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Achievements Of The 19th Century:
 A Century Of Achievement

 Transportation

 Communication

 Engineering

 Marvelous Machinery

 Light And Heat Including Photography

 Electricity

 Mining And Metallurgy

 Agriculture

 Chemistry

 Read More Articles About: Achievements Of The 19th Century

Electricity

( Originally Published Early 1900's )

Though the opinions of scientists vary in their estimate as to which is the greatest achievement of the Century, electricity is the foremost in the popular estimation. The reader of this book cannot but be impressed with the fact that electricity enters into all of the achievements of the Century. There is scarcely a branch of science and industry that is able to struggle along without its aid.

Yet though the Nineteenth Century has changed electricity from a philosopher's toy to man's most useful servant and this change dates from the time of Volta's pile in 1800 still electricity is one of the oldest things of which we know. Electricity, like fire, was probably the discovery of primitive man. Humboldt tells us that the Indians of the Orinoco generate the electric current by rubbing certain beans together until they acquire the properties of a magnet. Thales of Miletus, who lived six hundred years before Christ and was the father of Greek philosophy believed that there was a soul in amber, which rubbed acted as a magnet. Thus we get our word "electric" from the Greek word "elektron," meaning amber. It was not until the Sixteenth Century that the name was given by Dr. Gilbert, who made the discovery that amber is not the only substance that gives forth electricity when rubbed and that all substances may be attracted. Otto von Gueriche, burgomaster of Magdeburg, found out that he could excite a considerable quantity of electricity by turning a ball of sulphur between the bare hands and Sir Isaac Newton, by a slight improvement on this method, was able to create sparks several inches long. These were the most important discoveries in the field of electricity until the day of Franklin, when the American philosopher first put electricity to practical use in 1748 at a picnic by killing a turkey with the electric spark and roasting it by an electric jack before a fire kindled by means of a Leyden jar. But in these instances electricity did only that which could have been done as well and more economically by other means. Franklin announced his theory of a single fluid, terming vitreous electricity positive and resinous negative, in 1747, and in June, 1752, demonstrated the identity of the electric spark and lightning by drawing electricity from a cloud by a kite.

Such was the state of our knowledge of electricity in the very first year of the Century when Alexander Volta of Pavia, made public his device known as Volta's pile, from which have grown our present machines for the generation of electricity, though Volta's device was based upon Galvani's discovery. Galvani, a professor of anatomy in the University of Bologna, wished to tempt the appetite of his sick wife by making her some soup of frogs. He had skinned the batrachian and hung it on a copper hook so that, dangling, it hit an iron rail a little below. Galvani noticed that the casual contact caused a twitching in the dead frog's legs and in latter experiments produced the twitching by touching the nerve of the limb with a rod of zinc and the muscle with a rod of copper in contact with the zinc. The professor of anatomy thought that he had discovered the principle of life and built up on these experiments a theory that seems absurd now. He died in 1798 without knowing the renown that his frogs would win. Alessandra Volta, professor of physics in the University of Pavia, heard the story of the frogs and after investigation and experiment proved that the electricity was not in the animal, but was generated by the contact of the two dissimilar metals and the moisture of the flesh. His pile, given to the world in 1800, is the prototype of the modern battery. He arranged a series of bits of copper and zinc alternately, one above the other, but each bit of metal separated from its neighbor by a piece of cloth wet with dilute acid. The more bits of metal there were the stronger the current which could be produced. Since the day of Volta the voltaic cell and galvanic battery have been greatly improved, yet they remain essentially the same in principle and therefore science gives to Volta the credit of having made the greatest force in nature serviceable to man. The electrician has been taught his business by the voltaic cell, even if the voltaic cell has been largely sup-planted by other devices.

The next great step in the practical development of electricity was due to the discovery of H. C. Oersted, of Copenhagen, in 1819, of the action of the electric current on a magnetic needle and the relation between electricity and magnetism. Oersted found that if a magnet be moved near a piece of metal, preferably a coil of copper wire, a current of electricity is produced in the coil. Every electromagnet illustrates this discovery of Oersted's. Until you bring it very near or make it touch a steel magnet it is simply a piece of soft iron; then, for an instant, as the core becomes magnetic you excite electricity in the wire surrounding the electromagnet. You pay for that electric pulse in the forcible pull required to separate the electro-magnet and the steel magnet from each other. Replace this effort of the hand by the might of an engine with corresponding increase in the size and improvement in the form of the coil and your little experiment merges into building and driving a dynamo. Thus Oersted and his successors have made possible the dynamo.

Oersted's discovery owes much to the subsequent discoveries of Ampere and Faraday. Ampere exhibited the action of the voltaic pile on the magnetic needle and that of the terrestrial magnetism on the voltaic current. He also arranged the conducting wire in the form of a helix or spiral, invented a galvanometer and imitated the magnet by a spiral galvanic wire, in 182o. Two years later Faraday, who was a shop-assistant to Sir Humphrey Davy, explained electro-magnetic rotation. Working upon the discoveries of Oersted and Ampere he announced his discovery of induction which was announced in a series of papers read before the Royal Society of London. Faraday not only proved Oersted's investigation, but discovered magneto-electricity, its converse, by producing an electric spark by suddenly separating a coiled keeper from a permanent magnet and found an electric current in a copper disk rotated between the poles of a magnet. His brilliant experiments proved that the current developed by induction is the same in all its qualities with that of other currents and he demonstrated Franklin's theory that all electricity is the same; that there is but one kind.

Upon induction and its laws for the explanation of the principles of which we are indebted chiefly to Faraday, depend the simplest as well as the most complicated of our modern electrical appliances for a reason of action. Briefly explained, induction is the action which electrified bodies exert at a distance in a natural state. Faraday's and Ampere's spiral were the forerunners of the electric coil, which consists of two separate coils of insulated wire wound around a soft-iron core.

To give the barest summary of the developments step by step since that time would fill a volume, and so there is not space to allude to them here. The development of the telephone, telegraph and electric-light are sketched in other chapters, while many applications of electricity fall most naturally under the industry to which they are applied. Here will be given some account of the development of the electric motor and dynamo, together with the transmission of power and novel applications of electricity which do not fall properly under other divisions of this volume.

The germ of the electric motor is found in the invention of Joseph Henry, an American, who, though little known to the public, was one of the most prolific electrical inventors the world has seen. Many improvements were made by him in the magnet. Exhaustive research was made by him into the subject of the battery as a source of energy and the efficiency of the galvanic batteries, and in 1831 he constructed an electric motor, the first of the kind the world had ever known. In Henry's machine the current was actuated by a voltaic battery, but in the middle of the Century Moritz H. Jacobi, a German, found that a dynamo-electric machine can also work as a motor and that by coupling two dynamos in one circuit one as a generator and the other as a motor it was possible to transmit mechanical power by electricity. But how late a development the dynamo really is, can best be understood by the fact that the word is not mentioned in the latest English edition of the Encyclopedia Britannica the editions without the American supplement. There is some mention, however, of the magneto-electric machine of Gramme, made in 1870, which was the first to practically transmit power in the fashion in which it is used in nearly every town and civilized country today. During the past generation electricity has come to be universally recognized as the best way for the transmission of power, distributing steam, wind or water so as to bear upon any point desired. The most familiar application of this process is the electric light and the trolley line. Perhaps the first application of the electric motor, however, was about 1839, when Jacobi sailed an electric boat on the Neva with an electro-magnetic engine of one horse-power.

It is the dynamo, however, that has made possible the use of electricity for power. Cheapness is the factor that has led to this result, for the chemical way of obtaining electricity by the action of acids upon zinc was so costly that few people dreamed thirty years ago that electricity would ever become a rival to steam as a source of motive power. The first use of the word "Dynamo" was made by Siemens, who called his machine "dynamo-electric" the word dynamo being Greek for to be able and this expression contracted to the single word dynamo has since been universally employed. The modifications of the forms of and arrangements of the different dynamos that have been invented in recent years are endless, and every week new patents are granted for improvements to parts. On this account we shall not trace the history of the dynamo in great detail, nor shall we point out the difference between the various types. Instead, we shall briefly sketch a type of the dynamo as it is today, which will give the general principles of its action.

Originally the dynamo was a horseshoe magnet set on a shaft and made to revolve in front of two cores of soft iron wound round with wire and having their ends opposite the legs of a magnet. Then the magnet no longer was made to turn on a shaft, but on the lighter iron cores, and so today the huge field magnets of a modern dynamo are not made to turn around a stationary armature, but the armature is whirled around within the legs of the magnet with great rapidity. The number of magnets was increased, as was the number of wire-wound cores, while the magnets were gradually made compound, laminated. Siemens, of Berlin, in 1857, wound the iron core length-wise, with wire instead of round and round a spool, and then the shaft of the armature was placed cross-wise between the legs of the magnet, as in the modern dynamo. One of the ends of the wire used in this winding was fastened to the axle of the armature and the other to a ring insulated from the shaft, but turning with it. The cur-rent was carried away by wires attached to two springs, one bearing on the shaft and another on the ring. Siemens also originated the mechanical idea of hollowing out the legs of the magnet on the inside for the armature to turn in, close to the magnet, making it almost fit.

Alternating currents resulting because of induction, the commutator was then devised to cause the currents to flow in the same direction. The springs known as brushes were so arranged that their alternate action made the cur-rent carried away always direct. A machine in which a ring armature is used, doing away with the commutator, was then constructed by Pacinotti, of Florence, and it is extensively used for certain purposes.

The huge field magnet, which is really not a magnet at all, was made possible by the improvements of Wilde, of England, in 1866. He caused the current, after it had been rectified by the commutator, to return again to the coils of wire round the legs of his field magnets. This induced in them a new supply of magnetism and intensified the current from the armature. Step by step minor improvements followed, each inventor contributing his part to the perfection of the magnificent machine as we have it today. The machines are of various types and seem capable of but little further improvement, as there are dynamos in use to-day which give 92 per cent of a possible i00 per cent of their engine power. The engine which turns the dynamo, however, still wastes at least 90 per cent of the furnace heat.

The motor is the twin of the dynamo. If a dynamo in-stead of being driven by an engine and used to give a current, has a current from a separate source (as from another dynamo or from a battery) passed through it, its armature will revolve and the dynamo become a kind of electric engine capable of driving machinery. A dynamo when used in this manner is called an electro-motor or simply a motor. The difference between a motor and a dynamo has been well summarized in these words : It is the work of the dynamo to convert mechanical energy into the form of electrical energy; the motor in turn changes this electrical energy back again into mechanical energy.

No motor intervenes where the electric light is produced by the dynamo current. Some restriction upon the current converts the current into heat and light. The motor is always the intermediate machine when mechanical movements are to be produced by the current from the dynamo. The armature of the dynamo, rotated by steam or water power, produces electrical energy in the form of a mighty current, and this is transmitted over a wire. This current, reaching the motor, rotates the armature.

A new day has dawned in the workshop and factory by the introduction of the dynamo and electric motor. Availing himself of the fact that electricity is able to transmit power without any movement by the wire, the wilderness of whirling wheels and belts has been removed from the shops and a few wires have taken their place, each entering the electric motor which drives the separate ma-chine. The result is often an enormous saving of power that is required when steam or water is used direct to keep the multitude of needless pulleys and belts going. It was found once at the Waltham watch factory that three-quarters of the engine-power was absorbed by shafts and gearing without a single machine's being harnessed for duty.

And where one machine among many is to be set at work by itself, especially at a distance from the engine, the loss in the mechanical conveyance of power becomes inordinate, while the loss is almost entirely avoided by electrical transmission. The decrease in the weight of machinery and in vibration makes it possible to build the factory with thinner walls and to keep it cleaner and neater at all times.

A great step was made in the increased utilization of electricity when the problem of the transmission of power over long distances was solved. Now a current can not only be distributed through a workshop with the utmost convenience and economy, but it can be sent to a workshop from an engine or waterwheel many miles away. The Niagara Falls is yoked to the wheels and lamps of Buffalo. This in itself is typical of all the achievement of the Century, and is the crowning glory of electrical development.

The first experiments in this direction were made by Marcel Deprez at Creil in 1876 to 1886, and Deprez succeeded in transmitting mechanical power thirty-five miles for industrial purposes in the latter year. Many inventors busied themselves along these lines, and on February 3, 1892, Nikola Tesla, at the Royal Institution, exhibited his alternate-current motor, by which currents are trans-formed, by continually reversing the direction, into mechanical power. By means of Tesla's apparatus the force of 77 horse-power was transmitted from the rapids of the Neckar to Frankfort-on-Maine, 110 miles, September, 1891.

Possibilities of the utilization of waterfalls for the transmission of power electrically immediately attracted attention to the world's greatest waterfall, that of Niagara. At Niagara River and Falls, about 18,000,000 cubic feet of water flow per minute through a descent of more than 300 feet, including both falls and rapids; this represents something like 7,000,000 horse-power. Engineers had been aware that the enormous power which goes to waste over the Niagara was sufficient to turn the wheels of every factory in the United States, but there seemed to be no possibility of its utilization. While a few paper mills and flour mills had been established near there, the expense of the direct application of the power was too great to make the attempt desirable. But when dynamos had been perfected and electricity made commercially available, attention became attracted to the waste of power. Siemens, the great German inventor, in 1877 prophesied that a few more years would see the great water-courses like that of Niagara utilized in part to generate electricity and to transmit by its means electric light and power to surrounding industrial stations. It seemed a wild dream then, but before twenty years had passed it had been realized, and today the power of Niagara is turning machinery and running street cars in Buffalo, twenty-six miles away. Power from the falls has been used to operate machinery in New York, being thus employed at the electrical exposition.

When a waterfall is to be used for power the ordinary method is to dig a canal from a point above to a point below the waterfall, this canal being called a mill-race. The water in this canal is so directed as either to fall upon or to flow under a wheel, and the revolution of this wheel furnishes the motive power of the mill with whose machinery it is connected, by means of shafts and belts. ;Esthetic reasons alone would have prevented the employment of these means at Niagara, and would merely have resulted in building a canal which would be lined with mills. An entirely different method was proposed by Thomas Evershed, state engineer of New York, and his suggestion was adopted by the company. At a point about a mile above the falls, 1,200 acres of land were bought, and here a short canal was dug and an enormous pit, 140 feet in length, 18 feet in width and 178 feet deep was excavated. From the bottom of this pit a tunnel was also made to the river tunnel level some distance below the falls. This tunnel is 6,807 feet (over a mile and a quarter) in length, and it took a thousand men more than three years to dig it, even with the improved tunneling appliances of this generation. Enough limestone rock was dug out of the tunnel to make some twenty acres of new land worth $5,000 an acre along the shore of the Niagara, and the construction of the tunnel and main wheel pits cost twenty-seven lives. The tunnel is shaped like a horse shoe, being 18 feet 10 inches wide at its broadest part and 14 feet wide at the bottom. It is 21 feet high and has a downward pitch varying from 4 to 7 feet in 1,000. It is lined at the lower end with heavy steel plates, and the rest of the way with from four to six rings of brick, especially prepared to withstand the wear and tear of water for generations to come.

This tunnel is the "tail-race," as the millwright would call it. The water drawn from it, falls a distance of 154 feet to the bottom, where, by its fall, it may revolve ten enormous horizontal or turbine wheels. These in turn may revolve ten dynamos in the power-house above, each capable of furnishing 5,000 horse-power-only three of these turbines have as yet been built. The water having thus given its power to the company, which has transferred it into electricity, runs off through the tunnel and is discharged into the river below.

So far as the producing of water power is concerned, the only novel feature of the plan in operation at Niagara is the enormous size of the plant.

The turbine wheels, placed at the bottom of that mighty pit cut straight down for 200 feet into the solid rocks, are the monarchs of their kind. The force of the volume of water that each of the three now in place receives is so great that it would sweep away a considerable structure made as strong as man could build it with stone and masonry. Yet these turbines are so cunningly devised, and with such tough mingling of the strongest metals, that they will receive this prodigious blow only to turn with almost incredible swiftness upon their axles and thus communicate the force to the dynamos placed in position directly over them, although two hundred feet above. The dynamos are fitting mates for these mighty machines at the bottom of the pit, for they are not only said to be the largest of their kind, but they will, with the swiftness of the lightning's stroke, convert the force created by the water power upon the distant turbines.

The size of these turbines and dynamos will be better appreciated by comparison. The largest turbines ever constructed before these were built were of 1,100 horse-power each, and the largest dynamo was said to be that which generated 2,100 horse-power in the Intramural Electric Railway's power-house at the World's Columbian Exposition.

The armature of the dynamo is set so that its axis is perpendicular instead of horizontal, and with its cover it surmounts the pit like a huge cap. In front of each dynamo, stands a governor, an interesting and complicated mechanism in itself, which controls the movement of the big cylinder. Behind the dynamos, on a raised platform in the center of the dynamo room is the switch-board arrangement, where the mighty current from these great machines is received and sent out in whatever direction it may be required.

In generating the current use is made of what is called the Tesla polyphase alternating current system. Each generator delivers an alternating current to each of the two circuits. Being 180 degrees apart, each current attains its maximum when the other is at zero, and 3,000 times each minute the current is reversed. Heavy insulated cables convey the current thus produced to the switch-board, where other heavy lead-covered cables carry the current through a subway to the transforming house, a small structure on the other side of the canal. Wires intended for nearby consumers enter the conduit here, but the current for use in Buffalo is converted into one of r 1,000 voltage for transmission and is ready for its journey.

Heavy wires of bare copper strung on poles, with porcelain as insulators, transport the current to Buffalo. When the current reaches Buffalo it is again passed through transformers which lower the pressure to 370 volts. As the current at present is used to operate street railways it must be changed from alternating to direct currents. Machines, known as rotary converters, are employed for this work, and they change the 370 volts alternating current to 500 volts direct current, and it is then ready to operate the cars.

While the plant of the Niagara Falls Power Company was completed on March 23, 1895, the power was not used in Buffalo until November 16, 1896, when the company began the supplying of 1,000 horse-power of electrical energy for the running of the street railways in Buffalo; and now the citizen of Buffalo, gazing at the great falls, can realize the fact that it is the slave that carries him in his journeys about the city.

In time it is expected that the power at Niagara can be used to run machinery in New York and Chicago.

Nikola Tesla, whose polyphase alternating current system made possible the transmission for twenty-six miles, is at work about the problem, and there is every possibility of its success. For the present it has been shown that power may be transported from Niagara Falls to New York; for in May, 1896, about one-thirtieth of a horse-power was transmitted to the Electrical Exposition in New York City, the current being used to operate a two-phase alternating current motor, which operated a working model of the Niagara Falls Power Company's plant. The current was carried on two of the Western Union Telegraph Company's wires. This is the longest distance that an electrical current has ever been transmitted. The waste of the current makes its use on an extensive scale impractical, but the problem will be solved in the near future, in the opinion of all electricians. And when that time comes the whole of Niagara's great power may be utilized. What the use of this 7,000,000 horse-power will mean is told in a striking manner by C. F. Scott, of the Westinghouse Company. He says :

"Suppose pumps be placed below the fall for pumping the water up again to its former level. If a man exerts a force of about twenty pounds per stroke and works at a fair rate for eight hours per day, it would take about ten times the total population of the United States to pump the water back as fast as it is flowing over the falls. Consider for a moment what that means. If 70,000,000 of us were engaged in manual labor, all the work that we could do could be accomplished ten times over by the power now going to waste. All the work of laborers; all our actual exertions in digging, hammering, lifting, climbing stairs, running sewing machines, or riding bicycles, do not represent the one-hundredth part of this stupendous power."

Long-distance transmission of power is not confined to Niagara Falls. The water-courses of the United States are rapidly being made use of in this manner. The state in which are the largest number of long-distance transmission plants is California, which is especially favored by its natural topography for the development of electricity by water power. At Bodie, Cal., the current is transmitted thirty miles, and at Sacramento, Cal., 3,000 horse-power is transmitted twenty miles.

Utilization of water-power on a small scale, as well as by taking advantage of the greater waterfalls, has made possible a vast increase in the use of electric power. Electricity is now being developed from water power as cheaply as steam power can be made from coal. Some-times it is cheaper, and wherever the cost is about the same, the cleanliness of electricity and the absence of pulleys make it favored. There is also the advantage that the difference in first cost is in favor of electricity when the power is rented. In large cities and many towns electricity is therefore coming in greater use for running machinery. It is used to a great extent for traveling cranes, derricks and other heavy machinery. Most of the big newspapers and other establishments, where there is no necessity for a foundry, are gradually adopting electricity. Another application that is quite common is to electric elevators. It is said that in New York and Chicago as many people travel perpendicularly as travel horizontally; and however this may be, the elevator industry is very large, and electricity has become the favorite method of propelling elevators so general, in fact, that it seems almost incredible that the very first use of electric current for power purposes was upon a freight elevator in New York in 1882.

The problem of the electrician now is to obtain electricity direct from coal. While the dynamos of the best design give forth in the form of electricity 92 per cent of their engine's power, yet the engine which turns the dynamo wastes, as has been said, at best 90 per cent of the furnace heat, and does little better when steam is used without the intervention of the dynamo. Although great increase has been made in the obtaining of larger energy from steam-engines, it seems possible that but little further progress can be made in this direction, and electricians look to electricity as the method by means of which all, or the greater part, of the energy stored in coal may be conserved. The problem is being attacked from two sides one the thermo-electric on the principle of the thermoelectric couple. Edison has made some experiments, and one apparatus devised by him had as its operative feature the magnetization and demagnetization of iron by rapid alternations of temperature. Tesla is reported to have nearly perfected an invention along these lines, but he is not likely to make it public until it is ready for use. From the chemical side the problem has been attacked by Dr. W. Borchers, of Duisburg, Germany, who in a paper read before the German Electro-Chemical Society, announced that the problem of cold combustion of the gaseous products of coal and oil in a gas battery, and its direct conversion into electrical energy, can certainly be solved. The brains of many electricians are busy with these ideas, and there is a possibility that a few years may see the utilization of coal without the wasteful intervention of the steam engine.

Tesla's oscillator, which was exhibited at the World's Columbian Exposition, is a step in this direction. It makes the steam-cylinder operate the dynamo without the intervention of any other mechanism. The one exhibited was merely a steam chest, disassociated from the usual governing mechanism, that thrusts armatures into the fields of a force of an electro-magnetic coil. The invention is as yet in an imperfect state.

The storage battery-miscalled, for it is really not an attempt to store electricity is as yet in its infancy. It is really a secondary battery, the principle of its action being the decomposing of combined chemicals, by the action of a current applied from a stationary generator or dynamo, and these currents again unite as soon as they are allowed to do so by the completing of a circuit, and in recombining give off nearly as much electricity as was first used in separating them. Leaden plates, one cleaned and the other fouled by the action of a current, are the basis of the secondary battery. The expense and inconvenience of the arrangement has prevented its wide utilization, although it is used on some street railway lines and as a means of propulsion for motor carriages.

Electricity has been put to a number of minor uses. The electric bell, now in common use, was invented by John Mirand in 1850. On pressing a button, spring contact is made and the current flowing through the circuit strikes the bell. It has been improved so that the bells are serviceable as alarms in many ways. An undue rise in temperature may melt a piece of fusible metal and warn the proprietor of fire. Safes and show-cases as well as doors may be made to signal by a red light the fact that they have been burglarized. A thief was once photographed by a flashlight kindled in this way, and the likeness thus secured brought about his capture. The announcing of the entry of burglars into a house is of course an easy matter.

Electric clocks are familiar in every city or large town. Electric magnets are placed behind the dials, and, by means of an armature working at a frame and ratchet wheel as the current is sent from the standard clock, move the hands forward every minute or half minute.

The phonograph, which is startling, but has not as yet been made of great commercial use, is one of the most interesting of electrical devices, as it stores and reproduces speech. Edison announced his invention in 1878, and the instrument succeeded so well that a member of the Academy of Sciences at Paris declared that it was a, mere ventriloquist's trick. The phonograph, as perfected, is simple in its construction. Every vibration of the diaphragm causes a stylus at its end to make a corresponding mark on a cylinder which is set in operation. After the record is made the sounds are reproduced as the stylus again travels over the indentions. Aside from its use as an amusement, the phonograph is chiefly useful as a means of dictation, the words being repeated in the ear of a type-writer operator at whatever speed may be desired. It is also used to teach pronunciation, and will be invaluable in preserving exact records of the speech of the present and the voices of great singers for future ages.

So many and varied are the uses of electricity that it enters into every science, and many of these applications are mentioned in this volume under the heads of those general subjects. To barely enumerate these devices would require a volume. The induction balance has been used as a sonometer, or machine for measuring hearing, and the bottom of the sea has been explored by sonometers for sunken treasure. Leaks in water-pipes have been localized by the microphone, and the story is told of a Russian woman who was saved from premature burial because the microphone made audible her feeble heart-beats. The peculiar sensitiveness of electricity makes it a means of surpassing delicacy in measuring heat, light or chemical action. By the bolometer, invented by Prof.

S. P. Langley, a change of temperature of one-millionth of a degree Fahrenheit has been recorded, a refinement scarcely approached by any other means of scientific detection.

The automatic devices are endless. It is used for every purpose, and indeed the system of electrocution made use of in New York as a means of capital punishment makes it possible for a man to die by electricity as well as to live with its aid.

It is said that while much progress has been made during the Century in the application of electricity, men are still ignorant as to what it is. As a matter of fact, the' principles of electric action are known. We know that electricity will induce magnetic force and magnetic force will generate electricity; that electricity will induce chemical action and chemical action will induce electricity; that electricity will generate heat and heat will generate electricity; that electricity will develop light and light will generate electricity. We also know the conditions under which these actions take place and the relations between the cause and effect.

Because man does not know why electricity will make a motor revolve and give off power, he thinks we do not know much about electricity. It is possible to know what a natural phenomenon will do, and yet not know what it is. Consider for an instant the steam engine, and if you trace back to the primary cause of its motion you will find that we know nothing of the true nature of that cause. We know that heat gives steam an expansive force, but we do not know why. No one knows why heat expands matter. Although there are theories, no one knows what heat is.

So physicists, during the Century, have found out what electricity is, just as they have found out what sound, heat and light are. They are alike in some respects. They are all vibrations of that subtle and all-pervading medium which pervades the universe and is known as the ether. Young and Fresnel have shown that space is filled with luminiferous ether of which very little is known except the mathematical conditions under which waves are propagated in it. Clark-Maxwell, by the extension of the mathematical theory of light, has shown that light and electricity are of exactly the same nature, and Hertz, the German physicist, by his experiments, demonstrated the truth of this, independently of mathematical theory. Light and electric vibration have been shown to be one and the same thing, differing only in the lengths of the vibrations. The reason why we do not wonder what light, heat and sound are is not that we know, but that we are so familiar with them from our birth that we do not stop to wonder. We know what electricity is in the sense that we know what light, heat, and sound are, and in that respect only.

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