, in scientific
+inquiry, at any rate, it is to that one or two that we must look for
+light and guidance. Newton said that he made his discoveries by
+'intending' his mind on the subject; no doubt truly. But to equal his
+success one must have the mind which he 'intended.' Forty lesser men
+might have intended their minds till they cracked, without any like
+result. It would be idle either to affirm or to deny that the last
+half-century has produced men of science of the calibre of Newton. It
+is sufficient that it can show a few capacities of the first rank,
+competent not only to deal profitably with the inheritance bequeathed
+by their scientific forefathers, but to pass on to their successors
+physical truths of a higher order than any yet reached by the human
+race. And if they have succeeded as Newton succeeded, it is because
+they have sought truth as he sought it, with no other object than the
+finding it.
+
+       *       *       *       *       *
+
+[Sidenote: Progress from 1837 to 1887.]
+
+I am conscious that in undertaking to progress give even the briefest
+sketch of the progress of physical science, in all its branches,
+during the last half-century, I may be thought to have exhibited more
+courage than discretion, and perhaps more presumption than either. So
+far as physical science is concerned, the days of Admirable Crichtons
+have long been over, and the most indefatigable of hard workers may
+think he has done well if he has mastered one of its minor
+subdivisions. Nevertheless, it is possible for anyone, who has
+familiarised himself with the operations of science in one department,
+to comprehend the significance, and even to form a general estimate of
+the value, of the achievements of specialists in other departments.
+
+Nor is their any lack either of guidance, or of aids to ignorance. By
+a happy chance, the first edition of Whewell's 'History of the
+Inductive Sciences' was published in 1837, and it affords a very
+useful view of the state of things at the commencement of the
+Victorian epoch. As to subsequent events, there are numerous
+excellent summaries of the progress of various branches of science,
+especially up to 1881, which was the jubilee year of the British
+Association.[D] And, with respect to the biological sciences, with
+some parts of which my studies have familiarised me, my personal
+experience nearly coincides with the preceding half-century. I may
+hope, therefore, that my chance of escaping serious errors is as good
+as that of anyone else, who might have been persuaded to undertake the
+somewhat perilous enterprise in which I find myself engaged.
+
+There is yet another prefatory remark which it seems desirable I
+should make. It is that I think it proper to confine myself to the
+work done, without saying anything about the doers of it. Meddling
+with questions of merit and priority is a thorny business at the best
+of times, and unless in case of necessity, altogether undesirable when
+one is dealing with contemporaries. No such necessity lies upon me,
+and I shall, therefore, mention no names of living men, lest,
+perchance, I should incur the reproof which the Israelites, who
+struggled with one another in the field, addressed to Moses--'Who made
+thee a prince and a judge over us.'
+
+[Sidenote: The aim of physical science]
+
+Physical science is one and indivisible. Although, for practical
+purposes, it is convenient to mark it out into the primary regions of
+Physics, Chemistry, and Biology, and to subdivide these into
+subordinate provinces, yet the method of investigation and the
+ultimate object of the physical inquirer are everywhere the same.
+
+[Sidenote: the discovery of the rational order of the universe]
+
+The object is the discovery of the rational order which pervades the
+universe, the method consists of observation and experiment (which is
+observation under artificial conditions) for the determination of the
+facts of nature, of inductive and deductive reasoning for the
+discovery of their mutual relations and connection. The various
+branches of physical science differ in the extent to which at any
+given moment of their history, observation on the one hand, or
+ratiocination on the other, is their more obvious feature, but in no
+other way, and nothing can be more incorrect than the assumption one
+sometimes meets with, that physics has one method, chemistry another,
+and biology a third.
+
+[Sidenote: It is based on postulates]
+
+All physical science starts from certain postulates. One of them is
+the objective existence of a material world. It is assumed that the
+phenomena which are comprehended under this name have a 'substratum'
+of extended, impenetrable, mobile substance, which exhibits the
+quality known as inertia, and is termed matter.[E] Another postulate
+is the universality of the law of causation; that nothing happens
+without a cause (that is, a necessary precedent condition), and that
+the state of the physical universe, at any given moment, is the
+consequence of its state at any preceding moment. Another is that any
+of the rules, or so-called 'laws of nature,' by which the relation of
+phenomena is truly defined, is true for all time. The validity of
+these postulates is a problem of metaphysics; they are neither
+self-evident nor are they, strictly speaking, demonstrable. The
+justification of their employment, as axioms of physical philosophy,
+lies in the circumstance that expectations logically based upon them
+are verified, or, at any rate, not contradicted, whenever they can be
+tested by experience.
+
+[Sidenote: and uses hypotheses.]
+
+Physical science therefore rests on verified or uncontradicted
+hypotheses; and, such being the case, it is not surprising that a
+great condition of its progress has been the invention of verifiable
+hypotheses. It is a favorite popular delusion that the scientific
+inquirer is under a sort of moral obligation to abstain from going
+beyond that generalisation of observed facts which is absurdly called
+'Baconian' induction. But anyone who is practically acquainted with
+scientific work is aware that those who refuse to go beyond fact,
+rarely get as far as fact; and anyone who has studied the history of
+science knows that almost every great step therein has been made by
+the 'anticipation of Nature,' that is, by the invention of hypotheses,
+which, though verifiable, often had very little foundation to start
+with; and, not unfrequently, in spite of a long career of usefulness,
+turned out to be wholly erroneous in the long run.
+
+[Sidenote: Fruitful use of an hypothesis even when wrong.]
+
+The geocentric system of astronomy, with its eccentrics and its
+epicycles, was an hypothesis utterly at variance with fact, which
+nevertheless did great things for the advancement of astronomical
+knowledge. Kepler was the wildest of guessers. Newton's corpuscular
+theory of light was of much temporary use in optics, though nobody now
+believes in it; and the undulatory theory, which has superseded the
+corpuscular theory and has proved one of the most fertile of
+instruments of research, is based on the hypothesis of the existence
+of an 'ether,' the properties of which are defined in propositions,
+some of which, to ordinary apprehension, seem physical antinomies.
+
+It sounds paradoxical to say that the attainment of scientific truth
+has been effected, to a great extent, by the help of scientific
+errors. But the subject-matter of physical science is furnished by
+observation, which cannot extend beyond the limits of our faculties;
+while, even within those limits, we cannot be certain that any
+observation is absolutely exact and exhaustive. Hence it follows that
+any given generalisation from observation may be true, within the
+limits of our powers of observation at a given time, and yet turn out
+to be untrue, when those powers of observation are directly or
+indirectly enlarged. Or, to put the matter in another way, a doctrine
+which is untrue absolutely, may, to a very great extent, be
+susceptible of an interpretation in accordance with the truth. At a
+certain period in the history of astronomical science, the assumption
+that the planets move in circles was true enough to serve the purpose
+of correlating such observations as were then possible; after Kepler,
+the assumption that they move in ellipses became true enough in regard
+to the state of observational astronomy at that time. We say still
+that the orbits of the planets are ellipses, because, for all ordinary
+purposes, that is a sufficiently near approximation to the truth; but,
+as a matter of fact, the centre of gravity of a planet describes
+neither an ellipse or any other simple curve, but an immensely
+complicated undulating line. It may fairly be doubted whether any
+generalisation, or hypothesis, based upon physical data is absolutely
+true, in the sense that a mathematical proposition is so; but, if its
+errors can become apparent only outside the limits of practicable
+observation, it may be just as usefully adopted for one of the symbols
+of that algebra by which we interpret nature, as if it were absolutely
+true.
+
+The development of every branch of physical knowledge presents three
+stages which, in their logical relation, are successive. The first is
+the determination of the sensible character and order of the
+phenomena. This is _Natural History_, in the original sense of the
+term, and here nothing but observation and experiment avail us. The
+second is the determination of the constant relations of the phenomena
+thus defined, and their expression in rules or laws. The third is the
+explication of these particular laws by deduction from the most
+general laws of matter and motion. The last two stages constitute
+_Natural Philosophy_ in its original sense. In this region, the
+invention of verifiable hypotheses is not only permissible, but is one
+of the conditions of progress.
+
+[Sidenote: and mutual assistance of observation, experiment, and
+speculation.]
+
+Historically, no branch of science has followed this order of growth;
+but, from the dawn of exact knowledge to the present day, observation,
+experiment, and speculation have gone hand in hand; and, whenever
+science has halted or strayed from the right path, it has been, either
+because its votaries have been content with mere unverified or
+unverifiable speculation (and this is the commonest case, because
+observation and experiment are hard work, while speculation is
+amusing); or it has been, because the accumulation of details of
+observation has for a time excluded speculation.
+
+[Sidenote: Recognition of these truths in recent times, and consequent
+progress.]
+
+The progress of physical science, since the revival of learning, is
+largely due to the fact that men have gradually learned to lay aside
+the consideration of unverifiable hypotheses; to guide observation
+and experiment by verifiable hypotheses; and to consider the latter,
+not as ideal truths, the real entities of an intelligible world behind
+phenomena, but as a symbolical language, by the aid of which nature
+can be interpreted in terms apprehensible by our intellects. And if
+physical science, during the last fifty years, has attained dimensions
+beyond all former precedent, and can exhibit achievements of greater
+importance than any former such period can show, it is because able
+men, animated by the true scientific spirit, carefully trained in the
+method of science, and having at their disposal immensely improved
+appliances, have devoted themselves to the enlargement of the
+boundaries of natural knowledge in greater number than during any
+previous half-century of the world's history.
+
+[Sidenote: The three great achievements. Doctrines of (1) molecular
+constitution of matter, (2) conservation of energy, (3) evolution.]
+
+I have said that our epoch can produce achievements in physical
+science of greater moment than any other has to show, advisedly; and
+I think that there are three great products of our time which justify
+the assertion. One of these is that doctrine concerning the
+constitution of matter which, for want of a better name, I will call
+'molecular;' the second is the doctrine of conservation of energy; the
+third is the doctrine of evolution. Each of these was foreshadowed,
+more or less distinctly, in former periods of the history of science;
+and, so far is either from being the outcome of purely inductive
+reasoning, that it would be hard to overrate the influence of
+metaphysical, and even of theological, considerations upon the
+development of all three. The peculiar merit of our epoch is that it
+has shown how these hypotheses connect a vast number of seemingly
+independent partial generalisations; that it has given them that
+precision of expression which is necessary for their exact
+verification; and that it has practically proved their value as
+guides to the discovery of new truth. All three doctrines are
+intimately connected, and each is applicable to the whole physical
+cosmos. But, as might have been expected from the nature of the case,
+the first two grew, mainly, out of the consideration of
+physico-chemical phenomena; while the third, in great measure, owes
+its rehabilitation, if not its origin, to the study of biological
+phenomena.
+
+[Sidenote: (1) Molecular constitution of matter.]
+
+In the early decades of this century, a number of important truths
+applicable, in part, to matter in general, and, in part, to particular
+forms of matter, had been ascertained by the physicists and chemists.
+
+The laws of motion of visible and tangible, or _molar_, matter had
+been worked out to a great degree of refinement and embodied in the
+branches of science known as Mechanics, Hydrostatics, and Pneumatics.
+These laws had been shown to hold good, so far as they could be
+checked by observation and experiment, throughout the universe, on the
+assumption that all such masses of matter possessed inertia and were
+susceptible of acquiring motion, in two ways, firstly by impact, or
+impulse from without; and, secondly, by the operation of certain
+hypothetical causes of motion termed 'forces,' which were usually
+supposed to be resident in the particles of the masses themselves, and
+to operate at a distance, in such a way as to tend to draw any two
+such masses together, or to separate them more widely.
+
+[Sidenote: The two theories as to matter.]
+
+With respect to the ultimate constitution of these masses, the same
+two antagonistic opinions which had existed since the time of
+Democritus and of Aristotle were still face to face. According to the
+one, matter was discontinuous and consisted of minute indivisible
+particles or atoms, separated by a universal vacuum; according to the
+other, it was continuous, and the finest distinguishable, or
+imaginable, particles were scattered through the attenuated general
+substance of the plenum. A rough analogy to the latter case would be
+afforded by granules of ice diffused through water; to the former,
+such granules diffused through absolutely empty space.
+
+[Sidenote: Reassertion by Dalton of atomic theory.]
+
+In the latter part of the eighteenth century, the chemists had arrived
+at several very important generalisations respecting those properties
+of matter with which they were especially concerned. However plainly
+ponderable matter seemed to be originated and destroyed in their
+operations, they proved that, as mass or body, it remained
+indestructible and ingenerable; and that, so far, it varied only in
+its perceptibility by our senses. The course of investigation further
+proved that a certain number of the chemically separable kinds of
+matter were unalterable by any known means (except in so far as they
+might be made to change their state from solid to fluid, or _vice
+versa_), unless they were brought into contact with other kinds of
+matter, and that the properties of these several kinds of matter were
+always the same, whatever their origin. All other bodies were found to
+consist of two or more of these, which thus took the place of the four
+'elements' of the ancient philosophers. Further, it was proved that,
+in forming chemical compounds, bodies always unite in a definite
+proportion by weight, or in simple multiples of that proportion, and
+that, if any one body were taken as a standard, every other could have
+a number assigned to it as its proportional combining weight. It was
+on this foundation of fact that Dalton based his re-establishment of
+the old atomic hypothesis on a new empirical foundation. It is
+obvious, that if elementary matter consists of indestructible and
+indivisible particles, each of which constantly preserves the same
+weight relatively to all the others, compounds formed by the
+aggregation of two, three, four, or more such particles must exemplify
+the rule of combination in definite proportions deduced from
+observation.
+
+In the meanwhile, the gradual reception of the undulatory theory of
+light necessitated the assumption of the existence of an 'ether'
+filling all space. But whether this ether was to be regarded as a
+strictly material and continuous substance was an undecided point, and
+hence the revived atomism, escaped strangling in its birth. For it is
+clear, that if the ether is admitted to be a continuous material
+substance, Democritic atomism is at an end and Cartesian continuity
+takes its place.
+
+[Sidenote: The real value of hypothesis; it predicates the existence
+of units of matter.]
+
+The real value of the new atomic hypothesis, however, did not lie in
+the two points which Democritus and his followers would have
+considered essential--namely, the indivisibility of the 'atoms' and
+the presence of an interatomic vacuum--but in the assumption that, to
+the extent to which our means of analysis take us, material bodies
+consist of definite minute masses, each of which, so far as physical
+and chemical processes of division go, may be regarded as a
+unit--having a practically permanent individuality. Just as a man is
+the unit of sociology, without reference to the actual fact of his
+divisibility, so such a minute mass is the unit of physico-chemical
+science--that smallest material particle which under any given
+circumstances acts as a whole.[F]
+
+The doctrine of specific heat originated in the eighteenth century.
+It means that the same mass of a body, under the same circumstances,
+always requires the same quantity of heat to raise it to a given
+temperature, but that equal masses of different bodies require
+different quantities. Ultimately, it was found that the quantities of
+heat required to raise equal masses of the more perfect gases, through
+equal ranges of temperature, were inversely proportional to their
+combining weights. Thus a definite relation was established between
+the hypothetical units and heat. The phenomena of electrolytic
+decomposition showed that there was a like close relation between
+these units and electricity. The quantity of electricity generated by
+the combination of any two units is sufficient to separate any other
+two which are susceptible of such decomposition. The phenomena of
+isomorphism showed a relation between the units and crystalline forms;
+certain units are thus able to replace others in a crystalline body
+without altering its form, and others are not.
+
+Again, the laws of the effect of pressure and heat on gaseous bodies,
+the fact that they combine in definite proportions by volume, and that
+such proportion bears a simple relation to their combining weights,
+all harmonised with the Daltonian hypothesis, and led to the bold
+speculation known as the law of Avogadro--that all gaseous bodies,
+under the same physical conditions, contain the same number of units.
+In the form in which it was first enunciated, this hypothesis was
+incorrect--perhaps it is not exactly true in any form; but it is
+hardly too much to say that chemistry and molecular physics would
+never have advanced to their present condition unless it had been
+assumed to be true. Another immense service rendered by Dalton, as a
+corollary of the new atomic doctrine, was the creation of a system of
+symbolic notation, which not only made the nature of chemical
+compounds and processes easily intelligible and easy of recollection,
+but, by its very form, suggested new lines of inquiry. The atomic
+notation was as serviceable to chemistry as the binomial nomenclature
+and the classificatory schematism of Linnaeus were to zooelogy and
+botany.
+
+[Sidenote: In biology a like theory of molecularstructure.]
+
+Side by side with these advances arose in another, which also has a
+close parallel in the history of biological science. If the unit of a
+compound is made up by the aggregation of elementary units, the notion
+that these must have some sort of definite arrangement inevitably
+suggests itself; and such phenomena as double decomposition pointed,
+not only to the existence of a molecular architecture, but to the
+possibility of modifying a molecular fabric without destroying it, by
+taking out some of the component units and replacing them by others.
+The class of neutral salts, for example, includes a great number of
+bodies in many ways similar, in which the basic molecules, or the acid
+molecules, may be replaced by other basic and other acid molecules
+without altering the neutrality of the salt; just as a cube of bricks
+remains a cube, so long as any brick that is taken out is replaced by
+another of the same shape and dimensions, whatever its weight or other
+properties may be. Facts of this kind gave rise to the conception of
+'types' of molecular structure, just as the recognition of the unity
+in diversity of the structure of the species of plants and animals
+gave rise to the notion of biological 'types.' The notation of
+chemistry enabled these ideas to be represented with precision; and
+they acquired an immense importance, when the improvement of methods
+of analysis, which took place about the beginning of our period,
+enabled the composition of the so-called 'organic' bodies to be
+determined with, rapidity and precision.[G] A large proportion of
+these compounds contain not more than three or four elements, of which
+carbon is the chief; but their number is very great, and the diversity
+of their physical and chemical properties is astonishing. The
+ascertainment of the proportion of each element in these compounds
+affords little or no help towards accounting for their diversities;
+widely different bodies being often very similar, or even identical,
+in that respect. And, in the last case, that of _isomeric_ compounds,
+the appeal to diversity of arrangement of the identical component
+units was the only obvious way out of the difficulty. Here, again,
+hypothesis proved to be of great value; not only was the search for
+evidence of diversity of molecular structure successful, but the study
+of the process of taking to pieces led to the discovery of the way to
+put together; and vast numbers of compounds, some of them previously
+known only as products of the living economy, have thus been
+artificially constructed. Chemical work, at the present day, is, to a
+large extent, synthetic or creative--that is to say, the chemist
+determines, theoretically, that certain non-existent compounds ought
+to be producible, and he proceeds to produce them.
+
+It is largely because the chemical theory and practice of our epoch
+have passed into this deductive and synthetic stage, that they are
+entitled to the name of the 'New Chemistry' which they commonly
+receive. But this new chemistry has grown up by the help of
+hypotheses, such as those of Dalton and of Avogadro, and that
+singular conception of 'bonds' invented to colligate the facts of
+'valency' or 'atomicity,' the first of which took some time to make
+its way; while the second fell into oblivion, for many years after it
+was propounded, for lack of empirical justification. As for the third,
+it may be doubted if anyone regards it as more than a temporary
+contrivance.
+
+But some of these hypotheses have done yet further service. Combining
+them with the mechanical theory of heat and the doctrine of the
+conservation of energy, which are also products of our time,
+physicists have arrived at an entirely new conception of the nature of
+gaseous bodies and of the relation of the physico-chemical units of
+matter to the different forms of energy. The conduct of gases under
+varying pressure and temperature, their diffusibility, their relation
+to radiant heat and to light, the evolution of heat when bodies
+combine, the absorption of heat when they are dissociated, and a host
+of other molecular phenomena, have been shown to be deducible from the
+dynamical and statical principles which apply to molar motion and
+rest; and the tendency of physico-chemical science is clearly towards
+the reduction of the problems of the world of the infinitely little,
+as it already has reduced those of the infinitely great world, to
+questions of mechanics.[H]
+
+In the meanwhile, the primitive atomic theory, which has served as the
+scaffolding for the edifice of modern physics and chemistry, has been
+quietly dismissed. I cannot discover that any contemporary physicist
+or chemist believes in the real indivisibility of atoms, or in an
+interatomic matterless vacuum. 'Atoms' appear to be used as mere
+names for physico-chemical units which have not yet been subdivided,
+and 'molecules' for physico-chemical units which are aggregates of the
+former. And these individualised particles are supposed to move in an
+endless ocean of a vastly more subtle matter--the ether. If this ether
+is a continuous substance, therefore, we have got back from the
+hypothesis of Dalton to that of Descartes. But there is much reason to
+believe that science is going to make a still further journey, and, in
+form, if not altogether in substance, to return to the point of view
+of Aristotle.
+
+[Sidenote: Elementary bodies]
+
+The greater number of the so-called 'elementary' bodies, now known,
+had been discovered before the commencement of our epoch; and it had
+become apparent that they were by no means equally similar or
+dissimilar, but that some of them, at any rate, constituted groups,
+the several members of which were as much like one another as they
+were unlike the rest. Chlorine, iodine, bromine, and fluorine thus
+formed a very distinct group; sulphur and selenium another; boron and
+silicon another; potassium, sodium, and lithium another; and so on. In
+some cases, the atomic weights of such allied bodies were nearly the
+same, or could be arranged in series, with like differences between
+the several terms. In fact, the elements afforded indications that
+they were susceptible of a classification in natural groups, such as
+those into which animals and plants fall.
+
+[Sidenote: fall into different series.]
+
+Recently this subject has been taken up afresh, with a result which
+may be stated roughly in the following terms: If the sixty-five or
+sixty-eight recognised 'elements' are arranged in the order of their
+atomic weights--from hydrogen, the lightest, as unity, to uranium, the
+heaviest, as 240--the series does not exhibit one continuous
+progressive modification in the physical and chemical characters of
+its several terms, but breaks up into a number of sections, in each of
+which the several terms present analogies with the corresponding terms
+of the other series.
+
+Thus the whole series does not run:
+
+_a, b, d, e, f, g, h, i, k,_ &c.,
+
+but
+
+_a, b, c, d_, A, B, C, D, alpha, beta, gamma, delta, &c.;
+
+so that it is said to express a _periodic law_ of recurrent
+similarities. Or the relation may be expressed in another way. In each
+section of the series, the atomic weight is greater than in the
+preceding section, so that if _w_ is the atomic weight of any element
+in the first segment, _w+x_ will represent the atomic weight of any
+element in the next, and _w+x+y_ the atomic weight of any element in
+the next, and so on. Therefore the sections may be represented as
+parallel series, the corresponding terms of which have analogous
+properties; each successive series starting with a body the atomic
+weight of which is greater than that of any in the preceding series,
+in the following fashion:
+
+_d_       D         delta
+_c_       C         gamma
+_b_       B          beta
+_a_       A         alpha
+ -      -----     ---------
+_w_    _w + x_   _w + x + y_
+
+[Sidenote: The possibility of a primary form of matter.]
+
+This is a conception with, which biologists are very familiar, animal
+and plant groups constantly appearing as series of parallel
+modifications of similar and yet different primary forms. In the
+living world, facts of this kind are now understood to mean evolution
+from a common prototype. It is difficult to imagine that in the
+not-living world they are devoid of significance. Is it not possible,
+nay probable that they may mean the evolution of our 'elements' from a
+primary undifferentiated form of matter? Fifty years ago, such a
+suggestion would have been scouted as a revival of the dreams of the
+alchemists. At present, it may be said to be the burning question of
+physico-chemical science.
+
+In fact, the so-called 'vortex-ring' hypothesis is a very serious and
+remarkable attempt to deal with material units from a point of view
+which is consistent with the doctrine of evolution. It supposes the
+ether to be a uniform substance, and that the 'elementary' units are,
+broadly speaking, permanent whirlpools, or vortices, of this ether,
+the properties of which depend on their actual and potential modes of
+motion. It is curious and highly interesting to remark that this
+hypothesis reminds us not only of the speculations of Descartes, but
+of those of Aristotle. The resemblance of the 'vortex-rings' to the
+'tourbillons' of Descartes is little more than nominal; but the
+correspondence between the modern and the ancient notion of a
+distinction between primary and derivative matter is, to a certain
+extent, real. For this ethereal 'Urstoff' of the modern corresponds
+very closely with the prhote hyle of Aristotle, the _materia prima_ of
+his mediaeval followers; while matter, differentiated into our
+elements, is the equivalent of the first stage of progress towards the
+heschhate hyle, or finished matter, of the ancient philosophy.
+
+If the material units of the existing order of nature are specialised
+portions of a relatively homogeneous _materia prima_--which were
+originated under conditions that have long ceased to exist and which
+remain unchanged and unchangeable under all conditions, whether
+natural or artificial, hitherto known to us--it follows that the
+speculation that they may be indefinitely altered, or that new units
+may be generated under conditions yet to be discovered, is perfectly
+legitimate. Theoretically, at any rate, the transmutability of the
+elements is a verifiable scientific hypothesis; and such inquiries as
+those which have been set afoot, into the possible dissociative action
+of the great heat of the sun upon our elements, are not only
+legitimate, but are likely to yield results which, whether affirmative
+or negative, will be of great importance. The idea that atoms are
+absolutely ingenerable and immutable 'manufactured articles' stands on
+the same sort of foundation as the idea that biological species are
+'manufactured articles' stood thirty years ago; and the supposed
+constancy of the elementary atoms, during the enormous lapse of time
+measured by the existence of our universe, is of no more weight
+against the possibility of change in them, in the infinity of
+antecedent time, than the constancy of species in Egypt, since the
+days of Rameses or Cheops, is evidence of their immutability during
+all past epochs of the earth's history. It seems safe to prophesy
+that the hypothesis of the evolution of the elements from a primitive
+matter will, in future, play no less a part in the history of science
+than the atomic hypothesis, which, to begin with, had no greater, if
+so great, an empirical foundation.
+
+[Sidenote: The old and the new atomic theory.]
+
+It may perhaps occur to the reader that the boasted progress of
+physical science does not come to much, if our present conceptions of
+the fundamental nature of matter are expressible in terms employed,
+more than two thousand years ago, by the old 'master of those that
+know.' Such a criticism, however, would involve forgetfulness of the
+fact, that the connotation of these terms, in the mind of the modern,
+is almost infinitely different from that which they possessed in the
+mind of the ancient, philosopher. In antiquity, they meant little more
+than vague speculation; at the present day, they indicate definite
+physical conceptions, susceptible of mathematical treatment, and
+giving rise to innumerable deductions, the value of which can be
+experimentally tested. The old notions produced little more than
+floods of dialectics; the new are powerful aids towards the increase
+of solid knowledge.
+
+[Sidenote: (2) Conservation of energy.]
+
+Everyday observation shows that, of the bodies which compose the
+material world, some are in motion and some are, or appear to be, at
+rest. Of the bodies in motion, some, like the sun and stars, exhibit a
+constant movement, regular in amount and direction, for which no
+external cause appears. Others, as stones and smoke, seem also to move
+of themselves when external impediments are taken away. But these
+appear to tend to move in opposite directions: the bodies we call
+heavy, such as stones, downwards, and the bodies we call light, at
+least such as smoke and steam, upwards. And, as we further notice
+that the earth, below our feet, is made up of heavy matter, while the
+air, above our heads, is extremely light matter, it is easy to regard
+this fact as evidence that the lower region is the place to which
+heavy things tend--their proper place, in short--while the upper
+region is the proper place of light things; and to generalise the
+facts observed by saying that bodies, which are free to move, tend
+towards their proper places. All these seem to be natural motions,
+dependent on the inherent faculties, or tendencies, of bodies
+themselves. But there are other motions which are artificial or
+violent, as when a stone is thrown from the hand, or is knocked by
+another stone in motion. In such cases as these, for example, when a
+stone is cast from the hand, the distance travelled by the stone
+appears to depend partly on its weight and partly upon the exertion
+of the thrower. So that, the weight of the stone remaining the same,
+it looks as if the motive power communicated to it were measured by
+the distance to which the stone travels--as if, in other words, the
+power needed to send it a hundred yards was twice as great as that
+needed to send it fifty yards. These, apparently obvious, conclusions
+from the everyday appearances of rest and motion fairly represent the
+state of opinion upon the subject which prevailed among the ancient
+Greeks, and remained dominant until the age of Galileo. The
+publication of the 'Principia' of Newton, in 1686-7, marks the epoch
+at which the progress of mechanical physics had effected a complete
+revolution of thought on these subjects. By this time, it had been
+made clear that the old generalisations were either incomplete or
+totally erroneous; that a body, once set in motion, will continue to
+move in a straight line for any conceivable time or distance, unless
+it is interfered with; that any change of motion is proportional to
+the 'force' which causes it, and takes place in the direction in which
+that 'force' is exerted; and that, when a body in motion acts as a
+cause of motion on another, the latter gains as much as the former
+loses, and _vice versa_. It is to be noted, however, that while, in
+contradistinction to the ancient idea of the inherent tendency to
+motion of bodies, the absence of any such spontaneous power of motion
+was accepted as a physical axiom by the moderns, the old conception
+virtually maintained itself is a new shape. For, in spite of Newton's
+well-known warning against the 'absurdity' of supposing that one body
+can act on another at a distance through a vacuum, the ultimate
+particles of matter were generally assumed to be the seats of
+perennial causes of motion termed 'attractive and repulsive forces,'
+in virtue of which, any two such particles, without any external
+impression of motion, or intermediate material agent, were supposed to
+tend to approach or remove from one another; and this view of the
+duality of the causes of motion is very widely held at the present
+day.
+
+Another important result of investigation, attained in the seventeenth
+century, was the proof and quantitative estimation of physical
+inertia. In the old philosophy, a curious conjunction of ethical and
+physical prejudices had led to the notion that there was something
+ethically bad and physically obstructive about matter. Aristotle
+attributes all irregularities and apparent dysteleologies in nature to
+the disobedience, or sluggish yielding, of matter to the shaping and
+guiding influence of those reasons and causes which were hypostatised
+in his ideal 'Forms.' In modern science, the conception of the
+inertia, or resistance to change, of matter is complex. In part, it
+contains a corollary from the law of causation: A body cannot change
+its state in respect of rest or motion without a sufficient cause.
+But, in part, it contains generalisations from experience. One of
+these is that there is no such sufficient cause resident in any body,
+and that therefore it will rest, or continue in motion, so long as no
+external cause of change acts upon it. The other is that the effect
+which the impact of a body in motion produces upon the body on which
+it impinges depends, other things being alike, on the relation of a
+certain quality of each which is called 'mass.' Given a cause of
+motion of a certain value, the amount of motion, measured by distance
+travelled in a certain time, which it will produce in a given quantity
+of matter, say a cubic inch, is not always the same, but depends on
+what that matter is--a cubic inch of iron will go faster than a cubic
+inch of gold. Hence, it appears, that since equal amounts of motion
+have, _ex hypothesi_, been produced, the amount of motion in a body
+does not depend on its speed alone, but on some property of the body.
+To this the name of 'mass' has been given. And since it seems
+reasonable to suppose that a large quantity of matter, moving slowly,
+possesses as much motion as a small quantity moving faster, 'mass' has
+been held to express 'quantity of matter.' It is further demonstrable
+that, at any given time and place, the relative mass of any two bodies
+is expressed by the ratio of their weights.
+
+[Sidenote: Mechanical theory of heat.]
+
+When all these great truths respecting molar motion, or the movements
+of visible and tangible masses, had been shown to hold good not only
+of terrestrial bodies, but of all those which constitute the visible
+universe, and the movements of the macrocosm had thus been expressed
+by a general mechanical theory, there remained a vast number of
+phenomena, such as those of light, heat, electricity, magnetism, and
+those of the physical and chemical changes, which do not involve molar
+motion. Newton's corpuscular theory of light was an attempt to deal
+with one great series of these phenomena on mechanical principles, and
+it maintained its ground until, at the beginning of the nineteenth
+century, the undulatory theory proved itself to be a much better
+working hypothesis. Heat, up to that time, and indeed much later, was
+regarded as an imponderable substance, _caloric_; as a thing which was
+absorbed by bodies when they were wanned, and was given out as they
+cooled; and which, moreover, was capable of entering into a sort of
+chemical combination with them, and so becoming latent. Rumford and
+Davy had given a great blow to this view of heat by proving that the
+quantity of heat which two portions of the same body could be made to
+give out, by rubbing them together, was practically illimitable. This
+result brought philosophers face to face with the contradiction of
+supposing that a finite body could contain an infinite quantity of
+another body; but it was not until 1843, that clear and unquestionable
+experimental proof was given of the fact that there is a definite
+relation between mechanical work and heat; that so much work always
+gives rise, under the same conditions, to so much heat, and so much
+heat to so much mechanical work. Thus originated the mechanical theory
+of heat, which became the starting-point of the modern doctrine of the
+conservation of energy. Molar motion had appeared to be destroyed by
+friction. It was proved that no destruction took place, but that an
+exact equivalent of the energy of the lost molar motion appears as
+that of the _molecular_ motion, or motion of the smallest particles of
+a body, which constitutes heat. The loss of the masses is the gain of
+their particles.
+
+[Sidenote: Earlier approaches towards doctrine of conservation.]
+
+Before 1843, however, the doctrine of conservation of energy had been
+approached Bacon's chief contribution to positive science is the happy
+guess (for the context shows that it was little more) that heat may be
+a mode of motion; Descartes affirmed the quantity of motion in the
+world to be constant; Newton nearly gave expression to the complete
+theorem; while Rumford's and Davy's experiments suggested, though they
+did not prove, the equivalency of mechanical and thermal energy.
+Again, the discovery of voltaic electricity, and the marvellous
+development of knowledge, in that field, effected by such men as Davy,
+Faraday, Oersted, Ampere, and Melloni, had brought to light a number
+of facts which tended to show that the so-called 'forces' at work in
+light, heat, electricity, and magnetism, in chemical and in mechanical
+operations, were intimately, and, in various cases, quantitatively
+related. It was demonstrated that any one could be obtained at the
+expense of any other; and apparatus was devised which exhibited the
+evolution of all these kinds of action from one source of energy.
+Hence the idea of the 'correlation of forces' which was the immediate
+forerunner of the doctrine of the conservation of energy.
+
+It is a remarkable evidence of the greatness of the progress in this
+direction which has been effected in our time, that even the second
+edition of the 'History of the Inductive Sciences,' which was
+published in 1846, contains no allusion either to the general view of
+the 'Correlation of Forces' published in England in 1842, or to the
+publication in 1843 of the first of the series of experiments by which
+the mechanical equivalent of heat was correctly ascertained.[I] Such a
+failure on the part of a contemporary, of great acquirements and
+remarkable intellectual powers, to read the signs of the times, is a
+lesson and a warning worthy of being deeply pondered by anyone who
+attempts to prognosticate the course of scientific progress.
+
+[Sidenote: What this doctrine is.]
+
+I have pointed out that the growth of clear and definite views
+respecting the constitution of matter has led to the conclusion that,
+so far as natural agencies are concerned, it is ingenerable and
+indestructible. In so far as matter may be conceived to exist in a
+purely passive state, it is, imaginably, older than motion. But, as it
+must be assumed to be susceptible of motion, a particle of bare matter
+at rest must be endowed with the potentiality of motion. Such a
+particle, however, by the supposition, can have no energy, for there
+is no cause why it should move. Suppose now that it receives an
+impulse, it will begin to move with a velocity inversely proportional
+to its mass, on the one hand, and directly proportional to the
+strength of the impulse, on the other, and will possess _kinetic
+energy_, in virtue of which it will not only continue to move for ever
+if unimpeded, but if it impinges on another such particle, it will
+impart more or less of its motion, to the latter. Let it be conceived
+that the particle acquires a tendency to move, and that nevertheless
+it does not move. It is then in a condition totally different from
+that in which it was at first. A cause competent to produce motion is
+operating upon it, but, for some reason or other, is unable to give
+rise to motion. If the obstacle is removed, the energy which was
+there, but could not manifest itself, at once gives rise to motion.
+While the restraint lasts, the energy of the particle is merely
+potential; and the case supposed illustrates what is meant by
+_potential energy_. In this contrast of the potential with the actual,
+modern physics is turning to account the most familiar of Aristotelian
+distinctions--that between dunamis and energeia.
+
+That kinetic energy appears to be imparted by impact is a fact of
+daily and hourly experience: we see bodies set in motion by bodies,
+already in motion, which seem to come in contact with them. It is a
+truth which could have been learned by nothing but experience, and
+which cannot be explained, but must be taken as an ultimate fact
+about which, explicable or inexplicable, there can be no doubt.
+Strictly speaking, we have no direct apprehension of any other cause
+of motion. But experience furnishes innumerable examples of the
+production of kinetic energy in a body previously at rest, when no
+impact is discernible as the cause of that energy. In all such cases,
+the presence of a second body is a necessary condition; and the amount
+of kinetic energy, which its presence enables the first to gain, is
+strictly dependent on the relative positions of the two. Hence the
+phrase _energy of position_, which is frequently used as equivalent to
+potential energy. If a stone is picked up and held, say, six feet
+above the ground, it has _potential energy_, because, if let go, it
+will immediately begin to move towards the earth; and this energy may
+be said to be _energy of position_, because it depends upon the
+relative position of the earth and the stone. The stone is solicited
+to move but cannot, so long as the muscular strength of the holder
+prevents the solicitation from taking effect. The stone, therefore,
+has potential energy, which becomes kinetic if it is let go, and the
+amount of that kinetic energy which will be developed before it
+strikes the earth depends on its position--on the fact that it is,
+say, six feet off the earth, neither more nor less. Moreover, it can
+be proved that the raiser of the stone had to exert as much energy in
+order to place it in its position, as it will develop in falling.
+Hence the energy which was exerted, and apparently exhausted, in
+raising the stone, is potentially in the stone, in its raised
+position, and will manifest itself when the stone is set free. Thus
+the energy, withdrawn from the general stock to raise the stone, is
+returned when it falls, and there is no change in the total amount.
+Energy, as a whole, is conserved.
+
+Taking this as a very broad and general statement of the essential
+facts of the case, the raising of the stone is intelligible enough, as
+a case of the communication of motion from one body to another. But
+the potential energy of the raised stone is not so easily
+intelligible. To all appearance, there is nothing either pushing or
+pulling it towards the earth, or the earth towards it; and yet it is
+quite certain that the stone tends to move towards the earth and the
+earth towards the stone, in the way defined by the law of gravitation.
+
+In the currently accepted language of science, the cause of motion, in
+all such cases as this, when bodies tend to move towards or away from
+one or another, without any discernible impact of other bodies, is
+termed a 'force,' which is called 'attractive' in the one case, and
+'repulsive' in the other. And such attractive or repulsive forces are
+often spoken of as if they were real things, capable of exerting a
+pull, or a push, upon the particles of matter concerned. Thus the
+potential energy of the stone is commonly said to be due to the
+'force' of gravity which is continually operating upon it.
+
+Another illustration may make the case plainer. The bob of a pendulum
+swings first to one side and then to the other of the centre of the
+arc which it describes. Suppose it to have just reached the summit of
+its right-hand half-swing. It is said that the 'attractive forces' of
+the bob for the earth, and of the earth for the bob, set the former in
+motion; and as these 'forces' are continually in operation, they
+confer an accelerated velocity on the bob; until, when it reaches the
+centre of its swing, it is, so to speak, fully charged with kinetic
+energy. If, at this moment, the whole material universe, except the
+bob, were abolished, it would move for ever in the direction of a
+tangent to the middle of the arc described. As a matter of fact, it
+is compelled to travel through its left-hand half-swing, and thus
+virtually to go up hill. Consequently, the 'attractive forces' of the
+bob and the earth are now acting against it, and constitute a
+resistance which the charge of kinetic energy has to overcome. But, as
+this charge represents the operation of the attractive forces during
+the passage of the bob through the right-hand half-swing down to the
+centre of the arc, so it must needs be used up by the passage of the
+bob upwards from the centre of the arc to the summit of the left-hand
+half-swing. Hence, at this point, the bob comes to a momentary rest.
+The last fraction of kinetic energy is just neutralised by the action
+of the attractive forces, and the bob has only potential energy equal
+to that with which it started. So that the sum of the phenomena may be
+stated thus: At the summit of either half-arc of its swing, the bob
+has a certain amount of potential energy; as it descends it gradually
+exchanges this for kinetic energy, until at the centre it possesses an
+equivalent amount of kinetic energy; from this point onwards, it
+gradually loses kinetic energy as it ascends, until, at the summit of
+the other half-arc, it has acquired an exactly similar amount of
+potential energy. Thus, on the whole transaction, nothing is either
+lost or gained; the quantity of energy is always the same, but it
+passes from one form into the other.
+
+To all appearance, the phenomena exhibited by the pendulum are not to
+be accounted for by impact: in fact, it is usually assumed that
+corresponding phenomena would take place if the earth and the pendulum
+were situated in an absolute vacuum, and at any conceivable distance
+from, one another. If this be so, it follows that there must be two
+totally different kinds of causes of motion: the one impact--a _vera
+causa_, of which, to all appearance, we have constant experience; the
+other, attractive or repulsive 'force'--a metaphysical entity which is
+physically inconceivable. Newton expressly repudiated the notion of
+the existence of attractive forces, in the sense in which that term is
+ordinarily understood; and he refused to put forward any hypothesis as
+to the physical cause of the so-called 'attraction of gravitation.' As
+a general rule, his successors have been content to accept the
+doctrine of attractive and repulsive forces, without troubling
+themselves about the philosophical difficulties which it involves. But
+this has not always been the case; and the attempt of Le Sage, in the
+last century, to show that the phenomena of attraction and repulsion
+are susceptible of explanation by his hypothesis of bombardment by
+ultra-mundane particles, whether tenable or not, has the great merit
+of being an attempt to get rid of the dual conception of the causes
+of motion which has hitherto prevailed. On this hypothesis, the
+hammering of the ultra-mundane corpuscles on the bob confers its
+kinetic energy, on the one hand, and takes it away on the other; and
+the state of potential energy means the condition of the bob during
+the instant at which the energy, conferred by the hammering during the
+one half-arc, has just been exhausted by the hammering during the
+other half-arc. It seems safe to look forward to the time when the
+conception of attractive and repulsive forces, having served its
+purpose as a useful piece of scientific scaffolding, will be replaced
+by the deduction of the phenomena known as attraction and repulsion,
+from the general laws of motion.
+
+The doctrine of the conservation of energy which I have endeavored to
+illustrate is thus defined by the late Clerk Maxwell:
+
+'The total energy of any body or system of bodies is a quantity which
+can neither be increased nor diminished by any mutual action of such
+bodies, though it may be transformed into any one of the forms of
+which energy is susceptible.' It follows that energy, like matter, is
+indestructible and ingenerable in nature. The phenomenal world, so far
+as it is material, expresses the evolution and involution of energy,
+its passage from the kinetic to the potential condition and back
+again. Wherever motion of matter takes place, that motion is effected
+at the expense of part of the total store of energy.
+
+Hence, as the phenomena exhibited by living beings, in so far as they
+are material, are all molar or molecular motions, these are included
+under the general law. A living body is a machine by which energy is
+transformed in the same sense as a steam-engine is so, and all its
+movements, molar and molecular, are to be accounted for by the energy
+which is supplied to it. The phenomena of consciousness which arise,
+along with certain transformations of energy, cannot be interpolated
+in the series of these transformations, inasmuch as they are not
+motions to which the doctrine of the conservation of energy applies.
+And, for the same reason, they do not necessitate the using up of
+energy; a sensation has no mass and cannot be conceived to be
+susceptible of movement. That a particular molecular motion does give
+rise to a state of consciousness is experimentally certain; but the
+how and why of the process are just as inexplicable as in the case of
+the communication of kinetic energy by impact.
+
+When dealing with the doctrine of the ultimate constitution of matter,
+we found a certain resemblance between the oldest speculations and the
+newest doctrines of physical philosophers. But there is no such
+resemblance between the ancient and modern views of motion and its
+causes, except in so far as the conception of attractive and repulsive
+forces may be regarded as the modified descendant of the Aristotelian
+conception of forms. In fact, it is hardly too much to say that the
+essential and fundamental difference between ancient and modern
+physical science lies in the ascertainment of the true laws of statics
+and dynamics in the course of the last three centuries; and in the
+invention of mathematical methods of dealing with all the consequences
+of these laws. The ultimate aim of modern physical science is the
+deduction of the phenomena exhibited by material bodies from
+physico-mathematical first principles. Whether the human intellect is
+strong enough to attain the goal set before it may be a question, but
+thither will it surely strive.
+
+[Sidenote: (3) Evolution.]
+
+The third great scientific event of our time, the rehabilitation of
+the doctrine of evolution, is part of the same tendency of increasing
+knowledge to unify itself, which has led to the doctrine of the
+conservation of energy. And this tendency, again, is mainly a product
+of the increasing strength conferred by physical investigation on the
+belief in the universal validity of that orderly relation of facts,
+which we express by the so-called 'Laws of Nature.'
+
+[Sidenote: Early stages of this theory]
+
+The growth of a plant from its seed, of an animal from its egg, the
+apparent origin of innumerable living things from mud, or from the
+putrefying remains of former organisms, had furnished the earlier
+scientific thinkers with abundant analogies suggestive of the
+conception of a corresponding method of cosmic evolution from a
+formless 'chaos' to an ordered world which might either continue for
+ever or undergo dissolution into its elements before starting on a new
+course of evolution. It is therefore no wonder that, from the days of
+the Ionian school onwards, the view that the universe was the result
+of such a process should have maintained itself as a leading dogma of
+philosophy. The emanistic theories which played so great a part in
+Neoplatonic philosophy and Gnostic theology are forms of evolution. In
+the seventeenth century, Descartes propounded a scheme of evolution,
+as an hypothesis of what might have been the mode of origin of the
+world, while professing to accept the ecclesiastical scheme of
+creation, as an account of that which actually was its manner of
+coming into existence. In the eighteenth century, Kant put forth a
+remarkable speculation as to the origin of the solar system, closely
+similar to that subsequently adopted by Laplace and destined to become
+famous under the title of the 'nebular hypothesis.'
+
+The careful observations and the acute reasonings of the Italian
+geologists of the seventeenth and eighteenth centuries; the
+speculations of Leibnitz in the 'Protogaea' and of Buffon in his
+'Theorie de la Terre;' the sober and profound reasonings of Hutton, in
+the latter part of the eighteenth century; all these tended to show
+that the fabric of the earth itself implied the continuance of
+processes of natural causation for a period of time as great, in
+relation to human history, as the distances of the heavenly bodies
+from us are, in relation to terrestrial standards of measurement. The
+abyss of time began to loom as large as the abyss of space. And this
+revelation to sight and touch, of a link here and a link there of a
+practically infinite chain of natural causes and effects, prepared the
+way, as perhaps nothing else has done, for the modern form of the
+ancient theory of evolution.
+
+In the beginning of the eighteenth century, De Maillet made the first
+serious attempt to apply the doctrine to the living world. In the
+latter part of it, Erasmus Darwin, Goethe, Treviranus, and Lamarck
+took up the work more vigorously and with better qualifications. The
+question of special creation, or evolution, lay at the bottom of the
+fierce disputes which broke out in the French Academy between Cuvier
+and St.-Hilaire; and, for a time, the supporters of biological
+evolution were silenced, if not answered, by the alliance of the
+greatest naturalist of the age with their ecclesiastical opponents.
+Catastrophism, a short-sighted teleology, and a still more
+short-sighted orthodoxy, joined forces to crush evolution.
+
+Lyell and Poulett Scrope, in this country, resumed the work of the
+Italians and of Hutton; and the former, aided by a marvellous power of
+clear exposition, placed upon an irrefragable basis the truth that
+natural causes are competent to account for all events, which can be
+proved to have occurred, in the course of the secular changes which
+have taken place during the deposition of the stratified rocks. The
+publication of 'The Principles of Geology,' in 1830, constituted an
+epoch in geological science. But it also constituted an epoch in the
+modern history of the doctrines of evolution, by raising in the mind
+of every intelligent reader this question: If natural causation is
+competent to account for the not-living part of our globe, why should
+it not account for the living part?
+
+By keeping this question before the public for some thirty years,
+Lyell, though the keenest and most formidable of the opponents of the
+transmutation theory, as it was formulated by Lamarck, was of the
+greatest possible service in facilitating the reception of the sounder
+doctrines of a later day. And, in like fashion, another vehement
+opponent of the transmutation of species, the elder Agassiz, was
+doomed to help the cause he hated. Agassiz not only maintained the
+fact of the progressive advance in organisation of the inhabitants of
+the earth at each successive geological epoch, but he insisted upon
+the analogy of the steps of this progression with those by which the
+embryo advances to the adult condition, among the highest forms of
+each group. In fact, in endeavoring to support these views he went a
+good way beyond the limits of any cautious interpretation of the facts
+then known.
+
+[Sidenote: Darwin]
+
+Although little acquainted with biological science, Whewell seems to
+have taken particular pains with that part of his work which deals
+with the history of geological and biological speculation; and several
+chapters of his seventeenth and eighteenth books, which comprise the
+history of physiology, of comparative anatomy and of the
+palaetiological sciences, vividly reproduce the controversies of the
+early days of the Victorian epoch. But here, as in the case of the
+doctrine of the conservation of energy, the historian of the inductive
+sciences has no prophetic insight; not even a suspicion of that which
+the near future was to bring forth. And those who still repeat the
+once favorite objection that Darwin's 'Origin of Species' is nothing
+but a new version of the 'Philosophie zoologique' will find that, so
+late as 1844, Whewell had not the slightest suspicion of Darwin's main
+theorem, even as a logical possibility. In fact, the publication of
+that theorem by Darwin and Wallace, in 1859, took all the biological
+world by surprise. Neither those who were inclined towards the
+'progressive transmutation' or 'development' doctrine, as it was then
+called, nor those who were opposed to it, had the slightest suspicion
+that the tendency to variation in living beings, which all admitted as
+a matter of fact; the selective influence of conditions, which no one
+could deny to be a matter of fact, when his attention was drawn to the
+evidence; and the occurrence of great geological changes which also
+was matter of fact; could be used as the only necessary postulates of
+a theory of the evolution of plants and animals which, even if not at
+once, competent to explain all the known facts of biological science,
+could not be shown to be inconsistent with any. So far as biology is
+concerned, the publication of the 'Origin of Species,' for the first
+time, put the doctrine of evolution, in its application to living
+things, upon a sound scientific foundation. It became an instrument of
+investigation, and in no hands did it prove more brilliantly
+profitable than in those of Darwin himself. His publications on the
+effects of domestication in plants and animals, on the influence of
+cross-fertilisation, on flowers as organs for effecting such
+fertilisation, on insectivorous plants, on the motions of plants,
+pointed out the routes of exploration which have since been followed
+by hosts of inquirers, to the great profit of science.
+
+Darwin found the biological world a more than sufficient field for
+even his great powers, and left the cosmical part of the doctrine to
+others. Not much has been added to the nebular hypothesis, since the
+time of Laplace, except that the attempt to show (against that
+hypothesis) that all nebulae are star clusters, has been met by the
+spectroscopic proof of the gaseous condition of some of them.
+Moreover, physicists of the present generation appear now to accept
+the secular cooling of the earth, which is one of the corollaries of
+that hypothesis. In fact, attempts have been made, by the help of
+deductions from the data of physics, to lay down an approximate limit
+to the number of millions of years which have elapsed since the earth
+was habitable by living beings. If the conclusions thus reached should
+stand the test of further investigation, they will undoubtedly be very
+valuable. But, whether true or false, they can have no influence upon
+the doctrine of evolution in its application to living organisms. The
+occurrence of successive forms of life upon our globe is an historical
+fact, which cannot be disputed; and the relation of these successive
+forms, as stages of evolution of the same type, is established in
+various cases. The biologist has no means of determining the time over
+which the process of evolution has extended, but accepts the
+computation of the physical geologist and the physicist, whatever that
+may be.
+
+[Sidenote: and philosophy]
+
+Evolution as a philosophical doctrine applicable to all phenomena,
+whether physical or mental, whether manifested by material atoms or by
+men in society, has been dealt with systematically in the 'Synthetic
+Philosophy' of Mr. Herbert Spencer. Comment on that great undertaking
+would not be in place here. I mention it because, so far as I know, it
+is the first attempt to deal, on scientific principles, with modern
+scientific facts and speculations. For the 'Philosophic positive' of
+M. Comte, with which Mr. Spencer's system of philosophy is sometimes
+compared, though it professes a similar object, is unfortunately
+permeated by a thoroughly unscientific spirit, and its author had no
+adequate acquaintance with the physical sciences even of his own time.
+
+       *       *       *       *       *
+
+The doctrine of evolution, so far as the present physical cosmos is
+concerned, postulates the fixity of the rules of operation of the
+causes of motion in the material universe. If all kinds of matter are
+modifications of one kind, and if all modes of motion are derived from
+the same energy, the orderly evolution of physical nature out of one
+substratum and one energy implies that the rules of action of that
+energy should be fixed and definite. In the past history of the
+universe, back to that point, there can be no room for chance or
+disorder. But it is possible to raise the question whether this
+universe of simplest matter and definitely operating energy, which
+forms our hypothetical starting point, may not itself be a product of
+evolution from a universe of such matter, in which the manifestations
+of energy were not definite--in which, for example, our laws of motion
+held good for some units and not for others, or for the same units at
+one time and not at another--and which would therefore be a real
+epicurean chance-world?
+
+For myself, I must confess that I find the air of this region of
+speculation too rarefied for my constitution, and I am disposed to
+take refuge in 'ignoramus et ignorabimus.'
+
+[Sidenote: Other achievements in physical science.]
+
+The execution of my further task, the indication of the most important
+achievements in the several branches of physical science during the
+last fifty years, is embarrassed by the abundance of the objects of
+choice; and by the difficulty which everyone, but a specialist in each
+department, must find in drawing a due distinction between discoveries
+which strike the imagination by their novelty, or by their practical
+influence, and those unobtrusive but pregnant observations and
+experiments in which the germs of the great things of the future
+really lie. Moreover, my limits restrict me to little more than a bare
+chronicle of the events which I have to notice.
+
+[Sidenote: Physics and chemistry.]
+
+In physics and chemistry, the old boundaries of which sciences are
+rapidly becoming effaced, one can hardly go wrong in ascribing a
+primary value to the investigations into the relation between the
+solid, liquid, and gaseous states of matter on the one hand, and
+degrees of pressure and of heat on the other. Almost all, even the
+most refractory, solids have been vaporised by the intense heat of the
+electric arc; and the most refractory gases have been forced to assume
+the liquid, and even the solid, forms by the combination of high
+pressure with intense cold. It has further been shown that there is no
+discontinuity between these states--that a gas passes into the liquid
+state through a condition which is neither one nor the other, and that
+a liquid body becomes solid, or a solid liquid, by the intermediation
+of a condition in which it is neither truly solid nor truly liquid.
+
+Theoretical and experimental investigations have concurred in the
+establishment of the view that a gas is a body, the particles of which
+are in incessant rectilinear motion at high velocities, colliding with
+one another and bounding back when they strike the walls of the
+containing vessel; and, on this theory, the already ascertained
+relations of gaseous bodies to heat and pressure have been shown to be
+deducible from mechanical principles. Immense improvements have been
+effected, in the means of exhausting a given space of its gaseous
+contents; and experimentation on the phenomena which attend the
+electric discharge and the action of radiant heat, within the
+extremely rarefied media thus produced, has yielded a great number of
+remarkable results, some of which have been made familiar to the
+public by the Gieseler tubes and the radiometer. Already, these
+investigations have afforded an unexpected insight into the
+constitution of matter and its relations with thermal and electric
+energy, and they open up a vast field for future inquiry into some of
+the deepest problems of physics. Other important steps, in the same
+direction, have been effected by investigations into the absorption of
+radiant heat proceeding from different sources by solid, fluid, and
+gaseous bodies. And it is a curious example of the interconnection of
+the various branches of physical science, that some of the results
+thus obtained have proved of great importance in meteorology.
+
+[Sidenote: The spectroscope.]
+
+The existence of numerous dark lines, constant in their number and
+position in the various regions of the solar spectrum, was made out by
+Fraunhofer in the early part of the present century, but more than
+forty years elapsed before their causes were ascertained and their
+importance recognised. Spectroscopy, which then took its rise, is
+probably that employment of physical knowledge, already won, as a
+means of further acquisition, which most impresses the imagination.
+For it has suddenly and immensely enlarged our power of overcoming the
+obstacles which almost infinite minuteness on the one hand, and almost
+infinite distance on the other, have hitherto opposed to the
+recognition of the presence and the condition of matter. One
+eighteen-millionth of a grain of sodium in the flame of a spirit-lamp
+may be detected by this instrument; and, at the same time, it gives
+trust-worthy indications of the material constitution not only of the
+sun, but of the farthest of those fixed stars and nebulae which afford
+sufficient light to affect the eye, or the photographic plate, of the
+inquirer.
+
+[Sidenote: Electricity.]
+
+The mathematical and experimental elucidation of the phenomena of
+electricity, and the study of the relations of this form of energy
+with chemical and thermal action, had made extensive progress before
+1837. But the determination of the influence of magnetism on light,
+the discovery of diamagnetism, of the influence of crystalline
+structure on magnetism, and the completion of the mathematical theory
+of electricity, all belong to the present epoch. To it also appertain
+the practical execution and the working out of the results of the
+great international system of observations on terrestrial magnetism,
+suggested by Humboldt in 1836; and the invention of instruments of
+infinite delicacy and precision for the quantitative determination of
+electrical phenomena. The voltaic battery has received vast
+improvements; while the invention of magneto-electric engines and of
+improved means of producing ordinary electricity has provided sources
+of electrical energy vastly superior to any before extant in power,
+and far more convenient for use.
+
+It is perhaps this branch of physical science which may claim the palm
+for its practical fruits, no less than for the aid which it has
+furnished to the investigation of other parts of the field of physical
+science. The idea of the practicability of establishing a
+communication between distant points, by means of electricity, could
+hardly fail to have simmered in the minds of ingenious men since,
+well nigh a century ago, experimental proof was given that electric
+disturbances could be propagated through a wire twelve thousand feet
+long. Various methods of carrying the suggestion into practice had
+been carried out with some degree of success; but the system of
+electric telegraphy, which, at the present time, brings all parts of
+the civilised world within a few minutes of one another, originated
+only about the commencement of the epoch under consideration. In its
+influence on the course of human affairs, this invention takes its
+place beside that of gunpowder, which tended to abolish the physical
+inequalities of fighting men; of printing, which tended to destroy the
+effect of inequalities in wealth among learning men; of steam
+transport, which has done the like for travelling men. All these gifts
+of science are aids in the process of levelling up; of removing the
+ignorant and baneful prejudices of nation against nation, province
+against province, and class against class; of assuring that social
+order which is the foundation of progress, which has redeemed Europe
+from barbarism, and against which one is glad to think that those who,
+in our time, are employing themselves in fanning the embers of ancient
+wrong, in setting class against class, and in trying to tear asunder
+the existing bonds of unity, are undertaking a futile struggle. The
+telephone is only second in practical importance to the electric
+telegraph. Invented, as it were, only the other day, it has already
+taken its place as an appliance of daily life. Sixty years ago, the
+extraction of metals from their solutions, by the electric current,
+was simply a highly interesting scientific fact. At the present day,
+the galvano-plastic art is a great industry; and, in combination with
+photography, promises to be of endless service in the arts. Electric
+lighting is another great gift of science to civilisation, the
+practical effects of which have not yet been fully developed, largely
+on account of its cost. But those whose memories go back to the
+tinder-box period, and recollect the cost of the first lucifer
+matches, will not despair of the results of the application of science
+and ingenuity to the cheap production of anything for which there is a
+large demand.
+
+The influence of the progress of electrical knowledge and invention
+upon that of investigation in other fields of science is highly
+remarkable. The combination of electrical with mechanical contrivances
+has produced instruments by which, not only may extremely small
+intervals of time be exactly measured, but the varying rapidity of
+movements, which take place in such intervals and appear to the
+ordinary sense instantaneous, is recorded. The duration of the winking
+of an eye is a proverbial expression for an instantaneous action;
+but, by the help of the revolving cylinder and the electrical
+marking-apparatus, it is possible to obtain a graphic record of such
+an action, in which, if it endures a second, that second shall be
+subdivided into a hundred, or a thousand, equal parts, and the state
+of the action at each hundredth, or thousandth, of a second exhibited.
+In fact, these instruments may be said to be time-microscopes. Such
+appliances have not only effected a revolution in physiology, by the
+power of analysing the phenomena of muscular and nervous activity
+which they have conferred, but they have furnished new methods of
+measuring the rate of movement of projectiles to the artillerist.
+Again, the microphone, which renders the minutest movements audible,
+and which enables a listener to hear the footfall of a fly, has
+equipped the sense of hearing with the means of entering almost as
+deeply into the penetralia of nature, as does the sense of sight.
+
+[Sidenote: Photography as an instrument of science.]
+
+That light exerts a remarkable influence in bringing about certain
+chemical combinations and decompositions was well known fifty years
+ago, and various more or less successful attempts to produce permanent
+pictures, by the help of that knowledge, had already been made. It was
+not till 1839, however, that practical success was obtained; but the
+'daguerreotypes' were both cumbrous and costly, and photography would
+never have attained its present important development had not the
+progress of invention substituted paper and glass for the silvered
+plates then in use. It is not my affair to dwell upon the practical
+application of the photography of the present day, but it is germane
+to my purpose to remark that it has furnished a most valuable
+accessory to the methods of recording motions and lapse of time
+already in existence. In the hands of the astronomer and the
+meteorologist, it has yielded means of registering terrestrial, solar,
+planetary, and stellar phenomena, independent of the sources of error
+attendant on ordinary observation; in the hands of the physicist, not
+only does it record spectroscopic phenomena with unsurpassable ease
+and precision, but it has revealed the existence of rays having
+powerful chemical energy, or beyond the visible limits of either end
+of the spectrum; while, to the naturalist, it furnishes the means by
+which the forms of many highly complicated objects may be represented,
+without that possibility of error which is inherent in the work of the
+draughtsman. In fact, in many cases, the stern impartiality of
+photography is an objection to its employment: it makes no distinction
+between the important and the unimportant; and hence photographs of
+dissections, for example, are rarely so useful as the work of a
+draughtsman who is at once accurate and intelligent.
+
+[Sidenote: Astronomy,]
+
+The determination of the existence of a new planet, Neptune, far
+beyond the previously known bounds of the solar system, by
+mathematical deduction from the facts of perturbation; and the
+immediate confirmation of that determination, in the year 1846, by
+observers who turned their telescopes into the part of the heavens
+indicated as its place, constitute a remarkable testimony of nature to
+the validity of the principles of the astronomy of our time. In
+addition, so many new asteroids have been added to those which were
+already known to circulate in the place which theoretically should be
+occupied by a planet, between Mars and Jupiter, that their number now
+amounts to between two and three hundred. I have already alluded to
+the extension of our knowledge of the nature of the heavenly bodies by
+the employment of spectroscopy. It has not only thrown wonderful
+light upon the physical and chemical constitution of the sun, fixed
+stars, and nebulae, and comets, but it holds out a prospect of
+obtaining definite evidence as to the nature of our so-called
+elementary bodies.
+
+[Sidenote: its relation to geology.]
+
+The application of the generalisations of thermotics to the problem of
+the duration of the earth, and of deductions from tidal phenomena to
+the determination of the length of the day and of the time of
+revolution of the moon, in past epochs of the history of the universe;
+and the demonstration of the competency of the great secular changes,
+known under the general name of the precession of the equinoxes, to
+cause corresponding modifications in the climate of the two
+hemispheres of our globe, have brought astronomy into intimate
+relation with geology. Geology, in fact, proves that, in the course of
+the past history of the earth, the climatic conditions of the same
+region have been widely different, and seeks the explanation of this
+important truth from the sister sciences. The facts that, in the
+middle of the Tertiary epoch, evergreen trees abounded within the
+arctic circle; and that, in the long subsequent Quaternary epoch, an
+arctic climate, with its accompaniment of gigantic glaciers, obtained
+in the northern hemisphere, as far south as Switzerland and Central
+France, are as well established as any truths of science. But, whether
+the explanation of these extreme variations in the mean temperature of
+a great part of the northern hemisphere is to be sought in the
+concomitant changes in the distribution of land and water surfaces of
+which geology affords evidence, or in astronomical conditions, such as
+those to which I have referred, is a question which must await its
+answer from the science of the future.
+
+[Sidenote: Biological sciences.]
+
+[Sidenote: The 'cell theory.']
+
+Turning now to the great steps in that progress which the biological
+sciences have made since 1837, we are met, on the threshold of our
+epoch, with perhaps the greatest of all--namely, the promulgation by
+Schwann, in 1839, of the generalisation known as the 'cell theory,'
+the application and extension of which by a host of subsequent
+investigators has revolutionised morphology, development, and
+physiology. Thanks to the immense series of labors thus inaugurated,
+the following fundamental truths have been established.
+
+[Sidenote: Fundamental truths established.]
+
+All living bodies contain substances of closely similar physical and
+chemical composition, which constitute the physical basis of life,
+known as protoplasm. So far as our present knowledge goes, this takes
+its origin only from pre-existing protoplasm.
+
+All complex living bodies consist, at one period of their existence,
+of an aggregate of minute portions of such substance, of similar
+structure, called cells, each cell having its own life independent of
+the others, though influenced by them.
+
+All the morphological characters of animals and plants are the results
+of the mode of multiplication, growth, and structural metamorphosis of
+these cells, considered as morphological units.
+
+All the physiological activities of animals and plants--assimilation,
+secretion, excretion, motion, generation--are the expression of the
+activities of the cells considered as physiological units. Each
+individual, among the higher animals and plants, is a synthesis of
+millions of subordinate individualities. Its individuality, therefore,
+is that of a 'civitas' in the ancient sense, or that of the Leviathan
+of Hobbes.
+
+There is no absolute line of demarcation between animals and plants.
+The intimate structure, and the modes of change, in the cells of the
+two are fundamentally the same. Moreover, the higher forms are
+evolved from lower, in the course of their development, by analogous
+processes of differentiation, coalescence, and reduction in both the
+vegetable and the animal worlds.
+
+At the present time, the cell theory, in consequence of recent
+investigations into the structure and metamorphosis of the 'nucleus,'
+is undergoing a new development of great significance, which, among
+other things, foreshadows the possibility of the establishment of a
+physical theory of heredity, on a safer foundation than those which
+Buffon and Darwin have devised.
+
+[Sidenote: Spontaneous generation disproved.]
+
+The popular belief in abiogenesis, or the so-called 'spontaneous'
+generation of the lower forms of life, which was accepted by all the
+philosophers of antiquity, held its ground down to the middle of the
+seventeenth century. Notwithstanding the frequent citation of the
+phrase, wrongfully attributed to Harvey, 'Omne vivum ex ovo,' that
+great physiologist believed in spontaneous generation as firmly as
+Aristotle did. And it was only in the latter part of the seventeenth
+century, that Redi, by simple and well-devised experiments,
+demonstrated that, in a great number of cases of supposed spontaneous
+generation, the animals which made their appearance owed their origin
+to the ordinary process of reproduction, and thus shook the ancient
+doctrine to its foundations. In the middle of the eighteenth century,
+it was revived, in a new form, by Needham and Buffon; but the
+experiments of Spallanzani enforced the conclusions of Redi, and
+compelled the advocates of the occurrence of spontaneous generation to
+seek evidence for their hypothesis only among the parasites and the
+lowest and minutest organisms. It is just fifty years since Schwann
+and others proved that, even with respect to them, the supposed
+evidence of abiogenesis was untrustworthy.
+
+During the present epoch, the question, whether living matter can be
+produced in any other way than by the physiological activity of other
+living matter, has been discussed afresh with great vigor; and the
+problem has been investigated by experimental methods of a precision
+and refinement unknown to previous investigators. The result is that
+the evidence in favor of abiogenesis has utterly broken down, in every
+case which has been properly tested. So far as the lowest and minutest
+organisms are concerned, it has been proved that they never make their
+appearance, if those precautions by which their germs are certainly
+excluded are taken. And, in regard to parasites, every case which
+seemed to make for their generation from the substance of the animal,
+or plant, which they infest has been proved to have a totally
+different significance. Whether not-living matter may pass, or ever
+has, under any conditions, passed into living matter, without the
+agency of pre-existing living matter, necessarily remains an open
+question; all that can be said is that it does not undergo this
+metamorphosis under any known conditions. Those who take a monistic
+view of the physical world may fairly hold abiogenesis as a pious
+opinion, supported by analogy and defended by our ignorance. But, as
+matters stand, it is equally justifiable to regard the physical world
+as a sort of dual monarchy. The kingdoms of living matter and of
+not-living matter are under one system of laws, and there is a perfect
+freedom of exchange and transit from one to the other. But no claim to
+biological nationality is valid except birth.
+
+[Sidenote: Morphology.]
+
+In the department of anatomy and development, a host of accurate and
+patient inquirers, aided by novel methods of preparation, which
+enable the anatomist to exhaust the details of visible structure and
+to reproduce them with geometrical precision, have investigated every
+important group of living animals and plants, no less than the fossil
+relics of former faunae and florae. An enormous addition has thus been
+made to our knowledge, especially of the lower forms of life, and it
+may be said that morphology, however inexhaustible in detail, is
+complete in its broad features. Classification, which is merely a
+convenient summary expression of morphological facts, has undergone a
+corresponding improvement. The breaks which formerly separated our
+groups from one another, as animals from plants, vertebrates from
+invertebrates, cryptogams from phanerogams, have either been filled
+up, or shown to have no theoretical significance. The question of the
+position of man, as an animal, has given rise to much disputation,
+with the result of proving that there is no anatomical or
+developmental character by which he is more widely distinguished from
+the group of animals most nearly allied to him, than they are from one
+another. In fact, in this particular, the classification of Linnaeus
+has been proved to be more in accordance with the facts than those of
+most of his successors.
+
+[Sidenote: Anthropology.]
+
+The study of man, as a genus and species of the animal world,
+conducted with reference to no other considerations than those which
+would be admitted by the investigator of any other form of animal
+life, has given rise to a special branch of biology, known, as
+Anthropology, which has grown with great rapidity. Numerous societies
+devoted to this portion of science have sprung up, and the energy of
+its devotees has produced a copious literature. The physical
+characters of the various races of men have been studied with a
+minuteness and accuracy heretofore unknown; and demonstrative
+evidence of the existence of human contemporaries of the extinct
+animals of the latest geological epoch has been obtained, physical
+science has thus been brought into the closest relation with history
+and with archaeology; and the striking investigations which, during our
+time, have put beyond doubt the vast antiquity of Babylonian and
+Egyptian civilisation, are in perfect harmony with the conclusions of
+anthropology as to the antiquity of the human species.
+
+Classification is a logical process which consists in putting together
+those things which are like and keeping asunder those which are
+unlike; and a morphological classification, of course, takes notes
+only of morphological likeness and unlikeness. So long, therefore, as
+our morphological knowledge was almost wholly confined to anatomy, the
+characters of groups were solely anatomical; but as the phenomena of
+embryology were explored, the likeness and unlikeness of individual
+development had to be taken into account; and, at present, the study
+of ancestral evolution introduces a new element of likeness and
+unlikeness which is not only eminently deserving of recognition, but
+must ultimately predominate over all others. A classification which
+shall represent the process of ancestral evolution is, in fact, the
+end which the labors of the philosophical taxonomist must keep in
+view. But it is an end which cannot be attained until the progress of
+palaeontology has given us far more insight than we yet possess, into
+the historical facts of the case. Much of the speculative 'phylogeny,'
+which abounds among my present contemporaries, reminds me very
+forcibly of the speculative morphology, unchecked by a knowledge of
+development, which was rife in my youth. As hypothesis, suggesting
+inquiry in this or that direction, it is often extremely useful; but,
+when the product of such speculation is placed on a level with those
+generalisations of morphological truths which are represented by the
+definitions of natural groups, it tends to confuse fancy with fact and
+to create mere confusion. We are in danger of drifting into a new
+'Natur-Philosophie' worse than the old, because there is less excuse
+for it. Boyle did great service to science by his 'Sceptical Chemist,'
+and I am inclined to think that, at the present day, a 'Sceptical
+Biologist' might exert an equally beneficent influence.
+
+[Sidenote: Physiology.]
+
+Whoso wishes to gain a clear conception of the progress of physiology,
+since 1837, will do well to compare Mueller's 'Physiology,' which
+appeared in 1835, and Drapiez's edition of Richard's 'Nouveaux
+Elements de Botanique,' published in 1837, with any of the present
+handbooks of animals and vegetable physiology. Mueller's work was a
+masterpiece, unsurpassed since the time of Haller, and Richard's book
+enjoyed a great reputation at the time; but their successors transport
+one into a new world. That which characterises the new physiology is
+that it is permeated by, and indeed based upon, conceptions which,
+though not wholly absent, are but dawning on the minds of the older
+writers.
+
+Modern physiology sets forth as its chief ends: Firstly, the
+ascertainment of the facts and conditions of cell-life in general.
+Secondly, in composite organisms, the analysis of the functions of
+organs into those of the cells of which they are composed. Thirdly,
+the explication of the processes by which this local cell-life is
+directly, or indirectly, controlled and brought into relation with the
+life of the rest of the cells which compose the organism. Fourthly,
+the investigation of the phenomena of life in general, on the
+assumption that the physical and chemical processes which take place
+in the living body are of the same order as those which take place out
+of it; and that whatever energy is exerted in producing such phenomena
+is derived from the common stock of energy in the universe. In the
+fifth place, modern physiology investigates the relation between
+physical and psychical phenomena, on the assumption that molecular
+changes in definite portions of nervous matter stand in the relation
+of necessary antecedents to definite mental states and operations. The
+work which has been done in each of the directions here indicated is
+vast, and the accumulation of solid knowledge, which has been
+effected, is correspondingly great. For the first time in the history
+of science, physiologists are now in the position to say that they
+have arrived at clear and distinct, though by no means complete,
+conceptions of the manner in which the great functions of
+assimilation, respiration, secretion, distribution of nutriment,
+removal of waste products, motion, sensation, and reproduction are
+performed; while the operation of the nervous system, as a regulative
+apparatus, which influences the origination and the transmission of
+manifestations of activity, either within itself or in other organs,
+has been largely elucidated.
+
+[Sidenote: Practical value of physiological discovery.]
+
+I have pointed out, in an earlier part of this chapter, that the
+history of all branches of science proves that they must attain a
+considerable stage of development before they yield practical
+'fruits;' and this is eminently true of physiology. It is only within
+the present epoch, that physiology and chemistry have reached the
+point at which they could offer a scientific foundation to
+agriculture; and it is only within the present epoch, that zoology and
+physiology have yielded any very great aid to pathology and hygiene.
+But within that time, they have already rendered highly important
+services by the exploration of the phenomena of parasitism. Not only
+have the history of the animal parasites, such as the tapeworms and
+the trichina, which infest men and animals, with deadly results, been
+cleared up by means of experimental investigations, and efficient
+modes of prevention deduced from the data so obtained; but the
+terrible agency of the parasitic fungi and of the infinitesimally
+minute microbes, which work far greater havoc among plants and
+animals, has been brought to light. The 'particulate' or 'germ' theory
+of disease, as it is called, long since suggested, has obtained a firm
+foundation, in so far as it has been proved to be true in respect of
+sundry epidemic disorders. Moreover, it has theoretically justified
+prophylactic measures, such as vaccination, which formerly rested on a
+merely empirical basis; and it has been extended to other diseases
+with excellent results. Further, just as the discovery of the cause of
+scabies proved the absurdity of many of the old prescriptions for the
+prevention and treatment of that disease; so the discovery of the
+cause of splenic fever, and other such maladies, has given a new
+direction to prophylactic and curative measures against the worst
+scourges of humanity. Unless the fanaticism of philozoic sentiment
+overpowers the voice of philanthropy, and the love of dogs and cats
+supersedes that of one's neighbor, the progress of experimental
+physiology and pathology will, indubitably, in course of time, place
+medicine and hygiene upon a rational basis. Two centuries ago England
+was devastated by the plague; cleanliness and common sense were enough
+to free us from its ravages. One century since, small-pox was almost
+as great a scourge; science, though working empirically, and almost in
+the dark, has reduced that evil to relative insignificance. At the
+present time, science, working in the light of clear knowledge, has
+attacked splenic fever and has beaten it; it is attacking hydrophobia
+with no mean promise of success; sooner or later it will deal, in the
+same way, with diphtheria, typhoid and scarlet fever. To one who has
+seen half a street swept clear of its children, or has lost his own by
+these horrible pestilences, passing one's offspring through the fire
+to Moloch seems humanity, compared with the proposal to deprive them
+of half their chances of health and life because of the discomfort to
+dogs and cats, rabbits and frogs, which may be involved in the search
+for means of guarding them.
+
+[Sidenote: Scientific exploration.]
+
+An immense extension has been effected in our knowledge of the
+distribution of plants and animals; and the elucidation of the causes
+which have brought about that distribution has been greatly advanced.
+The establishment of meteorological observations by all civilised
+nations, has furnished a solid foundation to climatology; while a
+growing sense of the importance of the influence of the 'struggle for
+existence' affords a wholesome check to the tendency to overrate the
+influence of climate on distribution. Expeditions, such as that of the
+Challenger,' equipped, not for geographical exploration and discovery,
+but for the purpose of throwing light on problems of physical and
+biological science, have been sent out by our own and other
+Governments, and have obtained stores of information of the greatest
+value. For the first time, we are in possession of something like
+precise knowledge of the physical features of the deep seas, and of
+the living population of the floor of the ocean. The careful and
+exhaustive study of the phenomena presented by the accumulations of
+snow and ice, in polar and mountainous regions, which has taken place
+in our time, has not only revealed to the geologist an agent of
+denudation and transport, which has slowly and quietly produced
+effects, formerly confidently referred to diluvial catastrophes, but
+it has suggested new methods of accounting for various puzzling facts
+of distribution.
+
+[Sidenote: Palaeontology.]
+
+Palaeontology, which treats of the extinct forms of life and their
+succession and distribution upon our globe, a branch of science which
+could hardly be said to exist a century ago, has undergone a wonderful
+development in our epoch. In some groups of animals and plants, the
+extinct representatives, already known, are more numerous and
+important than the living. There can be no doubt that the existing
+Fauna and Flora is but the last term of a long series of equally
+numerous contemporary species, which have succeeded one another, by
+the slow and gradual substitution of species for species, in the vast
+interval of time which has elapsed between the deposition of the
+earliest fossiliferous strata and the present day. There is no
+reasonable ground for believing that the oldest remains yet obtained
+carry us even near the beginnings of life. The impressive warnings of
+Lyell against hasty speculations, based upon negative evidence, have
+been fully justified; time after time, highly organised types have
+been discovered in formations of an age in which the existence of such
+forms of life had been confidently declared to be impossible. The
+western territories of the United States alone have yielded a world of
+extinct animal forms, undreamed of fifty years ago. And, wherever
+sufficiently numerous series of the remains of any given group, which
+has endured for a long space of time, are carefully examined, their
+morphological relations are never in discordance with the requirements
+of the doctrine of evolution, and often afford convincing evidence of
+it. At the same time, it has been shown that certain forms persist
+with very little change, from the oldest to the newest fossiliferous
+formations; and thus show that progressive development is a
+contingent, and not a necessary result, of the nature of living
+matter.
+
+[Sidenote: Geology.]
+
+Geology is, as it were, the biology of our planet as a whole. In so
+far as it comprises the surface configuration and the inner structure
+of the earth, it answers to morphology; in so far as it studies
+changes of condition and their causes, it corresponds with physiology;
+in so far as it deals with the causes which have effected the progress
+of the earth from its earliest to its present state, it forms part of
+the general doctrine of evolution. An interesting contrast between the
+geology of the present day and that of half a century ago, is
+presented by the complete emancipation of the modern geologist from
+the controlling and perverting influence of theology, all-powerful at
+the earlier date. As the geologist of my young days wrote, he had one
+eye upon fact, and the other on Genesis; at present, he wisely keeps
+both eyes on fact, and ignores the pentateuchal mythology altogether.
+The publication of the 'Principles of Geology' brought upon its
+illustrious author a period of social ostracism; the instruction given
+to our children is based upon those principles. Whewell had the
+courage to attack Lyell's fundamental assumption (which surely is a
+dictate of common sense) that we ought to exhaust known causes before
+seeking for the explanation of geological phenomena in causes of which
+we have no experience. But geology has advanced to its present state
+by working from Lyell's[J] axiom; and, to this day, the record of the
+stratified rocks affords no proof that the intensity or the rapidity
+of the causes of change has ever varied, between wider limits, than
+those between which the operations of nature have taken place in the
+youngest geological epochs.
+
+An incalculable benefit has accrued to geological science from the
+accurate and detailed surveys, which have now been executed by skilled
+geologists employed by the Governments of all parts of the civilised
+world. In geology, the study of large maps is as important as it is
+said to be in politics; and sections, on a true scale, are even more
+important, in so far as they are essential to the apprehension of the
+extraordinary insignificance of geological perturbations in relation
+to the whole mass of our planet. It should never be forgotten that
+what we call 'catastrophes,' are, in relation to the earth, changes,
+the equivalents of which would be well represented by the development
+of a few pimples, or the scratch of a pin, on a man's head. Vast
+regions of the earth's surface remain geologically unknown; but the
+area already fairly explored is many times greater than it was in
+1837; and, in many parts of Europe and the United States, the
+structure of the superficial crust of the earth has been investigated
+with great minuteness.
+
+The parallel between Biology and Geology, which I have drawn, is
+further illustrated by the modern growth of that branch of the science
+known as Petrology, which answers to Histology, and has made the
+microscope as essential an instrument to the geological as to the
+biological investigator.
+
+The evidence of the importance of causes now in operation has been
+wonderfully enlarged by the study of glacial phenomena; by that of
+earthquakes and volcanoes; and by that of the efficacy of heat and
+cold, wind, rain, and rivers as agents of denudation and transport. On
+the other hand, the exploration of coral reefs and of the deposits now
+taking place at the bottom of the great oceans, has proved that, in
+animal and plant life, we have agents of reconstruction of a potency
+hitherto unsuspected.
+
+There is no study better fitted than that of geology to impress upon
+men of general culture that conviction of the unbroken sequence of the
+order of natural phenomena, throughout the duration of the universe,
+which is the great, and perhaps the most important, effect of the
+increase of natural knowledge.
+
+
+THE END.
+
+FOOTNOTES:
+
+     [A] There are excellent remarks to the same effect in
+     Zeller's _Philosophie der Griechen_, Theil II. Abth. ii p.
+     407, and in Eucken's _Die Methode der Aristotelischen,
+     Forschung_, pp. 136 _et seq_.
+
+     [B] Fresnel, after a brilliant career of discovery in some
+     of the most difficult regions of physico-mathematical
+     science, died at thirty-nine years of age. The following
+     passage of a letter from him to Young (written in November
+     1824), quoted by Whewell, so aptly illustrates the spirit
+     which animates the scientific inquirer that I may cite it:
+
+          'For a long time that sensibility, or that vanity,
+          which people call love of glory is munch blunted
+          in me. I labor much less to catch the suffrages of
+          the public than to obtain an inward approval which
+          has always been the mental reward of my efforts.
+          Without doubt I have often wanted the spur of
+          vanity to excite me to pursue my researches in
+          moments of disgust and discouragement. But all the
+          compliments which I have received from M.M. Arago,
+          De Laplace, or Biot, never gave me so much
+          pleasure as the discovery of a theoretical truth
+          or the confirmation of a calculation by
+          experiment.'
+
+     [C] 'Memorable exemple de l'impuissance des recherches
+     collectives appliquees a la decouverte des verites
+     nouvelles!' says one of the most distinguished of living
+     French _savants_ of the corporate chemical work of the old
+     Academie des Sciences. (See Berthelot, _Science et
+     Philosophie_, p. 201.)
+
+     [D] I am particularly indebted to my friend and colleague
+     Professor Ruecker, F.R.S., for the many acute criticisms and
+     suggestions on my remarks respecting the ultimate problems
+     of physics, with which he has favored me, and by which I
+     have greatly profited.
+
+     [E] I am aware that this proposition may be challenged. It
+     may be said, for example, that, on the hypothesis of
+     Boscovich, matter has no extension, being reduced to
+     mathematical points serving as centres of 'forces.' But as
+     the 'forces' of the various centres are conceived to limit
+     one another's action in such a manner that an area around
+     each centre has an individuality of its own extension comes
+     back in the form of that area. Again, a very eminent
+     mathematician and physicist--the late Clerk Maxwell--has
+     declared that impenetrability is not essential to our
+     notions of matter, and that two atoms may conceivably occupy
+     the same space. I am loth to dispute any dictum of a
+     philosopher as remarkable for the subtlety of his intellect
+     as for his vast knowledge; but the assertion that one and
+     the same point or area of space can have different
+     (conceivably opposite) attributes appears to me to violate
+     the principle of contradiction, which is the foundation not
+     only of physical science, but of logic in general. It means
+     that A can be not-A.
+
+     [F] 'Molecule' would be the more appropriate name for such a
+     particle. Unfortunately, chemists employ this term in a
+     special sense, as a name for an aggregation of their
+     smallest particles, for which they retain the designation of
+     'atoms.'
+
+     [G] 'At present more organic analyses are made in a single
+     day than were accomplished before Liebig's time in a whole
+     year.'--Hofmann, _Faraday Lecture_, p. 46.
+
+     [H] In the preface to his _Mecanique Chimique_ M. Berthelot
+     declares his object to be 'ramener la chimie tout entirere
+     ... aux memes principes mecaniques qui regissent deja les
+     diverses branches de la physique.'
+
+     [I] This is the more curious, as Ampere's hypothesis that
+     vibrations of molecules, causing and caused by vibrations of
+     the ether, constitute heat, is discussed. See vol. ii. p.
+     587, 2nd ed. In the _Philosophy of the Inductive Sciences_,
+     2nd ed., 1847, p. 239, Whewell remarks, _a propos_ of
+     Bacon's definition of heat, 'that it is an expansive,
+     restrained motion, modified in certain ways, and exerted in
+     the smaller particles of the body;' that 'although the exact
+     nature of heat is still an obscure and controverted matter,
+     the science of heat now consists of many important truths;
+     and that to none of these truths is there any approximation
+     in Bacon's essay.' In point of fact, Bacon's statement,
+     however much open to criticism, does contain a distinct
+     approximation to the most important of all the truths
+     respecting heat which had been discovered when Whewell
+     wrote.
+
+     [J] Perhaps I ought rather to say Button's axiom. For that
+     great naturalist and writer embodied the principles of sound
+     geology in a pithy phrase of the _Theoris de la Terre_:
+     'Pour juger de ce qui est arrive, et meme de ce qui
+     arrivera, nous n'avons qu'a examiner ce qui arrive.'
+
+
+
+
+THOMAS H. HUXLEY'S WORKS.
+
+
+SCIENCE AND CULTURE, AND OTHER ESSAYS.
+     12mo. Cloth, $1.50.
+
+THE CRAYFISH: AN INTRODUCTION TO THE STUDY OF ZOOeLOGY.
+     With 82 Illustrations. 12mo. Cloth, $1.75.
+
+SCIENCE PRIMERS: INTRODUCTORY.
+     18mo. Flexible cloth, 45 cents.
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+MAN'S PLACE IN NATURE.
+     12mo. Cloth, $1.25.
+
+ON THE ORIGIN OF SPECIES.
+     12mo. Cloth, $1.00.
+
+MORE CRITICISMS ON DARWIN, AND ADMINISTRATIVE NIHILISM.
+     12mo. Limp cloth, 50 cents.
+
+MANUAL OF THE ANATOMY OF VERTEBRATED ANIMALS.
+     Illustrated. 12mo. Cloth, $2.50.
+
+MANUAL OF THE ANATOMY OF INVERTEBRATED ANIMALS.
+     12mo. Cloth, $2.50.
+
+LAY SERMONS, ADDRESSES, AND REVIEWS.
+     12 mo. Cloth, $1.75.
+
+CRITIQUES AND ADDRESSES.
+     12mo. Cloth, $1.50.
+
+AMERICAN ADDRESSES; WITH A LECTURE ON THE STUDY OF BIOLOGY.
+     12mo. Cloth, $1.25.
+
+PHYSIOGRAPHY: AN INTRODUCTION TO THE STUDY OF NATURE.
+     With Illustrations and Colored Plates. 12mo. Cloth, $2.50.
+
+HUXLEY AND YOUMANS'S ELEMENTS OF PHYSIOLOGY AND HYGIENE.
+     By T.H. HUXLEY and W.J. YOUMANS. 12mo. Cloth, $1.50.
+
+
+
+
+JOHN TYNDALL'S WORKS.
+
+
+ESSAYS ON THE FLOATING MATTER OF THE AIR, in Relation to
+Putrefaction and Infection.
+     12mo. Cloth, $1.50.
+
+ON FORMS OF WATER, in Clouds, Rivers, Ice, and Glaciers.
+     With 35 Illustrations. 12mo. Cloth, $1.50.
+
+HEAT AS A MODE OF MOTION. New edition.
+     12mo. Cloth, $2.50.
+
+ON SOUND: A Course of Eight Lectures delivered at the Royal
+Institution of Great Britain.
+     Illustrated. 12mo. New edition. Cloth, $2.00.
+
+FRAGMENTS OF SCIENCE FOR UNSCIENTIFIC PEOPLE.
+     12mo. New revised and enlarged edition. Cloth, $2.50.
+
+LIGHT AND ELECTRICITY.
+     12mo. Cloth, $1.25.
+
+LESSONS IN ELECTRICITY, 1875-'76.
+     12mo. Cloth, $1.00.
+
+HOURS OF EXERCISE IN THE ALPS.
+     With Illustrations. 12mo. Cloth, $2.00.
+
+FARADAY AS A DISCOVERER. A Memoir.
+     12mo. Cloth, $1.00.
+
+CONTRIBUTIONS TO MOLECULAR PHYSICS in the Domain of Radiant Heat.
+     $5.00.
+
+SIX LECTURES ON LIGHT. Delivered In America in 1872-'73.
+     With an Appendix and numerous Illustrations. Cloth, $1.50.
+
+ADDRESS delivered before the British Association, assembled at
+Belfast. Revised with Additions.
+     12mo. Paper, 50 cents.
+
+RESEARCHES ON DIAMAGNETISM AND MAGNECRYSTALLIC ACTION, including the
+Question of Diamagnetic Polarity. With Ten Plates.
+     12mo, cloth. Price, $1.50.
+
+
+
+
+CHARLES DARWIN'S WORKS.
+
+
+ORIGIN OF SPECIES BY MEANS OF NATURAL SELECTION, OR THE PRESERVATION
+OF FAVORED RACES IN THE STRUGGLE FOR LIFE. From sixth and last London
+edition.
+     2 vols., 12mo. Cloth, $4.00.
+
+DESCENT OF MAN, AND SELECTION IN RELATION TO SEX. With many
+Illustrations. A new edition.
+     12mo. Cloth, $3.00.
+
+JOURNAL OF RESEARCHES INTO THE NATURAL HISTORY AND GEOLOGY OF
+COUNTRIES VISITED DURING THE VOYAGE OF H.M.S. BEAGLE ROUND THE WORLD.
+New edition.
+     12mo. Cloth, $2.00.
+
+EMOTIONAL EXPRESSIONS OF MAN AND THE LOWER ANIMALS.
+     12mo. Cloth, $3.50.
+
+THE VARIATIONS OF ANIMALS AND PLANTS UNDER DOMESTICATION. With a
+Preface, by Professor ASA GRAY.
+     2 vols. Illustrated. Cloth, $5.00.
+
+INSECTIVOROUS PLANTS.
+     12mo. Cloth, $2.00.
+
+MOVEMENTS AND HABITS OF CLIMBING PLANTS.
+     With Illustrations. 12mo. Cloth, $1.25.
+
+THE VARIOUS CONTRIVANCES BY WHICH ORCHIDS ARE FERTILIZED BY INSECTS.
+     Revised edition, with Illustrations. 12mo. Cloth, $1.75.
+
+THE EFFECTS OF CROSS AND SELF FERTILIZATION IN THE VEGETABLE
+KINGDOM.
+     12mo. Cloth, $2.00.
+
+DIFFERENT FORMS OF FLOWERS ON PLANTS OF THE SAME SPECIES. With
+Illustrations.
+     12mo. Cloth, $1.50.
+
+THE POWER OF MOVEMENT IN PLANTS. By CHARLES DARWIN, LL.D., F.R.S.,
+assisted by FRANCIS DARWIN.
+     With Illustrations. 12mo. Cloth, $2.00.
+
+THE FORMATION OF VEGETABLE MOULD THROUGH THE ACTION OF WORMS. With
+Observations on their Habits.
+     With Illustrations. 12mo. Cloth, $1.50.
+
+
+
+
+ALEXANDER BAIN'S WORKS.
+
+
+THE SENSES AND THE INTELLECT. By ALEXANDER BAIN. LL.D., Professor of
+Logic in the University of Aberdeen.
+     8vo. Cloth, $5.00.
+     The object of this treatise is to give a full and systematic
+     account of two principal divisions of the science of mind--the
+     senses and the intellect. The value of the third edition of the
+     work is greatly enhanced by an account of the psychology of
+     Aristotle, which has been contributed by Mr. Grote.
+
+THE EMOTIONS AND THE WILL. By ALEXANDER BAIN, LL.D.
+     8vo. Cloth, $5.00.
+     The present publication la a sequel to the former one on "The
+     Senses and the Intellect," and completes a systematic exposition
+     of the human mind.
+
+MENTAL SCIENCE. A Compendium of Psychology and the History of
+Philosophy. Designed as a Text-book for High-Schools and Colleges. By
+ALEXANDER BAIN, LL.D.
+     12mo. Cloth, leather back, $1.50.
+     This present volume is an abstract of two voluminous works, "The
+     Senses and the intellect" and "The Emotions and the Will," and
+     presents in a compressed and lucid form the views which are there
+     more extensively elaborated.
+
+MORAL SCIENCE. A Compendium of Ethics. By ALEXANDER BAIN, LL.D.
+     12mo. Cloth, leather back, $1.50.
+     The present dissertation falls under two divisions. The first
+     division entitled The Theory of Ethics, gives an account of the
+     questions or points brought into discussion, and handles at
+     length the two of greatest prominence, the Ethical Standard and
+     the Moral Faculty. The second division--on the Ethical
+     Systems--is a full detail of all the systems, ancient and modern.
+
+MIND AND BODY. Theories of their Relations. By ALEXANDER BAIN, LL.D.
+     12mo. Cloth, $1.50.
+     "A forcible statement of the connection between mind and body,
+     studying their subtile interworkings by the light of the most
+     recent physiological investigations."--_Christian Register_.
+
+LOGIC, DEDUCTIVE AND INDUCTIVE. By ALEXANDER BAIN, LL.D.
+     Revised edition, 12mo. Cloth, leather back, $2.00.
+
+EDUCATION AS A SCIENCE. By ALEXANDER BAIN, LL.D.
+     12mo. Cloth, $1.75.
+
+ENGLISH COMPOSITION AND RHETORIC. Enlarged edition. Part I.
+Intellectual Elements of Style. By ALEXANDER BAIN, LL.D., Emeritus
+Professor of Logic in the University of Aberdeen.
+     12mo. Cloth, leather back, $1.50.
+
+ON TEACHING ENGLISH. With Detailed Examples and an Inquiry into the
+Definition of Poetry By ALEXANDER BAIN, LL.D.
+     12mo. Cloth, $1.25.
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+PRACTICAL ESSAYS. By ALEXANDER BAIN, LL.D.
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