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diff --git a/34221.txt b/34221.txt new file mode 100644 index 0000000..6140dd4 --- /dev/null +++ b/34221.txt @@ -0,0 +1,5969 @@ +The Project Gutenberg EBook of Electricity and Magnetism, by Elisha Gray + +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: Electricity and Magnetism + Nature's Miracles, Vol. III. + +Author: Elisha Gray + +Release Date: November 6, 2010 [EBook #34221] + +Language: English + +Character set encoding: ASCII + +*** START OF THIS PROJECT GUTENBERG EBOOK ELECTRICITY AND MAGNETISM *** + + + + +Produced by Chris Curnow and the Online Distributed +Proofreading Team at http://www.pgdp.net (This file was +produced from images generously made available by The +Internet Archive) + + + + + + + + + + _NATURE'S MIRACLES, VOL. III._ + + Electricity + and Magnetism + + BY + ELISHA GRAY, PH.D., LL.D. + + + WILLIAM BRIGGS + 29-33 Richmond St. West, Toronto + C. W. COATES, Montreal, Que. + S. F. HUESTIS, Halifax, N.S. + + + + +CONTENTS. + + + CHAPTER PAGE + + INTRODUCTION v + I. THE AUTHOR'S DESIGN 1 + II. HISTORY OF ELECTRICAL SCIENCE 6 + III. HISTORY OF MAGNETISM 20 + IV. THEORY AND NATURE OF MAGNETISM 25 + V. THEORY OF ELECTRICITY 39 + VI. ELECTRICAL CURRENTS 49 + VII. ELECTRIC GENERATORS 62 + VIII. ATMOSPHERIC ELECTRICITY 77 + IX. ELECTRICAL MEASUREMENT 83 + X. THE ELECTRIC TELEGRAPH 88 + XI. RECEIVING MESSAGES 103 + XII. MISCELLANEOUS METHODS 108 + XIII. MULTIPLE TRANSMISSION 114 + XIV. WAY DUPLEX SYSTEM 129 + XV. THE TELEPHONE 134 + XVI. HOW THE TELEPHONE TALKS 145 + XVII. SUBMARINE TELEGRAPHY 154 + XVIII. SHORT-LINE TELEGRAPHS 159 + XIX. THE TELAUTOGRAPH 165 + XX. SOME CURIOSITIES 171 + XXI. WIRELESS TELEGRAPHY 176 + XXII. NIAGARA FALLS POWER--INTRODUCTION 186 + XXIII. NIAGARA FALLS POWER--APPLIANCES 190 + XXIV. NIAGARA FALLS POWER--APPLIANCES 199 + XXV. ELECTRICAL PRODUCTS--CARBORUNDUM 209 + XXVI. ELECTRICAL PRODUCTS--BLEACHING-POWDER 218 + XXVII. ELECTRICAL PRODUCTS--ALUMINUM 223 + XXVIII. ELECTRICAL PRODUCTS--CALCIUM CARBIDE 228 + XXIX. THE NEW ERA 234 + + + + +INTRODUCTION. + + +For the benefit of the readers of Vol. III, who have not read the +general Introduction found in Vol. I, a word as to the scope and object +of this volume will not be amiss. + +It will be plain to any one on seeing the size of the little book that +it cannot be an exhaustive treatise on a subject so large as that of +Electricity. This volume, like the others, is intended for popular +reading, and technical terms are avoided as far as possible, or when +used clearly explained. The subject is treated historically, +theoretically, and practically. + +As the author has lived through the period during which the science of +Electricity has had most of its growth, he naturally and necessarily +deals somewhat in reminiscence. All he hopes to do is to plant a few +seed-thoughts in the minds of his readers that will awaken an interest +in the study of natural science; and especially in its most fascinating +branch--Electricity. + +If Vol. I is at hand, please read the Introduction. It will bring you +into closer sympathy with the author and his mode of treatment. + +Again, if the reader is especially interested in the theory of +Electricity it will help him very much if he first reads Vols. I and II, +as a preparation for a better understanding of Vol. III. All the natural +sciences are so closely related that it is difficult to get a clear +insight into any one of them without at least a general idea of all the +others. + + + + +NATURE'S MIRACLES. + +ELECTRICITY AND MAGNETISM. + + + + +CHAPTER I. + +THE AUTHOR'S DESIGN. + + +The writer has spent much of his time for thirty-five years in the study +of electricity and in inventing appliances for purposes of transmitting +intelligence electrically between distant points, and is perhaps more +familiar with the phenomena of electricity than with those of any other +branch of physics; yet he finds it still the most difficult of all the +natural sciences to explain. To give any satisfactory theory as to its +place with and relation to other forms of energy is a perplexing +problem. + +It is said that Lord Kelvin lately made the statement that no advance +had been made in explaining the real nature of electricity for fifty +years. While this statement--if he really made it--is rather broad, it +must be acknowledged that all the theories so far advanced are little +better than guesses. But there is value in guessing, for one man's guess +may lead to another that is better, and, as it is rarely the case that +each one does not give us a little different view of the matter, it may +be that out of the multiplicity of guesses there may some time be a +suggestion given to some investigator that will solve the problem, or at +least carry the theme farther back and establish its true relationship +to the other forms of energy. I cannot but think that there is yet a +simple statement to be made of Energy in its relation to Matter that +will establish a closer relationship between the different branches of +physical science. And this, most likely, will be brought about by a +better understanding of the nature of the interstellar substance called +Ether, and its relation to all forms and conditions of sensible matter +and energy. + +In the talks that will follow it will be the endeavor of the writer to +give such a simple and popular exposition of the phenomena and +applications of electricity, in a general way only, that the popular +reader may get, at least, an elementary understanding of the subject so +far as it is known. As we have said, the descriptions will have to be +elementary, for nothing else can be done without such elaborate +technical drawings and specifications as would be impossible in our +limited space, and would not be clear to the ordinary reader who knows +nothing of the science. + +Thousands who are employed in various ways with enterprises, the +foundations of which are electrical, know nothing of electricity as a +science. A friend of mine, who is a professor of physics in one of our +colleges, was traveling a few years ago, and in his wanderings he came +across some sort of a factory where an electric motor was employed. +Being on the alert for information, he stepped in and introduced himself +to the engineer, and began asking him questions about the electric motor +of which he had charge. The professor could talk ohm, amperes, and volts +smoothly, and he "fired" some of these electrotechnical names at the +engineer. The engineer looked at him blankly and said: "You can't prove +it by me. I don't know what you're talking about. All I know is to turn +on the juice and let her buzz." How much "juice" is wasted in this +cut-and-dry world of ours and how much could be saved if only all were +even fairly intelligent regarding the laws of nature! A great deal of +the business of this world is run on the "let her buzz" theory, and the +public pays for the waste. It will continue to be so until a higher +order of intelligence is more generally diffused among the people. A +fountain can rise no higher than its source. A business will never +exceed the intelligence that is put into it, nor will a government ever +be greater than its people. + +Let us begin the subject of electricity by going somewhat into its past +history. It is always well to know the history of any subject we are +studying, for we often profit as much by the mistakes of others as by +their successes. I shall also give the theories advanced by different +investigators, and if I should have any thoughts of my own on the +subject I shall be free to give them, for I have just as good a right to +make a guess as any one. It must be confessed, however, that the older I +grow the less I feel that I know about the subject of electricity, or +anything else, in comparison with what I see there is yet to be known. I +once met a young man who had just graduated from college, and in his +conversation he stated that he had taken a course in electricity. I +asked him how long he had studied the subject. He said "three months." I +asked him if he understood it--and he said that he did. I told him that +he was the man that the world was looking for; that I had studied it for +thirty years and did not understand it yet. + +"A little learning is a dangerous thing"--for it puffs us up, and we +feel that we know it all and have the world in our grasp; but after we +have tried our "little learning" on the world for a while and have +received the many hard knocks that are sure to come, we are sooner or +later brought up in front of the mirror of experience, and we "see +ourselves as others see us," and are not satisfied with the view. + +Whatever the theories may be regarding electricity, and however +unsatisfactory they may be, there are certain well-defined facts and +phenomena that are of the greatest importance to the world. These we may +understand: and to this end let us especially direct our efforts. + + + + +CHAPTER II. + +HISTORY OF ELECTRICAL SCIENCE. + + +Electricity as a well-developed science is not old. Those of us who have +lived fifty years have seen nearly all its development so far as it has +been applied to useful purposes, and those who have lived over +twenty-five years have seen the major portion of its development. + +Thales of Miletus, 600 B.C., discovered, or at least described, the +properties of amber when rubbed, showing that it had the power to +attract and repel light substances, such as straws, dry leaves, etc. And +from the Greek word for amber--elektron--came the name electricity, +denoting this peculiar property. Theophrastus and Pliny made the same +observations; the former about 321 B.C., and the latter about 70 A.D. It +is also said that the ancients had observed the effects of animal +electricity, such as that of the fish called the torpedo. Pliny and +Aristotle both speak of its power to paralyze the feet of men and +animals, and to first benumb the fish which it then preyed upon. It is +also recorded that a freed-man of Tiberius was cured of the gout by the +shocks of the torpedo. It is further recorded that Wolimer, the King of +the Goths, was able to emit sparks from his body. + +Coming down to more modern times--A.D. 1600--we find Dr. Gilbert, an +Englishman, taking up the investigation of the electrical properties of +various substances when submitted to friction, and formulating them in +the order of their importance. In these experiments we have the +beginnings of what has since developed into a great science. He made the +discovery that when the air was dry he could soon electrify the +substances rubbed, but when it was damp it took much longer and +sometimes he failed altogether. In 1705 Francis Hawksbee, an +experimental philosopher, discovered that mercury could be rendered +luminous by agitating it in an exhausted receiver. (It is a question +whether this phenomenon should not be classed with that of +phosphorescence rather than electricity.) The number of investigators +was so great that all of them cannot be mentioned. It often happens that +those who do really most for a science are never known to fame. A number +of people will make small contributions till the structure has by +degrees assumed large proportions, when finally some one comes along and +puts a gilded dome on it and the whole structure takes his name. This is +eminently true of many of the more important developments in the +science and applications of electricity during the last twenty-five or +thirty years. + +Following Hawksbee may be mentioned Stephen Gray, Sir Isaac Newton, Dr. +Wall, M. Dupay and others. Dupay discovered the two conditions of +electrical excitation known now as positive and negative conditions. In +1745 the Leyden jar was invented. It takes its name from the city of +Leyden, where its use was first discovered. It is a glass jar, coated +inside and out with tin-foil. The inside coating is connected with a +brass knob at the top, through which it can be charged with electricity. +The inner and outer coatings must not be continuous but insulated from +each other. The author's name is not known, but it is said that three +different persons invented it independently, to wit, a monk by the name +of Kleist, a man by the name of Cuneus, and Professor Muschenbroeck of +Leyden. This was an important invention, as it was the forerunner of our +own Franklin's discoveries and a necessary part of his outfit with which +he established the identity of lightning and electricity. Every American +schoolboy has heard, from Fourth of July orations, how "Franklin caught +the forked lightning from the clouds and tamed it and made it +subservient to the will of man." How my boyish soul used to be stirred +to its depths by this oratorical display of electrical fireworks! + +Franklin had long entertained the idea that the lightning of the clouds +was identical with what is called frictional electricity, and he waited +long for a church spire to be erected in his adopted home, the Quaker +City, in order that he might make the test and settle the question. But +the Quakers did not believe in spires, and Franklin's patience had a +limit. + +Franklin had the theory that most investigators had at that time, that +electricity was a fluid and that certain substances had the power to +hold it. There were two theories prevalent in those days--both fluid +theories. One theory was that there were two fluids, a positive and a +negative. Franklin held to the theory of a single fluid, and that the +phenomenon of electricity was present only when the balance or natural +amount of electricity was disturbed. According to this theory, a body +charged with positive electricity had an excessive amount, and, of +course, some other body somewhere else had less than nature had allotted +to it; hence it was charged with negative electricity. A Leyden jar, for +instance, having one of its coatings (say the inside) charged with +positive or + electricity, the other coating will be charged with +negative or - electricity. The former was only a name for an amount +above normal and the latter a name for a shortage or lack of the normal +amount. + +As we have said, Franklin believed in the identity of lightning and +electricity, and he waited long for an opportunity to demonstrate his +theory. He had the Leyden jar, and now all he needed was to establish +some suitable connection between a thunder-cloud and the earth. + +Previous to 1750 Franklin had written a paper in which he showed the +likeness between the lightning spark and that of frictional electricity. +He showed that both sparks move in crooked lines--as we see it in a +storm-cloud, that both strike the highest or nearest points, that both +inflame combustibles, fuse metals, render needles magnetic and destroy +animal life. All this did not definitely establish their identity in the +mind of Franklin, and he waited long for an opportunity, and finally, +finding that no one presented itself, he did what many men have had to +do in other matters; he made one. + +In the month of June, 1752, tired of waiting for a steeple to be +erected, Franklin devised a plan that was much better and probably saved +the experiment from failure; for the steeple would probably not have +been high enough. He constructed a kite by making a cross of light cedar +rods, fastening the four ends to the four corners of a large silk +handkerchief. He fixed a loop to tie the kite string to and balanced it +with a tail, as boys do nowadays. He fixed a pointed wire to the upper +end of one of the cross sticks for a lightning-rod, and then waited for +a thunder-storm. When it came, with the help of his boy, he sent up the +kite. He tied a loop of silk ribbon on the end of the string next his +hand--as silk was known to be an insulator or non-conductor--and having +tied a key to the string he waited the result, standing within a door to +prevent the silk loop from getting wet and thus destroying its +insulating qualities. The cloud had nearly passed and he feared his long +waited for experiment had failed, when he noticed the loose fibers of +the string standing out in every direction, and saw that they were +attracted by the approach of his finger. The rain now wet the string and +made a better conductor of it. Soon he could draw sparks with his +knuckle from the key. He charged a Leyden jar with this electrical +current from the thunder-cloud, and performed all the experiments with +it that he had done with ordinary electricity, thus establishing the +identity of the two and confirming beyond a doubt what he had long +before believed was true. In after experiments Franklin found that +sometimes the electricity of the clouds was positive and at other times +negative. From this experiment Franklin conceived the idea of erecting +lightning-rods to protect buildings, which are used to this day. + +The news spread all over Europe, not through the medium of electricity, +however, but as soon as sailing vessels and stage-coaches could carry +it. Many philosophers repeated the experiments and at least one man +sacrificed his life through his interest in the new discovery. In 1753 +Professor Richman of St. Petersburg erected on his house a metal rod +which terminated in a Leyden jar in one of the rooms. On the 31st of May +he was attending a meeting of the Academy of Sciences. He heard a roll +of thunder and hurried home to watch his apparatus. He and one of the +assistants were watching the apparatus when a stroke of lightning came +down the rod and leaped to the professor's head. He was standing too +near it and was instantly killed. + +Passing over many names of men who followed in the wake of Franklin we +come to the next era-making discovery, namely, that of galvanic +electricity. In the year 1790 an incident occurred in the household of +one Luigi Galvani, an Italian physician and anatomist, that led to a new +and important branch of electrical science. Galvani's wife was preparing +some frogs for soup, and having skinned them placed them on a table near +a newly charged electric machine. A scalpel was on the table and had +been in contact with the machine. She accidentally touched one of the +frogs to the point of the scalpel, when, lo! the frog kicked, and the +kick of that dead frog changed the whole face of electrical science. She +called her husband and he repeated the experiment, and also appropriated +the discovery as well, and he has had the credit of it ever since, when +really his wife made the discovery. Galvani supposed it to be animal +electricity and clung to that theory the rest of his life, making many +experiments and publishing their results; but the discovery led others +to solve the problem. + +Alessandro Volta, a professor of natural philosophy at Pavia, Italy, +was, it must be said, the founder of the science of galvanic or voltaic +electricity. Stimulated by the discovery of Galvani he attributed the +action of the frog's muscles, not to animal electricity, but to some +chemical action between the metals that touched it. To prove his theory, +he constructed a pile made of alternate layers of zinc, copper, and a +cloth or pasteboard saturated in some saline solution. By repeating +these trios--copper, zinc, and the saturated cloth--he attained a pile +that would give a powerful shock. It is called the Voltaic Pile. + +I have a clear idea of the construction of this form of pile, founded on +experience. It was my habit when a boy to make everything that I found +described, if it were possible. The bottom of my mother's wash-boiler +was copper, and just the thing to make the square plates of copper to +match the zinc ones, made from another piece of domestic furniture used +under the stove. I shocked my mother twice--first with the voltaic pile +that I had constructed, and again when she found out where the metal +plates came from. The sequel to all this was--but why dwell upon a +painful subject! + +Galvanism and voltaic electricity are the same. Volta was the first to +construct what is termed the galvanic battery. The unit of electrical +pressure or electromotive force is called the volt, and takes its name +from Volta, the great founder of the science of galvanic or voltaic +electricity. From this pile constructed by Volta innumerable forms of +batteries have been devised. The evolution of the galvanic battery in +all its forms, from Volta to the present day, would fill a large volume +if all were described. + +The discoveries of Michael Faraday (1791-1867), the distinguished +English chemist and physicist, led to another phase of the science that +has revolutionized modern life. Faraday made an experiment that contains +the germ of all forms of the modern dynamo, which is a machine of +comparatively recent development. He found that by winding a piece of +insulated wire around a piece of soft iron and bringing the two ends +(of the wire) very close together, and then placing the iron across the +poles of a permanent magnet and suddenly jerking it away, a spark would +pass between the two ends of the wire that was wound around the piece of +soft iron. Here was an incipient dynamo-electric machine--the germ of +that which plays such an important part in our modern civilization. + +Having brought our history down to the present day, it would seem +scarcely necessary to recite that which everybody knows. It is well, +however, to call a halt once in a while and compare our present +conditions of civilization with those of the past. Our world is filled +with croakers who are always sighing for the good old days. But we can +easily imagine that if they could go back to those days their croaking +would be still louder than it is. + +Before the advent of electricity many things were impossible that are +easy now. In the old days the world was very, very large; now, thanks to +electricity, it is knocking at the door of every man's house. The +lumbering stage-coach that was formerly our limited express--limited to +thirty or forty miles a day--has been supplanted by one that covers 1000 +miles in the same time, and this high rate of speed is made possible +only by the use of the electric telegraph. + +In the old days all Europe could be involved in a great war and the news +of it would be weeks in reaching our shores, but now the firing of the +first gun is heard at every fireside the world over, almost before the +smoke has cleared away. Our planet is threaded with iron nerves that run +over mountains and under seas, whose trembling atoms, thrilled with the +electric fire, speak to us daily and hourly of the great throbbing life +of the whole civilized world. + +Electricity has given us a voice that can be heard a thousand miles, and +not only heard, but recognized. It has given us a pen that will write +our autograph in New York, although we are still in Chicago. It has +given us the best light, both from an optical and a sanitary standpoint, +that the world has ever seen. The old-fashioned, jogging horse-car has +been supplanted by the electric "trolley," and we no longer have our +feelings harrowed with pity for the poor old steeds that pulled those +lumbering coaches through the streets, with men and women crowded in and +hanging on to straps, while everybody trod on every other body's toes. + + "In olden times we took a car + Drawn by a horse, if going far, + And felt that we were blest; + Now the conductor takes the fare + And puts a broomstick in the air-- + And lightning does the rest. + + "In other days, along the street, + A glimmering lantern led the feet, + When on a midnight stroll; + But now we catch, when night is nigh, + A piece of lightning from the sky + And stick it on a pole. + + "Time was when one must hold his ear + Close to a whispering voice to hear, + Like deaf men--nigh and nigher; + But now from town to town he talks + And puts his nose into a box + And whispers through a wire." + +So jogs the old world along. We sometimes think it is slow, but when we +look back a few years and see what has been accomplished it seems to +have had a marvelously rapid development. + +Something like fifty years ago a professor of physics in one of our +colleges was giving his class a course in electricity. The electric +telegraph was too little known at that time to cut much of a figure in +the classroom, so the stock experiments were those made with the +frictional electric machine and the Leyden jar. One day the professor +had, in one hour's time, taken his class through a course of +electricity, and at the end he said: "Gentlemen, you were born too late +to witness the development of this great science." I often wonder if the +good professor is ever allowed to part the veil that separates us from +the great beyond and to look down upon this busy world of ours in which +electricity plays such an important part in our every-day life; and if +so, what he thinks of that little speech he made to the boys fifty years +or more ago. + +If we make an analysis of the history of the science of electricity we +shall see that it has progressed in successive eras, shortening as they +approach our time. For a period of 2300 years, from Thales to Franklin, +but little or no progress was made beyond the further development of the +phenomena of frictional electricity--the most important invention being +that of the Leyden jar. From Franklin to Volta was forty-eight years, +and from Volta to Faraday about thirty-two years. From this time on the +development was very rapid as compared with the old days. Soon after +Faraday, Morse, Henry, Wheatstone, and others began experiments that +have grown, during fifty or sixty years, into a most colossal system of +electric telegraphs, telephones, electric lights and electric railroads. +In the latter days marvel has succeeded marvel with such rapid strides +that the ink is scarcely dry from the description of one before another +crowds itself upon our attention. Where it will all end no one knows, +but that it has ended no one believes. The human mind has become so +accustomed to these periodic revelations of the marvelous that it must +have the stimulus once in a while or it suffers as the toper does when +deprived of his cups. The commercial instinct of the news-vender is not +slow to see the situation, and if the development is too slow to suit +the public demand his fertile brain supplies the lack. So that every few +days we hear of some great discovery made by some one it may be unknown +to fame. It has served its purpose. The public mind has had its mental +toddy and has been saved from a fit of intellectual delirium tremens +that it was in danger of from lack of its accustomed stimulus. + +Having given you a very limited outline of the history of electricity, +from ancient times down to the present, we will endeavor now to give you +an elementary notion of the science as it stands to-day. To the common +mind the science is a blank page. So little is known of it by the +ordinary reader, who is fairly intelligent in other matters, that to +account for anything that we do not understand it is only necessary to +say that it is an electrical phenomenon and he accepts it. Electricity +is a synonym for all that we cannot understand. Inasmuch as magnetism is +so closely related to electricity in its uses as related to every-day +life, we will carry the two subjects along together, as the one will to +a large extent help to explain the other. In our next chapter we will +look at the history of magnetism. + + + + +CHAPTER III. + +HISTORY OF MAGNETISM. + + +It is said that the word magnetism is derived from the name of a Greek +shepherd, called Magnes, who once observed on Mount Ida the attractive +properties of loadstone when applied to his iron shepherd's crook. It is +more likely that the name came from Magnesia, a country in Lydia, where +it was first discovered. It was also called Lapis Heracleus. Heraclea +was the capital of Magnesia. Loadstone is a magnetic ore or oxide of +iron found in the natural state, and has at some time by natural +processes been rendered magnetic--that is, given the power of attracting +iron, and, when suspended, of pointing to the North and South Poles. The +power of the natural magnet was known at a very early age in the history +of man. It was referred to by Homer, Pythagoras, and Aristotle. Pliny +also speaks of it, and refers to one Dinocares, who recommended to +Ptolemy Philadelphus to build a temple at Alexandria and suspend in its +vault a statue of the queen by the attractive power of "loadstones." +There is also mention of a statue being suspended in like manner in the +temple of Serapis, Alexandria. + +It is claimed that the Chinese knew of and used the magnetic needle in +the earliest times and that travelers by land employed this needle +suspended by a string to guide them in their journeys across the country +a thousand years before Christ. Notwithstanding the claims of the +Chinese and Arabians to the discovery of the use of the magnetic needle, +modern authors question whether the ancients were familiar with any +artificial construction of a magnetic needle, however much they may have +studied and used the loadstones. No doubt the loadstone in its natural +state was used by mariners to steer their ships by, long before its +artificial counterpart was invented. In a history of the discovery of +Iceland, by Are Frode, who was born in 1068, it is stated that a mariner +by name of Folke Gadenhalen sailed from Norway in search of Iceland in +the year 868, and that he carried with him three ravens as guides, for +he says, "in those times seamen had no loadstones in the northern +countries." The magnetic needle as applied to the mariner's compass was +known in the eleventh century, as proved by various authors. In an old +French poem, the manuscript of which still exists, the mariner's compass +is clearly mentioned. The author was Guyot, of Provence, who was alive +in 1181. + +Like electricity, magnetism has had a long history, but little use was +made of it till modern times beyond that of the mariner's compass. It +can readily be seen what an important factor it was in the science of +navigation. Long after the discovery of the compass needle there were +many perplexing problems arising, and all sorts of theories were +advanced to account for the various phenomena. The variation of the +needle was one of these problems. It is said that Columbus was the first +to discover the variation of the needle, as well as America. This is +disputed, however, as every man's pretensions usually are. However this +may be, Columbus had to invent some plausible theory to account for this +variation to prevent a mutiny among his crew. They were very +superstitious and thought that they were sailing into a new world where +the laws of nature were different from those of Spain. One phenomenon +that disturbed Columbus was the dip of the needle. As we move in a +northerly direction a magnetic needle dips, and it was the observation +of this phenomenon in different latitudes that finally resulted in the +invention of the dipping needle. It is well known that one pole of a +magnetic needle points to the north and the other to the south. In other +words, what is called the north pole of a needle points to one of the +magnetic poles of the earth which is in the direction of the north +pole, though not the same as the geographical pole. A dipping needle +revolves on an axis so that it can point to any declination. If we +should construct one that is perfectly balanced, so as to lie in a +perfectly horizontal direction before it is magnetized, it will dip--in +this latitude--downward toward the north after magnetization. If we keep +moving northward it will continue to dip downward till we come to the +true magnetic pole, when what is called the north pole of the needle +will point directly downward. If we go back to the equator the needle +will lie horizontally again. We call the end of the needle that points +to the north the north pole. It is really the south pole, because unlike +poles attract each other. If the magnetic poles of the earth are at the +north and south geographical poles, the south pole of the needle will +point north. But it is less confusing to call the end of the needle that +points north the north pole. The nomenclature is purely arbitrary. + +It was not until it was learned that magnets could be made by +electricity that they became commercially important outside of their use +in navigation. The advent of electricity has brought magnetism to the +front as one of the great factors in our modern civilization. And we +might say with equal force that the discovery of magnetism has brought +electricity to the front. The truth is that they depend upon each +other. Electricity would be robbed of a large part of its importance as +a factor in modern life if it were not for its relation to magnetism. +Even electric lighting would be impossible, commercially, if it were not +for the part magnetism plays in the production of electricity for this +purpose. It could not be successfully carried on with any battery but +the storage-battery, and the storage-battery is dependent upon the +dynamo, and the dynamo is a magneto-electric machine. When we come to +analyze the relation between magnetism and electricity we cannot +separate them without robbing each of a large part of its usefulness. +They are interdependent forces. + +As in the case of electricity there have been many theories regarding +magnetism. One philosopher in the old days accounts for the variation of +the compass-needle on the theory that there are two globes, one +revolving within the other, and that any derangement of their normal +movements in relation to each other affects the needle. Evidently there +were cranks in those days as well as now. Another theory of magnetism +was that there were two fluids--a boreal and an austral--one developing +north polarity and the other south polarity. In the next chapter the +nature of magnetism in the light of modern investigation will be +discussed. + + + + +CHAPTER IV. + +THEORY AND NATURE OF MAGNETISM. + + +Iron and steel have a peculiar property called magnetism. It is an +attraction in many ways unlike the attraction of cohesion or the +attraction of gravitation. It is very certain that magnetism is an +inherent property of the molecules of iron and steel, and, to a small +degree, other forms of matter. That is to say, the molecules are little +natural magnets of themselves. It is as unnecessary to inquire why they +are magnets as it is to inquire why the molecules of all ordinary +substances possess the attraction of cohesion. The one is as easy to +explain as the other. People of all ages have insisted upon making a +greater mystery of all electrical and magnetic phenomena than they do of +other natural forces. Ampere's theory is that electric currents are +flowing around the molecules which render them magnetic; but it is just +as easy to suppose that magnetism is an inherent quality of the +molecule. (The word molecule is here used as referring to the smallest +particle of iron.) + +These little molecular magnets, so small that 100,000 million million +million of them can be put into a cubic inch of space, have their +attractions satisfied by forming into little molecular rings, with their +unlike poles together, so that when the iron is in a natural or +unmagnetized condition it does not attract other iron. If I should take +a ring of hardened steel and cut it into two or more pieces and +magnetize them, each one of the pieces would be an independent magnet. +If now I put them together in the form of a ring they will cling +together by their mutual attraction for each other. Before I put them +together into a ring each piece would attract and adhere to other pieces +of iron or steel. But as soon as they are put together in the ring they +are satisfied with their own mutual attraction, and the ring as a whole +will not attract other pieces of iron. + +Suppose the pieces forming the ring--it may be only two, if you +choose--are as small as the molecules we have described, the same thing +would be true of them. Each molecular ring would have its magnetic +attractions satisfied and would not attract other molecules outside of +its own little circle. When the iron is in the neutral state it will not +as a mass attract another piece of iron, because the millions of little +natural magnets of which it is made up have their attractive force all +turned in upon themselves. + +Now, if we make a helix, or coil, of insulated wire and put a piece of +iron into it, and pass a current of electricity through the helix, the +iron becomes a magnet. Why? Because the electric current has the power +to break up these molecular magnetic rings and turn all their like poles +in one direction, so that their attractions are no longer satisfied +among themselves, and with a combined effort they reach outside and +attract any piece of iron that is within reach. In this state we say it +is magnetized. Most people think that we have put something into the +iron, but we have not; we have only developed and made active its +inherent power. It must be kept in mind that it takes power to develop +this magnetic power from its state of neutrality and that something is +never made from nothing. When this power is developed it will do work in +falling back to its natural state. The power is natural to the molecules +of the metal. It is only being exerted in a new direction. The millions +of little natural magnets have been forced to combine their attractions +into one whole and exert it on something outside of themselves. They are +under a strain in this condition, like a bent bow, and there is a +tendency to fly back to the natural position, and if it is soft iron and +not steel, they will fly back as soon as the power that wrenched them +apart and is holding them apart is taken away. This power is the +electric current. Now break the current, and the little natural magnets, +that have been so ruthlessly torn from their home circle attachments, +fly back to them again with the speed of lightning, and the iron rod as +a whole is no longer a magnet. The power to become so under the +electrical strain is in it still--only latent. + +The kind of magnet that we have been describing is called an +electromagnet. It is a magnet only so long as the electric current is +passing around it. There is another kind of magnet called a permanent +magnet that will remain a magnet after the current is taken away. The +permanent magnet is made of steel and hardened; then its poles are +placed, to the poles of a powerful magnet, either electro or permanent, +when its molecular rings are wrenched apart and arranged in a polarized +position as heretofore described. Now take it away from the magnet and +it will be found to retain its magnetism. The molecules tend to fly back +the same as those of the soft iron, but they cannot because hardened +steel is so much finer grained than soft iron, and the molecules are so +close together that they are held in position by a friction that is +called its coercive force. The soft iron is comparatively free from this +coercive force, because its molecules are free to move on each other, so +that when they are wrenched out of their natural position they fly back +by their own attractions as soon as the force holding them apart is +taken away. The molecules of hardened steel are unable to fly back, +although they tend to do it just as much as in the iron, and so it is +called a permanent magnet. Its molecules also are under a strain, like a +bent bow. (The form of such a magnet is usually that of a horse-shoe, or +U.) + +Let us use a homely illustration that may help us to understand. Let ten +boys represent the molecules in a piece of iron. Let them pair off into +five pairs and each one clasp his mate in his arms; each one, say, is +exerting a force of ten pounds, and it would require a force of twenty +pounds to pull any one of the pairs apart. The five pairs are exerting a +force of one hundred pounds, but this force is not felt outside of +themselves. Now let them unclasp themselves and take hold of a rope that +is tied to a post, and all pull with the same force that they were +using, to wit, ten pounds each, and all pull in the same direction, and +they would put a strain of one hundred pounds upon the post, the same +power that they were exerting upon themselves before they combined their +efforts on something outside of themselves. So with the magnet. So long +as the force of each molecule is wholly spent upon its neighbor there is +nothing left for exterior use. But as soon as they all line up and pull +conjointly in the same direction their combined force is felt outside. +The analogy may not be perfect, but it will help you to get a mental +picture of what takes place in iron when it is magnetized. + +We have now described the magnet and the inherent power residing in the +molecular structure of iron. It is this magic power slumbering in its +molecules and the ability of the electric current to arouse them to +action at will and to hold them in action and at will let them fly back +to their normal position, that gives to electricity and magnetism--twin +sisters in nature's household--their great value as the servants of man. +There would be no virtue in winding up a weight if it could not run down +and do work in its fall. Simply bending a bow would never send the arrow +flying over its course; it must be released as well. The magnet could +not accomplish the great work it does if we could only charge it and not +have the ability to discharge it. Without this ability the electric +motor would not revolve, the electric light would not burn, the click of +the telegraph would not be heard, the telephone would not talk, nor +would the telautograph write. + +I have said that the permanent magnet would hold its charge after once +having been magnetized. This is true only in a sense and under favorable +conditions. If made of the best of steel for the purpose and hardened +and tempered in just the right way, it will hold its charge if it is +given something to do. If a piece of iron is placed across its poles it +also becomes a magnet and its molecules turn and work in harmony with +those of the mother magnet. These magnetic lines of force reach around +in a circuit. Even before the iron, or "keeper," as it is called, is put +across its poles there are lines of force reaching around through the +air or ether from one pole to another. (For a description of Ether see +Chap. V.) This is called the "field" of the magnet, and when the iron is +placed in this field the lines of force pass through it in a closed +circuit, and if the "keeper" is large enough to take care of all the +lines of force in the field the magnet will not attract other bodies, +because its attraction is satisfied, like its prototype in the molecular +ring described above. + +We speak of lines of force, not that force is necessarily exerted in a +bundle of lines but as a convenient way of telling the strength of a +magnetic field. The practical limit of the magnetization of soft iron +(called saturation) is 18,000 lines to the square centimeter. As long as +we give our magnet something to do, up to the measure of its capacity, +it will keep up its power. We may make other magnets with it, thousands, +yea, millions of them, and it not only does not lose its power but may +be even stronger for having done this work. If, however, we hang it up +without its "keeper," and give it nothing to do, it gradually returns to +its natural condition in the home circle of molecular rings. Little by +little the coercive force is overcome by the constant tendency of the +molecule to go back to its natural position among its fellows. + +The magnet furnishes many beautiful lessons, as indeed do all the +natural phenomena. Every man has within him a latent power that needs +only to be aroused and directed in the right way to make his influence +felt upon his fellows. Like the magnet, the man who uses his power to +help his fellows up to the measure of his limitations not only has been +a benefactor to his race, but is himself a stronger and better man for +having done so. But, again, like the magnet, if he allows these +God-given powers to lie still and rust for want of legitimate use he +gradually loses the power he had and becomes simply a moving thing +without influence or use in a world in which he vegetates. But let us +leave philosophy and go back to science. + +One of the striking exhibitions of magnetism is found in the earth. The +earth itself is a great magnet; and there is good reason for believing +that it is an electromagnet of great power. The magnetic poles of the +earth are not exactly coincident with the geographical poles, and they +are not constant. There is a gradual deviation going on, but as it +follows a certain law mariners are able to tell just what the deviation +should be at a certain time. The magnetic pole revolves around the polar +axis of the earth once in about 320 years. A thermal current (one +produced by heat) of electricity seems to flow around the earth caused +by the irregularities of temperature at the earth's surface, as the sun +makes his daily round. These earth currents vary at times, and other +phenomena are the occasion. This will be discussed when we come to +electric storms. + +The value of the earth's magnetism is seen most in the science of +navigation. A magnetic needle is only a slender permanent magnet +suspended very delicately, and when not under local influence it points +north and south on the magnetic axis. The law of its action may be +explained as follows: Take a straight bar magnet of fairly good power +and suspend a magnetic needle over it. The needle will arrange itself +parallel to the bar magnet. The north pole of the needle will point +toward the south pole of the bar magnet. In the presence of the magnet +the needle is not affected by the earth, but yields to a superior force. +If, however, the bar magnet is taken out of the way of the needle it +will immediately arrange itself north and south. Of course if the +earth's magnetic axis changes the needle will vary with it. This +variation is uniform and in navigation is reduced to a science, so that +the mariner knows how much to allow for the variation. Columbus, as +heretofore mentioned, was supposed to have first noticed this variation +and it made him trouble. He did not know how to account for it, and as +his crew thought the laws of nature were changing because they were so +far from home he saw the necessity for some sort of explanation. So, +like the brave man that he was, he hatched up a theory that satisfied +the crew, and although in the light of the closing years of the +nineteenth century it was a questionable one, it worked well enough in +practice to serve his purpose. + +We have already stated that the earth was a great magnet, and that +probably it was an electromagnet, caused by earth currents circulating +around the globe. You want to know how the earth can be a magnet unless +it has an iron core like an electromagnet. Magnetism or magnetic lines +of force may be developed without the presence of iron. When we pass a +current of electricity through a wire, magnetic lines of force are +thrown out at right angles with the direction of the current. This will +be fully explained further on. If we wind the wire into a coil, or +helix, these magnetic lines are concentrated. If now we suspend this +helix, or, better, float it on water so that it can move freely, and +pass a current of electricity through it, the helix will arrange itself +north and south the same as a magnetic needle. Its attractive properties +are feeble in comparison with that of the iron, but it obeys the laws of +a magnet. The earth is probably a magnet of this kind, consisting mostly +of lines of force. + +However, the iron in the earth is affected magnetically, as we have +evidence in the loadstone. The earth has the power also to magnetize +iron through the medium of its magnetic field, that reaches out in lines +of force from pole to pole like those of the artificial magnet. If we +hold a bar of iron in line with the magnetic axis of the earth and dip +it in line with the dipping needle and then strike it a few blows on the +end, it will be found to be feebly magnetic. The blows have partly +loosened the molecules and during the moment that they unclasped +themselves the earth's magnetism has through its lines of force caught +them for a time and held them a little out of their natural position--as +they are in a state of rest. The peculiar changing light that we +sometimes see in the northern sky, that is called the Aurora Borealis +(Northern Light), is indirectly due to intense magnetic lines of force +that radiate from the north magnetic pole of the earth. Those lines of +force are able to cause the rarified air molecules to become feebly +incandescent, giving them the appearance that we see in a tube that is a +partial vacuum when electricity is passed through it. While these +auroral displays may be seen almost any night in the far north, they +vary greatly in their intensity, so it is only once in a while that they +are visible in the temperate latitudes. + +What are called magnetic storms occur occasionally, and at such times +the telegraph service will sometimes be paralyzed on all the east and +west lines for many hours. Strong earth-currents will flow east and +west, and be so powerful and so erratic that it is sometimes impossible +to use the telegraph. It sometimes happens that the operators can throw +off their batteries and work on the earth-current alone. Sometimes it is +necessary to make a complete metallic circuit to get away from the +influence of the earth in order to use the telegraph. Currents equal to +the force of 2,000 cells of ordinary battery have been developed +sometimes in telegraph wires. This of course is a mere fraction of what +is passing through the earth under the wire through which the current +flowed. On the 17th and 18th of November, 1882, a magnetic storm +occurred that extended around the globe, as it was felt wherever there +were telegraph wires. These magnetic storms are attended by brilliant +displays of the aurora, and this fact strengthens the theory that the +earth is a great electromagnet; for the stronger the electrical current +the more powerful we should expect the magnetism to be, and this is +shown by the action of the magnetic needle at such times. The stronger +the magnet the more intense will be the lines of force, and naturally +the more intense the light, if indeed these lines of force are the cause +of the light. There is evidently some close relation between the two. + +Another coincidence is that at the times of these storms there is an +unusual display of sun-spots. These sun-spots seem to be great holes +that have been blown through the photosphere of the sun. The photosphere +is a great luminous body of gaseous matter that is believed to envelop +the sun, so that we do not see the core of the sun unless it is when we +look into one of these spots. In some way, evidently, the sun affects +the earth by radiating magnetic lines of force which are cut by the +earth's revolution, and so creating currents of electricity. The sun is +the field-magnet, and the earth is the revolving armature of nature's +great dynamo-electric machine. It would seem that the radiant energy +that comes out through these spots or these holes in the sun's envelope, +are more potent to develop earth-currents than the ordinary rays; and +so, when for a brief while in the revolution of the earth about the sun, +these extra potent rays strike the earth, an unusual energy is +developed, and these unusual phenomena are the consequence. These +phenomena seem to occur periodically; some years (about eleven) +intervening. + +All the forces and phenomena of nature are thus seen to be in a state of +unrest. And it is to this unrest, which does not stop with visible +things, but pervades even the atoms of matter throughout the universe, +that we are indebted for the ability to carry on all the activities of +life, and for life itself. For universal quiet would mean universal +death. The cyclone and tornado that devastate and strike terror to a +whole region are only eccentricities of nature when she is setting her +house to rights. The play of natural forces has disturbed her +equilibrium, and she is but making an effort to restore it. + + + + +CHAPTER V. + +THEORY OF ELECTRICITY. + + +In the series of chapters on Heat (Vol. II) and in the chapter on +Magnetism the word molecule was frequently used synonymously with atom. +In chemistry a distinction is made, and as we can better explain the +theory, at least, of electricity by keeping this distinction in mind we +will refer to it here. + +It has been stated that there are between sixty and seventy elementary +substances. An elementary substance cannot be destroyed as such. It can +be united with other elements and form chemical compounds of almost +endless variety. The smallest particle of an elementary substance is +called in chemistry an atom. The smallest particle of a compound +substance is called a molecule. The atom is the unit of the element, and +the molecule is the unit of the compound as such. It follows, then, that +there are as many different kinds of atoms as there are elements, and as +many different kinds of molecules as there are compounds. If the +elements have a molecular Structure then two or more atoms of the same +kind must combine to make a molecule of an elementary substance. Two +atoms of hydrogen combine with one of oxygen to form one molecule of +water. It cannot exist as water in any smaller quantity. If we subdivide +it, it no longer exists as water, but as the original gases from which +it was compounded. + +We have shown in the series on Sound, Heat and Light that they are all +modes of motion. Sound is transmitted in longitudinal waves through air +and other material substance as vibration. Heat is a motion of the +ultimate particles or atoms of matter, and Light is a motion of the +luminiferous ether transmitted in waves that are transverse. Electricity +is also undoubtedly a mode of motion related in a peculiar way to the +atoms of the conductor. + +Notice that there is a difference between conduction and radiation. The +former transmits energy by a transference of motion from atom to atom or +molecule to molecule within the body, while the latter does it by a +vibration of the ether outside--as light, radiant heat, and +electromagnetic lines of force. + +For the benefit of those persons who have not read Vol. II, where the +nature of ether is discussed somewhat, let us refer to it here, as it +plays an important part in the explanation of electrical phenomena. +Ether is a tenuous and highly elastic substance that fills all +interstellar and interatomic space. It has few of the qualities of +ordinary matter. It is continuous and has no molecular structure. It +offers no perceptible resistance, and the closest-grained substances of +ordinary matter are more open to the ether than a coarse sieve is to the +finest flour. It fills all space, and, like eternity, it has no limits. +Some physicists suppose--and there is much plausibility in the +supposition--that the ether is the one substance out of which all forms +of matter come. That the atoms of matter are vortices or little +whirlpools in the ether; and that rigidity and other qualities of matter +all arise in the ether from different degrees or kinds of motion. + +Electricity is not a fluid, or any form of material substance, but a +form of energy. Energy is expressed in different ways, and, while as +energy it is one and the same, we call it by different names--as heat +energy, chemical energy, electrical energy, and so on. They will all do +work, and in that respect are alike. One difficulty in explaining +electrical phenomena is the nomenclature that the science is loaded down +with. All the old names were adopted when electricity was regarded as a +fluid, hence the word "current." It is spoken of as "flowing" when it +does not flow any more than light flows. + +If a man wants to write a treatise on electricity--outside of the mere +phenomena and applications--and wants to make a large book of it, he +would better tell what he does not know about it, for in that way he can +make a volume of almost any size. But if he wants to tell what it really +is, and what he really knows it is, a primer will be large enough. This +much we know--that it is one of many expressions of energy. + +Chemistry teaches that heat is directly related to the atoms of matter. +Atoms of different substances differ greatly in weight. For instance, +the hydrogen atom is the unit of atomic weight, because it is the +lightest of all of them. Taking the hydrogen atom as the unit, in round +numbers the iron atom weighs as much as 56 atoms of hydrogen, copper a +little over 63, silver 108, gold 197. Heat acts upon matter according to +the number of atoms in a given space, and not as its weight. Knowing the +relative weights of the atoms of the different metals named, it would be +possible to determine by weight the dimensions of different pieces of +metal so that they will contain an equal number of atoms. If we take +pieces of iron, copper, silver and gold, each of such weight as that all +the pieces will contain the same number of atoms, and subject them to +heat till all are raised to the same temperature, it will be found that +they have all absorbed practically the same quantity of heat without +regard to the different weights of matter. It will be observed that the +piece of silver, for instance, will have to weigh nearly twice as much +as the iron in order to contain the same number of atoms, but it will +absorb the same amount of heat as the piece of iron containing the same +number of atoms, if both are raised to the same temperature. In view of +the above fact it seems that heat acts especially upon the atoms of +matter and is a peculiar form of atomic motion. Heat is one kind of +motion of the atoms, while electricity may be another form of motion of +the same. The two motions may be carried on together. The earth has a +compound motion. It revolves upon its axis once in twenty-four hours, +and it also revolves around the sun once each year. So you see that +there are different kinds of motion that may be communicated to the same +body--all producing different results. + +The motion of the individual atom as heat may be, and is, as rapid as +light itself when the temperature is sufficiently high, but it does not +travel along a conductor rapidly as the electro-atomic motion will. If +we apply heat to the end of a metal rod it will travel slowly along the +rod. But if we make the rod a conductor of electricity it travels from +atom to atom with a speed nearer that of the light ray through the +ether. Some modern writers have attempted to explain all the phenomena +of electricity as having their origin in a certain play of forces upon +the ether, and there is no doubt but that the ether plays an important +part in all electrical phenomena as a medium through which energy is +transferred; but ether-waves that are set in motion by the electrical +excitation of ordinary matter are no more electricity than the +ether-waves set up by the sun in the cold regions of space are heat. +They become heat only when they strike matter. Heat, _as such_, begins +and ends in matter;--so (I believe) does electricity. + +Do not be discouraged with these feeble attempts to explain the theory +of electricity. All I even hope to do is to establish in your minds this +fundamental thought, to wit, that there is really but one Energy, and +that it is always expressed by some form of motion or the ability to +create motion. Motions differ, and hence are called by different names. + +If I should set an emery-wheel to revolving and hold a piece of steel +against it the piece of steel would become heated and incandescent +particles would fly off, making a brilliant display of fireworks. The +heat that has been developed is the measure of the mechanical energy +that I have used against the emery-wheel. Now, let us substitute for the +emery-wheel another wheel of the same size made of vulcanized rubber, +glass or resin. I set it to revolving at the same speed, and instead of +the piece of steel, I now hold a silk handkerchief or a catskin against +the wheel with the same force that I did the steel. If now I provide a +Leyden jar and some points to gather up the electricity that will be +produced (instead of the heat generated in the other case), it would be +found that the energy developed in the one case would exactly balance +that of the other, if it were all gathered up and put into work. The +electricity stored in the jar is in a state of strain, like a bent bow, +and will recoil, when it has a chance, with a power commensurate with +the time it has been storing and the amount of energy used in pressing +against the wheel. + +If now I connect my two hands, one with the inside and the other with +the outside of the jar, this stored energy will strike me with a force +equal to all the energy I have previously expended in pressing against +the wheel, minus the loss in heat. If I did it for a long enough time +this electrical spring would be wound up to such a tension that the +recoil would destroy life if one put himself in the path of its +discharge. If all the heat in the first case were gathered up and made +to bend a stiff spring, and one should put himself in its way when +released, this mechanical spring would strike with the same power that +the electrical spring did when the Leyden jar was discharged. This +statement assumes that all the energy in the second experiment was +stored as electricity in the jar. You will be able to see from the +above illustration that heat, electrical energy, and mechanical energy +are really the same. Then you ask, how do they differ? Simply in their +phenomena--their outward manifestations. + +While there is much that we cannot know about any of the phenomena of +nature, it is a great step in advance if we can establish a close +relationship between them. It helps to free electricity from many +vagaries that exist in the minds of most people regarding it; vagaries +that in ignorant minds amount to superstition. While it possesses +wonderful powers, they give it attributes that it does not possess. Not +long ago a favorite headline of the medical electrician's advertisement +was "Electricity Is Life," and it was a common thing to see +street-venders dealing out this "life" in shocking quantities to the +innocent multitudes--ten cents' worth in as many seconds. + +Science divides electricity into two kinds--static and dynamic. Static +comes from a Greek word, meaning to stand, and refers to electricity as +a stationary charge. Dynamic is from the Greek word meaning power, and +refers to electricity in motion. When Franklin made his celebrated kite +experiment, the electricity came down the string, and from the key on +the end of the string he stored it in a Leyden jar. While the +electricity was moving down the string it was dynamic, but as soon as +it was stored in the Leyden jar it became static. Current electricity is +dynamic. A closed telegraphic circuit is charged dynamically, while the +prime conductor of a frictional electric machine is charged statically. +The distinction is arbitrary and in a sense a misnomer. When we rub a +piece of hard rubber with a catskin it is statically charged because the +substances are what are called non-conductors, and the charge cannot be +conducted readily away. All substances are divided into two classes, to +wit, conductors or non-electrics, and non-conductors or electrics, more +commonly called dielectrics. These, however, are relative terms, as no +substance is either a perfect conductor or a perfect non-conductor. + +The metals, beginning with silver as the best, are conductors. Ebonite, +paraffine, shellac, etc., are insulators, or very poor conductors. The +best conductors offer some resistance to the passage of the current and +the best insulators conduct to some extent. If we make a comparison of +electric conductors we find that the metals that conduct heat best also +conduct electricity best. This, it seems to me, is a confirmation of the +atomic theory of electricity so far as it means anything. If a good +conductor, as silver, is subjected to intense cold by putting it into +liquid air, its conductivity is greatly increased. It is well known +that heating a conductor ordinarily diminishes its power to conduct +electricity. This shows that, in order that electrical motion of the +atom may have free play, the heat motion must be suppressed. + + + + +CHAPTER VI. + +ELECTRIC CURRENTS. + + +The simplest form of an electric machine is one in which the operator is +a prominent part of the operation. Electricity, like magnetism, operates +in a closed circuit, even when it is static--so-called. Take a stick of +sealing-wax, say, in your left hand, and rub it with a piece of fur or +silk with your right hand, and you have the simplest form of electric +machine--the one that was known to the ancients, and the one from which +the science, great as it is to-day, had its beginnings. The stick of +sealing-wax is one element of the battery, and the piece of fur or silk +is the other, while your hands, arm and body form the conductor that +connects the two poles, and the friction is the exciting agent and may +be said to take the place of the fluid of a battery. The electrical +conditions are not wholly static, as a slow current is passing around +through your arms and body from one pole to the other. Even if the +conditions were wholly static there would be polarized lines of force, +in a state of strain, reaching around in a closed circuit. + +If we rub the wax with the fur and then take it away the wax has a +charge of electricity and will attract light objects. If we had rubbed a +piece of metal or some good conductor it would have been warmed instead +of electrified. In both cases the particles of the substances have been +affected, and if the atomic theory is correct--and it seems +plausible--in the former case the atoms are partly put into electrical +motion and partly into a state of electrical strain that we call static +(standing) electricity; while in the latter case the atoms are put into +the peculiar motion that belongs to heat. The former we call +electricity, and the latter we call heat. The electro-atomic motion +under some circumstances readily turns to heat, which seems to be the +tendency of all forms of energy. The electric light is a result of this +tendency. All non-conductors, or electrics, have a complex molecular +structure, and, while their atoms when subjected to friction are put +into a state of electrostatic strain, they are not able readily to +respond as a conductor of dynamic electricity. The electric-light +filament in the incandescent lamp is a much poorer conductor than the +copper wire that leads up to it. The copper wire is readily responsive +to the electrical influence, but the carbon filament is not. So +electrical action that freely passes along the wire, is resisted and +becomes heat action in the filament, and light is the attendant of +intense heat. But, to go back to the sources of electricity. + +Frictional electric machines have been constructed in great variety. +All, however, embrace the essentials set forth in the sealing-wax +experiment, and would be difficult to describe without cuts. Let us, +therefore, consider another source of electricity, which was the +outgrowth of the discovery of Galvani (or rather his wife), and reduced +to concrete form by Volta. We refer to the galvanic or voltaic battery. +If we put a bar of zinc into a glass vessel and pour sulphuric acid and +water into it, there will be a boiling, and an evolution of hydrogen +gas, and energy is released in the form of heat, so that the fluid and +the glass vessel become heated. Now let us put a bar of copper or a +stick of carbon into the glass, but not in contact with the zinc; +connect the ends (that are not immersed) of the two elements--copper and +zinc--with a metal wire or any conductor, and a new condition is set up. +Heat is no longer evolved to the same extent, but most of the energy +becomes electrical in character, and an electrical chain of action takes +place in the circuit that has now been formed. Taking the zinc as the +starting point, the so-called current flows from the zinc through the +fluid to the copper and from the copper through the wire to the zinc. + +A chain of polarized atomic activity is established in the circuit, +similar to the closed circuit of magnetic lines of force, only the +latter is static, while the former is dynamic. + +You ask what is the difference? Well, it is much easier to ask a +question than it is to answer it. You will remember that in the chapter +on magnetism it was stated that the molecules of a magnet were little +natural magnets, and that their attractions were satisfied within +themselves; that when their local attachments were broken up and all +their like poles turned in one direction they could act upon other +pieces of iron outside of the magnet. Outside and between the poles +there are magnetic lines of force reaching out from one pole to the +other. If we put a piece of iron across the poles these lines of force +are gathered up and pass through the iron. This is purely a static +condition. Let us go back to the cell of battery. When the elements are +in position (the copper, the acidulated water and the zinc), and the two +wires attached to the two metals which are the two poles of the battery +not yet connected, there is a condition induced in these two wires that +did not exist before the acidulated water was poured in, although the +circuit is not yet established. If we test the two wires we find a +difference of potential--a state of strain, so to speak--that did not +exist before the acid acted on the zinc and liberated what was stored +energy. It is in a static condition, like the magnet, and electrical +lines of force are reaching out from both wires so that the ether is in +a state of strain between the two poles. The air molecules may partake +of it, but we have to bring in the ether as a substance, because the +same conditions would practically exist if the two wires were in a +vacuum. If now we connect the two wires, we have established a metallic +circuit between the two poles of the battery, the static conditions are +relieved, the lines of force are gathered up into the wire, and the +phenomenon that we call a current is established and we have dynamic or +moving electricity. + +Having established the so-called electric current we will now try to +show you that there really is no current. The idea of a current involves +the idea of a fluid substance flowing from one point to another. When +you were a boy did you never set up a row of bricks on their ends, just +far enough apart so that if you pushed one over they all fell one after +another? Now, imagine rows of molecules or atoms, and in your +imagination they may be arranged like the bricks, so that they are +affected one by the other successively with a rapidity that is akin to +that of light-waves, and you can conceive how a motion may be +communicated from end to end of a wire hundreds of miles in length in a +small fraction of a second, and no material substance has been carried +through the wire--only energy. We do not mean to say that the row of +bricks illustrates the exact mode of molecular or atomic motion that +takes place in a conductor. What we mean is, that in some way motion is +passed along from atom to atom. + +To give you a better conception of an electric current, let us go back +of the galvanic cell to the electric machine. If both poles of the +machine are attached to rods terminating in round knobs we can set the +machine in action and keep up a steady stream of disruptive discharges +that will, if their frequency is great enough, perform the function of a +current, and we have dynamic electricity from a statical machine; when +the acid of the galvanic battery breaks down a molecule of zinc, energy +is set free, and in the battery we have what corresponds to a disruptive +discharge of infinitesimal proportions. This discharge would have been +immediately converted into heat energy if the copper element had been +left out of the battery, but as it is, it impresses itself on the atomic +"brick" next to it, which establishes a chain of atomic movement +throughout the circuit. This may constitute, if you please, a line of +electrical force. But as thousands of these disruptive discharges are +taking place simultaneously as many different lines of force are +established. You must not conceive of these chains of atoms as simply +thrown down like the bricks and left lying there, but that the atom is +active; that it has the power to pick itself up again in an +infinitesimally short time and is again knocked down (following the +illustration of the bricks) by the next discharge along its line or +chain of atoms. + +If you could get a mental picture of this action you would see that the +whole conductor is in a most violent state of atomic motion of a +peculiar kind. At the same time a part of this electrical motion is +being converted into a heat motion of the atoms, and finally it all +returns to heat unless some of it is stored up somewhere as potential +energy. If the current has driven a motor that has wound up a weight, a +part is stored up in the weight, which has the ability to do work if it +is allowed to run down. If it drives machinery as it runs down, the +mechanical motion is the expression of the stored energy. When the +weight has run down the energy will be represented by the heat created +by friction of the journals of the wheels and pulleys and the heating of +the air. If the weight is allowed to fall suddenly it will heat the air +to some extent, but mostly the earth and the weight itself will be +heated. If the source of energy (the battery) is great and the pressure +high and the conductor is too small to carry the energy developed in the +battery as electricity, heat is developed, and if the heat is +sufficiently intense, light also. + +We have seen (Vol. II) that heat motion when it reaches a sufficiently +high rate throws the ether into a vibratory motion that we call light. +However, this vibratory motion of the ether is set up long before it +reaches the luminous stage; in other words, there are dark rays of the +ether. We find that the electro-atomic motions of a conductor have the +power to impress themselves upon the ether. + + [Illustration: Fig. 1. + + A is the primary line; _a_, the battery: _b_, the key. B is the + secondary line in which is placed the galvanometer _c_.] + +Let us try another experiment to show that this is the case, not only, +but that the impressed ether can transfer these impressions to still +another conductor. Suppose we stretch two parallel wires for, say, half +a mile, or any distance, only a few feet apart, and make of each a +complete circuit by rounding the end of the course and returning the +wire to the starting point (as shown in Fig. 1). Put in one of these +circuits a battery, and a circuit-breaker (a common telegraph-key), and +in the other circuit a galvanometer (an instrument for detecting the +presence and measuring the intensity of a galvanic current, by means of +a dial and a deflecting needle or pointer). Now if we touch the key and +close the circuit in A, the needle of the galvanometer in B will swing +in one direction from zero on the dial; and if we release the key, +breaking the circuit in A, the needle will swing back in the opposite +direction. In neither case will the needle stay deflected, but will at +once return to zero. + +This shows that when the battery current was allowed to complete its +circuit through wire A by closing its key, an electrical action was +instantly felt in wire B, although there was no material connection +between them other than the air, which is a non-conductor. + +The current in the second circuit is called an induced current. Why this +current? According to one theory, when we close the primary circuit the +surrounding ether is thrown into a peculiar state of strain that we will +call magnetic or electrical lines of force. When the ether wave strikes +the second wire there is a molecular movement from a state of rest to a +state of static strain. During the time that the molecules are moving +from the normal to the strained position in sympathy with the ether we +have the condition of a dynamic current, which lasts only a moment. This +state of strain continues till the circuit is opened (breaking the +wire-line), when all the electrical lines of force vanish and the +molecular strain of the second wire is relieved, and we again have the +conditions, momentarily, for a current of the opposite polarity, and the +needle will swing in the opposite direction because the molecules or +atoms have, in their recoil to the natural state, moved in an opposite +direction. + +Going back to Fig. 1, let us further study the phenomena under other +conditions. In our first circuit (A) there is a battery and a +circuit-breaker, which is a common telegraph-key. Now close the key so +that a current will be established. (Remember that "current" is only a +name for a condition of dynamic charge.) Place a piece of soft iron +across the wire at right angles with the direction of the wire, when of +course it will be at right angles with the direction of the current, and +you will find now that the iron is more or less magnetic, depending upon +the amount of current passing through the wire. If we wind a number of +turns of insulated wire through which the current is passing around the +iron the magnetism will be increased. In practice there are a certain +number of turns and a certain sized wire that will give the best results +with a given number of cells of battery (or a given voltage or +pressure), operating in a closed circuit of a given resistance. All +these questions are worked out mathematically in many standard books on +the subject. It is not the intention in these talks to develop the +science mathematically but to set out the fundamental physical facts and +applications of electricity. + +Under the conditions above named magnetism is developed in the soft iron +bar. If we open the key the current will cease and the magnetism will +vanish--that is to say, the molecules will turn back to their neutral +position by their own attractions, as has been described in a previous +chapter. Magnetism developed in this way is called electromagnetism. +(See Chap. IV.) If we use a piece of hardened steel instead of the soft +iron it will become magnetic and remain so when the circuit is opened, +because the natural tendency of the molecules to turn back to the +neutral position is not great enough to overcome the coercive force, or +molecular friction, of hardened steel, as has been also described in a +previous chapter. To make the best electromagnet we need qualities of +iron just the opposite from those of the permanent magnet. For the +former we need the purest of soft iron, well annealed (heated to redness +and slowly cooled, making it less brittle), so that its molecules are +free to turn; while for the latter we need hardened steel, so that when +the molecules are once wrenched into the magnetic condition they cannot, +of themselves, turn back to the neutral state. The great value of the +electromagnet lies in its ability to readily discharge, or go back to +the neutral state, when the current is broken. + +Let us now go back to the beginning of our experiment. When we closed +the key and established the current through the wire we found that a +piece of iron held at right angles to the wire, although not touching +it, became magnetic. We have already said that when the circuit was +open, the battery being in circuit, there were electrical lines of force +established in the ether, between the two poles of the battery, and that +they were gathered up into the conducting wire when the circuit was +closed. We now find that there are other lines of force of a different +nature established in the ether when the circuit is closed. These we +call magnetic lines of force, or the magnetic field of the charged wire, +and they are established at right angles to the direction of the +current. These magnetic lines of force acting through the ether from an +electrically charged conductor are able to break up the natural +molecular magnetic rings, referred to in Chapter IV, and turn all their +like poles in the same direction--thus making one compound magnet of the +iron which in the neutral state consisted of millions of little natural +magnets whose attractions were satisfied by a joining of their unlike +poles. + +Most writers account for all of the phenomena of induced currents in a +second wire as coming directly from these magnetic lines of force +developed upon closing the circuit. + +So much for theory based upon a set of facts that make the theory seem +probable. If you don't like it give us a better one. If it is correct +the writer claims no credit; it is merely a compilation of suggestions +from many sources, including his own experience. We are simply seeking +after truth. The man who is an earnest seeker after scientific truth +cannot afford to pursue his investigations with any prejudice in favor +of one theory more than another, unless the facts sustain him, and then +he is not acting from prejudice, but is led by the facts. Many people +make pets of their theories; and they become attached to them as they do +their children; and they look upon a man who destroys them by a +presentation of the facts as an enemy. I once knew a lady who became so +attached to her family doctor that, she said, she would rather die under +his treatment, if necessary, than to be cured by any other doctor. There +are many people who are imbued with this kind of spirit not only in +matters scientific, but in matters religious as well. Such people are +not the kind who contribute to the world's progress, but are the +hindrances that have to be overcome. + + + + +CHAPTER VII. + +ELECTRIC GENERATORS. + + +Of the sources of electricity we have mentioned two: Friction, and +Galvanism or chemical action. There are hundreds of forms of the latter +species of apparatus for generating electrical energy, so we will +mention only a few of the more prominent ones. It is not our intention +to go into the chemistry of batteries. There are too many exhaustive +works on this subject lying on the shelves of libraries that are +accessible to all. All galvanic batteries act on one general +principle--the generation of electricity by the chemical action of acid +on metal plates; but the chemistry of their action is very different. In +all batteries the potential energy of one element is greater than the +other. The acid of the battery dissolves the element of greater +potentiality, and its energy is freed and under right conditions takes +on the form of electricity. The potential of zinc, for instance, is +greater than that of copper, and the measure of the difference is called +the "electromotive force," the unit of which is the "volt." +Electromotive force is another name for pressure; the symbol for which +is _E.M.F._ + +If we were to put two zinc plates in the battery fluid and connect them +in the ordinary way there would be no electricity evolved (assuming that +they were perfectly homogeneous), because they are both of the same +potential, or have the same possible amount of stored electrical energy +measured by its working power. If one of the zinc plates were softer +than the other, a feeble current would be developed, for one would be +more readily acted upon by the acids than the other. The battery that +has been most used in America for telegraphic purposes is called the +gravity-battery. It is constructed by putting a copper plate in some +form at the bottom of a jar, usually of glass, and filling it partly +full of the crystals of sulphate of copper, commonly called "bluestone." +Zinc, usually cast in some open form, so as to expose a large surface to +the solution, is suspended in the upper part of the jar, which is then +filled with water till it covers the zinc. The zinc is the positive +metal, but it is called the negative pole. The energy developed by the +zinc passes from zinc to copper and out on the circuit from the copper +pole. Hence the copper came to be called the positive pole, although in +relation to zinc it is negative. Copper would, however, be positive to +some other metal whose potential was less. So you see that metals are +relative, not absolute, in their character as positive and negative +elements. + +The galvanic battery has been almost entirely superseded in this country +for telegraphic purposes by the dynamo, a machine developing electrical +currents by mechanical power. Another form of battery that is +extensively used for some kinds of heavy current work is called the +storage-battery. The man who did the most, perhaps, to bring the +storage-battery to its present state of perfection was Plante, a +Frenchman, who died only a short time ago. Although very many types of +battery have been developed, it is found that, after all, the lines on +which he developed it make the most efficient battery. There is a common +notion that electricity is stored in the storage-battery. Energy is +stored, that will produce electricity when it is set free, just the same +as energy is stored in zinc. The storage-battery, when ready for action, +is one form of acid or primary battery. It has been made by passing a +current of electricity through it until the chemical relations of the +two lead plates have been changed so that the potential of one is +greater than that of the other. A simple storage-battery element is made +up of two plates of lead held out of contact with each other by some +insulating substance the same as the elements of an ordinary battery. +The cell is filled with dilute sulphuric acid, and there will be no +electrical action till the cell has been charged by running a current of +electricity through it and forming a lead oxide on one plate. Now, take +off the charging battery and connect the two poles, and electricity will +flow until the oxide has partly changed back into spongy metallic lead, +when it must be renewed by recharging. + +I remember perfectly well the first galvanic battery I ever saw, for it +was of my own construction. It is now nearly fifty years ago, and yet it +seems but yesterday--such is the flight of time. I related to you in +another chapter how I made a voltaic battery--or pile, as it was +called--by cutting up my mother's boiler and her stove-zinc, and the +domestic incident that followed. Well, a little later I made a real +galvanic battery as follows: I lived in the country and far from town or +city, and my facilities were extremely limited, so that I pursued my +scientific investigations under great difficulties. My only text-book +was an old Comstock's Philosophy. In the book was a crude cut of a Morse +register and a short description of its construction, including the +battery. I determined to make a register, and I did. It was all +constructed of wood except the magnet and its armature and the +embossing-point, which latter was made of the end of a nail. The thing +that seemed out of reach was the electromagnet. I had no money; and +there was no one that believed I could do it, and if I could "what good +would come of it?" I made friends with a blacksmith by keeping flies off +a horse while he nailed the shoes on, and "blowing the bellows" and +occasionally using the "sledge" for him. When I thought the obligation +had accumulated a sufficient "voltage" (to express it electrically) I +communicated to the blacksmith the situation and what I wanted. + +The good-natured old fellow was not long in bending up a U magnet of +soft iron and forging out an armature. The next step was to wind the U +with insulated wire. The only thing that I had ever seen of the kind was +an iron wire called "bonnet" wire that was wrapped with cotton thread. +This, however, was not available, so I captured a piece of brass +bell-wire and wound strips of cotton cloth around it for insulation--and +in that way completed the magnet. + +Now everything was ready but the battery. I went at its construction +with a feeling almost akin to awe, for I could not believe that it would +do as described in the book. I procured a candy-jar from the grocer and +found some pieces of sheet zinc and copper. These I rolled together into +loose spirals and placed one inside the other so that they would not +touch, when I was ready for the solution. The druggist trusted me for a +half pound of "blue vitriol," and I put it into my battery and filled it +with water. I waited awhile for it to dissolve, and then connected my +magnet in circuit, when--to my astonishment and delight--it would lift a +pound or more. It was a great triumph. I never have had one since that +gave me the same satisfaction. But I had my triumph all to myself. I was +still the same "tinker" (a name I had long carried), and a nuisance to +be endured but not encouraged. + +The dynamo is the form of generator now in general use where heavy +currents of electricity are needed. It is aptly described by a writer in +Modern Machinery, Mr. John A. Grier, as a thing that when "at rest is a +lifeless piece of mechanism; in action it has a living spirit as full of +mystery as the soul of man." This is a poetic way of describing it that +conveys to the mind a sense of the power and beauty of natural law in +action, that would not come from a mere recital of the cold scientific +facts. The facts, however, are necessary: but let us draw from them all +the poetry and all the practical lessons that we can as we go along; for +it is this blending of the poetic with the practical that lends a charm +to our every-day "grind," and lightens the load of many a weary hour. + +The dynamo is a machine that converts mechanical into electrical energy, +and the great practical value of energy in this form is that it can be +distributed through a conductor economically for many miles. We can +transmit mechanical power by means of a rope or cable for a limited +distance, but at tremendous loss through friction. We can transmit power +through pipes by compressed air or steam, but there is a great loss, +especially in the case of steam, by condensation from cold. None of +these methods are available for long distances. Another advantage +electricity has over other forms of energy is the speed with which it +can be transmitted from one place to another. In this respect it has no +rival except light. But we have not been able to harness light and make +it available to carry either freight or news, except in the latter case +for a short distance by flashing it in agreed signals. + +The heliostat can be used when the sun shines to transmit news by +flashes of sunlight chopped up into the Morse code and thrown from point +to point by a moving mirror. But this is limited as to distance; +besides, the sun does not always shine. It has the disadvantage in that +respect that the old semaphore-telegraph did that was in use in +Wellington's day. These semaphores were constructed in various ways, but +a common form was that of moving arms that could be seen from hill to +hill or point to point. By a code of moving signals news was repeated +from point to point and it can be easily imagined that many mistakes +occurred, to say nothing of the time it required for repetition. When +the battle of Waterloo was fought--so the story goes--news was sent to +England by means of the semaphore-telegraph. The dispatch read, +"Wellington defeated--" At that point in the message a thick fog came up +and lasted for three days, so that no further news could be sent or +received. In the telegraphic parlance of to-day the line was "busted." +For three long days all London was in deep mourning, when finally the +fog lifted, which repaired the telegraphic line, and the balance of the +dispatch was received--"the French at Waterloo." Mourning changed to +rejoicing and the English have rejoiced ever since when they think of +either Wellington or Waterloo. + +But to return to the dynamo. The name dynamo is an abbreviation for +dynamo-electric machine. A machine for producing dynamic electricity. +There are many forms of the dynamo, just as there are in the evolution +of every important machine, and there will be many more. But the +fundamental, underlying principle of them all is contained in an +experiment made by Faraday. Faraday took the soft iron "keeper" of a +permanent magnet and wound insulated wire around it and brought the two +ends of the wire close together. He now placed the keeper, with the +wire wound around it, across the poles of the permanent magnet, and +wrenched it away suddenly, when he observed a spark pass between the +ends of the wires. This would occur when he approached the poles as well +as when he took it away. He discovered that the currents were momentary +and occurred at the moment of approach or recession, and that the +currents developed by the approach were of opposite polarity to those +occurring at the recession. When the "keeper" was put on the poles of +the magnet it was magnetized by having its molecular rings broken up and +the poles of the little natural magnets all turned in one direction. +During the time that the molecules of the keeper are changing they are +in a dynamic or moving condition. By some mysterious action of the ether +between the iron and the wire wrapped around it there is a corresponding +molecular action in the wire that is dynamic for a moment only, and +during that moment we have the phenomenon of an electric current. When +the magnet and soft iron are separated this molecular state of strain is +relieved and the molecules of both the iron and the wire wound about it +return to normal, and in the act of returning we have a dynamic or +moving condition, resulting in a current, only in the opposite +direction. (See Chap. VI.) + +Now mount the permanent magnet in a frame and mount the soft iron with +the wire on it (which in this shape is an electromagnet) on a revolving +arm and so set it on the arm that its ends will come close to, but not +touch, the poles of the permanent magnet. Now revolve the arm, and every +time the electromagnet or keeper approaches the permanent magnet a +current of one polarity will be momentarily developed in the wire of the +electromagnet, which is moving. When it is opposite the poles, it has +reached the maximum charge and, now, as it passes on it discharges and a +current of the opposite polarity is developed in the wire. The more +rapidly we revolve the arm the more voltage (electrical pressure) the +current it develops will have. + +It will be plain to all that we might make the electromagnet stationary +and revolve the permanent magnet and get the same result. If the +permanent magnet were strong enough and the electromagnet the right size +as to iron, windings, etc., and we revolve the arm with sufficient +rapidity, we could get an alternating current of electricity that would +produce an electric light. I have not and cannot here give you the +construction of a modern alternating-current dynamo. I have simply +described the simplest form of dynamo, and all of them operate upon the +fundamental principle of a permanent magnetic field and an +electromagnet, moving in a certain relation to each other. The field +may revolve or the electromagnet may revolve, whichever is the most +convenient to construct. The field-magnet may be a permanent magnet or +an electromagnet, made permanent during the operation of the dynamo by a +part of the current generated by the machine being directed through a +coil surrounding soft iron; or the field-current may come from an +outside source. This is the kind of field-magnet universally used for +dynamo work, as a much stronger magnetism is developed in this way than +it is possible to obtain from any system of permanent steel magnets. + +The usual construction is to have a stationary field-magnet and then a +series of electromagnets mounted and revolving upon a shaft in the +center of the magnetic field. The rotating part is called the armature, +and is so wound with insulated wire that successive induced currents are +created in the armature windings and discharged through brushes which +rest on revolving segments that connect with the armature windings. +These induced currents succeed each other with such rapidity as to +amount in practice to a steady current. However, the separate pulsations +are easily heard in any telephone when the circuit is near to that of a +dynamo circuit. The dynamo current is not nearly so steady as the +battery current, although both are probably made up of separate +discharges. In the dynamo there is a discharge every time the +electromagnet of the armature cuts through the lines of force of the +magnetic field, and in the galvanic battery every time a molecule is +broken up and its little measure of energy is set free. In the dynamo +the pulsations are so far apart as to make a musical tone of not very +high pitch, but in the galvanic battery the pitch of the tone, if there +is one, would require a special ear to hear it--one tuned, it may be, up +near the rate of light vibration. + +There are two types of dynamo, one generating a direct and the other an +alternating current. (By alternating we mean first a positive and then a +negative current impulse.) We cannot enter into a technical description +of the dynamo in a popular treatise such as this. + +The dynamo has evolved from the germ discovered by Faraday, till to-day +it is a machine, the construction of which requires the highest class of +engineering skill. When in action it seems like a great living presence, +scattering its energy in every direction in a way that is at once a +marvel and a blessing to mankind. But we must not give all the credit to +the dynamo. As the moon shines with a reflected light, so the dynamo +gives off energy by a power delegated to it by the steam-engine that +rotates it, and the steam-engine owes its life to the burning coal, and +the burning coal is only giving up an energy that was stored ages ago +by the magic of the sunbeam; and the sun--? Well, we are getting close +on to the borders of theology, and being only scientists we had better +stop with the sun. + +There is still another way of generating electricity besides those that +we have named; which are friction, chemical action, and the +magneto-electric mode of generating a current. Electricity may be +generated by heat. If we connect antimony and bismuth bars together and +apply heat at the junction of the metals and then connect the free ends +of the two bars to a galvanometer, it will indicate a current. These +pairs can be multiplied, and in this way increase the voltage or +pressure, and, of course, increase the current, if we assume that there +is resistance in the circuit to be overcome. If there were absolutely no +resistance in the circuit--a condition we never find--there would be no +advantage in adding on elements in series. + +Substances differ in their resistance to the passage of electricity--the +less the resistance the better the conductor. The German electrician, G. +S. Ohm (1789-1854), investigated this and propounded a law upon which +the unit for resistances is based, and this unit takes his name and is +called the "ohm." + +Any two metals having a difference of potential will give the phenomena +of thermo-electricity. Antimony and bismuth having a great difference +of potential are commonly used. The use made of thermal currents is +chiefly for determining slight differences of temperature. An apparatus +called the thermo-electric pile has been constructed out of a great +number of pairs of antimony and bismuth bars. This instrument in +connection with a galvanometer makes a most delicate means of +determining slight changes of temperature. If one face of a thermopile +is exposed to a temperature greater than its own, the needle will move +in one direction; if to a temperature lower than its own, the needle +will be deflected in the opposite direction. If both faces of the pile +are exposed to the same changes of temperature simultaneously, of course +no electrical manifestations will occur. + +The earth is undoubtedly a great thermal battery that is kept in action +by the constant changes of temperature going on at the earth's surface, +caused by its rotation every twenty-four hours on its axis. The sun, of +course, is at some point heating the earth, which at other points is +cooling, making a constant change of potential between different points. +If we heat a metal ring at one point a current of electricity will flow +around it--especially if it is made of two dissimilar metals--until the +heat is equally distributed throughout the ring. + +Some years ago, when the Postal Telegraph Company first began operations +between New York and Chicago, the writer made observations twice a day +for some time of the temperature and direction of the earth-current. The +first two wires constructed gave only two ohms resistance to the mile, +which facilitated the experiments. I found that in almost every instance +the current flowed from the point of higher temperature to the lower. If +the temperature in New York were higher at the time of observations than +in Chicago the current would flow westward, and if the conditions were +reversed the current would be reversed also. + + + + +CHAPTER VIII. + +ATMOSPHERIC ELECTRICITY. + + +Nature has another mode of generating electricity, called atmospheric. +The normal conditions of potential between the earth and the upper +atmosphere seem to be that the atmosphere is positively electrified and +the earth negatively. These conditions change, apparently from local +causes, for short periods during storms. In some way the sun's rays have +the power directly or indirectly to give the globules of moisture in the +air a potential different from that of the earth. + +In clear weather we find the air near to the earth in a neutral +condition, but gradually assuming the condition of a positive charge as +we ascend; so that the upper air and the earth are oppositely charged +like the two sides of a Leyden jar or two leaves of a condenser. This +condition is intensified and localized when a thunder-cloud passes over +the earth. The moisture globules have been charged with potential energy +by the power of the sun's rays when evaporation took place; but in this +state the energy is neither heat nor electricity, but a state of strain +like a bent bow or a wound-up spring. When these moisture globules +condense into drops of water the potential energy is set free and +becomes active either as heat or electricity. The cloud gathers up the +energy into a condensed form, and when the tension gets too great a +discharge takes place between the cloud and the earth or from one cloud +to another, which to an extent equalizes the energy. + +In most cases of thunder and lightning it is only a discharge from cloud +to cloud unequally charged. This does not relieve the tension between +the earth and the cloud, but distributes it over a larger area. The +reason for this constant electrical difference between the earth and the +upper regions of atmosphere is not well understood, except that +primarily it is an effect of the sun's rays. Evaporation may and +probably does play a part, and the same causes that give rise to the +auroral display may contribute in some way to the same result. +Evaporation does not always take place at the earth's surface. Cloud +formations may be evaporated in the upper air into invisible moisture +spherules, and charged at the time with potential energy. If we go up +into a high mountain when the conditions are right, we can witness the +effect of this condition of electrical charge or strain between the +upper regions of the atmosphere and the earth, and the tendency to +equalize the potentials between the clouds and the earth. Often one's +hair will stand on end, not from fright, but from electricity passing +down from the upper regions to the earth. When the tension is very great +a loud hissing sound as of many musical tones of not very good quality +may be heard, and a brush or fine-pointed radiation of electricity may +be seen from every point, even from your finger-ends. The thunder is not +usually so loud on high mountains for two reasons--one because the air +is rare, but the chief reason is that the mountain acts as a great +lightning-rod and gradually discharges the cloud or atmosphere, for +often the phenomena may occur when the sky is clear. + +I remember being on top of what is called the Mosquito Range, between +Alma and Leadville in Colorado, during the passage of a thunder shower. +There was no heavy thunder, but a constant fusillade of snapping sounds, +accompanied by flashes not very intense. I could feel the shocks, but +not painfully. A part of the time I was in the cloud and became for the +time being a veritable lightning-rod. After the cloud passed it crawled +down the mountainside as if clinging to it, all the time bombarding it +with little electric missiles. After the cloud left the mountain and +passed over the valley I could hear loud thunder, because the charge +would have to accumulate quite a quantity, so to speak, before it could +discharge. These heavy discharges when the cloud is some distance from +the earth would be dangerous to life, while the light ones, when the +cloud is in contact with the earth, are not. + +Many wonderful and destructive effects come from these lightning +discharges and many lives are lost every year from this cause. I do not +suppose it is possible to be on one's guard continually, but many lives +are needlessly lost either from ignorance or carelessness. Although +there is a just prejudice against lightning-rods as ordinarily +constructed, it is still just as possible to protect your house and its +inmates from the destroying effects of lightning as from rain. If, for +instance, we lived in metal houses that had perfect contact all round +them with moist earth, or better, with a water-pipe that has a large +surface contact with the earth, the lightning would never hurt the house +or the inmates. In such a case you simply carry the surface of the earth +to the top of your house, electrically speaking, and neutralization +takes place there in case the lightning strikes the house. A house that +is heated with hot water can easily be made lightning-proof by a little +work at the top and bottom of the heating system. All the heavy metal of +the house should be a part of the lightning-rod. Points should be +erected at the chimneys, and if there is a metal roof they should be +connected with it. Then connect the roof with rods from several points +with the ground. Here is where most rods fail. The ground connection is +not sufficient. The earth is a poor conductor, and we have to make up by +having a large metal surface in contact with it. It is best to have the +rod connected with the water pipe, if there is one, and have it +connected with metal running all around the house as low down as the +bottom of the cellar, for sometimes there is an upward stroke, and you +never can tell where it is coming up. If you have a heating system it +should be thoroughly grounded and the top pipe connected with the rods +at the chimneys. These rods need not be insulated as is the usual +practice. + +If you are outdoors during a thunder-storm never get under a tree, but +if you are twenty or thirty feet away it may save your life, because, if +it comes near enough to strike you, it will probably take the tree in +preference. It seeks the earth by the easiest passage. An oil-tank and a +barn are dangerous places, if the one has oil in it and the other is +filled with hay and grain. A column of gas is rising that acts as a +conductor for lightning. Of course if the barn is properly protected +with rods it will be safe. Sometimes a cloud is so heavily charged that +the lightning comes down like an avalanche, and in such a case the rods +must have great capacity and be close together to fully protect a +building. + +There is a popular notion that rods draw the lightning and increase the +damage rather than otherwise. This is a mistake. Points will draw off +electricity from a charged body silently. It would be possible to so +protect a district of any size in such a way that thunder would never be +heard within its boundaries if we should erect rods enough and run them +high enough into the upper air. The points--if they were close enough +together--would silently draw off the electricity from a cloud as fast +as it formed, and thus effectually prevent any disruptive discharge from +taking place. + + + + +CHAPTER IX. + +ELECTRICAL MEASUREMENT. + + +Having given a short account of some of the sources of electricity, let +us now proceed to describe some of the practical uses to which it is +put, and at the same time describe the operation of the appliances used. +Before proceeding further, however, we ought to tell how electricity is +measured. We have pounds for weight, feet and inches for lineal measure, +and pints, quarts, gallons, pecks and bushels for liquid and dry +measure, and we also have ohms, volts, amperes and ampere-hours for +electricity. + +When a current of electricity flows through a conductor the conductor +resists its flow more or less according to the quality and size of the +conductor. Silver and copper are good conductors. Silver is better than +copper. Calling silver 100, copper will be only 73. If we have a mile of +silver wire and a mile of iron wire and want the iron wire to carry as +much electricity as the silver and have the same battery for both, we +will have to make the iron wire over seven times as large. That is, the +area of a cross-section of the iron wire must be over seven times that +of the silver wire. But if we want to keep both wires the same size and +still force the same amount of current through each we must increase the +pressure of the battery connected with the iron wire. We measure this +pressure by a unit called the "volt," named for Volta, the inventor or +discoverer of the voltaic battery. The volt is the unit of pressure or +electromotive force. (In all these cases a "unit" is a certain amount or +quantity--as of resistance, electromotive force, etc.--fixed upon as a +standard for measuring other amounts of the same kind.) + +The iron wire offers a resistance that is about seven times greater than +silver to the passage of the current. To illustrate by water pressure: +If we should have two columns of water, and a hole at the bottom of each +column, one of them seven times larger than the other, the water would +run out much faster from the larger hole if the columns were the same +height. Now, if we keep the column with the larger hole at a fixed +height a certain amount of water will flow through per second. If we +raise the height of the column having the small hole we shall reach a +point after a time when there will be as much water flow through the +small hole per second as there is flowing through the large hole. This +result has been accomplished by increasing the pressure. So, we can +accomplish a similar result in passing electricity through an iron wire +at the same rate it flows through a silver wire of the same size, by +increasing the pressure, or electromotive power; and this is called +increasing the voltage. + +The quality of the iron wire that prevents the same amount of current +from flowing through it as the silver is called its resistance. The unit +of resistance, as mentioned in the last chapter, is called the ohm, and +the more ohms there are in a wire as compared with another, the more +volts we have to put into the battery to get the same current. + +The unit for measuring the current is called the "ampere," named after +the French electrician, A. M. Ampere (1789-1836). + +Now, to make practical application of these units. The volt is the +potential or pressure of one cell of battery called a standard cell, +made in a certain way. The electromotive force of one cell of a Daniell +battery is about one volt. One ohm is the resistance offered to the +passage of a current having one volt pressure by a column of mercury one +millimeter in cross-section and 106.3 centimeters in length. Ordinary +iron telegraph-wire measures about thirteen ohms to the mile. Now +connect our standard cell--one volt--through one ohm resistance and we +have a current of one ampere. Unit electromotive force (volt) through +unit resistance (ohm) gives unit of current (ampere). It is not the +intention to treat the subject mathematically, but I will give you a +simple formula for finding the amount of current if you know the +resistance and the voltage. The electromotive force divided by the +resistance gives the current. C = E/R or current (amperes) equals +electromotive force (volts) divided by the resistance (ohms). + +But still further: One ampere of current having one volt pressure will +develop one watt of power, which is equal to 1/746 of a horse-power. +(The watt is named in honor of James Watt, the Scottish inventor of the +steam-engine--1786-1813). In other words, 746 watts equal one +horse-power. By multiplying volts and amperes together we get watts. + +If we want to carry only a small current for a long distance we do not +need to use large cells, but many of them. We increase the pressure or +voltage by increasing the number of cells set up in series. If we have a +wire of given length and resistance and find we need 100 volts to force +the right amount or strength of current through it, and the +electromotive force of the cells we are using is one volt each, it will +require 100 cells. If we have a battery that has an E. M. F. of two +volts to the cell, as the storage-battery has, fifty cells would +answer. If we want a very strong current of great volume, so to speak, +for electric light or power, and use a galvanic battery, we should have +to have cells of large surface and lower resistance both inside and +outside the cells. + +When dynamos are used they are so constructed that a given number of +revolutions per minute will give the right voltage. In fact, the dynamo +has to be built for the amount of current that must be delivered through +a given resistance. The same holds good for a dynamo as for a galvanic +battery. If any one factor is fixed, we must adapt the others to that +one in order to get the result we want. There are many other units, but +to introduce them here would only confuse the reader. The advanced +student is referred to the text-books. + +With this much as a preliminary we are prepared to take up the +applications of electricity, which to most people will be more +interesting than what has gone before. + + + + +CHAPTER X. + +THE ELECTRIC TELEGRAPH. + + +In the year 1617 Strada, an Italian Jesuit, proposed to telegraph news +without wires by means of two sympathetic needles made of loadstone so +balanced that when one was turned the other would turn with it. Each +needle was to have a dial with the letters on it. This would have been +very nice if it had only worked, but it was not based on any known law +of nature. + +Many attempts at telegraphing with electricity were made by different +people during the eighteenth century. About 1748 Franklin succeeded in +firing spirits by means of a wire across the Schuylkill River, using, as +all the other experimenters had done, frictional electricity. In 1753 an +anonymous letter was written to Scott's Magazine describing a method by +which it was possible to communicate at a distance by electricity. The +writer proposed the use of a wire for each letter of the alphabet, that +should terminate in pith balls at the receiving end, and under the balls +were to be strips of paper corresponding to the letters of the +alphabet. The message was to be sent by discharging static electricity +through the wire corresponding to the first letter of a word when the +paper would be attracted to the pith ball and read by the observer. Then +the wire corresponding to the second letter of the word was to be +charged in like manner, and so on till the whole message was spelled +out. This was the first practical (i.e., possible) suggestion for a +telegraph. The writer also proposed to have the wires strung on +insulators, which was a great advance over the other attempts. + +The communication was anonymous, as no doubt, like many others, the +author feared the ridicule of his neighbors. It requires a vast amount +of moral courage to stand up before the world and openly advocate some +new theory that has never come within the experience of any one before. +It requires much now, but it required more then; for a man in those days +would have been roasted for what in these days he would be toasted. The +rank and file of humanity have been opposed to innovations in all ages, +but no progress could have been made without innovations. There always +has to be a first time. Galileo is said to have been forced to retract, +on his knees, some theory he advanced about the motion of the earth, and +its relation to the sun and other heavenly bodies. Notwithstanding this +retraction the seed-thought sown by Galileo took root in other minds, +which led to the triumph of scientific truth over religious fanaticism. + +The writer in Scott's Magazine did not have the opportunity to put his +ideas into practice, so the glory of the invention fell to others. Such +men as this unknown writer are made of finer stuff, and they stand alone +on the frontier of progress. They do not fear the bullets of an enemy +half so much as the gibes of a friend. Much of their work is done +quietly and without notice, and when something of real importance is +worked out theoretically and experimentally, some one seizes upon it and +proclaims it from the housetops and attaches to it his name; but perhaps +years after the real inventor (the man who taught the so-called inventor +how to do it) is dead, some one writes a book that reveals the truth, +and then the hero-loving people erect a monument to his memory. + +Such a man was our own Professor Joseph Henry, so long the presiding +genius at the Smithsonian Institution at Washington. He worked out all +the problems of the present American telegraphic system and demonstrated +it practically. Everything that made the so-called Morse telegraph a +success had long before been described and demonstrated by Henry. Yet +with the modest grace that was ingrained in the man he yielded all to +the one who was instrumental in constructing the first telegraph line +between Baltimore and Washington. Great credit is due to such men as +Morse and Cyrus W. Field--neither of them inventors, but promoters of +great systems of communication that are of unspeakable benefit to +mankind. Henry pointed out the way, and Morse carried it into effect. +Morse has had no more credit than was due him, but has Henry had as much +as is due him? No great invention was ever yet the work, wholly, of one +man. We Americans are too apt to forget this. + +I shall always remember Henry as a most unassuming, kindly, genial man, +and I shall never forget his kindness to me. In 1874 I began my +researches in telephony, having applied for a patent for an apparatus +for transmitting musical tones telegraphically. This consisted of a +means of transmitting musical tones through a wire and reproducing them +on a metal plate (stretched on the body of a violin to give it +resonance) by rubbing the plate with the hand--the latter being a part +of the circuit. The examiner refused the application at first on the +ground that the inventor or operator could not be a part of his machine. +I took my apparatus and went to Washington, first calling upon Professor +Henry, never having met him before. He received me most kindly, and +allowed me to string wires from room to room in the institute, and when +he had witnessed the experiments he seemed as delighted as a child. I +now brought the patent office official over to the Smithsonian and soon +convinced him that the inventor could be a part of his own machine. + +The same year I went abroad, and Henry gave me a letter to Tyndall. It +was very fortunate for me that he did, for Tyndall was very shy at +first, and it was only Henry's letter that gave me a hearing for a +moment. The history of the few days that followed this first interview +with Tyndall at the Royal Institution would make very interesting +reading, if I felt at liberty to publish it. Suffice it to say that he +was convinced in a few minutes after he had reached the experimental +stage that not all my work had been anticipated by Wheatstone, as he +asserted before seeing the experiments. Wheatstone had transmitted the +tones of a piano, mechanically, from one room to another by a wooden rod +placed upon the sound-board and terminating in another room in contact +with another sound-board. But this was very different from transmitting +musical tones and melodies from one city to another through a wire, as I +could do with my electrotelephonic apparatus. + +It is a curious fact that the world is divided into two great classes, +leaders and followers. Or we might say, originators and copyists; the +former division being very small, while the latter is very large. As +late as 1820 the European philosophers were trying to construct a +telegraphic system based upon two ideas, announced a long time before, +to wit, the use of static or frictional electricity, and a wire for +every letter. It does not seem to have occurred to any one to devise a +code consisting of motions differently related as to time, and to use +simply one wire. + +In 1819 Oersted discovered the effect of a galvanic current on a +magnetic needle, and published a pamphlet concerning his discovery. This +stimulated others, and Ampere applied it to the galvanometer the same +year. Arago applied it to soft iron, and here was the germ of the +electromagnet. We see that as far back as 1820 we had the galvanic +battery and the electromagnet, the two great essentials of the modern +telegraph. + +However, there remained another great discovery to be made before these +elements could be utilized for telegraphic purposes. One cell of battery +was used, and the magnet was made by winding one layer of wire spirally +around the iron, so that each spiral was out of touch with its neighbor. +Barlow of England, a Fellow of the Royal Society, tried the effect of a +current through a wire 200 feet long, and found that the power was so +diminished that he was discouraged, and in a paper gave it as his +opinion that galvanism was of no use for telegraphing at a distance. +This paper stimulated others, and it was reserved for our own Joseph +Henry, already referred to, to show not only how to construct a magnet +for long-distance telegraphy, but also how to adapt the battery to the +distance. He showed us that by insulating the wire and using several +layers of whirls, instead of one, and by using enough cells of battery +coupled up in series to get more voltage, as we now express it, it was +possible to transmit signals to a distance. He not only set forth the +theory, but he constructed a line of bell-wire 1060 feet long and worked +his magnet by making the armature strike a bell for the signals, which +is the basis of the modern "sounder." + +Nothing was needed but to construct a line and devise a code to be read +by sound, to have practically our modern Morse telegraph. This line was +constructed in 1831. In 1835 Henry, who was then at Princeton, +constructed a line and worked it as it is to-day worked, with a relay +and local circuit, so that at that period all the problems had been +worked out. But, like the speaking-telephone in its early inception, no +one appreciated its real importance. Henry himself did not think it +worth while to take out a patent. Two years later the Secretary of the +Treasury sent out a circular letter of inquiry to know if some system of +telegraphic communication could not be devised. The learned heads of +the Franklin Institute of Philadelphia, the oldest scientific society in +America, advised that a semaphore system be established between New York +and Washington, consisting of forty towers with swinging arms, the same +as used in the days of Wellington. Among other replies to the circular +letter of the secretary was one from Samuel F. B. Morse. Morse was not a +scientist or even an inventor, at least not at that time. He was an +artist of some note. In 1832, while crossing the ocean, Morse, in +connection with one Dr. Jackson of Boston, devised a code of telegraphic +signs intended to be used in a chemical telegraph system. + +Some years later Morse adapted Henry's signal-instrument to a recorder, +called the Morse register, and this was the instrument used in the early +days of the Morse telegraph. + +What Morse seems to have really invented was the register, which made +embossed marks on a strip of paper, and the code of dots and dashes +representing letters, now known as the Morse alphabet, although this +latter is questioned. Morse took his apparatus to Washington and +exhibited it to the members of Congress in the year 1838, but it was +four years before a bill was passed that enabled him to try the +experiment between Baltimore and Washington. We will let him describe in +his own words the closing day of Congress. He says: + +"My bill had indeed passed the House of Representatives and it was on +the calendar of the Senate, but the evening of the last day had +commenced with more than 100 bills to be considered and passed upon +before mine could be reached. Wearied out with the anxiety of suspense, +I consulted one of my senatorial friends. He thought the chance of +reaching it to be so small that he advised me to consider it as lost. In +a state of mind which I must leave you to imagine, I returned to my +lodgings to make preparations for returning home the next day. My funds +were reduced to the fraction of a dollar. In the morning, as I was about +to sit down to breakfast, the servant announced that a young lady +desired to see me in the parlor. It was the daughter of my excellent +friend and college classmate, the commissioner of patents, Henry L. +Ellsworth. She had called, she said, by her father's permission, and in +the exuberance of her own joy, to announce to me the passage of my +telegraph bill at midnight, but a moment before the Senate adjourned. +This was the turning-point of the telegraph invention in America. As an +appropriate acknowledgment of the young lady's sympathy and kindness--a +sympathy which only a woman can feel and express--I promised that the +first dispatch by the first line of telegraph from Washington to +Baltimore should be indited by her; to which she replied: 'Remember, +now, I shall hold you to your word.' About a year from that time the +line was completed, and, everything being prepared, I apprised my young +friend of the fact. A note from her inclosed this dispatch: 'What hath +God wrought?' These were the first words that passed on the first +completed line in America." + +The first telegraph-line in America was put into operation in the spring +of 1844 at the beginning of Polk's administration. I remember as a boy +having the two cities, Baltimore and Washington, pointed out to me on +the map, and how the story of the telegraph impressed me. Congress +appropriated $30,000 for the construction of the line, and $8000 to keep +it running the first year. It was placed under the control of the +postmaster-general, and the line was thrown open to the public. The +tariff was fixed at one cent for every four words. It was open for +business on April 1, 1844, and for the first few days the revenue was +exceedingly small. On the morning of the first day a gentleman came in +and wanted to "see it work." The operator told him that he would be glad +to show it at the regular tariff of one cent for four words. The +gentleman grew angry and said that he was influential with the +administration, and that if he did not show him the working free of +charge he would see to it that he lost his job. His bluff did not +succeed. The operator referred him to the postmaster-general, and thus +the stormy interview ended. No patrons came in for the next three days, +but a great number stood around hoping to see the instrument start up, +but no one was willing to invest a cent--probably from fear of being +laughed at. + +On the fourth day the same gentleman who had threatened the young man +with dismissal came back and invested a cent, and this was the first and +only revenue for four days. The message that was sent only came to +one-half cent, but as the operator could not make change the stranger +laid down the cent and departed. His name ought to be known to fame as +the first man patron of the telegraph. + + [Illustration: Fig. 2. + + A gives a diagram view of a Morse telegraph-line with three + stations. B is the battery; C C C, the transmitting keys in the + three offices; D D D, the relay magnets; E E E, the armatures + that are actuated by the magnets.] + +The operation of the Morse telegraph is very simple if we grant all that +has gone before. All that is needed is the wire, the battery, and the +key, as shown in Fig. 2 (page 99), and a relay--an extra electromagnet +which receives the electric current and by its means puts into or out of +action a small local battery on a short circuit in which is placed the +receiving or recording apparatus. Thus we have a wire starting from the +earth in New York and passing through a battery, a key and a relay, and +thence to Boston on poles, with insulators on which the wire is strung, +and through another instrument, key and battery in Boston, the same as +at the New York end, and into the ground, leaving the earth to complete +one-half of the circuit. When the keys at both ends are closed the +batteries are active and the armatures or "keepers" are attracted so +that the armature levers rest on the forward stops. (See diagram Fig. +2.) If either one of the keys is opened the current stops flowing and +the magnetism vanishes from all the electromagnets on the line, and a +spring or retractile of some kind pulls the armatures away from the +magnets and the levers rest on their back stops. In this way all the +levers of all the magnets are made to follow the motions of any key. If +there are more than two magnets in circuit (and there may be twenty or +more) they all respond in unison to the working of one key, so that when +any one station is sending a dispatch all the other stations get it. + +But there is a "call" for each office, so that the operator only heeds +the instrument when he hears his own call. Operators become so expert in +reading by sound that they may lie down and sleep in the room, and, +although the instrument is rattling away all the time, he does not hear +it till his own call is made, when he immediately awakes. + +In the old days messages were received on slips of paper by the Morse +register by means of dots and dashes. Gradually the operator learned to +read by sound, till now this mode of receiving is almost universal the +world over. Reading by sound was of American origin. It is a spoken +language, and when one becomes accustomed to it it is like any other +language. This code language has some advantages over articulate speech, +as well as many disadvantages. A gentleman who was connected with a +Louisville telegraph office told me that one of the best operators he +ever knew was as deaf as a post. He would receive the message by holding +his knee against the leg of the table upon which the sounder was +mounted, and through the sense of feeling receive the long and short +vibrations of the table, and by this means read as well or better than +through the ear, because he was not distracted by other sounds. + +A story is told of the late General Stager that at one time he was on a +train that was wrecked at some distance from any station. He climbed a +telegraph pole, cut the wire and by alternately joining and separating +the ends sent a message, detailing the story of the wreck, to +headquarters, and asked for assistance. He then held the two ends of the +wire on each side of his tongue and tasted out the reply--that help was +coming. Any one who has ever tasted a current knows that it is very +pronounced. + +A story similar to this is told of the early days when the Bain chemical +system was used between Washington City and some other point. This +system made marks on chemically-prepared paper; as the current passed +through it left marks on the paper from the decomposition of the +chemicals. Some of the preparations emitted an odor during the time that +the current passed. The occurrence to which we refer took place at +presidential election time. At some station out of Washington an +operator was employed who had a blind sister, and this sister knew the +Morse alphabet well before she became blind. One evening a signal came +to get ready for a message containing the returns from the election. In +the hurry, and just as the message had started, the lamp was upset and +they were in total darkness--at least, the brother was. The sister, poor +girl, had been in darkness a long time. The blind sister leaned over the +stylus through which the current flowed to the paper and smelled out as +well as spelled out the message, and repeated it to her astonished +brother. + +By the old semaphore system the motions were sensed through the eye as +well as the early method of cable signaling. It will be seen from the +above that the Morse code may be communicated through any one of the +five senses. + + + + +CHAPTER XI. + +RECEIVING MESSAGES. + + +With but few exceptions the Morse code is the one almost universally +used the world over. As it is used in Europe, it is slightly changed +from our American code, but they all depend upon dots, dashes, and +spaces, related in different combinations, for the different letters. +Notwithstanding its universal use it is not free from serious +difficulties in transmission unless it is repeated back to the sender +for correction; and then in some cases it is impossible to be sure, +owing to difficulties of punctuation and capitalizing, and the further +difficulty of running the signals together, caused, it may be, by faulty +transmission, induced currents from other wires, "swinging crosses" or +atmospheric electricity. Sometimes it is a psychological difficulty in +the mind of the receiving-operator. The telegraph companies have to +suffer damages from all these and many other unforeseen causes. + +Prescott tells some curious things that happened in the early days, +growing out of the peculiarities of the receiving-operator. At one time +he was reporting by telegraph one of Webster's speeches made at Albany +in 1852 in which there were many pithy interrogative sentences, and he +was desirous of having the interrogation-points appear. So to make sure, +whenever he wished an interrogation-point he said "question" at the end +of almost every sentence. Next day he was horrified on reading the +speech to see the ends of the sentences bristling with the word +"question." + +Some time back in the fifties a gentleman in Boston telegraphed to a +house in New York to "forward sample forks by express." The message when +received by the New York merchant read: "Forward sample for K. S. by +express." The New York merchant did not know who K. S. was, nor did he +gather from the dispatch what kind of sample he wanted. So he went to +the telegraph office to have the matter cleared up. The Boston operator +repeated the message, saying "sample forks." "That's the way I received +it and so delivered it--sample for K. S.," said New York. "But," says +Boston, "I did not say for K. S.; I said f-o-r-k-s." New York had read +it wrong in the start and could not get it any other way. "What a fool +that Boston fellow is. He says he did not say for K. S., but for K. S." +Boston had to resort to the United States mail before the mystery was +solved. + +Curiously enough, the old method of recording the dots and dashes on +the paper strip was not so reliable as the present mode of reading by +sound. A man can put his individuality to some extent into a sounder, +and when one becomes used to his style it is much easier to read him +accurately by sound than by the paper impressions. Some people never +could learn to read either by paper or sound. An instance of this kind +is given of a middle-aged man who was employed by a railroad company as +depot master and telegraph operator, in the old days of the paper strip. +One day he rushed out and hailed the conductor of a train that had just +pulled into the station, and told him that ---- train had broken both +driving-wheels and was badly smashed up. The conductor could read the +mystic symbols, so he took the tape and deciphered the dispatch as +follows: "Ask the conductor of the Boston train to examine carefully the +connecting-rods of both driving-wheels, and if not in good condition to +await orders." It is further related of this same operator that when he +got into real difficulty with his "tape" he used to run over to the +regular commercial office to have his messages translated. One day he +rushed into his neighbor's office trailing the tape behind him and +saying: "I am sure an awful accident has happened by the way the message +was rattled off." A playful dog had torn off a large part of the strip +as it trailed along, so only a part was left. It read, "Good morning, +Uncle Ben. When are you----" The dog had swallowed the balance of the +dispatch. + +Sometimes the Morse code is not only funny but disastrous. A gentleman +wanted to borrow money of some capitalists who, not knowing his +financial standing, telegraphed to a banker who they knew could post +them. They received an answer, "Note good for large amount." The +gentleman borrowed a "large amount," but afterward when it came to be +investigated it was found that the dispatch was originally written +"not," instead of "note," which made "all the difference in the world." + +It has been stated that any one of the five senses may be called into +service to interpret the Morse code into words and ideas. A story is +told by Mr. Prescott that he says is true, as he knew the party. A +friend of his, by name Langenzunge, who knew the Morse code, had served +under General Taylor (who at this time was President) at Palo Alto, in +Mexico. The general had just promised him an office; soon after he left +Washington for the west over the Baltimore and Ohio on a freight train; +the President was taken seriously ill, and his friend hearing of it was +troubled not only because he loved the old general, but on account of +the change in his own prospects. The train stopped somewhere on the +Potomac at midnight and remained there for four hours. Uneasy and sad, +he wandered down the track and climbed a pole, cut the wire and placed +the ends each side of his tongue and tasted out the fatal message--"Died +at half-past ten." The shock (not the electric) was so great that he +almost fell from the pole. + +What a situation! A man climbs a pole at midnight miles from the sick +friend he loves, puts his tongue to inanimate wire, and is told in +concrete language--through the sense of taste--that his friend is dead. +This is only one of the many, many wonderful episodes of the telegraph. + + + + +CHAPTER XII. + +MISCELLANEOUS METHODS. + + +"It never rains but it pours." Almost simultaneously with the +demonstration of the Morse telegraph other types were devised. There +were the needle systems of Cooke and Wheatstone, the chemical telegraph +of Alexander Bain, and soon the printing telegraph of House, and later +that of Hughes. The latter is in use on the continent of Europe, and a +modification of it has a very limited use on some American lines. The +Bain telegraph used a key and battery the same as the Morse system, but +it did not depend upon electromagnetism as the Morse system does. When +in operation a strip of paper was made to move under an iron stylus at +the receiving-end of the line. The paper was saturated with some +chemical that would discolor by the electrolytic action of the current. +When a message was sent the paper was set to moving by a clock mechanism +or otherwise, under the stylus that was pressing on the paper as it +passed over a metal roller or bed-plate. The transmitting-operator +worked his key precisely as in sending an ordinary message by the Morse +system. The effect was to send currents through the receiving-stylus +chopped into long or short marks, or the dots and dashes of the Morse +code, and recorded on the tape in marks that were blue or brown, +according to the chemical used. A few lines were established in this +country on the Bain system, but it never came into general use. + +A number of systems, called "automatic," grew out of the Bain system. +Bain himself devised, perhaps, the first automatic telegraph. The +fundamental principle of all automatic telegraphs depends upon the +preparation of the message before sending, and is usually punched in a +strip of paper and then run through between rollers that allow the +stylus to ride on the paper and drop through the holes that represent +the dots and lines of the Morse alphabet. Every time the stylus drops +through a hole in the paper it makes electrical contact and sends a +current, long or short, according to the length of the hole. The object +of the automatic system was to send a large amount of business through a +single wire in a short time. It does not save operators, as the messages +have to be prepared for transmission, and then translated at the +receiving-end and put into ordinary writing for delivery. + +The automatic system is not used except for special purposes, and the +one that seems to be the most favored is that of Wheatstone. The system +is in use in England and in America to a limited degree. + +Early in the history of the telegraph a printing system was devised. +Wheatstone and others had proposed systems of printing telegraphs in +Europe, but these never passed the experimental stage. The first +printing telegraph introduced in America was invented by Royal E. House +of Vermont, and first introduced in 1847 on a line between Cincinnati +and Jeffersonville, a distance of 150 miles. In 1849 a line for +commercial use was established between New York and Philadelphia, and +for some years following many lines were equipped with the House +printing telegraph instrument. The late General Anson Stager was a House +operator at one time. All printing telegraph instruments, while +differing greatly in detail, have certain things in common, to wit: a +means for bringing the type into position, an inking device, a printing +mechanism, a paper feed, and a means for bringing the type-wheels into +unison. There are two general types of printing instruments, the +step-by-step, and the synchronously moving type-wheels. The House +printer was a step-by-step instrument and consisted of two parts, a +transmitter and a receiver. The transmitter consists of a keyboard like +a piano, with twenty-eight keys. These keys are held in position by +springs. Under the keys is a cylinder having twenty-eight pins on it +corresponding to the twenty-six letters of the alphabet and a dot and a +space. This cylinder was driven by some power. In those days it was by +man-power. It was carried by a friction, so that it could be easily +stopped by the depression of any one of the keys that interfered with +one of the pins. One revolution of the cylinder would break and close +the current twenty-eight times, making twenty-eight steps. + +The receiving-instrument consisted of a type-wheel and means for driving +it. It was somewhat complicated, and can only be described in a general +way. If the cylinder of the transmitter was set to rotating it would +break and close twenty-eight times each revolution. (There were fourteen +closes and fourteen breaks, each break and each close of the current +representing a step.) The type-wheel of the receiver was divided into +twenty-eight parts, having twenty-six letters and a dot and space, each +break moved it one step and each close a step; so that if the cylinder, +with its twenty-eight pins, started in unison with the type-wheel, with +its twenty-eight letters and spaces, they would revolve in unison. The +keys were lettered, and if any one was depressed the pin corresponding +to it on the cylinder would strike it and stop the rotation of the +cylinder, which stopped the breaking and closing of the circuit, which +in turn stopped the rotation of the type-wheel--and not only stopped it, +but also put it in a position so that the letter on the type-wheel +corresponding to the letter on the key that was depressed was opposite +the printing mechanism. The printing was done on a strip of paper, which +was carried forward one space each time it printed. The printing +mechanism was so arranged that so long as the wheel continued to rotate +it was held from printing, but the moment the type-wheel stopped it +printed automatically. + +The messages were delivered on strips of paper as they came from the +machine. + +In 1855 David E. Hughes of Kentucky patented a type-printing telegraph +that employed a different principle for rotating the type-wheel. The +electric current was used for printing the letters and unifying the +type-wheels with the transmitting-apparatus. The transmitter, cylinder, +and the type-wheel revolved synchronously, or as nearly so as possible, +and the printing was done without stopping the type-wheel. Whenever a +letter was printed the type-wheel was corrected if there was any lack of +unison. + +This type of machine in a greatly improved form is still used on some of +the Western Union lines, especially between New York, Boston, +Philadelphia, and Washington. It is also in use in one of its forms in +most of the European countries. + + + + +CHAPTER XIII. + +MULTIPLE TRANSMISSION. + + +Although the printing and automatic systems of telegraphing are used in +America to some extent, the larger part is done by the Morse system of +sound-reading and copying from it, either by pen or the typewriter. In +the early days only one message could be sent over one wire at the same +time, but now from four to six or even more messages may be sent over +the same wire simultaneously without one message interfering with the +other. Like most other inventions, many inventors have contributed to +the development of multiple transmission, till finally some one did the +last thing needed to make it a success. The first attempts were in the +line of double transmission, and many inventors abroad have worked on +this problem. + +Moses G. Farmer of Salem, Mass., proposed it as early as 1852, and +patented it in 1858. Gintl, Preece, Siemens and Halske and others abroad +had from time to time proposed different methods of double transmission, +but no one of them was a perfect success. When the line was very long +there was a difficulty that seemed insurmountable. In the common +parlance of telegraphy, there was a "kick" in the instrument that came +in and mutilated the signals. About 1872 Joseph B. Stearns of Boston +made a certain application of what is called a "condenser" to duplex +telegraphy that cured the "kick," and from that time to this it has been +a success. Farther along I will tell you what occasioned this "kick" and +how it was cured. If this or some other method could be applied as +successfully to cure the many chronic "kickers" in the world it would be +a great blessing to mankind. + +It has always been a mystery to the uninitiated how two messages could +go in opposite directions and not run into one another and get wrecked +by the way. If you will follow me closely for a few minutes I will try +to tell you. + +We have already stated that an electromagnet is made by winding an +insulated wire around a soft iron core. If we pass a current of +electricity through this wire the core becomes magnetic, and remains so +as long as the current passes around it. In duplex telegraphy we use +what is called a differential magnet. A differential electromagnet is +wound with two insulated wires and so connected to the battery that the +current divides and passes around the iron core in opposite directions. +Now if an equal current is simultaneously passed through each of the +wires of the coil in opposite directions the effect on the iron will be +nothing, because one current is trying to develop a certain kind of +polarity at each pole of the magnet, while the current in the other wire +is trying to develop an opposite kind in each pole. There is an equal +struggle between the two opposing forces, and the result is no +magnetism. This assumes that the two currents are exactly the same +strength. + +If we break the current in one of the coils we immediately have +magnetism in the iron; or if we destroy the balance of the two currents +by making one stronger than the other we shall have magnetism of a +strength that measures the difference between the two. + +Without specifically describing here the entire mechanism--since this is +not a text-book or a treatise--we may say that a duplex telegraph-line +is fitted with these differentially wound electromagnets at every +station. When Station A (Fig. 3) is connected to the line by the +positive pole of its battery, Station B will have its negative pole to +line and its positive to earth. When A depresses his key to send a +message, half the current passes by one set of coils around his +differential magnet through a short resistance-coil to the earth, and +the other half by the contrary coil around the magnet to the line, and +so to Station B. The divided current does not affect A's own station, +being neutralized by the differential magnet, but it does affect B, +whose instrument responds and gives him the message. + +Now B may at the same time send a message to A by half of his own +divided current from his own end of the line. + + [Illustration: Fig. 3. + + Represents a duplex 500-mile telegraph-line. A and B are the two + terminal stations; B B', the batteries; K K', the keys; D D', + the small resistance-coils, equal to the battery-resistance when + the latter is not in circuit; R R', resistances each equal to + the 500-mile line; and C C', condensers giving the artificial + lines R R' the same capacity as the 500-mile line.] + +The puzzle to most people is: How can the signals pass each other in +different directions on the same wire? But the signals do not have to +pass each other. In effect, they pass; but in fact, it is like going +round a circle--the earth forming half. A sends his message over the +line to B. B sends his message to A through the earth and up A's +ground-wire. The operative who is sending with positive pole to line +_pushes_ his current through--so to speak--while the operative who is +sending with the negative pole to line _pulls_ more current in the same +direction through the line whenever he closes his key. + +This may not be a strictly scientific statement; but, as long as we +speak of a "current" flowing from positive to negative poles (which is +the invariable course electricity takes), it is the way to look at the +matter understandingly. + +The short "resistance-coil" at each end, fortified by a "condenser" made +of many leaves of isolated tin-foil, to give it capacity, offers +precisely the same resistance to the current as the 500 miles of wire +line; so that the twin currents that run around the differential magnet +exactly neutralize each other and make no effect in the office the +message starts from; while one of them takes to the earth, and the other +to the line to carry the message. + +This condenser is necessary, because the short resistance-coil affects +the current immediately, while the long line with its greater amount of +metal does not give the same amount of resistance till it is filled from +end to end, which requires a fraction of a second. During this time, +however, more current is passing through the differential coil connected +with the line than through the short resistance-coil; and the unequal +flow causes the relay armature to jump, or "kick." The condenser, with +the many leaves of tin-foil, supplies the greater metal surface to be +traversed by the short line current, causes the flow to be equal in both +circuits at all times, and thus cures the "kick." It is this quality of +a condenser that enables us to give to an artificial line of any +resistance all the qualities, including capacity, and exhibit all the +phenomena of a real line of any length, and it was this quality that +enabled Mr. Stearns to take the "kick" out of duplex transmission and +thus change the whole system, which created a new era in telegraphy. + +We have just spoken of the "capacity" of a circuit, and stated that it +was determined by the mass of metal used. This capacity is measured by a +standard of capacity that is arbitrary and consists of a condenser, +constructed so that a given amount of surface of tin-foil may be plugged +in or out. The practical unit of capacity is called the micro-farad, the +real unit is the farad, and takes its name from Faraday. + +But let us go back to multiple systems of transmission. There are many +other systems of simultaneous transmission aside from the duplex, and +all of them are classed under the general head of multiple telegraphy. +First there is the quadruplex, that sends two messages each way +simultaneously, making one wire do the work of four single wires--as +they were used at first. The quadruplex is very extensively used by the +Western Union Telegraph Company and others. It would be difficult to +explain it in a popular article, so we will not attempt it. There is +another form of multiple telegraph that was used on the Postal Telegraph +line when it first started--which was invented and perfected by the +writer--that can be more easily explained. + +In 1874 I discovered a method of transmitting musical tones +telegraphically, and the thing that set my mind in that direction was a +domestic incident. It is a curious fact that most inventions have their +beginnings in some incident or observation that comes within the +experience of some one who is able to see and interpret the meaning of +such incidents or observations. I do not mean to say that inventions are +usually the result of a happy thought, or accident; the germ may be, but +the germ has to have the right kind of soil to take root in and the +right kind of culture afterward. It is a rare thing that an invention, +either of commercial or scientific importance, ever comes to perfection +without hard work--midnight oil and daylight toil; and it is rarely, if +ever, that a discovery or an invention based upon a discovery does not +have, sooner or later, a practical use, although we sometimes have to +wait centuries to find it put. We had to wait forty-four years after +the galvanic battery was discovered before it became a useful servant of +man. It was fifty years or more after the discovery by Faraday of +magneto-electricity before it found a useful application beyond that of +a mere toy, but now it is one of the most useful servants we have, as +shown in its wonderful development in electric lighting and electric +railroads, to say nothing of its heating qualities and the useful +purpose it serves in driving machinery. The interesting discoveries of +Professor Crookes in passing a current of electricity through tubes of +high vacua waited many years before they found a practical use in the +X-ray, that promises to be of great service in medicine and surgery. + +The transmission of musical harmonies telegraphically, while in itself +of great scientific interest, was of no practical use, but it led to +other inventions, of which it is the base, that are transcendently +useful in every-day life. The transmission of harmonic sounds by +electricity underlies the principle of the telephone. There is a vast +difference, in principle, between the transmission of simple melody, +which is a combination of musical tones transmitted successively--one +tone following another--and the transmission of harmony, which involves +the transmission of two or more tones simultaneously. The former can be +transmitted by a make-and-break current. In the latter case one tone +has to be superposed upon another and must be transmitted with a varying +but a continuously closed current. I make a distinction between a closed +circuit and a closed current. In the case of the arc-light the circuit +is open (that is, broken), technically speaking, but the current is +still flowing. The reason why the Reiss and other metallic contact +telephone transmitters cannot successfully be used for telephone +purposes is that metal points will not allow of sufficient separation of +the transmitting points without breaking the current as well as the +circuit. Carbon contacts admit of a much wider separation without +actually stopping the flow of the current, which latter is a necessity +for perfect telephonic transmission, and it was the use of carbon that +made that form of transmitter a success. + +There are other forms, or at least one other form that does not depend +upon the length of the voltaic arc formed when the electrodes are +separated. Of this we will speak another time. Now let us go back to the +domestic incident referred to above. + +One evening in the winter of 1873-4 I came home from my laboratory work +and went into the bathroom to make my toilet for dinner. I found my +nephew, Mr. Charles S. Sheppard, together with some of his playmates, +taking electrical "shocks" from a little medical induction-coil that I +heard humming in the closet. He had one terminal of the coil connected +to the zinc lining of the bathtub--which was dry at that time--while he +held the other in his left hand, and with his right was taking shocks +from the lining of the tub by rubbing his hand against the zinc. I +noticed that each time he made contact with the tub, as he rubbed it for +a short distance, a peculiar sound was emitted from under his hand, not +unlike the sound made by the electrotome that was vibrating in the +closet. My interest was immediately aroused, and I took the electrode +out of his hand and for some time experimented with it, going to the +cupboard from time to time to change the rate of vibration of the +electrotome, and thus change the quality of the sound. I noticed that +the sound or tone under my hand, if it could be so called, changed with +each change of the rate of vibration. The thing that most interested me +was that the peculiar characteristics of the noise were reproduced. In +those few minutes I laid out work enough for years of experiment, and as +a result I was late to dinner. + +This discovery opened up to my mind the possibility of three things--the +transmission of music and of speech or articulate words through a +telegraph-wire, and the transmission of a number of messages over a +single wire. I constructed a keyboard consisting of one octave and made +a set of reeds tuned to the notes of the scale, and then when some one +would play a melody I could reproduce it in two ways: One by placing my +body in the circuit and rubbing a metal plate--it might be the bottom of +a tin pan, a joint of stovepipe or otherwise--anything that was metal +and would vibrate would give the effect. Another way was to connect an +electromagnet (having a diaphragm or reed across its poles) in the +circuit at the receiving-end and mount it on some kind of a soundboard. +I made a great number of different kinds of receivers that were capable +of receiving either musical or articulate sounds, as has many times been +proven by experiment. I carried two sets of experiments along together; +the one looking toward a system of multiple telegraphy and the other the +transmission of articulate speech. Let us first look into the multiple +telegraph and take the other up under the head of the telephone. + +When the electrical keyboard was completed I found that I could transmit +not only a melody but a harmony; that more than one tone could be +transmitted simultaneously. This discovery opened up a long series of +experiments with the view of sending a number of messages simultaneously +by means of musical tones differing in pitch. I had already demonstrated +that several tones could be transmitted at once, but they would speak +all alike (with the same loudness) on the receiving-instrument. I now +went to work on an instrument that responded for one note only and +succeeded beyond my expectations. I made three different kinds of +receiving-instruments. The first was a steel strap about eight inches +long by three-eighths wide. This strap was mounted in an iron frame in +front of an electromagnet. A thumbscrew enabled me to stretch the strap +till it would vibrate at the required pitch. If, for instance, the +sending-reed vibrated at the rate of 100 times per second and the strap +of the receiver was stretched to a tension that would give 100 +vibrations per second when plucked, it would then respond to the +vibrations of the sending-reed but not to those of another reed of a +different rate of vibration. If we take mounted tuning-forks tuned in +pairs of different pitches, say four pairs, so that each fork has a mate +that is in exact accord with it, and place them all in the same room, +and sound one of them for a few seconds and then stop it, upon examining +the other forks you will find all of them quiet except the mate of the +one that was sounded. This one will be sounding. If we now sound four of +the forks and then stop them the other four will be sounding from +sympathy because the mate of each one of them has been sounded. If only +two forks differing in pitch are sounded only two of the others will +sound in sympathy. In the first case only one set of sound-waves were +set up in the air, and the fork that found itself in accord with this +set responded. When four forks differing in pitch were sounded there +were four sets of tone-waves superposed upon each other existing in the +air, so that each of the remaining forks found a set of waves in +sympathy with its own natural rate of vibration and so responded. + +Now apply this principle to the harmonic telegraph and you can +understand its operation. At the transmitting-end of a line of +wire there are a certain number of forks or reeds kept vibrating +continuously. These reeds each have a fixed rate of vibration +and bear a harmonic relation to each other so as not to have +sound-interference or "beats." At the receiving-end of the line +there are as many electromagnets as there are transmitting-reeds, and +each magnet has a reed or strap in front of it tuned to some one of the +transmitting-reeds, so that each transmitting-reed has a mate in exact +harmony with it at the receiving-end of the line. Keys are so arranged +at the transmitting-end as to throw the tones corresponding to them to +line when depressed. In other words, when the key belonging to battery B +and vibrator 1 is depressed (see Fig. 4) the effect is to send +electrical pulsations through the line corresponding in rate per second +to that of the vibrator. The same is true of battery B' and vibrator 2. +During the time any key is depressed--we will say of tone No. 1--this +tone will be transmitted through the line and be reproduced by its +mate--the one tuned in accord with it--at the receiving-station. By a +succession of long and short tones representing the Morse code a message +can be sent. Numbers two, three and four might be sending at the same +time, but they would not interfere with number one or with each other. +In 1876-7 the writer succeeded in sending eight simultaneous messages +between New York and Philadelphia by the harmonic method. + + [Illustration: Fig. 4. + + In this diagram, 1 and 2 are tuned reeds; 1A 2A are receivers + tuned to the reeds 1 and 2 respectively; 1 and 1A are in unison, + also 2 and 2A, but the two groups (the 1s and the 2s) differ + from each other in pitch.] + +There were two ways of reading by the harmonic method. One was by the +long and short tone-sounds and the other by the ordinary sounder. + +The vibration of the receiving-reed was made to open and close a local +circuit like a common Morse relay and thus operate the sounder. It is +useless to try to send a message if the sender and receiver are out of +tune with each other in this system. + +What is true in science is true in life. If we are out of tune with our +surroundings we only beat the air, and our efforts are in vain. We get +no sympathetic response. + + + + +CHAPTER XIV. + +WAY DUPLEX SYSTEM. + + +A novel form of double transmission was invented by the writer soon +after the completion of the harmonic system, and was an outgrowth of it. +It is still in use on some of the railroad-lines. An ordinary railroad +telegraph-line has an instrument in circuit in every office along the +road, chiefly for purposes of train-dispatching. As we have heretofore +explained, whenever any one office is sending, the dispatch is heard in +all of the offices. The "Way duplex" system permits of the use of the +line for through business simultaneously with the operation of the local +offices. That is to say, any station along the line may be telegraphing +with any other station by the ordinary Morse method, and at the same +time messages may be passing back and forth between the two end offices. + +This is accomplished by the following method: At each end of the line +there is a tuned reed, such as we have described in our last chapter, +that is kept constantly in vibration by a local battery during working +hours. This vibrator is so arranged in relation to the battery that +whenever the key belonging to it is depressed the current all through +the line is rendered vibratory. There is also in circuit at each end of +the line a harmonic relay, that is tuned in accord with the vibrating +reed of the sender. If either key belonging to this part of the system +is opened, as in the act of sending a message, these harmonic relays, +being tuned in sympathy with the sending-vibrator, will respond, thus +sending Morse characters made up of a tone broken into dots and dashes. +This tone can be read directly from the relay, or, as is usually the +case, it causes the sounder to operate in the common way. + +You will at once inquire why the ordinary Morse instruments in the local +offices are not affected by these vibratory signals, and also why the +harmonic instruments at the end office are not affected by the working +of the local offices. The local office does not open the circuit +entirely, but simply cuts out a resistance by the operation of the +special harmonic key. When a resistance is thrown into an electric +circuit it weakens the current in proportion to the amount of resistance +interposed. You will see that there is some current still left in the +line when the key is open, but the spring of the relay at the local +office is so adjusted as to pull the armatures away from the magnets +whenever the current is weakened by throwing in the resistance, so that +by this means an ordinary Morse telegraphic relay may be worked without +ever entirely opening the circuit. In the Way duplex system there is a +resistance at each station that is cut in and out by the operation of +its key, which causes all the instruments in the line to work +simultaneously except the two harmonic relays located one at each end of +the line. These will not respond to anything but the vibratory signal. + +In order to prevent the Morse relays at the local offices from +responding to the vibratory current a condenser is connected around +them. This condenser serves two purposes: It enables the short impulses +of the vibrating current to pass around the relays without having to be +resisted by the coils of the magnets, and between the pulsations each +condenser will discharge through the relay at the local offices, and +thus fill in the gap between the pulsations, producing the effect on the +relay of a steady current. When a line is thus equipped it may be +treated in every respect as two separate wires, one of them doing way +business and the other through business. It is a curious blending of +science and mechanism. + +Another interesting application was made of the system of transmission +by musical tones--by Edison, some years ago. We refer to the +transmission of messages to and from a moving railroad-train with the +head office at the end of the line. In this case the message was +transmitted a part of the distance through the air;--another instance of +wireless telegraphy. The operation was as follows: One of the wires +strung on the poles nearest to the track was fitted up with a vibrator +and key at the end of the line similar to that of the Way duplex just +described. In one of the cars was another battery, key and vibrator, and +as only one tone was used, no tone-selecting device or harmonic relay +was needed, but instead an ordinary receiving-telephone was used to read +the long and short sounds sent over the lines. One end of the battery in +the car was connected through the wheels to the earth, while the other +end was connected to the metal roof of the car. Being thus equipped, we +will suppose our train to be out on the road forty or fifty miles from +either end of the line, moving at the rate of forty miles an hour. The +operator at Chicago, say, wishes to send a message to the moving train; +he operates his key in the ordinary manner, which makes the current on +the line vibratory during the time the key is depressed. These +electrical vibrations cause magnetic vibrations, or ether-waves, to +radiate in every direction from the wire, at right angles to the +direction of the current, like rays of light. When they strike the roof +of the car they create electrical impulses in the metal by induction +(described in Chap. VI). These impulses pass through a telephone located +in the car to the ground. A Morse operator listening, with the telephone +to his ear, will hear the message through the medium of a musical tone +chopped up into the Morse code. In like manner the operator in the car +may transmit a message to the roof of the car and thence through the air +to the wire, which will be heard, by any one listening, in a telephone +which is connected in that circuit,--and, as a matter of fact, it will +be heard from any wire that may be strung on any of the poles on either +side of the road. + +Some years ago an experiment of this kind was made on one of the roads +between Milwaukee and Chicago. + +What wonderful things can be done with electricity! As a servant of man +it is reliable and accurate--seeming almost to have the qualities of +docility--when under intelligent direction, that is in accord with the +laws of nature; but under other conditions it changes from the willing +servant to a hard master, hesitating not to destroy life or property +without regard to persons or things. + + + + +CHAPTER XV. + +TELEPHONY. + + +In the foregoing chapters I have described the method of transmitting +musical tones telegraphically and its applications to multiple +telegraphy, as well as to a mode of communicating with a moving +railroad-train. As I stated in a former chapter, after discovering a +method of transmitting harmony as well as melody, I had in mind two +lines of development, one in the direction of multiple telegraphy, and +the other that of the transmission of articulate speech. I will not +attempt to give the names of all the people who have contributed to the +development of the telephone (as this alone would fill a volume) but +only describe my own share in the work--leaving history to give each one +due credit for his part. While I do not intend, here, to enter into any +controversy regarding the priority of the invention of the telephone, I +wish to say that from the time I began my researches, in the winter of +1873-4, until some time after I had filed my specification for a +speaking or articulating telephone, in the winter of 1875-76, I had no +idea that any one else had done or was doing anything in this direction. +I wish to say further that if I had filed my description of a telephone +as an application for a patent instead of as a caveat, and had +prosecuted it to a patent, without changing a word in the specification +as it stands to-day, I should have been awarded the priority of +invention by the courts. I am borne out in this assertion by the highest +legal authority. In law, a _caveat_ (Latin word, meaning "Let him +beware") is a warning to other inventors, to protect an incomplete +invention; whereas in fact the invention to be protected may be +complete. An _application_ for a patent is presumed by the law to be for +a completed invention; but it may be, and very often is, incomplete. It +would often make a very great difference if decisions were rendered +according to the facts in the case rather than according to rules of law +and practice, that sometimes work great injustice to individuals. + +As has been said in another chapter, in the summer of 1874 I went to +Europe in the interest of the telephone, taking my apparatus, as then +developed, with me. I came home early in the fall and resumed my +experimental work. Many interesting as well as amusing things occurred +during these experiments. + +I remember that in the fall or early winter of 1874 I was in Milwaukee +with my apparatus carrying on some experiments on a wire between +Milwaukee and Chicago. I had my musical transmitter along, and one +evening, for the entertainment of some friends at the Newhall House, a +wire was stretched across the street from the telegraph office into one +of the rooms of the hotel. A great number of tunes were played at the +telegraph-office by Mr. Goodridge, who was my assistant at that time, +which were transmitted across the street, as before stated. In those +days it was a common practice in telegraphy to use one battery for a +great number of lines. For instance, starting with one ground-wire which +connected with, say, the negative pole of the battery, from the positive +pole two, three or a half-dozen lines might be connected, running in +various directions, connecting with the ground at the further end, thus +completing their circuits. For use in transmitting tones across the +street that evening we connected our line-wire on to the telegraph +company's battery, which consisted of 100 or more cells, and which had +four or five more lines radiating from the end of the battery to +different parts of Wisconsin. Our line was tapped on to the battery +(without changing any of its connections) twenty cells from the +ground-wire. In transmitting, each vibration would momentarily shut off +these twenty cells from the lines that were connected with the whole +battery. The effect of this (an effect that we did not anticipate at the +time) was to send a vibratory current out on all the lines that were +connected with that single battery as well as across the street. A great +many familiar tunes were played during the course of an hour or two +which, unconsciously for us, were creating great consternation +throughout the State of Wisconsin, in many of the offices through which +these various lines passed. + +Next morning reports and inquiries began to come in from various towns +and cities west, northwest and north, giving details of the phenomena +that were noticed on the instruments located in the various offices +along the lines. They reported their relays as singing tunes; one party +said he thought the instruments were holding a prayer-meeting from the +fact that they seemed to be singing hymn-tunes for quite a while, but +this notion was finally dissipated, because they grew hilarious and sang +"Yankee Doodle." + +One operator, up in the pine woods of northern Wisconsin, did not seem +to take the cheerful view of it that some of the others did. He was +sitting alone in the telegraph-office that evening when he thought he +heard the notes of a bugle in the distance; he got up and went to the +door to listen, but could hear nothing; but on coming back into the room +he heard the same bugle notes very faintly. He was inclined to be +somewhat superstitious and grew very nervous; finally, on looking +around, he located the sound in his relay, but this did not help matters +with him. With superstitious awe he listened to the instrument for a few +moments, while it gave out the solemn tones of "Old Hundred," then it +suddenly jumped into a hilarious rendering of "Yankee Doodle." This was +too much for our nervous friend, and hastily putting on his overcoat, he +left the office for the night. + +On another occasion, when I was giving a lecture in one of the cities +outside of Chicago, where exhibitions of music transmitted from Chicago +were given, one of the operators along the line was very much astonished +by his switchboard suddenly becoming musical. Orders had been given for +the instruments in all the local offices to be cut out of the particular +line that I was using. Hence the instrument in this particular office +was not in the circuit through which the tunes were being transmitted. +The wire, however, ran through his switchboard, and owing probably to a +loose connection, or an induced effect, there was a spark that leaped +across a short space at each electrical pulsation that passed through +the line, thus reproducing the notes of the various tunes played. + +You will remember in one of the chapters on sound (Volume II.), it is +stated that a musical tone is made up of a succession of sounds +repeated at equal intervals, and that the pitch of the tone is +determined by the number of sound-impulses per second. Applying this law +to the sparks, you will be able to see how the switchboard played tunes +for the operator. + +In the foregoing experiments in transmitting musical tones +telegraphically, I used a great many different varieties of receivers. +Some of them were designed with metal diaphragms mounted over single +electromagnets, not unlike the receiver of an ordinary telephone. These +instruments would both transmit and receive articulate speech when +placed in circuit with the right amount of battery to furnish the +necessary magnetism. However, they were not used in that way at the time +they were first made--in 1874. These I called common receivers, as they +were designed to reproduce all tones equally well. I designed and +constructed another form of receiver, based somewhat upon the theory of +the harmonic telegraph. + +This consisted of an electromagnet of considerable size, mounted upon a +wooden rod about ten feet long. Mounted upon this rod were also +resonating boxes or tubes made of wood of the right size to have their +air-cavities correspond with the various pitches of the +transmitting-reeds, so that each tone would be re-enforced by some one +of these air-cavities, thus giving a louder and more resonant effect to +the musical notes. + +Here were two types of receiver, one that would receive one sound as +well as another, but none of them so loud, while the other was +constructed on the principle of selection and re-enforcement, so that a +particular note would be sounded by the box having a cavity +corresponding to the pitch of the tone, and was much louder and of much +better quality than I could get from the diaphragm receiver. One of +these receivers pointed to the harmonic telegraph and the other to the +speaking telephone. I knew that I had a receiver that would reproduce +articulate speech or anything else that could be transmitted. + +My first conceptions of an articulate speech-transmitter were somewhat +complicated. I conceived of a funnel made of thin metal having a great +number of little riders, insulated from the funnel at one end and +resting lightly in contact with the funnel at the other end. These +riders were to be made of all sizes and weights so as to be responsive +to all rates of vibration. In the light of the present day we know that +such an arrangement would have transmitted articulate speech, but +perhaps not so well as a single point would do when properly adjusted. +My mind clung to this idea till in the fall of 1875, when an observation +I made upon the street changed the whole course of my thinking and +solved the problem. The incident I refer to took place in Milwaukee, +where I was then experimenting. One day while out on an errand I noticed +two boys with fruit-cans in their hands having a thread attached to the +center of the bottom of each can and stretched across the street, +perhaps 100 feet apart. They were talking to each other, the one holding +his mouth to his can and the other his ear. At that time I had not heard +of this "lovers' telegraph," although it was old. It is said to have +been used in China 2000 years ago. + +The two boys seemed to be conversing in a low tone with each other and +my interest was immediately aroused. I took the can out of one of the +boy's hands (rather rudely as I remember it now), and putting my ear to +the mouth of it I could hear the voice of the boy across the street. I +conversed with him a moment, then noticed how the cord was connected at +the bottom of the two cans, when, suddenly, the problem of electrical +speech-transmission was solved in my mind. I did not have an opportunity +immediately to construct an instrument, as I had a partner who was +furnishing money for the development of the harmonic telegraph and would +not listen to any collateral experiments. I remember sitting down by +this partner one day and telling him what I could do in the way of +transmitting speech through a wire. I told him I thought it would be +very valuable if worked out. He gave me a look that I shall never +forget, but he did not say a word. The look conveyed more meaning than +all the words he could have said, and I did not dare broach the subject +again. + +However, as soon as I found opportunity, without saying a word to +anybody except my patent lawyer, I filed a description, accompanied by +drawings, of a speaking telephone which stands in history to-day as the +first complete description on record of the operation of the speaking +telephone. It described an apparatus which, when constructed, worked as +described, and it is a matter of history that the first articulate +speech electrically transmitted in this country was by a transmitter +constructed on the principle described, and almost identically after the +drawings in my caveat. While the transmitter described in this caveat +was not the best form, it would transmit speech, and it contained the +foundation principle of all the telephone transmitters in use to-day. + +There are two methods of transmitting speech. One is known as the +magneto method and the other that of varying the resistance of the +circuit. My first transmitter was devised on the latter principle. + +I append to this extracts from my specification filed Feb. 14, 1876: + + _To All Whom It May Concern:_--Be it known that I, Elisha Gray + of Chicago, in the County of Cook and State of Illinois, have + invented a new art of transmitting vocal sounds + telegraphically, of which the following is a specification: It + is the object of my invention to transmit the tones of the + human voice through a telegraphic circuit, and reproduce them + at the receiving-end of the line, so that actual conversations + can be carried on by persons at long distances apart. I have + invented and patented methods of transmitting musical + impressions or sounds telegraphically, and my present invention + is based upon a modification of the principle of said + invention, which is set forth and described in letters patent + of the United States, granted to me July 27, 1875, respectively + numbered 166,095 and 166,096, and also in an application for + letters patent of the United States, filed by me, Feb. 23, + 1875. * * * My present belief is that the most effective method + of providing an apparatus capable of responding to the various + tones of the human voice is a tympanum, drum, or diaphragm, + stretched across one end of the chamber, carrying an apparatus + for producing fluctuations in the potential of the electric + circuit and consequently varying in its power. * * * The + vibrations thus imparted are transmitted through an electric + circuit to the receiving-station, in which circuit is included + an electromagnet of ordinary construction, acting upon a + diaphragm to which is attached a piece of soft iron, and which + diaphragm is stretched across a receiving vocalizing chamber + _C_, somewhat similar to the corresponding vocalizing chamber + _A_. + + The diaphragm at the receiving-end of the line is thus thrown + into vibrations corresponding with those at the + transmitting-end, and audible sounds or words are produced. + + The obvious practical application of my improvement will be to + enable persons at a distance to converse with each other + through a telegraphic circuit, just as they now do in each + other's presence, or through a speaking-tube. + + I claim as my invention the art of transmitting vocal sounds or + conversations telegraphically through an electric circuit. + +This specification was accompanied by cuts of the transmitter and +receiver connected by a line-wire and showing one person talking to the +transmitter and another listening at the receiver. These cuts may be +seen in various books on the subject of telephony. + + + + +CHAPTER XVI. + +HOW THE TELEPHONE TALKS. + + +Everybody knows what the telephone is because it is in almost every +man's house. But while everybody knows what it is, there are very few +(comparatively speaking) that know how it works. If you remember what +has been said about sound and electromagnetism it will not be hard to +understand. + +When any one utters a spoken word the air is thrown into shivers or +vibrations of a peculiar form, and every different sound has a different +form. Therefore, every articulate word differs from every other word, +not only as a shape in the air, but as a sensation in the brain, where +the air-vibrations have been conducted through the organ of hearing; +otherwise we could not distinguish between one word and another. Every +different word produces a different sensation because there is a +physical difference, as a shape or motion, in the air where it is +uttered. If one word contains 1000 simultaneous air-motions and another +1500 you can see that there is a physical or mechanical difference in +the air. + +The construction of the simplest form of telephone is as follows: Take a +piece of iron rod one-half or three-quarters of an inch long and +one-quarter inch thick, and after putting a spool-head on each end to +hold the wire in place wind it full of fine insulated copper wire; +fasten the end of this spool to the end of a straight-bar permanent +magnet. Then put the whole into a suitable frame, and mount a thin +circular diaphragm (membrane or plate) of iron or steel, held by its +edges, so that the free end of the spool will come near to but not touch +the center of the diaphragm. This diaphragm must be held rigidly at the +edges. + +Now if the two ends of the insulated copper wires are brought out to +suitable binding-screws the instrument is done. + +The permanent steel magnet serves a double purpose. When the telephone +was first used commercially, the instrument now used as a receiver was +also used as a transmitter. As a transmitter it is a dynamo-electric +machine. Every time the iron diaphragm is moved in the magnetic field of +the pole of the permanent magnet, which in this case is the free end of +the spool (the iron of the spool being magnetic by contact with the +permanent magnet), there is a current set up in the wire wound on the +spool; a short impulse, lasting only as long as the movement lasts. The +intensity of the impulse will depend upon the amplitude and quickness +of the movement of the diaphragm. If there is a long movement there will +be a strong current and vice versa. If a sound is uttered, and even if +the multitude of sounds that are required to form a word, be spoken to +the diaphragm, the latter partakes in kind of the air-motions that +strike it. It swings or vibrates in the air, and if it is a perfect +diaphragm it moves exactly as the air does, both as to amplitude and +complexity of movement. You will remember that in the chapter on +sound-quality (Vol. II) it was said that there were hundreds and +sometimes thousands of superposed motions in the tones of some voices +that gave them the element we call quality. + +All these complex motions are communicated by the air to the diaphragm, +and the diaphragm sets up electric currents in the wire wound on the +spool, corresponding exactly in number and form, so that the current is +molded exactly as the air-waves are. Now, if we connect another +telephone in the circuit, and talk to one of them, the diaphragm of the +other will be vibrated by the electric current sent, and caused to move +in sympathy with it and make exactly the same motions relatively, both +as to number and amplitude. + +It will be plain that if the receiving diaphragm is making the same +motions as the transmitting diaphragm, it will put the air in the same +kind of motion that the air is in at the transmitting end, and will +produce the same sensation when sensed by the brain through the ear. If +the air-motion is that of any spoken word it will be the same at both +ends of the line, except that it will not be so intense at the +receiving-end; it is the same relatively. And this is how the telephone +talks. + +I have said that the permanent magnet had two functions. In the case of +the transmitter it is the medium through which mechanical is converted +into electrical energy. It corresponds to the field-magnet of the +dynamo, while the diaphragm corresponds to the revolving armature, and +the voice is the steam-engine that drives it. In the second place, it +puts a tension on the diaphragm and also puts the molecules of the iron +core of the magnet in a state of tension or magnetic strain, and in that +condition both the molecules and the diaphragm are much more sensitive +to the electric impulses sent over the wire from the transmitter. This +fact was experimented upon by the writer as far back as 1879 and +published in the Journal of the American Electrical Society. At the +present day this form of telephone is used only as a receiver. + +Transmitters have been made in a variety of forms, but there are only +two generic methods of transmission. One is the magneto method--the one +we have described--and the other is effected by varying the resistance +of a battery current. The former will work without a battery, as the +voice acting on the wire around the magnet through the diaphragm creates +the current; in the latter the current is created by the battery but +molded by the voice. In the latter method the current passes through +carbon contacts that are moved by the diaphragm. Carbon is the best +substance, because it will bear a wider separation of contact without +actually breaking the current. When carbon points are separated that +have an electric current passing through them, there is an arc formed on +the same principle as the electric arc-light. + +Great improvements in details have been made in the telephone since its +first use, but no new principles have been discovered as applied to +transmission. + +We have spoken in another place regarding the various claimants to the +invention of the telephone, but here is one that has been overlooked. A +young man from the country was in a telegraph-office at one time and was +left alone while the operator went to dinner. Suddenly the sounder +started up and rattled away at such a rate that the countryman thought +something should be done. He leaned down close to the instrument and +shouted as loudly as possible these words: "The operator has gone to +dinner." From what we know now of the operation of the telephone I have +no doubt but that he transmitted his voice to some extent over the wire. +This young man's claims have never been put forward before, and we are +doing him tardy justice. But his claim is quite as good as many others +set forth by people who think they invent, whenever it occurs to them +that something new might possibly be done, if only somebody would do it. +And when that somebody does do it they lay claim to it. + +In the early days of the telephone it was not supposed that a vocal +message could be transmitted to a very great distance. However, as time +went on and experiments were multiplied the distance to which one could +converse with another through a wire kept on increasing. + +In these days, as every one knows, it is a daily occurrence that +business men converse with each other, telephonically, for a distance of +1000 miles or more; in fact, it is possible to transmit the voice +through a single circuit about as great a distance as it is possible to +practically telegraph. This leads us to speak of another telegraphic +apparatus which we have not heretofore mentioned, and that is the +telegraphic repeater. It is a common notion that messages are sent +through a single circuit across the continent, but this is not the +case, although the circuits are very much longer than they were some +years ago. The repeater is an instrument that repeats a message +automatically from one circuit to another. For instance, if Chicago is +sending a message to New York through two circuits, the division being +in Buffalo, the repeater will be located at Buffalo and under the +control of both the operator at Chicago and the operator in New York. +When Chicago is sending, one part of the repeater works in unison with +the Chicago key and is the key to the New York circuit, which begins at +Buffalo. When New York is sending the other part of the repeater +operates, which becomes a key which repeats the message to the Chicago +line. In this way the practical result is the same as though the circuit +were complete from New York to Chicago. At the present day some of the +copper wires and perhaps some of the larger iron wires are used direct +from Chicago to New York without repetition, but all messages between +New York and San Francisco are automatically repeated at least twice and +under certain conditions of weather oftener. I can remember that in wet +weather in the old days, with such wires as they had then (being No. 9 +iron with bad joints, which gave the circuit a high resistance) that +these repeaters would be inserted at Toledo, Cleveland, Buffalo and +Albany in order to work from Chicago to New York. Under such conditions +the transmission would necessarily be slow, because an armature time +will be lost at each repeater. Regarding each repeater as a key, when +Chicago depresses his key the armature of the next repeater must act, +and then the next successively, and all of this takes time, although +only a small fraction of a second. + +The repeater was a very delicate instrument and had to be handled by a +skilled operator. Every wire must be in its place or the instrument +would fail to operate. I remember on one occasion in Cleveland that +along in the middle of the night the repeater failed to work. The +operator knew nothing of the principle of its operation, so that when it +failed he had to appeal to some of his superiors. + +At this time there was no one in the office who knew how to adjust it, +so they had to send up to the house of the superintendent and arouse him +from his sleep and bring him down to the office. He looked under the +table and found that one of the wires had loosened from its binding-post +and was hanging down. He said immediately, "Here's the trouble; I should +think you could have seen it yourself." The operator replied, "I did see +that, but I didn't think one wire would make any difference." He learned +the lesson that all electricians have had to learn--that even one wire +makes all the difference in the world. But this operator was no worse +in that respect than some of his superiors. One of the heads of the +Cleveland office at one time in the early days wanted to give some +directions to the office at Buffalo. He told the operator at the key to +tell Buffalo so and so, when the operator replied: "I can't do it; +Buffalo has his key open." The official immediately said with severity: +"Tell him to close it." He forgot that it would be as difficult for him +to tell him to close it, as it would have been to have sent the original +message. + +But let us go back to the telephone. While it is possible to send a +message from New York to San Francisco by telegraph, it is not possible +to telephone that distance, because as yet no one has been able to +devise a repeater that will transfer spoken words from one line to +another satisfactorily. But unless the printer and publisher bestir +themselves some one may accomplish the feat before this little book +reaches the reader. If this proves to be true, let the writer be the +first to congratulate the successful inventor. + + + + +CHAPTER XVII. + +SUBMARINE CABLES. + + +The first attempts at transmitting messages through wires laid in water +were made about 1839. These early experiments were not very successful, +because the art of wire-insulation had not attained any degree of +perfection at that time. It was not until gutta-percha began to be used +as an insulator for submarine lines that any substantial progress was +made. + +The first line, so history states, that was successfully laid and +operated was across the Hudson River in 1848. This line was constructed +for the use of the Magnetic Telegraph Company. + +In the following year experiments with gutta-percha insulation were +successfully made, and about 1850 a cable was laid across the English +Channel between Dover and Calais (twenty-seven miles), consisting of a +single strand of wire having a covering of gutta-percha. The insulation +was destroyed in a day or two, which demonstrated the fact that all +submarine cables must be protected by some kind of armor. In 1851 +another cable was laid between these two points, containing four +conductors insulated with gutta-percha, and over all was an armor of +iron wire. Twenty-one years later this cable was still working, and for +all we know is working now. After this successful demonstration other +cables were laid for longer distances. + +These short-line cables served to demonstrate the relative value of +different material for insulating purposes under water, and it has been +found that gutta-percha possesses qualities superior to almost every +other material as an insulator for submarine cables, although there are +many better materials for air-line insulation. Gutta-percha when exposed +to air becomes hardened and will crack, but under water it seems to be +practically indestructible. + +Ocean telegraphy really dates from the laying of the first successful +Atlantic cable. There were many problems that had to be solved, which +could be done only by the very expensive experiment of laying a cable +across the Atlantic Ocean. In the first place a survey had to be made of +the bottom of the ocean between the shores of America and Great Britain. +The most available route was discovered by Lieutenant Maury of the +United States Navy, who made a series of deep-sea soundings, and +discovered that, from Newfoundland to the west coast of Ireland the +bottom of the ocean was comparatively even, but gradually deepening +toward the coast of Ireland until it reached a depth of 2000 fathoms. It +was not so deep but that the cable could be laid on the bottom, nor so +shallow as to be in danger of the waves, icebergs or large sea-animals. + +The water below a certain depth is always still and not affected by +winds or ocean currents. At many other points in crossing the ocean, +high mountains and deep valleys are encountered, possessing all the +topographical features of dry land--as the ocean bed is only a great +submerged continent. + +The beginning of the laying of the first Atlantic cable was on Aug. 7, +1857. On the morning of Aug. 7, 1858, a year later, after a series of +mishaps and adverse circumstances that would have discouraged most men, +the country was electrified by a dispatch from Cyrus W. Field of New +York (to whom the final success of the Atlantic cable is mainly due), +that the cable had been successfully laid and worked. But this cable +worked only from the 10th of August to the 1st of September, having sent +in that time 271 messages. The insulation became impaired at some point, +when an attempt to force the current through by means of a large battery +only increased the difficulty. + +The failure of this first cable served to teach manufacturers and +engineers how to construct cables with reference to the conditions under +which they are to be used. It was found that in the deep sea a much +smaller and less expensive cable could be used than would answer at the +shore ends, where the water is shallow. The shore ends of an ocean cable +are made very large, as compared to the deep-sea portions, so as to +resist the effect of the waves and other interfering obstacles. It was +further learned that the most successful mode of transmitting signals +through the cable was with a small battery of low voltage, and by the +use of very delicate instruments for receiving the messages. It is not +possible to employ such instruments on cables as are used on land-lines, +while it would not be a difficult feat to transmit even twice the +distance over land-lines strung on poles, using the ordinary Morse +telegraph. + +The water of the ocean is a conductor, as well as the heavy armor that +surrounds the insulation of the cable. When a current is transmitted +through the conducting wires, in the center of the cable, they set up a +countercharge in the armor and the water above it, somewhat as an +electrified cloud will induce a charge in the earth under it, of an +opposite nature. This countercharge, being so close to the conducting +wire, has a retarding effect upon the current transmitted through it. +An ordinary land-line that is strung on poles that are high up from the +ground has this effect reduced to a minimum, but the greater the number +of wires clustered together on the same poles the more difficult it +becomes to send rapid signals through any one of them. + +The instrument used for receiving cable messages was devised by Sir +William Thompson, now Lord Kelvin. One form consists of a very short and +delicate galvanometer-needle carrying a tiny mirror. This mirror is so +related to a beam of light thrown upon it that it reflects it upon a +graduated screen at some distance away, so that its motions are +magnified many hundred times as it appears upon the screen. An operator +sits in a dark room with his eye on the screen and his hand upon the key +of an ordinary Morse instrument. He reads the signal at sight, and with +his key transmits it to a sounder, which may be in another room, where +it is read and copied by another operator. Another form of +receiving-instrument carries, instead of the mirror, a delicate +capillary glass tube that feeds ink from a reservoir, and by this means +the movements of the needle are recorded on a moving strip of paper. The +symbols (representing letters) are formed by combinations of zigzag +lines. This instrument is the syphon-recorder. + + + + +CHAPTER XVIII. + +SHORT-LINE TELEGRAPHS. + + +Early in the history of the telegraph short lines began to be used for +private purposes, and as the Morse code was familiar only to those who +had studied it and were expert operators on commercial lines, some +system had to be devised that any one with an ordinary English education +could use; as the expense of employing two Morse operators would be too +great for all ordinary business enterprises. These short lines are +called private lines, and the instruments used upon them were called +private-line telegraph-instruments. Of course they are now nearly all +superseded by the telephone, but they are a part of history. + +One of the earliest forms of short-line instruments was called the +dial-telegraph. One of the first inventors, if not the first, of this +form of instrument was Professor Wheatstone of England, who perfected a +dial-telegraph-instrument about the year 1839. The receiving-end of this +instrument consisted of a lettered dial-face, under which was clockwork +mechanism and an escape-wheel controlled by an electromagnet. Each time +the circuit was opened or closed the wheel would move forward one step, +and each step represented one of the letters of the alphabet, so that +the wheel, like the type-wheel of a printing telegraph, had fourteen +teeth, each tooth representing two steps. As the reciprocating movement +of the escapement had a pallet or check-piece on each side of the wheel, +its movement was arrested twenty-eight times in each revolution. These +twenty-eight steps correspond to the twenty-six letters of the alphabet, +a dot and a space. On the shaft of the escape-wheel is fastened a hand +or pointer, which revolves over a dial-face having the twenty-six +letters of the alphabet, also a dot and space. The pointer was so +adjusted that when the escape-wheel was arrested by one of the pallets +it would stop over a letter, showing thus, letter by letter, the message +which the sender was spelling out. + +The transmitter consisted of a crank with a knob and a pointer on it, +which was mounted over a dial that was lettered in the same way as the +face of the receiving-instrument. A revolution of this crank would break +and close the circuit twenty-eight times; that is to say, there were +fourteen breaks and fourteen closes of the circuit. If now the +transmitting-pointer and the receiving-pointer are unified so that they +both start from the same point on the dial, and the transmitting-crank +is rotated from left to right, the receiving-pointer will follow it up +to the limit of its speed. In transmitting a message the sender would +turn his crank, or pointer, to the first letter of the word he wished to +transmit, making a short pause, and then move on to the next letter, and +so on to the end of the message, making a short pause on each letter. +The end of a word was indicated by turning the pointer to the space-mark +on the dial. The receiving-operator would read by the pauses of the +needle on the various letters. This was a system of reading by sight. + +There have been many forms of this dial-telegraph worked out by +different inventors at different times, and quite a number of them were +used in the old days. It was a slow process of telegraphing, but it was +suited to the age in which it flourished. One of the difficulties of a +dial-telegraph consisted in the readiness with which the transmitter and +receiver would get out of unison with each other; and when this happened +of course a message is unintelligible, and you have to stop and unify +again. + +About 1869 the writer invented a dial-telegraph to obviate this +difficulty. In this system a transmitter and receiver were combined in +one instrument, and instead of a crank there were buttons arranged +around the dial in a circle, one opposite each letter. When not in +operation the pointers of both instruments at both stations stood at +zero. In the act of transmitting the operator would depress the button +opposite the letter he wished to indicate, when immediately the pointers +of both instruments would start up and move automatically, step by step, +until the pointer came in contact with the stem of the depressed button, +when it would be arrested, and at the same time cut out the automatic +transmitting-mechanism and cause both needles to remain stationary +during the time the button was depressed. Upon releasing the button the +pointers both fall back to zero at one leap. + +The first private line equipped by this instrument was for Rockefeller, +Andrews & Flagler, which was the firm name of the parties who afterward +organized the Standard Oil Company. This line was built between their +office on the public square in Cleveland and their works over on the +Cuyahoga flats. + +It seemed, however, to be the fate of the writer to make new inventions +that would supersede the old ones before they were fairly brought into +use. Very soon after the dial-telegraph began to be used, printing +telegraph instruments for private-line purposes superseded them. About +1867 a printing instrument was devised for stock reporting, which in one +of its forms is still in use. Soon after the invention of this form of +printer a company was organized to operate not only these +stock-reporting lines, but short lines for all sorts of private +purposes. Following the invention of the stock-reporting instrument +there were several adaptations made of the printing telegraph for +private-line purposes. Among others the writer invented one known as +"Gray's automatic printer," a cut and a description of which may be +found on page 684 in "Electricity and Electric Telegraph," by George B. +Prescott, published in 1877. This instrument was adopted by the Gold and +Stock Telegraph Company as their standard private-line printer. It was +first introduced in the year 1871, and at the time the telephone began +to be used there were large numbers of these printers in operation in +all of the leading cities and towns in the United States. While this has +been superseded to a large extent by the telephone, there are still a +few isolated cases where it is used. + +Short lines have multiplied for all sorts of purposes, until to-day the +money invested in them largely exceeds the amount invested in the +regular commercial telegraphic enterprises. + +The invention of the telephone created such a demand for short-line +service that some scheme had to be devised not only to make room for the +necessary wires, but to so cheapen the instruments as to bring them +within reach of the ability of the ordinary man of business. + +This problem has been solved (but not without many difficulties) by the +inauguration of what is known as the "central station." By this system +one party simply controls a single wire from his office or residence to +the central station; here he can have his line connected with any other +wire running into this same station, by calling the central operator and +asking for the required number. It is useless to tell the public that +very often this number is "busy," and here is the great drawback to the +central-station system. This is especially true in large cities, where +there are a great number of lines. The switchboards in large cities are +necessarily very complicated affairs, and it requires a number of +operators to answer the many calls that are constantly coming in. Each +central-station operator presides over a certain section of the board, +and as this section has to be related in a certain way to every other +section, it is easy to see wherein arises the complication. + +In large cities the central stations themselves have to be divided and +located in different districts, being connected by a system of trunk +lines. + + + + +CHAPTER XIX. + +THE TELAUTOGRAPH. + + +So far we have described several methods of electrical communication at +a distance, including the reading of letters and symbols at sight (as by +the dial-telegraph and the Morse code embossed on a strip of paper); +printed messages and messages received by means of arbitrary sounds, and +culminating in the most wonderful of all, the electrical transmission of +articulate speech. + +None of these systems, however, are able to transmit a message that +completely identifies the sender without confirmation in the form of an +autograph letter by mail. + +In 1893 there was exhibited in the electrical building at the World's +Fair an instrument invented by the writer called the Telautograph. As +the word implies, it is a system by which a man's own handwriting may be +transmitted to a distance through a wire and reproduced in facsimile at +the receiving-end. This instrument has been so often described in the +public prints that we will not attempt to do it here, for the reason +that it would be impossible without elaborate drawings and +specifications. It is unnecessary to state that it differs in a +fundamental way from other facsimile systems of telegraphy. Suffice it +to say that as one writes his message in one city another pen in another +city follows the transmitting-pen with perfect synchronism; it is as +though a man were writing with a pen with two points widely separated, +both moving at the same time and both making exactly the same motions. +By this system a man may transact business with the same accuracy as by +the United States mail, and with the same celerity as by the electric +telegraph. + +A broker may buy or sell with his own signature attached to the order, +and do it as quickly as he could by any other method of telegraphing, +and with absolute accuracy, secrecy and perfect identification. + +In 1893, when this apparatus was first publicly exhibited, it operated +by means of four wires between stations, and while the work it did was +faultless, the use of four wires made it too expensive and too +cumbersome for commercial purposes; so during all the years since then +the endeavor has been to reduce the number of wires to two, when it +would stand on an equality with the telephone in this respect. It is +only lately that this improvement has been satisfactorily accomplished, +and, for reasons above stated, no serious attempt has been made to +introduce it as yet; but it has been used for a long enough time to +demonstrate its practicability and commercial value. Companies have been +organized both in Europe and America for the purpose of putting the +telautograph into commercial use. + +By means of a switch located in each subscriber's office the wires may +be switched from a telephone to a telautograph, or vice versa, in a +moment of time. By this arrangement a man may do all the preliminary +work of a business transaction through the telephone, and when he is +ready to put it into black and white switch in the telautograph and +write it down. For ordinary exchange work this is undoubtedly the true +way to use the telautograph, because one system of wires and one +central-station system will answer for both modes of communication, and +in this way an enormous saving can be made to the public. There is no +question in the mind of any one who is familiar with the operation of +both the telephone and telautograph but that some day they will both be +used, either in the same or separate systems, as they each have +distinctly separate fields of usefulness,--the telephone for desultory +conversation, the telautograph for accurate business transactions. The +question may arise in the minds of experts how the two systems can be +worked in the same set of cables, and this leads us to discuss the +phenomena of induction. + +Every one who has listened at a telephone has heard a jumble of noises +more or less pronounced, which is the effect of the working of other +wires in proximity to those of the telephone. If, when a Morse telegraph +instrument is in operation on one of a number of wires strung on the +same poles, we should insert a telephone in any one of the wires that +were strung on the same poles or on another set of poles even across the +street, we could hear the working of this Morse wire in the telephone, +more or less pronounced, according to the distance the wire is from the +Morse circuit. This phenomenon is the result of induction, caused by +magnetic ether-waves that are set up whenever a circuit is broken and +closed, as explained in Chapter VI. + +The telephone is perhaps the most sensitive of all instruments, and will +detect electrical disturbances that are too feeble to be felt on almost +any other instrument, hence the telephone is preyed upon by every other +system of electrical transmission, and for this reason has to adopt +means of self-protection. It has been found that the surest way to +prevent interference in the telephone from neighboring wires is to use +what is called a metallic circuit--that is to say, instead of running a +single wire from point to point and grounding at each end, as in +ordinary telegraph systems, the telephone circuit is completed by using +a second wire instead of the earth. + +As a complete defense against the effects of induced currents the wires +should be exactly alike as to cross-section (or size) and resistance. +They should be insulated and laid together with a slight twist. This +latter is to cause the two wires so twisted to average always the same +distance from any contiguous wire. + +One factor in determining the intensity of an induced current is the +distance the wire in which it flows is from the source of induction. A +telephone put in circuit at the end of the two wires that are thus laid +together will be practically free from the effects of induced currents +that are set up by the working of contiguous wires--for this reason: +Whenever a current is induced in one of the slack-twisted wires it is +induced in both alike; the two impulses being of the same polarity meet +in the telephone, where they kill each other. In order to have a perfect +result we must have perfect conditions, which are never attained +absolutely, but nearly enough for all practical purposes. + +In the early days of telephony great difficulty was experienced in using +a single wire grounded at each end in the ordinary way, if it ran near +other wires that were in active use. As time passed on and the electric +light and electric railroad came into operation these difficulties were +immensely increased, till now in large cities the telephone companies +are fast being driven to the double-wire system, which will soon become +universal for telephonic purposes the world over, except perhaps in a +few country places where there is freedom from other systems of +electrical transmission. To successfully work the telephone and +telautograph through the same cables, these protective devices against +induction must be very carefully provided and maintained. + + + + +CHAPTER XX. + +SOME CURIOSITIES. + + +Until within recent years it was never supposed that a sunbeam would +ever laugh except in poetry. But the modern scientist has taken it out +of the realm of poetry and put it into the prosy play of every-day life. +The Radiophone, invented by A. G. Bell, is an instrument by which +articulate or other sounds are transmitted through the medium of a ray +of light. It has as yet no practical application and has never gone +beyond the experimental stage, but as a bit of scientific information it +is very interesting. + +If we introduce into an electric circuit a piece of selenium, prepared +in a certain way, its resistance as an electric conductor undergoes a +radical change when a beam of sunlight is thrown upon it. For instance, +a selenium cell, so called, that in the dark would measure 300 ohms +resistance, would have only about 150 ohms when exposed to sunlight. +This amount of variation in a short circuit of low resistance would +produce a considerable change in the strength of a current passing +through it from a battery of a given voltage. + +If now we connect a selenium cell to one pole of a battery, and thence +through a telephone and back to the other pole, we have completed an +electric circuit, of which the selenium cell is a part, and any +variation of resistance in this cell, if made suddenly, will be heard in +the telephone. Let the diaphragm of a telephone transmitter have a very +light, thin mirror on one side of it, and a beam of sunlight be thrown +upon it and reflected from that on to the selenium cell, which may be +some distance away. Then, if the diaphragm is thrown into vibration by +an articulate word or other sound, the light-ray is also thrown into +vibration, which causes a vibratory change of resistance in the selenium +cell in sympathy with the light-vibrations; and this in turn throws the +electric current into a sympathetic vibratory state which is heard in +the telephone. So that if a person laughs or talks or sings to the +diaphragm, the sunbeam laughs, talks and sings and tells its story to +the electric current, which impresses itself upon the telephone as +audible sounds--articulate or otherwise. Instead of the telephone, +battery and selenium cell, a block of vulcanite or certain other +substances may be used as a receiver; as a light-ray thrown into +vibration has the power to produce sound or sympathetic vibration in +certain substances. + +Another curious application of the selenium cell has been attempted, but +has scarcely gone beyond the domain of theory. This apparatus, if +perfected, might be called a Telephote. It is an apparatus by which an +illuminated picture at one end of a line of many wires is reproduced +upon a screen at the other end. The light is not actually transmitted, +but only its effects. Suppose a picture is laid off into small squares +and there is a selenium cell corresponding to each square and for each +selenium cell there is a wire that runs to a distant station in which +circuit there is a battery. At the distant station there are little +shutters, one for each wire, that are controlled by the electric current +and so adjusted that when the cell at the transmitting-end is in the +dark the shutter will be closed. Now if a strong light be thrown upon +the picture at the transmitting-end, and each square of the picture +reflects the light upon its corresponding selenium cell, the high lights +of the picture will reflect stronger light than the shadows, and +therefore the wires corresponding to the high-light squares will have a +stronger current of electricity flowing through them, because the +resistance of the circuit is less than the ones connected with the +darker shadows. So that the degree of current-strength in the various +wires will correspond to the intensity of light reflected by the +different sections of the picture. The shutters are so adjusted that the +amount of opening depends upon the strength of current. The shutters +corresponding to the high lights of the picture will open the widest and +throw the strongest light upon the screen, from a source of light that +is placed behind the shutters. The shutters that open the least will be +those that are operated upon by the shadows of the picture. Inasmuch as +a picture thrown on a screen from a source of light is wholly made up of +lights and shadows, the theory is that this apparatus perfectly +constructed would transmit any picture to a distance, through +telegraph-wires. It must not be understood that the rays of light are +transmitted through the wires as sound-vibrations are. Light, per se, +can be transmitted only through the luminiferous ether, as we have seen +in the chapter on light in Volume II. + +While we are talking about these curious methods of telegraphic +transmission, I wish to refer to an apparatus constructed by the writer +in 1874-5, for the purpose of receiving musical tones or compositions +transmitted from a distance through a wire by electricity. (A cut of +this apparatus is shown on page 875 of "Electricity and Electric +Telegraph," by Prescott, issued in 1877.) It consists of a disk of +metal rotated by a crank mounted on a suitable stand. The electric +circuit passes through the disk to the hand of the operator in contact +with it, thence running through the line-wire to the distant station. +Now, if a tune is played at that station, upon an electrical key-board, +as described in a previous chapter, and the disk rotated with the +fingers in contact with it, the tune or other sounds will be reproduced +at the ends of the fingers. After the telephone was invented and put +into use I used this revolving disk as a receiver for speech as well as +music, and by this means persons may carry on an oral conversation +through the ends of their fingers. This apparatus has been confounded in +the minds of some people with Edison's electromotograph. The phenomena +of the electromotograph were produced by chemical effects, while that of +the apparatus just described is electrostatic in its action. The +electrostatic disk was made in the winter of 1873-4, while Edison's +electrochemical discovery was made some time later. + + + + +CHAPTER XXI. + +WIRELESS TELEGRAPHY. + + +Broadly speaking, "Wireless Telegraphy" is any method of transmitting +intelligible signals to a distance without wires; and this includes the +old Semaphore systems of visual signals, such as flags and long arms of +wood by day, and lights by night; also the Heliograph (an apparatus for +flashing sunlight), and Sound Signals, made either through the air or +water. Electrical conduction, either through rarefied air or the earth, +also comes under this heading. + +The name "Wireless Telegraphy," however, is specifically applied to a +system of signaling by means of ether-waves induced by electrical +discharges of very high voltage. Ether-waves of a greater or less degree +are always set up whenever there are sudden electrical disturbances, +however slight. Ether-waves, electrically induced, are probably as old +as the universe. When "there were thunders and lightnings" from the +cloud that hovered over Mount Sinai in the time of Moses, ether-waves of +great power were sent out through the camp of Israel. But the people of +those days had no "coherer" or telephone or any other means of +converting these waves into visual or audible signals. Thousands of +years had to elapse before the intellect of man could grasp the meaning +of these natural phenomena sufficiently to harness them and make them +subservient to his will. + +Many people have been powerfully "shocked"--some even killed--by the +impact of ether-waves set up by powerful discharges of lightning between +the clouds and the earth--when they were not in the direct path of the +lightning-stroke. + +The history of Electro-Wireless Telegraphy, like that of all inventions, +is one of successive stages, and all the work was not done by one man. +The one who gets the most credit is usually the one who puts on the +finishing touches and brings it out before the public. He may have done +much toward its development or he may have done but little. + +In the year 1842 Morse transmitted a battery current through the water +of a canal eighty feet wide so as to affect a galvanometer on the +opposite side from the battery. This was wireless telegraphy by +_conduction_ through water. + +In 1835 Joseph Henry produced an effect on a galvanometer by ether-waves +through a distance of twenty feet by an arrangement of batteries and +circuits like that shown in Fig. 1, Chapter VI. This was called +_induction_, and is still so called when electrical effects are produced +from one wire to another through the ether for short distances. All +induction-coils and transformers (see Chapter XXIV) are operated by +effects produced through the ether from the primary to the secondary +coil--but through very short distances. + +In 1880 Professor Trowbridge transmitted an electrical current through +the earth for one mile so as to produce signals in a telephone. In +1881-2 Professor Dolbear used for a short distance (fifty feet) +substantially the same arrangement as Marconi now uses, except that the +former used a telephone as a receiver. He used an induction-coil having +one end of the secondary wire connected with the earth, while the other +was attached to a wire running up into the air. At the receiving-end a +wire starting from the earth extended into the air, passing through a +telephone, which acted as a receiver. In 1886 he used a kite to elevate +the wire, through which electrical discharges of high voltage were made +into the air to produce ether-waves--the receiver being 2000 feet away. +Dolbear's experiments were public fourteen years ago, but at that time +there was no interest in such matters, so that his work received little +or no attention. In 1887 Dr. Hertz of Germany made some experiments in +producing and detecting ether-waves, and he did a great deal to awaken +an interest in the subject, so that others began investigations that +have led to its present use as a means of telegraphing to a distance of +many miles. + +In 1891 Professor Branly of Paris invented the coherer. In 1894 it was +improved by Lodge and by him used as a detector of ether-waves. In 1896, +ten years after Dolbear had used it with the kite at the +transmitting-end and telephone at the receiving-end, Marconi, an +Italian, substituted the coherer of Branly for the telephone of Dolbear. +This coherer is constructed and operated as follows: + +It consists of a glass tube, of comparatively small diameter, loosely +filled with metal filings of a certain grade. This body of metal-dust is +made a part of a local battery circuit in which is placed an ordinary +electric bell or telegraphic sounder. The resistance of this body of +filings is so great that current enough will not pass through it to ring +the bell or actuate the sounder until an ether-wave strikes it and the +wire attached to it, when the metal particles are made to cohere to such +an extent that the conductivity of the mass is greatly increased; so +that a current of sufficient volume will now pass through the +bell-magnet to ring it. Before the next signal comes the filings must be +made to de-cohere; and to accomplish this a little "tapper," that works +automatically between the signals, strikes the glass tube with a +succession of light blows. + +Briefly stated, the wireless system of Marconi, in its essentials, +consists of a powerful induction-coil with one end of the secondary wire +connected with the earth, while the other extends into the air a greater +or less distance according to the distance it is desired to send +signals. The greater the distance the higher the wire should extend into +the air. At the receiving-end a wire of corresponding height is erected, +also connected with the earth. In this wire--as a part of its +circuit--is placed the coherer. In a local circuit that is connected to +the upright wire in parallel with the coherer is placed a battery, a +sounder, or a bell, that is rung when the filings cohere. + +When an ether-wave is set up by a discharge of electricity into the air +it strikes the perpendicular wire of the receiver, and that portion of +the wave that strikes is converted into electricity, which is called an +induced current. It is this current, as it discharges through the +coherer to the earth, that causes the filings to unite so as to close +the local circuit and operate the sounder. To send a message it is only +necessary to make the discharges into the air, at the sending-end, +correspond to the Morse alphabet. + +While Marconi has done more than any other man to improve and popularize +wireless telegraphy, history shows that he invented none of the +essential elements so far as the system has been made public. + +What he seems to have really done was to substitute the coherer of +Branly and Lodge, with its adjuncts, for the telephone of Dolbear. There +is no doubt but that Marconi has done much to improve and enlarge the +capacity of the apparatus and to demonstrate to the world some of its +possibilities. He has been an indefatigable worker and deserves great +credit; but without the work of those who preceded him he could not have +succeeded: the honors should be divided. + +This system has been used at various times for reporting yacht-races, +and between ships. It is said also to have been used to some extent in +the South African War. There is much to be done yet, however, before it +can be made entirely reliable for defensive work in time of war. As it +is now, all an enemy would have to do to destroy its usefulness would be +to set an ether-wave-producer to work automatically anywhere within the +"sphere of influence" of the system--to speak diplomatically--when it +would render unintelligible any message that should be sent. To make the +system of the greatest value some sort of selective receiver must be +invented that will select signals sent from a transmitter that is +designed to work with it. + +There is no doubt but that wireless telegraphy will some time play an +important part in many spheres of usefulness. + +There is another mode (already referred to) for transmitting signals +electrically without wires through the earth instead of through the air, +but in this case it is not through the medium of induction, but +conduction. It has been explained in former chapters that earth-currents +are constantly flowing from one point to another where the potentials +are unequal. Sometimes these inequalities of potential are caused by +heat and sometimes by electricity, as in the case of a thunder-storm. If +a cloud is heavily charged with positive electricity, say, the earth +underneath will have an equal charge of negative electricity. Let us +illustrate it by the tides. As the moon passes over the ocean it +attracts the water toward it and tends to pile up, as it were, at the +nearest point between the earth and the moon. Suppose that (while the +water is thus piled up at a point under the moon) we could suddenly +suspend the attraction between the earth and the moon--the water would +begin immediately to flow off by the force of gravitation until it had +found a common level. Suppose in the place of the moon we have a cloud +containing a static charge of positive electricity--it attracts a +negative charge to a point on the earth nearest the cloud. If now a +discharge takes place between the earth and cloud the potential between +the two will suddenly become equalized and the static charge that was +accumulated in the earth is released and it dissipates in every +direction, seeking an equilibrium, following the analogy of the water; +the difference being that in one case the movement is very slow, while +in the other it is as "quick as lightning." + +About eighteen years ago I had a short telephone-line between my house +and that of one of my neighbors. This line was equipped with what was +known in those days as magneto-transmitters, such as we have described +in a previous chapter on the subject of telephony. When a line is +equipped in this way no batteries are needed, as the voice generates the +current, on the principle employed in the dynamo-electric machine. Often +on summer evenings, when the sky appears to be cloudless, we can see +faint flashes of lightning on the horizon, an appearance which is +commonly called "heat-lightning." As a matter of fact, I do not suppose +there is any such thing as heat-lightning, but what we see is the effect +of very distant storm-clouds. Often at such times I have held the +telephone receiver to my ear and could hear simultaneously with each +flash a slight sound in the telephone. This effect could be produced in +the earth by a simple discharge between two or more clouds, which would +distribute the electrical discharge over a greater area. And because my +line had connection with the earth it could have been disturbed +electrically by conduction instead of induction; or it may have been the +effect of ether-waves set up by the lightning discharges. There is no +doubt in my mind but that both of these effects (ether-waves and +conduction through earth) may be felt when a discharge takes place +between a cloud and the earth. + +If we could, by operating an ordinary telegraphic key, cause the +lightning to discharge from cloud to earth, and some one was listening +at a telephone in a circuit that was grounded at both ends 100 miles or +more distant from the cloud, the man who controlled the discharges by +the key could transmit the Morse code through the earth to the man who +was listening at the telephone. Thousands of people might be listening +at telephones in every direction from the transmitting-station, and they +would all get the same message. If the receiving-station is near to the +point where there is a heavy discharge from the clouds to the earth the +earth-current is very strong--flowing out in every direction. For some +years I had an underground line between my house and laboratory, and no +part of the line between the two stations was above ground. Many and +many times during the prevalence of a thunder-storm have the +telephone-bells been made to ring at both ends of the line by a +discharge from the cloud to the earth, and in some cases the discharge +was several miles away. The wires could not have been affected so +powerfully in any other way than through the earth. + +It will be seen by the foregoing statements that it is possible to +transmit messages through the earth for long distances, but the +difficulty in the way of its becoming a general system is twofold. +First, we cannot always have a thunder-cloud at hand from which to +transmit our signals, and, secondly, the signals would be received alike +at every station simultaneously. + + + + +CHAPTER XXII. + +NIAGARA FALLS POWER--INTRODUCTION. + + +As our readers know, Niagara Falls is situated upon the Niagara River, +which is the connecting-link between Lake Erie and Lake Ontario. The +surface of Lake Erie lies 330 feet above that of Lake Ontario. The high +level upon which Lake Erie is situated abruptly terminates at +Queenstown, which is near the point where the Niagara River empties into +Lake Ontario. From Lake Erie to the falls the level of the river is +gradually lowered a little less than 100 feet, and most of this (making +"the rapids") occurs in the last mile above the point where it takes a +perpendicular plunge of 165 feet into a narrow gorge extending for seven +miles, through which the river runs, gradually falling also 100 feet in +that distance. The river above the falls is broad, varying from one to +three miles in width, but below that point it is suddenly narrowed up to +a distance of from 200 to 400 yards. + +It is supposed that at one time the fall was situated at the bluff +overlooking Queenstown, near Lake Ontario, and at that time was very +much higher than it is at present. Through long ages of time the water +has gradually eaten away the rock, thus forming the gorge. It is +estimated by different geologists that the time required to wear away +the rock back to the present position of the fall has required from +15,000 to 35,000 years. Some authorities place the rate of wear at three +feet per annum and others not more than one. It is well known, however, +that this erosion is constantly going on, and if nothing is done to +check it the time will come when the gorge will extend up to Lake Erie +and drain it, practically, to the bottom. This is a matter, however, +that the people of this and those of several succeeding generations need +not worry about. + +In the early days, before the country was settled and the banks of the +river were lined with trees, and no houses, hotels or horse-cars were to +be seen; when the puffing of the locomotive was not heard echoing from +shore to shore; when no bridges spanned the river to mar its beauty, and +when nature was the only architect and beautifier, Niagara Falls must +have been one of the most attractive spots on the earth; at least it is +the place of all places where the mighty energies of nature are gathered +together in one grand exhibition of sublime power. Here for ages this +same grand exhibition had been going on, and although there was no +human eye to see it, those of us who believe that nature is not a thing +of chance, but that it was planned by an intelligence infinitely +superior to that of any man, can easily imagine that the Great Architect +and beautifier of this same nature, not only plans but enjoys the work +of His own hand. Why not? For ages the same sun, in his daily round, has +reflected that beautifully colored rainbow, here the product of sunshine +and mist. The same water, through these successive ages, has been lifted +to the clouds by the power of the sun's rays, and has been carried back +to the fountain-heads on the wings of the wind, and there has been +condensed into raindrops, that have fallen on land, lake and river, and +in turn has been carried over this same waterfall in its onward course +toward the sea, only again to be caught up into the clouds; and thus +through an eternal round it has been kept moving by that mighty engine +of nature, the sun. It is said that "the mill will never grind with the +water that has passed." This is true only in poetry. As a matter of +fact, "the water that has passed" may often return to help the mill to +grind again. + +Water-powers have been utilized in a small way for many years for the +purpose of generating electricity through the medium of the dynamo, but +nowhere in the world has the application of the force been made for this +purpose on such a grand scale as at Niagara Falls. When one stands on +the bank of the river and sees the great waterfall as it plunges over +the precipice, exerting a force of from five to ten million horse-power, +one is overwhelmed in contemplation of its possibilities as a source of +energy that may be converted into work, mechanical and chemical, through +the medium of electricity. + +The genius of man has devised a way by which some of this constantly +wasting energy may be converted into electricity and distributed to +different points to perform various kinds of work. But the amount +utilized as yet is scarcely a drop when compared with that which might +be if the whole torrent could be set to work in the same manner as a +very small portion of it now is. + + + + +CHAPTER XXIII. + +NIAGARA FALLS POWER--APPLIANCES. + + +Some years ago a company was formed for the purpose of utilizing, to +some extent, this greatest of all water-powers. A tunnel of large +capacity was run from a point a short distance below the falls on a +level a little above the river at that point. The general direction of +this tunnel is up the river; it is about a mile and one-half in length, +terminating at a point near the bank of the river a mile or more above +the falls. Above the end of this tunnel an upright pit comes to the +surface, where a power-house of large dimensions has been constructed of +solid masonry. It is long enough at present to contain ten dynamos of +mammoth size. Along the side of this power-house a deep broad canal is +cut, which communicates with the river at that point, and through which +flows the water that is to furnish the power. Of course the water level +of this canal is the same as that of the river. + +The foundations of the power-house extend to the bottom of the tunnel, +which at that point is 180 feet below the surface of the ground. To put +it in other words, the cellar or pit under the power-house is 180 feet +deep and communicates with the great tunnel, which has its outlet below +the falls. + +Each of the ten dynamos is driven by a turbine water-wheel situated near +the bottom of the pit heretofore described. The turbine-wheel is on the +lower end of a continuous shaft, which reaches from a point near the +bottom of the tunnel to a point ten or fifteen feet above the floor of +the power-house (which is about on a level with the surface of the +ground). + +This shaft is incased in a water-tight cylinder of such diameter as will +admit a sufficient amount of water, and connects with the turbine wheel +at the bottom in the ordinary way. The water is admitted into the top of +this cylinder from the canal, so that the wheel is under the pressure of +a falling column of water over 140 feet high. The water, forcing its way +out at the bottom through the turbine, revolves it and its long, +upward-reaching shaft with great power, and enables it to work the +dynamos in the power-house above, as will be described. The water +discharges through the wheel in such a manner as to lift the whole +shaft, thus taking away the tremendous end-thrust downward that would +otherwise interfere greatly with the running of the machine through +friction. After the water has done its work it flows off through the +tunnel into the river below the falls. + +To the upper end of the power-shaft is attached a great revolving +umbrella-shaped hood; to the periphery (circumference) of this hood is +attached a forged steel ring, 5 inches in thickness, about 12 feet in +diameter and from 4 to 5 feet in width. The whole of the revolving +portion--including the ring upon which are mounted the field-magnets, +the hood, and the shaft running to the bottom of the pit, where the +turbine wheel is attached--weighs about thirty-five tons. + +The dynamos belong to the alternating type, and are comparatively simple +in construction. In a previous chapter upon the dynamo it was stated +that the fundamental feature was the relation that the field-magnet and +the armature sustained to each other, and that in some cases the +field-magnet revolves while the part that is technically called the +armature remains stationary. In other cases the armature revolves and +the field-magnets are stationary. In the latter case brushes and +commutators are used, to catch and transfer the generated electricity, +while in the former these are not needed, which simplifies the +construction of the machine. + +As we have stated, the dynamos used at Niagara are constructed with +revolving field-magnets that are bolted on to the inner surface of the +steel ring that is carried by the hood, so that there are no brushes +connected with the machine except the small ones used to carry the +current to the field-magnets. + +The current for power purposes is generated in a large stationary +armature about ten feet in diameter and of the same depth as the +revolving ring. The revolutions of the ring send out currents of +alternating polarity, and each of the ten machines will furnish +electrical energy equal to 5000 horse-power, so that when the work that +is now under way is completed 50,000 horse-power can be furnished in the +form of electricity. About 35,000 horse-power is now actually delivered +to the various industrial enterprises. The dynamos are set horizontally, +since the shaft which connects them with the turbine wheel stands in a +perpendicular position. + +Not all of the energy that is developed by the water-wheel is converted +into electricity, but some of it appears as heat. In order to prevent +the heat from becoming so great as to be dangerous to the machine it +must be constructed in such a way as to admit of sufficient ventilation +for cooling purposes. The armature is so constructed that there are +air-passages running all through it, and on top of the revolving hood +are two bonnet-shaped air-tubes set in such a way as to force the air +down through the armature, which carries off the heat and warms the +power-house, on the principle of a hot-air furnace. This great +machine--which, in a way, is so simple in its construction--when in +action conveys to the mind of the beholder a sense of wonderful power. +It is only when we stand in the presence of such exhibitions as may be +seen in this power-house, devised and executed by the genius of man, and +in that greater presence, the mighty Falls of Niagara, that we get +something of a conception of the power of the silent yet potent energy +of the great king of daylight, the sun. + +There are very many interesting details that work in connection with +this great power-plant, some of which we will describe, in a general +way. + +Standing within a few feet of each one of the great dynamos is a very +beautifully constructed piece of machinery called the governor. The +governor regulates the speed of the dynamos by partially opening and +closing the water-gates that regulate the flow of water into the +turbines. The question may be asked, why is there any regulation needed, +if there is always an even head of water? There are two reasons--one +because the load on the dynamo is constantly changing, and another that +the head of water changes, although this latter fluctuation is in long +periods. If the circuit leading out from the dynamo is broken, the +rotating part of the dynamo will move with great ease and little power, +as compared with what is required when the circuit is closed, and the +current is going out and doing work. The increased amount of energy that +will be required to keep the dynamo moving at a certain rate of speed +when the load is on--in other words, when the circuit is closed--will +depend upon the amount of current that is going out from the dynamo to +perform work at other points. As the amount of current used outside for +the various purposes is constantly changing, it follows that the load on +the dynamo is constantly changing also. As the load changes, the speed +will change, unless the amount of water that is flowing into the turbine +is changed in a like proportion; hence the necessity for a governor that +will perform this work. You can easily imagine that it will require a +great amount of power to move the gate up or down with such a pressure +of water behind it. It is not possible here to explain the operation of +the governor in detail, as that could not be done without elaborate +drawings; suffice it to say that the whole thing is controlled by a +small ball governor such as we see used in ordinary steam-engines for +regulating steam-pressure. + +The rising or falling of the balls of this governor to only a very +slight extent will bring into action a power that is driven by the +turbine itself, which is able to move the water-gate in either direction +according as the balls rise or fall. For instance, if the balls rise +beyond their normal position, it shows that the dynamo is increasing in +speed, and immediately machinery is brought into action that shuts the +water off in a small degree, just enough to bring the speed back to +normal. If the balls drop to any extent, it shows that the load is too +great for the amount of water, and that the dynamo is decreasing in +speed; immediately the power is brought into action, now in the opposite +direction, and the water-gate is opened wider. These slight variations +of speed are constantly going on, and the constant opening and closing +of the gate follows with them. It is a beautiful piece of machinery, and +is beautifully adapted to the work it has to perform. It is continually +standing guard over this greater piece of machinery that is exerting an +energy of 5000 horse-power and prevents it from going wrong, both in +doing "that which it should not do and leaving undone that which it +should do." It is a machine that, when in action, points a moral to +every thinking person who beholds it. Every man has such a governor if +he only has the inclination to use it. + +I have said further back that the water-head varies, but usually at long +periods. This variation is chiefly caused by changes of wind, and it is +very much greater than one would suppose without studying the causes. +Lake Erie lies in an easterly and westerly direction, and when the wind +blows constantly for a time from the west, with considerable force, the +water piles up at the eastern end of the lake, which causes the level of +the Niagara River to rise to a very sensible extent. It is not so +noticeable above the falls as below, because of the great difference in +the width of the river at these two points. Sometimes the river below +the falls, as it flows through the narrow gorge, will vary in height +from twenty to forty feet. When the wind stops blowing from the west and +suddenly changes and blows from the east, it carries the water of the +lake away from the east toward the west end, which will produce a +corresponding depression in the Niagara River. No doubt there is an +effect produced by the difference of annual rainfall, but the effect +from this cause is not so marked as that from the changing winds. + +Another appliance used in the power-house, chiefly for handling heavy +loads and transferring them from one point to another, is called the +electric crane. It is mounted upon tracks located on each side of the +power-house. The crane spans the whole distance, and runs on this track +by means of trucks from one end of the power-house to the other. Running +across this crane is another track which carries the lifting-machinery, +consisting of block and tackle, able to sustain a weight of fifty tons. +Situated at one end of the crane are one or more electric motors, which +are able, under the control of the engineer, to produce a motion in any +direction, which is the resultant of a compound motion of the two cars +acting crosswise to each other together with the perpendicular motion of +the lifting-rope connected with the block and tackle. It seems like a +thing endowed with human reason, when we see it move off to a distant +part of the building, reach down and pick up a piece of metal weighing +several tons, carry it to some other portion of the building and lower +it into place, to the fraction of an inch. While the machine itself does +not reason, there is a reasoning being at the helm, who controls it and +makes it subservient to his will. The machine is to the engineer who +manipulates it what a man's brain is to the man himself. The brain is +the instrument through which the unseen man expresses his will and +impresses his work upon men and things in the visible world. + + + + +CHAPTER XXIV. + +NIAGARA FALLS POWER--APPLIANCES. + + +In the last chapter I described some of the appliances used in +connection with the power-house. There are many things that are +commonplace as electrical appliances when used with currents of low +voltage and small quantity, that become extremely interesting when +constructed for the purpose of handling such currents as are developed +by the dynamos used at Niagara. For instance, it is a very commonplace +and simple thing to break and close a circuit carrying such a current as +is used for ordinary telegraphic purposes, but it requires quite a +complicated and scientifically constructed device to handle currents of +large volume and great pressure. If such a current as is generated by a +dynamo giving out 5000 horse-power under a pressure of 2200 volts should +be broken at a single point in a conductor, there would be a flash and a +report, attended with such a degree of heat and such power for +disintegration that it would destroy the instrument. + +The circuit-breakers used at Niagara are constructed with a very large +number of contacts made of metal sleeves, or tubes, say one inch in +diameter, so constructed that one will slide within the other; the +sleeves being slotted so as to give them a little spring that secures a +firm contact. These are all connected together electrically, on each +half of the switch, as one conductor, so that when the switch is closed +the current is divided into as many parts as there are points of contact +in the switch. Suppose there are 100 of these contact-points, a +one-hundredth part of the current would be flowing through each one of +them. If, now, these points are so arranged that they can be all +simultaneously separated, the spark that will occur at each break will +be very small as compared with what it would be if the whole current +were flowing through a single point, and it would be so small that there +would be no danger attending the opening of the switch. These switches +are carefully guarded, being boxed in and under the control of a single +individual. + +There is another apparatus that is a necessary part of every +manufacturing or other kind of plant that uses electricity from this +power-house, and this is called the transformer. Many of you are +familiar with the box-shaped apparatus that is used in connection with +electric lighting when the alternating current is used. Where simply +heating effects are required, such as in electric lighting, for +instance, the alternating current can be used to greater advantage than +the direct current when it has to be carried to some distance, owing to +the fact that it may be a current of high voltage. A greater amount can +be carried through a small conductor; thus greatly reducing the cost of +an electrical plant that distributes power to a distance. A transformer +is an apparatus that changes the current from one voltage to another. + +In the ordinary electric-light plant, such as is used in a small town or +village, the current that is sent out from the power-station has a +pressure of from 1000 to 1500 volts, according to the distance to which +it is sent. It would not do, however, for the current to enter a +dwelling at this high pressure, because it is dangerous to handle, and +the liability to fires originating from the current would be greatly +increased. At some point, therefore, outside of the building, and not a +great distance from it, a transformer is inserted which changes the +voltage, say, from 1000 down to 50 or 100, according to the kind of +lamps used. Some lamps are constructed to be used with a current of +fifty volts and others for 100 or more. The lamp must always be adapted +to the current or the current to the lamp, as you choose. The human body +may be placed in a circuit where such low voltage is used without +danger, but it would be exceedingly dangerous to be put in contact with +a pressure of 1000 or more volts, such as is used for lighting purposes. + +In principle the transformer is nothing more or less than an +induction-coil on a very large scale. The ordinary induction-coil, such +as is used for medical purposes, is ordinarily constructed by winding a +coarse wire around an iron core. This core is usually made of a bundle +of soft iron wires, because the wires more readily magnetize and +demagnetize than a solid iron core would. Around this coil of coarse +wire, which we call the primary coil, is wound a secondary coil of finer +wire. If now a battery is connected with the primary coil, which is made +of the coarse wire, and the circuit is interrupted by some sort of +mechanical circuit-breaker, each time the primary or battery circuit is +opened there will be a momentary impulse in the secondary circuit of a +much higher voltage; and at the moment the primary circuit is closed +there will be another impulse in this secondary circuit in the opposite +direction. The latter impulse is called the initial and the former the +terminal impulse. A current created in this manner is called an +_induced_ current. The initial current is not so strong as the terminal +in this particular arrangement. + +If we should take hold of the two wires connected with the two poles of +the battery and bring them together so as to close the circuit, and then +separate them so as to break it we should scarcely feel any +sensation--if there were only one or two cells, such as are ordinarily +used with such coils. But if we connect these wires to the coils of the +induction apparatus and then take hold of the two ends of the secondary +coil and break and close the primary circuit we should feel a painful +shock at each break and close, although the actual amount of current +flowing through the secondary wire is not as great as that which flows +through the primary; but the voltage (or electromotive force) is higher, +and thus is able to drive what current there is through a conductor of +higher resistance, such as the human body. For this reason there is more +current forced through the body, which is a poor conductor, than can be +by a direct battery current which has a lower voltage. If now we should +take a battery of a number of cells, so as to get a voltage equal to +that given off by the secondary coil, and connect it with the fine-wire +coil instead of the coarse-wire coil--thus making what was before the +secondary coil the primary--by breaking and closing the battery circuit +as before we shall get a secondary or induced current in the coarse-wire +coil, but it will be a current of low voltage, and will not produce the +painful sensation that the secondary coil did. + +We have now described the principle of a transformer as it is worked out +in an ordinary induction-coil. As has been stated, at Niagara Falls the +current comes from the dynamos with an electromotive force or pressure +of 2200 volts. For some purposes this voltage is not high enough, and +for other purposes it is too high; therefore it has to be transformed +before it is used! For some purposes this transformation takes place in +the power-house, and for others it takes place at the establishment +where it is used. For instance, take the current that is sent to +Buffalo, a distance of from twenty to thirty miles. The current first +runs to a transformer connected with the power-house, where it is +"stepped-up" (to use the parlance of the craft) from a voltage of 2200 +to 10,000. It is carried to Buffalo through wire conductors that are +strung on poles, and is there "stepped-down" again through another +transformer to the voltage required for use at that place. The object of +raising the voltage from 2200 to 10,000 in this case is to save money in +the construction of the line of conductors between the two points. If +the voltage were left at 2200--the conductors remaining the same as they +are now--the loss in transmission would be very great, owing to the +resistance which these wires would offer to a current of such +comparatively low voltage as 2200. To overcome this difficulty--if the +voltage is not increased--it would be necessary to use conductors that +are very much larger in cross-section (thicker) than the present ones +are. And as these conductors are made of copper the expense would be too +great to admit of any profit to the company. + +If we go back to an illustration we used in one of the early chapters on +electricity we can better explain what takes place by increasing the +voltage. If we have a column of water kept at a level say of ten feet +above a hole where it discharges, that is one inch in diameter, a +certain definite amount of water will discharge there each minute. If +now we substitute for the hole that is one inch in diameter one that is +only one-half inch in diameter a very much smaller amount of water will +discharge each minute, if the head is kept at the same point--namely, +ten feet. But if now we raise the column of water we shall in time reach +a height which will produce a pressure that will cause as much water to +discharge per minute through the one-half-inch hole as before discharged +through the one-inch hole with only the pressure of a ten-foot column. +This is exactly what takes place when the voltage is "stepped-up," which +is equivalent to an increase of pressure. + +It will be seen from the foregoing that these transformers have to be +made with reference to the use the current is to be put to. In general +shape they are alike in appearance, the difference being chiefly in the +relation the primary sustains to the secondary coils. There is another +kind of transformer that is used when it is necessary to have the +current always running in the same direction. This transformer, as +heretofore explained, does not change the voltage of the current, but +simply transforms what was an alternating into a direct current. By +alternating current we mean one that is made up of impulses of +alternating polarity--first a positive and then a negative. The direct +current is one whose impulses are all of one polarity. The direct +current is required for all purposes where electrolysis (chemical +decomposition by electricity, as of silver for silver-plating, etc.) is +a part of the process. The alternating current may be used without +transformation in all processes where heat is the chief factor. For +motive power either current may be used, only the electromotors have to +be constructed with reference to the kind of current that is used. + +The rotary transformer, which may be driven by any power, consists of a +wheel carrying a rotating commutator so arranged with reference to +brushes that deliver the current to the commutator and carry it away +from the same, that the brushes leading out from the transformer will +always have impulses of the same polarity delivered to them. In the +parlance of the craft, the transformers that are used to change the +voltage from high to low, or vice versa, are called "static +transformers," simply because they are stationary, we suppose. The +others are called rotary, or moving transformers, to distinguish them +from the other forms. The operation of the latter is purely mechanical, +while the former is electrical. In some instances where the static +transformers are very large they develop a great amount of heat, so much +that it is necessary to devise means for dissipating it as fast as +created. In some instances this is done by air-currents forced through +them, but in others, where they are very large, oil is kept circulating +through the transformer from a tank that is elevated above it, the oil +being pumped back by a rotary pump into the tank where it is cooled by a +coil of pipe located in the oil, through which cold water is continually +circulating. By this means cold oil is constantly flowing down through +the transformer, where it absorbs the heat, which in turn is pumped back +into the tank, where it is cooled. + +Having now traced the energy from the water-wheel through the various +transformations and having described in a very general way the apparatus +both for generating electricity and for transforming it to the right +voltage necessary for the various uses to which it is put, we will +proceed in our next chapter to follow it out to the points where it is +delivered, and trace it through its processes, and the part it plays in +creating the products of these various commercial establishments. + + + + +CHAPTER XXV. + +ELECTRICAL PRODUCTS--CARBORUNDUM. + + +The production of electricity in such enormous quantities as are +generated at Niagara Falls has led to many discoveries and will lead to +many more. Products that at one time existed only in the chemical +laboratory for experimental purposes, have been so cheapened by +utilizing electrical energy in their manufacture, as to bring them into +the play of every-day life. Still other products have only been +discovered since the advent of heavy electrical currents. A substance +called carborundum, which was discovered as late as 1891, has now become +the basis of an industry of no small importance. It is a substance not +unlike a diamond in hardness, and not very unlike it in its composition. +The chief use to which it is put is for grinding metals and all sorts of +abrasive work. It is manufactured into wheels, in structure like the +emery-wheel, and serves the same purpose. It is much more expensive than +the emery-wheel, but it is claimed that it will do enough more and +better work to make it fully as economical. + +It was my pleasure and privilege to visit the factory at Niagara Falls, +and through the courtesy of Mr. Fitzgerald, the chemist in charge of the +works, I learned much of the manufacture and use of carborundum. The +crude materials used in the manufacture of carborundum are, sand, coke, +sawdust and salt; the compound is a combination of coke and sand. It +combines at a very high heat, such as can be had only from electricity. +When cooled down the product forms into beautiful crystals with +iridescent colors. The predominating colors are blue and green, and yet +when subjected to sunlight it shows all the colors of the solar spectrum +to a greater or less degree. The crystals form into hexagonal shapes, +and sometimes they are quite large, from a quarter to a half inch on a +side. The salt does not enter into the product as a part of the +compound, neither does the sawdust. The salt acts as a flux to +facilitate the union of the silica and carbon. The sawdust is put into +the mixture to render it porous so that the gases that are formed by the +enormous heat can readily pass off, thus preventing a dangerous +explosion that might otherwise occur. In fact, these explosions have +occurred, which led to the necessity of devising some means for the +ready escape of the gases. + +The process of manufacture as it is carried on at Niagara is +interesting. The visitor is first taken into the rooms where are stored +the crude material, the sand, coke, sawdust and salt. The sand is of the +finest quality and very white. The coke is first crushed and screened, +the part which is reduced to sufficient fineness is mixed by machinery +with the right proportion of sand, salt and sawdust. The coarser pieces +of coke are used for what is called the core of the furnace, which will +be described later on. + +This mixture is carried to the furnace-room, which has a capacity for +ten furnaces, but not all of these will be found in operation at one +time. Here the workmen will be taking the manufactured material from a +furnace that has been completed, and there another furnace is in process +of construction, while a third is under full heat, so that one sees the +whole process at a glance. These furnaces are built of brick, about +sixteen feet in length and about five feet in width and depth. The ends +and bed of the furnace are built of brick, and might be called +stationary structures. The sides are also built of brick laid up loosely +without mortar; each time the material is placed in the furnace, and +each time the furnace is emptied, the side-walls are taken down. + +A furnace is made ready for firing by placing a mass of the mixture on +the bottom, and building the sides up about four feet high (or half the +height when it shall be completed). A trough, about twenty or twenty-one +inches wide and half as deep, is scooped out the whole length of the +pulverized stuff, and in this is placed what has before been referred to +as the core of the furnace, namely, pure coke broken into small pieces, +but not pulverized, as in the case of the other mixture. The amount used +is carefully weighed, so as to have the core the proper size that +experiment has proved to give the best results. The core is filled in +and rounded over till it is in circular form, being about twenty-one +inches in diameter. At each end of the furnace the core connects with a +number of carbon rods--about sixty in all--that are thirty inches long +and three inches in diameter. These carbon rods are connected with a +solid iron frame that stands flush with the outer end of the furnace. On +the inside the spaces between the rods are packed full of graphite, +which is simply carbon or coke with all the impurities driven out, so as +to make good electrical connections with the core. This core +corresponds, electrically speaking, to the filament in an ordinary +incandescent lamp, only it is fourteen feet long and twenty-one inches +in diameter. The mixed material is now piled up over this core, and the +walls at the sides are built up until the whole structure stands about +eight feet from the floor--a mass of the fine pulverized mixture, with +a core of broken coke electrically connected at the ends. It is now +ready for the application of electricity, which completes the work. + +Let us go back to the transformer-room and examine the electrical +appliances that bring the current down to a proper voltage to produce +the heat necessary to cause a union between the silica of the sand and +the carbon of the coke, which results in the beautiful carborundum +crystals that we have heretofore described. + +The current is delivered from the Niagara Power Company under a pressure +of 2200 volts. The conductors run first into the transformer-room, which +adjoins the furnace-room, and is there transformed down from 2200 volts +to an average of about 200 volts. The transformers at these works have a +capacity of about 1100 horse-power. About 4 per cent of this power is +converted into heat in the process of transformation, making a loss in +electrical energy of a little over 40 horse-power. This heat would be +sufficient to destroy the transformer if some arrangement were not +provided to carry it off. We have already described how this is done +through the medium of a circulation of oil. Because of the low voltage +and enormous quantity of the current passing from the transformer to the +furnace very large conductors are required. The two conductors running +to the furnace have a cross-section of eight square inches, and this +enormous current, representing over 1000 horse-power, is passed through +the core of the furnace, and is kept running through it constantly for a +period of twenty-four to thirty-six hours. + +Let us consider for a moment what 1000 horse-power means; as this will +give us some conception of the enormous energy expended in producing +carborundum. A horse-power is supposed to be the force that one horse +can exert in pulling a load, and this is the unit of power. However, a +horse-power as arbitrarily fixed is about one-quarter greater than the +average real horse-power. If 1000 horses were hitched up in series, one +in front of the other, and each horse should occupy the space of twelve +feet, say, it would make a line of horses 12,000 feet long, which would +be something over two miles. Imagine the load that a string of horses +two miles long could draw, if all were pulling together, and you will +get something of an idea of the energy expended during the burning of +one of these carborundum furnaces. + +Within a half hour after the current is turned on a gas begins to be +emitted from the sides and top of the furnace, and when a match is +applied to it, it lights and burns with a bluish flame during the whole +process. It is estimated that over five and one-half tons of this gas +is thrown off during the burning of a single furnace. This gas is called +carbon monoxide, and is caused by the carbon of the coke uniting with +the oxygen of the sand. When we consider the vast amount of material +that comes away from the furnace in the form of gas it is easy to see +why it is necessary to introduce sawdust or some equivalent material +into the mixture, in order to give the whole bulk porosity, so that the +gas can readily escape. We should also expect that after five and +one-half tons had been taken away from the whole bulk that it would +shrink in size. This is found to be the case. The top of the mass of +material sinks down to a considerable extent by the end of the time it +has been exposed to this intense heat. Gradually, after the current has +been turned on, the core becomes heated, first to a red, and afterwards +to an intense white heat. This heat is communicated to the material +surrounding the core, producing various effects in the different strata, +owing to the fact that it is not possible to keep a uniform heat +throughout the whole bulk of material. Some of it will be "overdone" and +some of it "underdone." The material which lies immediately in contact +with the core will be overheated, and that, which at one stage was +carborundum, has become disintegrated by overheating. + +The silica of the compound has been driven off, leaving a shell of +graphitic substance formed from the coke. + +After the current is shut off and the furnace has cooled down, a +cross-section through the whole mass becomes a very interesting study. +The core itself, owing to the intense heat it has been subjected to, has +had the impurities driven out of the coke, leaving a substance like +black lead, that will make a mark like a lead-pencil, and is really the +same substance, known as plumbago, in one of its forms. It is the carbon +left after the impurities have been driven out of the coke. Surrounding +the core for a distance of ten or twelve inches, radiating in every +direction, beautifully colored crystals of carborundum are found, so +that a single furnace will yield over 4000 pounds of this material. +Beyond this point the heat has not been great enough to cause the union +between the carbon and silica, which leaves a stratum of partly-formed +carborundum; outside of that the mixture is found to be unchanged. + +These carborundum crystals are next crushed under rollers of enormous +weight, after which the crushed material is separated into various +grades for use in making grinding-wheels of different degrees of +fineness. This crushed material is now mixed with certain kinds of clay, +to hold it together, and then pressed into wheels of various sizes in a +hydraulic press, and afterward carried into kilns and burned the same +as ordinary pottery or porcelain. These wheels vary in size from one to +sixteen inches. The substances used as a bond in manufacturing wheels +are kaolin, a kind of clay, and feldspar. + +While carborundum has already a large place as a commercial product, +there is no doubt but that the uses to which it will be put will vastly +increase as time goes on. This product may be called an artificial one, +and never would have been known had it not been for the intense heating +effects that are obtained from the use of electricity. It certainly +never could have been brought into play as one of the useful agencies in +manufacturing and the arts. It is not known to exist as a natural +product, which at first thought would seem a little strange in view of +the evidences of intense heat that at one time existed in the earth. Its +absence in nature is explained by Mr. Fitzgerald by the fact that "the +temperatures of formation and of decomposition lie very close +together." + + + + +CHAPTER XXVI. + +ELECTRICAL PRODUCTS--BLEACHING-POWDER. + + +Another industry that has assumed large proportions at Niagara Falls, +owing to the vast quantity of electricity produced there, is the +manufacture of a commercial product called bleaching-powder, or chloride +of lime. Every one knows that chloride of sodium is simply common salt, +so extensively used wherever people and animals exist. Simple and +harmless as it is, while it exists as a compound of the original +elements, when separated into those elements they are each very +unpleasant and even dangerous substances to handle. Salt is one of the +most common substances in nature. It is found in many parts of the world +in solid beds, and is one of the prominent constituents of sea-water. + +Salt is a compound of chlorine and a metal called sodium. Sodium in its +pure state has a strong affinity for oxygen, so much so that when a lump +of it is thrown into water it takes fire and burns violently with a +yellow flame. Chlorine, the substance with which it unites to form +common salt, is a greenish-colored gas, the fumes of which are very +offensive and very dangerous even to breathe, if the quantity is very +considerable. + +It is a curious fact in nature that two such substances as chlorine and +sodium, both of them so difficult and dangerous to handle, should unite +together to form such a useful and harmless compound as common salt. The +important element in bleaching-powder is the chlorine which it contains. +It is extensively used in the manufacture of paper and in all other +materials where bleaching is required. The object of combining it with +lime, forming a chloride of lime, is simply to have a convenient method +of holding the chlorine in a safe and convenient manner until it is +needed for use. + +The chemical works at Niagara Falls manufacture bleaching-powder on a +very large scale. The part that electricity plays is to separate the +chlorine from the sodium as it exists in common salt. At the works I was +first taken into a room where a large quantity of salt was stored. A +belt with little carrier-buckets on it picked up this salt and carried +it into another room, where it was thrown into a vast mixing-vat +containing water. The salt was mixed with water until a saturated +solution was obtained. In a large room, covering one-half acre or more +of ground, were assembled a great number of shallow vessels, about 4 by +5 feet square and 1 foot deep. These vessels were sealed up so that they +were gas-tight. Communicating with all of these vessels were pipes +connecting with the great tank containing the saturated solution of +salt. + +From the top or cover of each vessel is a pipe running to a main pipe +that carries off the chlorine gas into another room as fast as it is +formed. Through each one of these vessels a current of electricity +passes; the whole system consuming about 2000 horse-power. The electric +current, as it passes through the brine, separates the chlorine from the +sodium, the chlorine passing in the form of gas up through the pipes, +before mentioned, into the main pipe, where it is carried into another +large room and discharged into a system of gas-tight chambers. Upon the +floor of these chambers is spread a coating of unslacked lime ground +into a fine powder. The lime has a strong affinity for the chlorine gas +and rapidly absorbs it, forming chloride of lime. When the lime is fully +saturated with the chlorine the gas is turned off from that chamber, +which is then opened up and the chloride taken out for shipment. A new +coating of lime is now spread in the chamber and the gas is turned on +and the process repeated. + +There are a number of these chambers, so that the operation in all of +its phases is going on continuously. The room where the chlorine gas is +formed is thoroughly ventilated, a precaution which is very necessary in +case any one of the vats should spring a leak, as they sometimes do. + +In each one of these vats where the electrolytic process is going on +there are two products constantly passing off; one, as before mentioned, +is chlorine gas, and the other caustic soda in solution. The solution in +the vat is constantly being renewed by the saturated solution of salt +from the reservoir before mentioned. There is one stream continuously +coming into the vat and two going out, caused by the decomposing power +of the electric current. The solution of caustic soda is carried to +large evaporating-pans, where the water is driven out of it, leaving the +caustic soda in dry, white sticks of crystalline formation. In this +process the electric current, which comes from the power-house with an +energy of 2000 horse-power, has to be transformed twice; first, to bring +it to the proper voltage for the work of decomposition, and, secondly, +to change it from an alternating to a direct current, by which all +electrolytic processes are carried on. + +You will notice that the electrical energy expended in this +establishment is double that used in the manufacture of carborundum. + +The caustic soda, which is one of the products from the decomposition of +salt, is taken to another establishment, where, by still another +electrical process, metallic sodium is manufactured. The process here +being a secret one, the writer did not have the privilege of examining +the details. + + + + +CHAPTER XXVII + +ELECTRICAL PRODUCTS--ALUMINUM. + + +Another comparatively new article of manufacture now produced in large +quantities at Niagara Falls is aluminum. Until within the last few years +this metal was not used to any extent by manufacturers, because of the +great expense attending its production. Now, however, it is produced in +such quantities as to make it about as cheap as brass, bulk for bulk. +Aluminum is a very light metal, with a color somewhat lighter than +silver; its specific gravity being about one-third that of iron. +Aluminum is found in one of its compounds in great quantities in nature, +especially in certain kinds of clay and in a state of silicate, as in +feldspar and its associated minerals. It is found in great quantities in +southern Georgia, where it is mixed with the red oxide of iron that +abounds in that region. Here, it exists as alumina, which is an oxide of +aluminum. Before it is taken to the reduction-works the alumina is +separated from all other substances. It is a white powder, tasteless, +and not easily acted upon by acids. + +Electricity is the chief agent in the production of metallic aluminum. +The reduction company buys this alumina, which has been separated from +the clay or ores where it is mined. In a large room there are located a +great number of iron vats or crucibles, lined with carbon, about two or +two and one-half feet deep, five or six feet long and four feet wide. + +Immediately over each vat is constructed a metal framework, through +which are inserted a large number of carbon rods about eighteen or +twenty inches long and from two to two and one-half inches in diameter. +This framework is electrically insulated from the iron crucibles. The +framework and the carbons are connected with the positive conductor of +the electric current, and the vat or crucible with the negative. These +conductors are very large, something like a foot in width and an inch in +thickness, and made of some good conductor of electricity. They have to +be very large because they carry a current equal to 3050 horse-power. +The current is one of great volume, but very low voltage; the +electromotive force at each vat or crucible being only about seven +volts. As the process is electrolytic, and not simply a heating process, +the direct current must be used, and therefore the current coming from +the power-house must be transformed twice; first to bring it to a +proper voltage and secondly to change it from an alternating to a direct +current. These iron vats or crucibles are connected up in series, +electrically, and then they are filled with the alumina and certain +other materials, which act either as a flux or as a means of increasing +the conductivity of the mixture; just what this substance is, is +probably one of the secrets of the process. When all of the crucibles +are filled with the mixture the current is turned on and is kept on +continuously night and day seven days in the week. All of the material +in the different crucibles is heated to redness, when the process of +separation takes place. The oxygen of the alumina is thrown off as a +gas, and other residuum floats to the top of the crucible and is skimmed +off. + +Metallic aluminum in a melted state sinks to the bottom of the crucible, +where it is dipped out from time to time with large iron ladles and +poured into sand and molded into blocks similar to that of pig iron. +From time to time, as the metal is dipped out, fresh alumina with the +other substances are thrown in on top of the crucible, so that the +process is continually going on, day and night, week in and week out. +The heat in the process of reducing alumina, as we have before seen, is +not the chief factor; it simply serves to reduce the compound to a fluid +state so that the electrolytic action can readily take place. + +Therefore it is not necessary to be brought to a white heat, as it is in +the case of the production of carborundum, described elsewhere. + +It was extremely interesting to observe the wonderful magnetic effects +that were produced in iron when brought into proximity with these +enormous electrical conductors. The voltage was so low that one could +handle them with impunity. The iron crucibles became so magnetic that a +heavy bar of iron seven or eight feet long would cling to their sides, +so that it would be held in an upright position. Bars of iron would +cling to the conductor at any point along its length, and, although +these conductors were carrying an energy of over 3000 horse-power, they +produced no perceptible effect upon the human body. The reason for this +lies in the fact, first, that the body is not made of magnetic material, +and, secondly, the pressure is so low that the body--being a poor +conductor--would not easily allow the low-pressure current to pass +through it. + +Aluminum is fast becoming an important article of commerce, and it is +destined to become more and more so on account of its extreme lightness +as compared to other metals. + +It is found to be valuable also when used as an alloy with many of the +other metals. One of the great drawbacks to its more extensive use lies +in the fact that as yet no satisfactory method has been devised for +soldering it. Undoubtedly in time this difficulty will be solved, when +its use will be greatly increased. It is estimated that in its various +compounds aluminum forms about one-twelfth of the crust of the earth. + + + + +CHAPTER XXVIII. + +ELECTRICAL PRODUCTS--CALCIUM CARBIDE. + + +Another important use to which electricity is put at Niagara Falls is +the manufacture of a new product, called calcium carbide. Like +carborundum and aluminum, this product could not have been produced in +commercial quantities in advance of a means for producing electricity in +enormous volume. + +Calcium carbide is a compound of calcium and carbon. Calcium is a white +metal not found in the natural state, but exists chiefly as a carbonate +of lime, which is ordinary limestone, including the various forms of +marble. As a pure metal it is hard to obtain and very hard to maintain, +as it readily oxidizes when in contact with the air. The symbol for +calcium carbide is CaC_{2}, which means that a molecule of this carbide +is compounded of one atom of calcium and two atoms of carbon. Ca stands +for calcium and C for carbon. When the symbol has no figure following +it, it means that one atom only enters into the compound; but if a +figure follows, it means that as many atoms enter in as the figure +represents. + +The process of manufacturing calcium carbide is as follows: Ordinary +lime before it is slacked is ground to a fine powder; then it is mixed +with powdered coke or carbon in the proper quantities, so that when a +chemical union takes place the proportion will be as before stated, one +atom of calcium to two of carbon. As is well known, lime is procured by +exposing ordinary limestone to a red heat for some hours together. The +heat disengages the carbon dioxide, leaving only a combination of +calcium and oxygen, which is common lime. + +The mixture of ground lime and coke is put into a crucible that +surrounds the arc of an electric light of enormous dimensions; the +carbon conductors amounting to an area of one square foot or more. In +order to cause the carbon to unite with the calcium a very intense heat +is required, such a heat as can be obtained only in the arc of an +electric light. When the enormous current is turned on (amounting to +over 3000 horse-power) the mixture is melted, and after an exposure to +this intense heat for a given length of time the oxygen of the unslacked +lime is thrown off and the carbon unites with the calcium, which remains +in the proportions of one atom of calcium to two of carbon, as before +stated. This, it will be noted, is purely a heat process, and an intense +one at that. No electrolytic action being required, the alternating +current is used without transformation to the direct current, as is +necessary in the manufacture of bleaching-powder and aluminum, both of +which are electrolytic processes. + +When the operation is completed the current is turned off and the +compound allowed to cool. In cooling it assumes a slate color, which is +slightly iridescent when exposed to light. It also crystallizes to a +certain extent. + +The value of this new product consists in its ability to evolve +Acetylene gas in large quantities. A molecule of acetylene gas is +composed of two atoms of carbon to two of hydrogen. To evolve the gas it +is necessary only to pour water upon the calcium carbide, when a union +takes place between the carbon of the carbide and the hydrogen of the +water in the proportions above stated. If there is water enough the +whole of the carbon will pass off with the gas, leaving a residuum of +slacked lime. + +The value of acetylene gas lies in its very intense illuminating power. +This is due to the fact that the gas is very rich in carbon as compared +with other illuminating gases. It burns with a pure white light when +properly mixed with air or oxygen, but if there is a lack of air it +burns with a smoky flame. In this case the carbon is not all consumed +and escapes into the air in the form of soot or smoke, but when burned +with the proper mixture of oxygen or common air it becomes one of the +most brilliant of illuminants. Acetylene, like most other gases, becomes +explosive when mixed with air in certain proportions. Whether it is more +dangerous to handle than ordinary illuminating gases the writer is not +prepared to say, as he has not had the opportunity to make a thorough +comparison between it and other gases from an experimental standpoint. + +Experiment, after all, is the only sure road to absolute knowledge. +Theories are beautiful in books and lectures, but they often fail in the +laboratory. + +Acetylene is now being introduced as an illuminating gas for domestic +and other purposes. Several methods of handling it have been proposed. +One is to condense it into strong metal cylinders and deliver it in that +form; another is to erect generators at convenient places and generate +the gas as it is used. A very ingenious contrivance has been invented +for regulating the generation of the gas. A certain amount of the +calcium carbide is placed in a gas-tight vessel containing water. As +soon as the water comes in contact with the carbide the evolution of the +gas begins. When the pressure on the inside of the vessel has reached a +certain degree it is made, through mechanical contrivances, to lift the +carbide out of the water and thus stop the evolution of the gas. When +the pressure is relieved through the consumption of the gas at the +burners it allows the carbide to drop into the water, when the evolution +of the gas begins again. + +Of course there is the same objection to this mode of lighting that +attends all open burners; it is constantly discharging into the air the +products of combustion, chiefly carbon dioxide, which is poisonous to +animal life. As has been explained in some of the chapters on heat, in +Volume II, the illuminating property of any gas is determined by the +number of carbon particles that are contained in it, which become heated +to incandescence as soon as they come in contact with the oxygen of the +air, and remain so, for a brief period, during their passage between the +two extremes of the flame. While acetylene equals electricity in its +illuminating properties, the latter still stands without a rival when +considered from a sanitary standpoint, as the use of electricity does +not in any degree vitiate the air in a room where it is used. + +We have now given somewhat in detail the following processes that are +carried on at Niagara Falls through the agency of electricity, viz.: The +reduction of aluminum from its oxide alumina; the production of the new +and useful compound called carborundum; the formation of calcium carbide +used for the production of acetylene gas, and a large chemical works, +where bleaching-powder is made. In addition to these works, there is an +establishment for the production of sodium from caustic potash, which is +one of the products arising from the decomposition of salt in the +bleaching-powder works. There is also another establishment for the +production of phosphorus made from the bones and shells obtained from +the phosphate beds that abound in some of the southern states, on the +coast of the Atlantic Ocean. There is in process of construction a plant +for the purpose of manufacturing chlorate of potash by an electrical +process. In addition to these establishments mentioned, the electricity +is furnished for power purposes to the Niagara Electric Light Company; +to the electric railway between Niagara and Buffalo; to the Niagara +Falls Railway, on the opposite side of the river; to the Niagara Power +and Conduit Company of Buffalo, and the Niagara Development Company. +This is only a small beginning of the uses to which electricity will be +put as an agent for the development of heat, light and power as well as +for the production of all substances where electrolysis is the chief +factor. Sixteen companies or more are now using electricity from the +Niagara power-house,--the whole amounting to about 35,000 horse-power. + + + + +CHAPTER XXIX. + +THE NEW ERA. + + +When we consider the number of new products for whose existence we are +indebted to electricity, and the number of old products that have +heretofore existed experimentally, in the laboratory of the chemist +only, that have now been brought into play as useful agents in the +various arts and industries, we begin to realize that this is truly an +electrical age and the dawning of a new era. How many, many things there +are, familiar to the children of to-day, that were not even imagined by +the children of twenty-five to fifty years ago. Fifty years ago the only +useful purpose to which electricity was put was that of transmitting +news from city to city by the Morse telegraphic code. It will be +fifty-seven years the first of April, 1901, since the first +telegraph-line was thrown open to the public. Less than thirty years ago +but little advance had been made in the use of electrical appliances +beyond the perfection of certain private-line instruments, and a means +for multiple transmission. About twenty years ago there were evidences +of the beginning of a new era in electrical development. At no time in +the history of the world has wonder succeeded wonder with such rapidity, +producing such astounding results that have revolutionized all our modes +of doing business and all of the operations of commercial and domestic +life, as during the last two decades. We set our watches by time +furnished by electricity from one central point of observation. We read +the tape from hour to hour, upon which is recorded the commercial pulse +of the world, as it throbs in the marts of trade, by means of this same +speedy messenger. We enter a street-car that is lighted and heated, and +at the same time propelled by the same wonderful agent. In our homes and +on our streets night is turned into day by a light that outrivals all +other illuminants. + +When we wish to speak to a friend who may be a mile or a thousand miles +away we step to the end of a wire that comes within the walls of our +dwelling and we talk to him as though face to face, and means are at +hand by which we may write a letter to that same friend and deliver it +to him in our own handwriting and over our own signatures, so quickly +that it will appear before him in full form and completeness as soon as +the last period is made at the end of the last line. + +One sees, and hears, and lives more in a single day in this age of +electricity and steam than he did in twelve months sixty years ago. And +yet there are those who cry out against modern inventions and modern +civilization, and are constantly quoting the days of their grandfathers +and great-grandfathers when "life was simple" and there was "time to +rest." "Why are we tormented with this thought-stimulating age?" they +say. "Why are our emotions called into action by modern music and modern +art? Why are we called upon to help the downtrodden and oppressed, and +to help to elevate mankind to a higher level? Why cannot we be left +alone in peace and quiet, to live in the easiest way?" + +If this be good philosophy, then the swine, if he were a reasoning +being, ought to be ranked among the greatest of philosophers--when he +seeks a wallow in the sunshine and sleeps away his useless existence. If +he is useful it is because some other being of a higher order uses him +to help along his own existence. The man in these days who does not +"keep up with the procession" is soon trodden under foot and some other +man uses him as a stepping-stone to elevate himself. + +Yet this is a selfish motive, after all. The world is now rapidly +advancing in light, in knowledge, in power to use the infinite gifts +that the Creator has hidden in nature; but hidden only to stimulate and +reward our seeking. Every man can help in this grand progress,--if not +by research and positive thought-power, at least by grateful acceptance +and realization of what is gained. _Look forward!_ As Emerson puts it: +"To make habitually a new estimate--that is elevation." + + + + +INDEX. + + + Acetylene gas at Niagara, 230. + + Alexandria, temple with loadstone, 20. + + Amber--elektron, 6. + + Ampere, theory of magnetism, 25. + unit of electrical current, 85. + galvanometer, 93. + + Aluminum at Niagara, 223. + + Arabians, magnetic needle, 21. + + Arago, germ of electromagnet, 93. + + Aristotle mentions torpedo, 6. + refers to magnet, 20. + + Atmospheric electricity, Ch. VIII, 77. + + Atoms and molecules, 39. + of substances differ in weight, 42. + relations to heat, 42. + + Aurora Borealis, 35. + + + Bain chemical telegraph register, 101. + + Barlow on galvanism in telegraphy, 93. + + Bell, Alexander Graham, radiophone, 171. + + Bleaching-powder at Niagara, 218. + + Branly invents the coherer, 179. + + + Cables, submarine. See Submarine Cables. + + Calcium-carbide at Niagara, 228. + + Capacity of a circuit, 118, 119. + + Caustic soda, 221. + + Chinese, magnetic needle, 21. + + Chlorine and sodium, 219. + + Circuit-breaker at Niagara, 199. + + Closed circuit and current, 122. + + Coherer (wireless telegraphy), 179. + + Columbus, compass variations, 22, 34. + + Condenser in resistance-coil, 118. + in Morse relays, 131. + + Conductors and non-conductors of electricity, 47. + relation to electric light, 50. + different resistances, 74, 83. + + Cooke, needle telegraph, 108. + + Crookes, Prof., X-ray, 121. + + Cuneus and the Leyden jar, 8. + + Curiosities, Ch. XX, 171. + + + Daniell battery, 85. + + Differential magnet, 115. + + Dinocares and the loadstone, 20. + + Dolbear, Amos E., wireless telegraphy, 178. + + Dupay discovers positive and negative electricity, 8. + + Duplex telegraphy, 114. + + Dynamo-electric machines, 67. + invented by Faraday, 14, 69. + usual construction, 70. + at Niagara, 192. + + Double transmission, 115. + + + Earth electric currents, in telegraphy, 99, 116, 182. + + Earth magnetism, 32. + effects of, on iron, 35. + Aurora, 35. + telegraph-lines, 36. + from sun's heat, 75. + + Edison, Thomas, railway telegraphy, 131. + electromotograph, 175. + + Electric currents, Ch. VI, 49. + not currents but atomic motion, 54. + induction of, 56. + guarded against, 169. + at Niagara, 193. + + Electric generators, Ch. VII, 62. + frictional, 49. + galvanic batteries, 62. + storage-batteries, 64. + dynamos, 67, 192. + metal heating, 74. + + Electricity, science of, 6. + achievements of, 16. + eras in science of, 18. + theory of, Ch. V, 39. + not a fluid, a form of energy, 40. + static and dynamic, 46. + measurement of, Ch. IX, 83. + + Electric light, cause of, 50. + + Electric machines, 49. + frictional, 51. + galvanic or chemical, 51. + mechanical, 70. + + Electromagnet invented by Faraday, 14. + commercial value, 23. + theory of (soft iron), 26. + permanent (steel), 28. + condition of use, 30. + the earth a, 32. + germ of, 93. + differential, 115. + + Electromotograph, 175. + + Ellsworth, Miss, sends first telegraphic message, 96. + + Ether, lines of force, 31. + nature of, 40. + + Ether, impressed by atomic motion, 56. + inducing electric action, 56. + + + Farad, unit of capacity, 118. + + Faraday, Michael, 14. + + Farmer, Moses G., double transmission, 114. + + Field, Cyrus W., lays first Atlantic cable, 156. + + Field of a magnet, 31. + + Fitzgerald, Niagara Falls chemist, 210. + + Franklin catches the lightning, 8. + identity of lightning and electricity, 10. + kite experiment, 11. + electric firing-telegraph, 88. + + Frode, history of Iceland, 21. + + + Gadenhalen uses magnetic needle 868 A.D., 21. + + Galileo's seed-thought, 89. + + Galvani, Luigi, and galvanism, 12. + + Galvanic batteries, 62. + author's experience, 65. + + Galvanometer, 75, 93. + + Gilbert, Dr., frictional electricity, 7. + + Gintl, double transmission, 114. + + Gray, Elisha, constructs voltaic pile, 65. + electrically transmits music, 91. + experiments on transmission of music, articulate speech, + and multiple messages, 123. + files telephone caveat, 135. + musical experiments, 136. + speech receivers, 139. + boys' telephone, 141. + first telephone specification on record, 143. + dial-telegraph, 161. + automatic-printing telegraph, 163. + telautograph, 165. + electric musical receiver, 175. + + Gray, Stephen, electrician, 8. + + Grier, John A., quoted, 67. + + Guyot of Provence mentions mariner's compass, 21. + + + Halske, double transmission, 114. + + Harmonic telegraphy, 120. + receivers, 125. + relay, 130. + + Hawksbee, Francis, electrician, 7. + + Heat, a mode of motion, 40. + related to atoms, 42. + begins and ends in matter, 44. + electrical and mechanical energy the same, 46. + + Henry, Joseph, first practical telegrapher, 90. + constructs long-distance line, 94. + produces induction, 177. + + Heraclea and the loadstone, 20. + + Hertz experiments in ether-waves, 178. + + Homer refers to loadstone, 20. + + Horse-power, 214. + + House, Royal E., printing telegraph, 108, 110. + + Hughes, David E., printing telegraph, 108, 112. + + + Induction, 56. + guarded against, 169. + produced by Henry, 177. + + + Keeper of a magnet, 31. + + Kelvin, Lord (Sir W. Thompson), cable message receiver, 158. + + "Kick," in telegraphy, 115, 118. + + Kleist and the Leyden jar, 8. + + + "Let her buzz," 3. + + Leyden jar invented, 8. + + Lightning, electricity; Franklin, 8. + restoration of equilibrium, 78. + + Lightning-rods, 80. + dangerous conductors, 81. + + Loadstone, 20, 21. + + + Maury, Lieut., deep-sea soundings, 155. + + Magnes, Magnesia, 20. + + Magnet, electro. See Electromagnet. + + Magnetic earth poles, 23, 32. + + Magnetic lines of force, 31, 34, 60. + + Magnetic needle, 21. + variation of, 22. + dip of, 22. + action of, 33. + + Magnetism, history of, 20. + and electricity mutually dependent, 24. + theories of, 24. + in iron and steel, 25. + in the earth, 32, 36. + and sun-spots, 37. + + Magnetization, limit of, 31. + + Marconi, wireless telegraphy, 178-180. + + Measurement of electricity, 83. + ampere, unit of, 85. + method of, 86. + + Mercury luminous by shaking, 7. + + Micro-farad, unit of capacity, 119. + + Molecules of iron and steel natural magnets, 25. + and atoms, 39. + + Morse, S. F. B., devises code of telegraphic signals, 95. + induces Congress to construct line, 96. + transmits battery current through water, 177. + + Motion universal, 38. + causes sound, heat, light, and electricity, 39. + + Multiple transmission, Ch. XIII, 114. + duplex, 116. + quadruplex, 118. + + Multiple transmission, musical, 120. + + Musical message receivers, 125, 139. + + Musical tones transmitted, 91, 92, 120, 136. + + Muschenbroeck, Prof., and the Leyden jar, 8. + + Newton, Sir Isaac, electrician, 8. + + + Niagara Falls Power, Chs. XXII to XXVIII, 186 to 233. + Introduction--rock, water, power, 186. + Appliances: + tunnel, power-house, 190. + shaft, dynamos, 192. + current, 193. + governor, 194. + water-head, 195. + crane, 196. + circuit-breaker, 199. + transformer, 200. + electromotive force, 204. + Electrical Products--Carborundum, 209. + materials, 210. + furnaces, 211. + electric current, 213. + horse-power, 214. + method of work, 215. + Bleaching-powder, 218. + chlorine and sodium, 219. + method of work, 220. + caustic soda, 221. + Aluminum, 223. + crucibles and methods, 224. + magnetic effects, 226. + Calcium carbide, 228. + process, 229. + acetylene gas, 230. + Other products, 232. + + Oersted, galvanic current on magnetic needle, 93. + + Ohm, G. S., resistance unit, 74. + + + Patents--Caveat and application, 135. + + Plante, storage-battery plates, 64. + + Pliny mentions electrical properties of amber, 67. + loadstone, 20. + + Preece, double transmission, 114. + + Prescott, Geo. B., quoted, 104, 106, 163, 174. + + Ptolemy Philadelphus and loadstones, 20. + + Pythagoras refers to natural magnets, 20. + + + Radiophone, 171. + + Railway train telegraphy, 131. + + Richman, Prof., killed, 12. + + Reiss, metallic telephone transmitters, 122. + + Resistance, unit of, 74. + -coil, 118. + + + Siemens, double transmission, 114. + + Selenium in radiophone, 172. + + Shephard, Charles S., induction-coil, 122. + + Stager, Gen. Anson, telegrapher, 110. + + Stearns, Joseph B., cures the "kick" in double transmission, 115. + + Storage-battery, 24. + + Strada, loadstone telegraph, 88. + + Submarine cables, Ch. XVII, 154. + first lines, 154-5. + Maury's deep-sea soundings, 155. + first Atlantic, 156. + retardations, 157. + receiver, 158. + + Sun-spots and magnetic storms, 37. + + + Telautograph, Ch. XIX, 165. + + Telegraph: + heliostat, 68. + semaphore, 68. + loadstone, 88. + Franklin's electric firing, 88. + electrically dropped balls, 88. + electric transmission of musical tones, 91. + of signals, 94. + Morse register, 95. + first line, 97. + description, 98. + reading by various senses, 100. + Bain, chemical recorder, 101. + Cooke needle, 108. + Wheatstone needle, 108. + House printing, 108, 110. + Hughes printing, 108, 112. + automatic systems, 109, 112. + multiple transmission, 114. + musical transmission, 120. + musical receivers, 125. + Way duplex, 129. + from moving railway trains, 131. + repeater, 150. + short-line dials, 159. + printing, 163. + wireless, Ch. XXI, 176. + + Telegraphic messages, receiving, 103. + + Telephone, Chs. XV, XVI, 134, 145. + author's first experiment, 91. + experiments, 123. + caveat, 135. + speech receivers, 139. + boys' telephone, 141. + first specification of, on record, 143. + how telephone talks, 145. + simple construction, 146. + two methods of transmission: magneto and varied + resistance, 142, 149. + limit of transmission, 153. + central station, 164. + affected by heat-lightning, 183. + + Telephote, 173. + + Thales of Miletus first described electrical properties of amber, 6. + + Theophrastus mentions amber, 6. + + Thermo-electric pile, 75. + + Torpedo, the, 6. + + Transformers at Niagara, 200. + + Transmission, multiple, Ch. XIII, 114. + + Trowbridge, Prof., telephones through the earth, 188. + + Tunnel at Niagara, 190. + + Tyndall, and Gray's experiments, 92. + + + Unrest of the universe, 38. + + + Volt, unit of electrical pressure, 85. + + Volta, Alessandro, and the voltaic pile, 13. + + + Watt, James, 86. + unit of electrical power, 86. + + Way duplex system, Ch. XIV, 129. + + Wheatstone transmits musical tones mechanically, 92. + needle telegraph, 108. + dial-telegraph, 159. + + Wireless telegraphy, Ch. XXI, 176. + signaling by ether-waves, 176. + Morse and Henry, 177. + Trowbridge, Dolbear, Hertz, 178. + Branly, Marconi, 179. + Marconi's system, 180. + by earth-currents, 182. + + Wolimer, King of Goths, a natural battery, 7. + + + + + +End of Project Gutenberg's Electricity and Magnetism, by Elisha Gray + +*** END OF THIS PROJECT GUTENBERG EBOOK ELECTRICITY AND MAGNETISM *** + +***** This file should be named 34221.txt or 34221.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/4/2/2/34221/ + +Produced by Chris Curnow and the Online Distributed +Proofreading Team at http://www.pgdp.net (This file was +produced from images generously made available by The +Internet Archive) + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. 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