Messages from the Executive Mansion at Washington to the battlefield at Santiago were sent and responses received within twelve minutes, while a message dispatched from the House of Representatives in Washington to the House of Parliament in London, in the chess match of 1898, was transmitted and a reply received in thirteen and one-half seconds.

To-day the cable with the still small voice, more divine than human, speaks with one accent to all the nations of the earth. Differing though they may in tongue and skin, in thought and religion, in physical development and clime, the telegraph speaks to them all alike, and by all is understood. Truly it fulfils the prophecy so gracefully expressed in the verses quoted, and has become the common bond of union among the nations of the earth.

CHAPTER V.

THE DYNAMO AND ITS APPLICATIONS.

OBSERVATIONS OF FARADAY AND HENRY--MAGNETO-ELECTRIC MACHINES OF PIXII AND OF SAXTON--HJORTH'S DYNAMO OF 1855--WILDE'S MACHINE OF 1866--SIEMENS' OF 1867--GRAMME'S OF 1870--TESLA'S POLYPHASE CURRENTS.

In the last thirty-five years of the Nineteenth Century there has grown up into the full stature of mechanical majority this stalwart son of electrical lineage. As the means for furnishing electrical power it stands to-day the great fountain head of electrical generation, and in its peculiar field ranks as of equal importance with the steam engine.

Until about 1865 the voltaic battery, which generated electricity by chemical decomposition, was practically the only means for producing electricity for industrial and commercial purposes. It was through its agency that the telegraph, the electric light, and many other discoveries in electricity were made and rendered possible. Its cost and limited amount of current, however, restricted the limits of its practical application, and although its current could furnish beautiful laboratory experiments, its mechanical work was more in the nature of ill.u.s.tration than utilization. But with the advent of the dynamo electricity has taken a new and very much larger place in the commercial activities of the world. It runs and warms our cars, it furnishes our light, it plates our metals, it runs our elevators, it electrocutes our criminals; and a thousand other things it performs for us with secrecy and dispatch in its silent and forceful way. But what is a dynamo? To the average mind the most satisfactory answer would be--that it is simply a machine which converts mechanical power into electricity.

Attach a dynamo to a steam engine, and the power of the steam engine will, through the dynamo, become transformed or converted into a powerful electric current. Any other source of mechanical power, such as a water wheel, gas engine, wind wheel, or even a horse or man, will serve to operate the dynamo; its primary and sole function being to take power and convert it into electricity.

The stepping stone to the dynamo in its development was the _magneto-electrical machine_. This is a machine founded upon the general principle observed by Faraday in 1831 and 1832, and also by Prof. Henry about the same time, that when a magnet is made to approach a helix of insulated wire it causes a current of electricity to flow in the helix as long as the magnet advances. If the magnet is pa.s.sed through the helix, the current is reversed as soon as the magnet pa.s.ses the middle point. The principle is the same if the magnet be made to approach and recede from the poles of an electro-magnet having a helix wound around a soft iron core. Likewise the same result occurs if the electro-magnet with its helix is made to approach and recede from a permanent magnet, the current in the helix flowing in one direction when it approaches the permanent magnet, and in the opposite direction when leaving the said magnet. The movement of the two elements in relation to each other requires some force to overcome the repellent and attractive actions, and this force is converted into electrical energy. This is the principle of the magneto-electric machine.

[Ill.u.s.tration: FIG. 17.--PIXII MAGNETO-ELECTRIC MACHINE, 1832.]

Saxton in the United States and Pixii in France were the first to produce organized devices of this cla.s.s for generating electricity from magnetism. Pixii's machine (1832) consisted of a permanent horse-shoe magnet which was caused to revolve in proximity to an armature upon which was wound a coil of insulated wire. On March 30, 1852, Sonnenberg and Rechten obtained a United States patent, No. 8,843, for an electrical machine for killing whales, and on August 19, 1856, Shepard obtained U. S. Pat. No. 15,596 for the machine which came to be known as the "Alliance" machine. Both of these machines had permanent field magnets, and were early types of magneto-electric machines. The efficiency of these magneto-electric machines was necessarily limited to the strength of the inducing field magnets, which, being permanent magnets, were a positive and fixed factor. It was an easy step to subst.i.tute electro-magnets for permanent magnets, as the field or inducing magnets, and also to excite the (electro) field magnet by voltaic batteries, but the important step which resulted in the machine which is called the "dynamo" (from the Greek "???a??"--power) was yet to come.

[Ill.u.s.tration: FIG. 18.--HJORTH'S DYNAMO ELECTRIC MACHINE.]

[Ill.u.s.tration: FIG. 19.--HJORTH'S DYNAMO ELECTRIC MACHINE, PLAN VIEW.]

This step consisted in taking the current induced in the revolving helix or armature (by the field magnets) and sending it back through the coils of the field magnets which produced it, thereby increasing the energy of the field magnet coils, and they in turn with an increased efficiency and reciprocal action induce still stronger currents in the armature coils, and so a building up process, or principle of mutual and reciprocal excitation, is carried on until the maximum efficiency is reached. This principle was the discovery of Soren Hjorth, of Copenhagen, and is fully described in his British patent, No. 806 of 1855, for "An Improved Magneto-Electric Battery." As the prototype of the dynamo, it is worthy of ill.u.s.tration. In the ill.u.s.tration, Figs. 18 and 19, _a_ is a revolving wheel bearing the armature coils, _C_ permanent magnets, _d_ electro-magnets (field magnets), and _g_ the commutator. Quoting from his specifications, he says: "The permanent magnets acting on the armatures brought in succession between their poles, induce a current in the coils of the armatures, which current, after having been caused by the commutator to flow in one direction, pa.s.ses round the electro-magnets (field magnets), charging the same and acting on the armatures. By the mutual action between the electro-magnets and the armatures an accelerating force is obtained, which in result produces electricity greater in quant.i.ty and intensity than has heretofore been obtained by similar means."

Although the principle of the dynamo was clearly embodied in the Hjorth patent, its value was not appreciated until some time later. Eleven years later Wilde (U. S. Pat. No. 59,738, Nov. 13, 1866), employed a small machine with permanent magnets to excite the coil-wound field magnets of a larger machine. But Siemens (British Pat. No. 261 of 1867), taking up the principle employed by Hjorth, dispensed with his superfluous permanent magnets, having found that the residual magnetism, which always remained in iron which has once been magnetized, was sufficient as a basis to start the building up process. Farmer, Wheatstone and Varley also recognized this fact about the same time.

Siemens' patent also was the first embodiment of what is known as the bobbin armature. Gramme and D'Ivernois (British Pat. 1,668 of 1870, and U. S. Pat. No. 120,057, of Oct. 17, 1871), were the first to bring out the continuously wound ring armature.

Active development now began in various types and by various inventors, including Weston, Brush, Edison, Thomson and Houston, Westinghouse, and others, who have brought the dynamo to its present high efficiency.

The revolving coils of the dynamo are called the armature, and the fixed electro-magnets are called the field magnets, and these latter may be two or more in number. When two are used they are arranged on opposite sides of the armature, and form what is known as the bipolar machine. A larger number const.i.tutes the multipolar machine. The field magnets in the multipolar machine usually are arranged in radial position around the entire circ.u.mference of the revolving armature, and are held in a fixed circular frame. To give a clear idea of the principles of the dynamo, the bipolar machine is best suited for ill.u.s.tration, and is here given in Figs. 20 and 21, in which Fig. 20 represents the dynamo complete, and Fig. 21 a detail of the end of the armature and commutator. This armature consists of coils or bobbins of insulated wire, each section having its terminals connected with separate insulated plates on the hub, which plates are known as the commutator.

When any section of the armature approaches the pole of a field magnet, the current induced in that section of the armature coils by the field magnet, is taken off from a corresponding plate of the commutator by flat springs, seen in Fig. 20, and known as brushes. The field magnets A and B, Fig. 20, are shown with only a few turns of wire about them for clearer ill.u.s.trations of the connections, which are made as follows: The wire _a_ is extended in coils around the field magnet B, and thence around field magnet A, and thence to the upper brush on the commutator, thence through the wire coils or bobbins of the rotary armature C, and thence by the lower brush to the wire _b_. The terminals of the wires _a_ and _b_ extend to the point of utilization of the current, whether this be electric lights, motors, or other applications. In this ill.u.s.tration, the circuit, it will be seen, pa.s.ses through both the coils of the field magnets and the coils of the armature, involving the principle of mutual excitation.

[Ill.u.s.tration: FIG. 20.--BIPOLAR DYNAMO.]

There are two princ.i.p.al kinds of dynamos--those producing the alternating currents, and those producing the continuous current. In the first the current alternates in direction, or is composed of an infinite number of impulses of opposite polarity: one polarity when a section of the armature coil is approaching a north field magnet pole or receding from a south pole, and the other polarity when receding from a north field magnet pole and approaching a south pole. In the continuous current machine, the commutator and brushes are so arranged as to take up all the impulses of the same polarity and conduct them away by one brush, and gathering all the impulses of the opposite polarity and conducting them away by another brush. Thus the current of each brush, in the continuous current machine, is always of the same polarity, and the polarity of one being always positive, and that of the other negative, the current flows continuously in the same direction. A third species of dynamo is the pulsatory, in which the current flow is invariable in direction, but proceeds in waves.

[Ill.u.s.tration: FIG. 21.--ARMATURE OF BIPOLAR DYNAMO.]

A change in the character of the current generated by the dynamo is made by what is known as the "transformer," in which the principle of the induction coil is made available. In this way, for instance, the high potential currents generated by the powerful water wheels at Niagara Falls are taken twenty miles to Buffalo, and are there transformed into other currents of lower potential, suited to incandescent lighting and other various uses. A similar scheme is in process of fulfillment in the establishment of a water power electric plant near Conowingo, Maryland, on the Susquehanna River, to furnish electrical power to Baltimore, Wilmington and Philadelphia.

An important development in electrical generation and transmission is to be found in what is known as the _polyphase_, _multiphase_, or _rotating_ current, pioneer patents for which were granted to Tesla May 1, 1888, Nos. 381,968, 381,969, 382,279, 382,280, 382,281 and 382,282.

Realizing the possibilities of the dynamo, the Legislature of New York in 1888 pa.s.sed a law, which went into effect in 1889, in that State, subst.i.tuting death by electricity for the hangman's noose. The criminal is strapped in the chair, seen in Fig. 22, one terminal of the wire from the dynamo is strapped upon his forehead, and the other to anklets on his legs, and like a flash of lightning the deadly energy of the dynamo performs its work.

Not the least of the applications of the dynamo is its use in electro-metallurgy for plating metals, and also for promoting chemical reactions. The electric furnace, stimulated into higher heat by the dynamo than can be otherwise obtained, has brought about many valuable discoveries, and made great advances in various arts. The metal aluminum, and the hard abrasive or polishing and grinding material known as "carborundum" are the products of the electric furnace, and so is the product known as "calcium carbide," which, when immersed in water, gives off acetylene gas and is a product now universally used for that purpose, and rapidly increasing in commercial importance.

[Ill.u.s.tration: FIG. 22.--ELECTROCUTION CHAIR.]

In Fig. 23 is seen the Acheson electric furnace for producing carborundum. The electric current traverses the furnace through a series of horizontal electrodes at each end, and highly heats a central core of carbon, which is disposed in a ma.s.s of silicious and carbonaceous material, and which latter is converted by the heat into silicide of carbon, or carborundum. In Fig. 24 is shown a continuous electric furnace constructed as a revolving wheel, under the Bradley patents. Rim sections 5 are placed on the wheel on one side and filled with a mixture of carbon and lime, through which the electric current is pa.s.sed from the dynamo _g_. The heat of the current fuses the ma.s.s and converts it into calcium carbide, and as the wheel slowly revolves the rim sections 5 are removed from the opposite side, and the ma.s.s of calcium carbide, seen at _x_, is broken off. The electrolytic production of copper through the agency of the dynamo amounts to 150,000 tons annually, and the commercial reduction of aluminum by the electric furnace has grown from eighty-three pounds in 1883 to 5,200,000 pounds in 1898, and its cost has been reduced to about 33 cents per pound.

[Ill.u.s.tration: FIG. 23.--PART SECTIONAL VIEW OF CARBORUNDUM FURNACE.]

The storage battery, holding in reserve its stored up electric energy, also owes its practical value entirely to the dynamo which charges it, and thus makes available a portable source of supply.

[Ill.u.s.tration: FIG. 24.--BRADLEY ELECTRIC FURNACE FOR PRODUCING CALCIUM CARBIDE.]

To contemplate the dynamo with its clumsy, enormous spools, it suggests to the imagination of the average observer the gigantic toy of some Brobdingnagian boy--but the dynamo is no toy. It is the most compact, business-like, and dangerous of all utilitarian devices. To touch its brushes may be instant death, for the dynamo is the prison house of the lightning, and resents intrusion. Hidden away from public gaze in some sequestered power house, and working night and day like some tireless, dumb, and mighty genii, it sends its magnetic thrills of force silently through the many miles of wire extending like radii from some great nerve center through the conduits in our streets, and stretching from pole to pole like giant cobwebs through the air. Responding to its force, thousands of little incandescent threads leap into radiant brightness and shed their mellow and genial light in our offices, our stores, hotels, and homes. Brilliant arc lamps, rivaling the sun in power, make night into day, and produce along our streets coruscations, silhouettes, and dancing shadows in spectacular and unceasing pageants.

From the towering lighthouses of our coasts its beams are thrown seaward, and a beacon for the mariner shines beyond all other lights.

The great search light of our ships is in itself but a hollow mockery until the dynamo whispers in its ear the word "light!" and then its beam, reaching for miles along the horizon, discovers a stealthy enemy, or signals the safe return to port. The mighty force of the dynamo entering the electric motors on the street cars turns the wheels and transports its load with scarcely a pa.s.senger inside realizing how it is all done. The same energy turns the electric fan, and with kindly service soothes the weary sufferer, and at another place remorselessly takes the life of the condemned criminal. The dynamo is one of the great factors of modern civilization, and its potential name, like that of "dynamite," rightly defines its character.

[Ill.u.s.tration: FIG. 25.--MODERN MULTIPOLAR DYNAMO.]

CHAPTER VI.

THE ELECTRIC MOTOR.

BARLOW'S SPUR WHEEL--DAL NEGRO'S ELECTRIC PENDULUM--PROF. HENRY'S ELECTRIC MOTOR--JACOBI'S ELECTRIC BOAT--DAVENPORT'S MOTOR--THE NEFF MOTOR--DR. PAGE'S ELECTRIC LOCOMOTIVE--DR. SIEMENS' FIRST ELECTRIC RAILWAY AT BERLIN, 1879--FIRST ELECTRIC RAILWAY IN UNITED STATES, BETWEEN BALTIMORE AND HAMPDEN, 1885--THIRD RAIL SYSTEM--STATISTICS ELECTRIC RAILWAYS AND GENERAL ELECTRIC CO.--DISTRIBUTION ELECTRIC CURRENT IN PRINc.i.p.aL CITIES.

Although the electric motor of to-day depends for practical value entirely upon the dynamo which supplies it with electric power, nevertheless the motor considerably antedated the dynamo. The genesis of the electric motor began in 1821 with Faraday's observation of the phenomenon of the conversion of an electric current into mechanical motion. In his experiment a copper wire was supported in a vertical position so as to dip into a cup of mercury, while a small bar magnet was anch.o.r.ed at one end by a thread to the bottom of the cup and floated in the mercury in upright position. The ma.s.s of mercury being connected to one pole of a battery, and the vertical wire to the other, it was found that when the circuit was completed by clipping the wire into the mercury, the floating bar magnet would revolve around the wire as a center.

[Ill.u.s.tration: FIG. 26.--BARLOW'S WHEEL.]

In 1826 Barlow, of Woolwich, made his electrical spur wheel, Fig. 26, and in 1830 the Abbe Dal Negro, in Padua, is said to have constructed a sort of vibrating electrical pendulum, both of which devices were crude forms of magnetic engines. Dal Negro's machine, see Fig. 27, consisted of a magnet A, movable about an axis situated about one-third of its length, and the upper extremity of which was capable of oscillating between the two branches of an electro-magnet E. A current being sent into the electro-magnet, pa.s.sed through an eight-cupped mercurial commutator C, which the oscillating magnet controlled by means of a rod _t_ and a fork F. When the magnet had been attracted toward one of the poles of the electro-magnet this very motion of attraction acting upon the commutator changed the direction of the current, and the magnet was repelled toward the other branch of the electro-magnet, and so on.

[Ill.u.s.tration: FIG. 27.--DAL NEGRO'S ELECTRIC MOTOR.]

In 1828 Prof. Joseph Henry produced his energetic electro-magnets sustaining weights of some thousands of pounds, and gave prophetic suggestion of the possibilities of electricity as a motive power. In 1831 he devised the electric motor shown in Fig. 28, which is described in Prof. Henry's own words as follows:

"A B is the horizontal magnet, about seven inches long, and movable on an axis at the center; its two extremities when placed in a horizontal line are about one inch from the north poles of the upright magnets C and D. G and F are two large tumblers containing diluted acid, in each of which is immersed a plate of zinc surrounded with copper; _l m s t_ are four bra.s.s thimbles soldered to the zinc and copper of the batteries and filled with mercury.

"The galvanic magnet A B is wound with three strands of copper bell wire, each about twenty-five feet long; the similar ends of these are twisted together so as to form two stiff wires _q r_, which project beyond the extremity B, and dip into the thimbles _s t_.

[Ill.u.s.tration: FIG. 28.--PROF. HENRY'S ELECTRIC MOTOR.]

"To the wires _q r_ two other wires are soldered so as to project in an opposite direction, and dip into the thimbles _l m_. The wires of the galvanic magnet have thus, as it were, four projecting ends; and by inspecting the figure it will be seen that the extremity _p_, which dips into the cup _m_, attached to the copper of the battery in G, corresponds to the extremity _r_ which dips into the cup _t_, connecting, with the zinc in battery F. When the batteries are in action, if the end B is depressed until _q r_ dips into the cups _s t_, A B instantly becomes a powerful magnet, having its north pole at B; this, of course, is repelled by the north pole D, while at the same time it is attracted by C; the position is consequently changed, and _o p_ comes in contact with the mercury in _l m_; as soon as the communication is formed, the poles are reversed, and the position again changed. If the tumblers be filled with strong diluted acid, the motion is at first very rapid and powerful, but it soon almost entirely ceases. By partially filling the tumblers with weak acid, and occasionally adding a small quant.i.ty of fresh acid, a uniform motion, at the rate of seventy-five vibrations in a minute, has been kept up for more than an hour; with a large battery and very weak acid the motion might be continued for an indefinite length of time."

Following Prof. Henry came Sturgeon's rotary motor of 1832, Jacobi's rotary motor of 1834, Fig. 29, which had electro-magnets both in the field and armature; Davenport's motor of 1834, Zabriskie's motor of 1837, in which a vibrating magnet converted reciprocating into rotary motion; Davenport's motor of 1837 (U. S. Pat. No. 132, Feb. 25, 1837), Fig. 30; Page's rotary motor of 1838, Walkley's motor of 1838 (U. S.

Pat. No. 809, June 27, 1838); Stimson's motor of 1838 (U. S. Pat. No.

910, Sept. 12, 1838); Page's motor of 1839, Cook's of 1840 (U. S. Pat.

No. 1,735, Aug. 25, 1840); Elias' motor of 1842, invented in Holland; Lillie's motor of 1850 (U S. Pat. No. 7,287, April 16, 1850); the Neff motor of 1851 (U. S. Pat. No. 7,889, Jan. 7, 1851), of which ill.u.s.tration is given in Fig. 31, and Page's motor of 1854 (U. S. Pat.