CHAPTER VIII.
ENGINEERING AND TRANSPORTATION.
The field of service of a civil engineer has thus been eloquently stated by a recent writer in Chambers’s Journal:
“His duties call upon him to devise the means for surmounting obstacles of the most formidable kind. He has to work in the water, over the water, and under the water; to cause streams to flow; to check them from overflowing; to raise water to a great height; to build docks and walls that will bear the dashing of waves; to convert dry land into harbours, and low water shores into dry land; to construct lighthouses on lonely rocks; to build lofty aqueducts for the conveyance of water, and viaducts, for the conveyance of railway trains; to burrow into the bowels of the earth with tunnels, shafts, pits and mines; to span torrents and ravines with bridges; to construct chimneys that rival the loftiest spires and pyramids in height; to climb mountains with roads and railways; to sink wells to vast depths in search of water. By untiring patience, skill, energy and invention, he produces in these several ways works which certainly rank among the marvels of human power.”
The pyramids of Egypt, the roads, bridges and aqueducts built by the Chinese and by Rome; the great bridges of the Middle Ages, and especially those built by that strange fraternal order known as the “Brothers of the Bridge”; the ocean-defying lighthouses of a later period—these, and more than these, attest the fact that there were great engineers before the nineteenth century.
But the engineering of to-day is the hand-maid of all the Sciences; and as they each have advanced during the century beyond all that was imagined, or dreamed of as possible in former times, so have the labours of engineering correspondingly multiplied. No longer are such labours classified and grouped in one field, called Civil Engineering, but they have been necessarily divided into great additional new and independent fields, known as Steam Engineering, Mining Engineering, Hydraulic Engineering, Electrical Engineering and Marine Engineering. Within each of these fields are assembled innumerable appliances which are the offspring of the inventive genius of the century just closed.
We have seen how one discovery, or the development of a certain art, brings in its train and often necessitates other inventions and discoveries. The development and dedication of the steam engine to the transportation of goods and men called for improvements in the roads and rails on which the engine and its load were to travel, and this demand brought forth those modern railway bridges which are the finest examples in the art of bridge making that the world has ever seen.
The greatest bridges of former ages were built of stone and solid masonry. Now iron and steel have been substituted, and these light but substantial frameworks span wide rivers and deep ravines with almost the same speed and gracefulness that the spider spins his silken web from limb to limb. These, too, waited for their construction on that next turn in the wheel of evolution, which brought better processes in the making of iron and steel, and better tools and appliances for working metals, and in handling vast and heavy bodies.
The first arched iron bridge was over the Severn at Coalbrookdale, England, erected by Abraham Darby in 1777. In 1793 one was erected by Telford at Buildwas, and in the same year Burden completed an arch across the weir at Sunderland. The most prominent classes of bridges in which the highest inventive and constructive genius of the engineers of the century are illustrated are known as the suspension, the tubular and the tubular arch, the truss and cantilever.
Suspension bridges consisting of twisted vines, of iron chains, or of bamboo, or cane, or of ropes, have been known in different parts of the world from time immemorial, but they bear only a primitive and suggestive resemblance to the great iron cable bridges of the nineteenth century. The first notable structure of this kind was constructed by Sir Samuel Brown, across the Tweed at Berwick, England, in 1819. Brown was born in London in 1776 and died in 1852. He entered the navy at the age of 18, was made commander in 1811, and retired as captain in 1842. We have alluded to the spider’s web, and Smiles, in his Self Help, relates as an example of intelligent observation that while Capt Brown was occupied in studying the character of bridges with the view of constructing one of a cheap description to be thrown across the Tweed, near which he lived, he was walking in his garden one dewy autumn morning when he saw a tiny spider’s web suspended across his path. The idea immediately occurred to him of a bridge of iron wires. In 1829 Brown also was the engineer for suspension bridges built over the Esk at Montrose and over the Thames at Hammersmith. Before that time, a span in a bridge of 100 feet was considered remarkably long. Suspension bridges are best adapted for long spans, and have been constructed with spans more than twice as long as any other form. Sir Samuel Brown’s bridge had a span of 449 feet. This class of bridges is usually constructed with chains or cables passing over towers, with the roadway suspended beneath. The ends of the chains or cables are securely anchored. The cables are then passed over towers, on which they are supported in movable saddles, so that the towers are not overthrown by the strain on the cables. Nice calculations have to be made as to the tension to be placed on the cables, the allowance for deflection, and the equal distribution of weight. The floor-way in the earlier bridges of this type was supported by means of a series of equidistant vertical rods, and was lacking stiffness, but this was remedied by trussing the road bed, using inclined stays extending from the towers and partially supporting the roadway for some distance out from the tower.
The next finest suspension bridge was constructed by Thomas Telford and finished in 1826, across the Menai Strait to connect the island of Anglesea with the mainland of Wales. Telford was born in Dumfriesshire, Scotland, in 1757, and died in Westminster in 1834. Beginning life as a stone mason, he rose by his own industry to be a master among architects and a prince among builders of iron bridges, aqueducts, canals, tunnels, harbours and docks.
The Menai bridge was composed of chains or wire ropes, each nearly a third of a mile in length, and which descended 60 feet into sloping pits or drifts, where they were screwed to cast-iron frames embedded in the rocks. The span of the suspended central arch was 560 feet, and the platform was 100 feet above high water. Seven stone arches of 52½ feet span make up the rest of the bridge.
But a suspension bridge was completed in 1834 by M. Challey of Lyon over the Saane at Fribourg, Switzerland, which greatly surpassed the Menai bridge. The span is 880 feet from pier to pier, and the roadway is 167 feet above the river. It is supported by four iron wire cables, each consisting of 1056 wires. It was tested by placing 15 pieces of artillery, drawn by 50 horses and accompanied by 300 men crowded together as closely as possible, first at the centre, and then at each extreme, causing a depression of 39½ inches, but no sensible oscillation was experienced.
Isambard K. Brunel was another great engineer, who constructed a suspension bridge at the Isle of Bourbon in 1823, and the Charing Cross over the Thames at Hungerford in 1845, which was a footbridge, having a span of 675 feet, the longest span of any bridge in England. Then followed finer and larger suspension bridges in other parts of the world. It was across the Niagara in front of the great falls that in 1855 British America and the United States were joined by a magnificent suspension bridge, one of the finest in the world, and the two English speaking countries were then physically and commercially united. At the opening of the bridge, one portion of which was for a railway, the shriek of the locomotive and the roar of the train mingled with the roar of the wild torrent 250 feet below. The bridge, 800 feet long, is a single span, supported by four enormous cables of wire stretching from the Canadian cliff to the opposite United States cliff. The cables pass over the tops of lofty stone towers arising from these cliffs, and each cable consists of no less than 4,000 distinct wires. The roadway hangs from these cables, suspended by 624 vertical rods.
The engineer of this bridge was John A. Roebling, a native of Prussia, born there in 1806, and who died in New York in 1869. He was educated at the Polytechnic School in Berlin, and emigrated to America at the age of 25. His labors were first as a canal and railway engineer, then he became the inventor and manufacturer of a new form of wire rope, and then turned his attention to the construction of aqueducts and suspension bridges. After the Niagara bridge, above described, he commenced another bridge of greater dimensions over the same river, which was finished within two or three years. His next work was the splendid suspension bridge at Cincinnati, Ohio, which has a clear span of 1057 feet. In 1869, in connection with his son, Washington A. Roebling, he commenced that magnificent suspension bridge to unite the great cities of New York and Brooklyn, and which, by its completion, resulted in the consolidation of those cities as Greater New York. The Roeblings, father and son, were to the engineering of America what George Stephenson and his son Robert were to the locomotive and railway and bridge engineering of Great Britain.
The Brooklyn bridge, known also as the East River bridge, was formally opened to the public on the 24th of May 1883. Most enormous and unexpected technical difficulties were met and overcome in its construction. Its total length is nearly 6,000 feet. The length of the suspended structure from anchorage to anchorage is 3,454 feet. A statement of the general features of this bridge indicates the nature of the construction of such bridges as a class, and distinguishes them from the comparatively simple forms of past ages. This structure is supported by two enormous towers, having a height of 276 feet above the surface of the water, carrying at their tops the saddles which support the cables, and having a span between them of 1,595 feet. The towers are each pierced by two archways, 31½ feet wide, and 120½ feet high, through which openings passes the floor of the bridge at the height of 118 feet above high water mark. There are four supporting cables, each 16 inches in diameter, and each composed of about 5,000 single wires. The wire is one-eighth size; 278 single wires are grouped into a rope, and 19 ropes bunched to form a cable. The iron saddles at the top of the lofty towers, and on which the cables rest, are made movable to permit its expansion and compression—and they glide through minute distances on iron rollers in saddle plates embedded and anchored in the towers, in response to strains and changes of temperature. The enormous cables pass from the towers shoreward to their anchorages 930 feet away, and which are solid masses of masonry, each 132 x 119 feet at base and top, 89 feet high, and weighing 60,000 tons. The bridge is divided into five avenues: one central one for foot passengers, two outer ones for vehicles, and the others for the street cars. The cost of the bridge was nearly $15,000,000.
Twenty fatal and many disabling accidents occurred during the construction of the bridge. The great engineer Roebling was the first victim to an accident. He had his foot crushed while laying the foundation of one of the stone piers, and died of lockjaw.
It was necessary to build up the great piers by the aid of caissons, which are water-tight casings built of timber and metal and sunk to the river bed and sometimes far below it, within which are built the foundations of piers or towers, and into which air is pumped for the workmen. A fire in one of the caissons, which necessitated its flooding by water, and to which the son, Washington Roebling, was exposed, resulted in prostrating him with a peculiar form of caisson disease, which destroyed the nerves of motion without impairing his intellectual faculties. But, although disabled from active work, Mr. Roebling continued to superintend the vast project through the constant mediation of his wife.
Tubular Bridges.—These are bridges formed by a great tube or hollow beam through the center of which a roadway or railway passes. The name would indicate that the bridge was cylindrical in form, and this was the first idea. But it was concluded after experiment that a rectangular form was the best, as it is more rigid than either a cylindrical or elliptical tube. The adoption of this form was due to Fairbairn, the celebrated English inventor and engineer of iron structures. The Menai tubular railway bridge, adjacent to the suspension bridge of Telford across the same strait, and already described, was the first example of this type of bridge. Robert Stephenson was the engineer of this great structure, aided by the suggestions of Fairbairn and other eminent engineers. This bridge was opened for railway traffic in March, 1850. It was built on three towers and shore abutments. The width of the strait is divided by these towers into four spans—two of 460 feet each, and two of 230 feet. In appearance, the bridge looked like one huge, long, narrow iron box, but it consisted really of four bridges, each made of a pair of rectangular tubes, and through one set of tubes the trains passed in going in one direction, and through the other set in going the opposite direction. These ponderous tubes were composed of wrought-iron plates, from three-eighths to three-fourths of an inch thick, the largest 12 feet in length, riveted together and stiffened by angle irons. They varied in height—the central ones being the highest and those nearest the shore the lowest. The central ones are 30 feet high, and the inner ones about 22 feet. Their width was about 14 feet. They were built upon platforms on the Caernarvon shore, and the great problem was how to lift them and put them in place, especially the central ones, which were 460 feet in length. Each tube weighed 1,800 pounds, and they were to be raised 192 feet. This operation has been described as “the grandest lift ever effected in engineering.” It was accomplished by means of powerful hydraulic presses. Another and still grander example of this style of bridge is the Victoria at Montreal, Canada. This also was designed by Robert Stephenson and built under his direction by James Hodges of Montreal. Work was commenced in 1854 and it was completed in December, 1859, and opened for travel in 1860. It consists of 24 piers, 242 feet apart, except the centre one, from which the span is 330 feet. The tube is in sections and quadrangular in form. Every plate and piece of iron was made and punched in England and brought across the Atlantic. In Canada little remained to be done but to put the parts together and in position. This, however, was in itself a Herculean task. The enormous structure was to be placed sixty feet above the swift current of the broad St. Lawrence, and wherein huge masses of ice, each block from three to five feet in thickness, accumulated every winter. The work was accomplished by the erection of a vast rigid stage of timber, on which the tubes were built up plate by plate. When all was completed the great staging was removed, and the mighty tube rested alone and secure upon its massive wedge-faced piers rising from the bedrock of the flood below.
The Tubular Arch Bridge.—This differs from the tubular bridge proper, in that the former consists of a bridge the body of which is supported by a tubular archway of iron and steel, whereas in the latter the body of the bridge itself is a tube. The tubular arch is also properly classed as a girder bridge because the great tube which covers the span is simply an immense beam or girder, which supports the superstructure on which the floor of the bridge is laid. A fine illustration of this style of bridge is seen in what is known as the aqueduct bridge over Rock Creek at Washington, D. C., in which the arch consists of two cast-iron jointed pipes, supporting a double carriage and a double street car way, and through which pipes all the water for the supply of the City of Washington passes. General M. C. Meigs was the engineer.
Another far grander illustration of such a structure, in combination with the truss system, is that of the Illinois and St. Louis bridge, across the Mississippi, of which Captain James B. Eads was the engineer. There are three great spans, the central one of which has a length of about 520 feet, and the others a few feet less. Four arches form each span, each arch consisting of an upper and lower curved member or rib, extending from pier to pier, and each member composed of two parallel steel tubes.
Truss and truss arched bridges.—These, for the most part, are those quite modern forms of iron or wooden bridges in which a supplementary frame work, consisting of iron rods placed obliquely, vertically or diagonally, and cemented together, and with the main horizontal beams either above or below the same, to produce a stiff and rigid structure, calculated to resist strain from all directions.
Previous to the 19th century, the greatest bridges being constructed mostly of solid masonry piers and arches, no demand for a bridge of this kind existed; but after the use of wrought iron and steel became extensive in bridge making, and as these apparently light and airy frames may be extended, piece by piece across the widest rivers, straits, and arms of the sea, a substitute for the great, expensive, and frequent supporting piers became a want, and was supplied by the system of trusses and truss arches. The truss system has also been applied to the construction of vast modern bridges in places where timber is accessible and cheap. Each different system invented bears the name of its inventor. Thus, we have the Rider, the Fink, the Bollman, the Whipple, the Howe, the Jones, the Linville, the McCallum, Towne’s lattice and other systems.
What is called the cantilever system has of late years to a great extent superseded the suspension construction. This consists of beams or girders extending out from the opposite piers at an upward diagonal angle, and meeting at the centre over the span, and there solidly connected together, or to horizontal girders, in such manner that the compression load is thrown on to the supporting piers, upward strains received at the centre, and side deflections provided against. It is supposed that greater rigidity is obtained by this means than by the suspension, and, like the suspension, great widths may be spanned without an under supporting frame work. Two fine examples of this type are found, one in a bridge across the Niagara adjacent to the suspension bridge above described and one across the river Forth at Queens Ferry in Scotland. The Niagara Bridge is a combination of cast steel and iron. It was designed by C. C. Schneider and Edmund Hayes. It was built for a double-track railroad. The total length of the bridge is 910 feet between the centres of the anchorage piers. The cantilevers rest on two gigantic steel towers, standing on massive stone piers 39 feet high. The clear span between the towers is 470 feet, and the height of the bridge, from the mad rush of waters to the car track is 239 feet.
Messrs Fowler and Baker were the engineers of the Forth railway bridge. It was begun in 1883 and finished in 1890. It is built nearly all of steel, and is one of the most stupendous works of the kind. It crosses two channels formed by the island of Inchgarvie, and each of the channel spans is 1710 feet in the clear and a clear headway of 150 feet under the bridge. Three balanced cantilevers are employed, poised on four gigantic steel tube legs supported on four huge masonry piers. The height of the bridge above the piers is 330 feet. The cantilever portion has the appearance of a vast elongated diamond. Steel lattice work of girders, forms the upper side of the cantilever, while the under side consists of a hollow curve approaching in form a quadrant of a circle drawn from the base of the legs or struts to the ends of the cantilever.
Such is the growth of these great bridges with their tremendous spans across which man is spinning his iron webs, that when seen at night with a fiery engine pulling its thundering train across in the darkness, one is reminded of Milton’s description, “over the dark abyss whose boiling gulf tamely endured a bridge of wondrous length, from Hell continued, reaching the utmost orb of this frail world.”
The lighthouses of the century, in masonry, do not greatly excel in general principles those of preceding ones, as at Eddystone, designed by Smeaton. Nicholas Douglass, however, invented a new system of dovetailing, and great improvements have been made in the system of illuminating.
Lighthouses are also distinguished from those of preceding centuries by the substitution of iron and cast steel for masonry. The first cast-iron lighthouse was put up at Point Morant, Jamaica, in 1842. Since then they have taken the form of iron skeleton towers.
One of the latest and most picturesque of lighthouses is that of Bartholdi’s statue of Liberty enlightening the world, the gift of the French government to the United States, framed by M. Eiffel, the great French engineer, and set up by the United States at Bedloe’s Island in New York harbor. It consists of copper plates on a network of iron. Although the statue is larger than any in the world of such composite construction, its success as a lighthouse is not as notable as many farther seaward.
In excavating, dredging and draining, the inventions of the century have been very numerous, but, like numerous advances in the arts, such inventions, so far as great works are concerned, have developed from and are closely related to steam engineering.
The making of roads, railroads, canals and tunnels has called forth thousands of ingenious mechanisms for their accomplishment. A half dozen men with a steam-power excavator or dredger can in one day perform a greater extent of work than could a thousand men and a thousand horses in a single day a few generations ago.
An excavating machine consisting of steel knives to cut the earth, iron scoops, buckets and dippers to scoop it up, endless chains or cranes to lift them, actuated by steam, and operated by a single engineer, will excavate cubic yards of earth by the minute and at a cost of but a few dollars a day.
Dredging machines of a great variety have been constructed. Drags and scoops for elevating, and buckets, scrapers and shovels, and rotating knives to first loosen the earth, suction pumps and pipes, which will suck great quantities of the loosened earth through pipes to places to be filled—these and kindred devices are now constantly employed to dig and excavate, to deepen and widen rivers, to drain lands, to dig canals, to make harbours, to fill up the waste places and to make courses for water in desert lands.
Inventions for the excavating of clay, piling and burning it in a crude state for ballast for railways, are important, especially for those railways which traverse areas where clay is plentiful, and stones and gravel are lacking.
Sinking shafts through quicksands by artificially freezing the sand, so as to form a firm frozen wall immediately around the area where the shaft is to be sunk, is a recent new idea.
Modern countries especially are waking up to the necessity of good roads, not only as a necessary means of transportation, but as a pre-requisite to decent civilisation in all respects. And, therefore, great activity has been had in the last third of a century in invention of machines for finishing and repairing roads.
In the matter of sewer construction, regarded now so necessary in all civilised cities and thickly-settled communities as one of the means of proper sanitation, great improvements have been made in deep sewerage, in which the work is largely performed below the surface and with little obstruction to street traffic.
In connection with excavating and dredging machines, mention should be made of those great works in the construction of which they bore such important parts, as drainage and land reclamation, such as is seen in the modern extensions of land reclamation in Holland, in the Haarlem lake district in the North part of England, the swamps of Florida and the drainage of the London district; in modern tunnels such as the Hoosac in America and the three great ones through the Alps: the Mont Cenis, St. Gothard, and Arlberg, the work in which developed an entirely new system of engineering, by the application of newly-discovered explosives for blasting, new rock-drilling machinery, new air-compressing machines for driving the drill machines and ventilating the works, and new hydraulic and pumping machinery for sinking shafts and pumping out the water.
The great canals, especially the Suez, developed a new system of canal engineering. Thus by modern inventions of devices for digging and blasting, dredging and draining and attendant operations, some of the greatest works of man on earth have been produced, and evinced the exercise of his highest inventive genius.
If one wishes an ocular demonstration of the wonders wrought in the 19th century in the several domains of engineering, let him take a Pullman train across the continent from New York to San Francisco. The distance is 3,000 miles and the time is four days and four nights. The car in which the passenger finds himself is a marvel of woodwork and upholstery—a description of the machinery and processes for producing which belongs to other arts. The railroad tracks upon which the vehicle moves are in themselves the results of many inventions. There is the width of the track, and it was only after a long and expensive contest that countries and corporations settled upon a uniform gauge. The common gauge of the leading countries and roads is now 4 feet 8½ inches. A greater width is known as a broad gauge, a less width as a narrow gauge. Then as to the rail: first the wooden, then the iron and now the steel, and all of many shapes and weights. The T-rail invented by Birkensaw in 1820, having two flanges at the top to form a wide berth for the wheels of the rolling stock, the vertical portion gripped by chairs which are spiked to the ties, is the best known. Then the frogs, a V-shaped device by which the wheels are guided from one line of rails to another, when they form angles with each other; the car wheel made with a flange or flanges to fit the rail, and the railway gates, ingenious contrivances that guard railway crossings and are operated automatically by the passing trains, but more commonly by watchmen. The car may be lighted with electricity, and as the train dashes along at the rate of 30 to 80 miles an hour, it may be stopped in less than a minute by the touch of the engineer on an air brake. Is it midwinter and are mountains of snow encountered? They disappear before the railway snow-plough more quickly than they came. It passes over bridges, through tunnels, across viaducts, around the edges of mountain peaks, every mile revealing the wondrous work of man’s inventive genius for encompassing the earth with speed, safety and comfort. Over one-half million miles of these railway tracks are on the earth’s surface to-day!
Not only has the railway superseded horse power in the matter of transportation to a vast extent, but other modes of transportation are taking the place of that useful animal. The old-fashioned stage coach, and then the omnibus, were successively succeeded by the street car drawn by horses, and then about twenty years ago the horse began to be withdrawn from that work and the cable substituted.
Cable transportation developed from the art of making iron wire and steel wire ropes or cables. And endless cables placed underground, conveyed over rollers and supported on suitable yokes, and driven from a great central power house, came into use, and to which the cars were connected by ingeniously contrived lever grips—operated by the driver on the car. These great cable constructions, expensive as they were, were found more economical than horse power. In fact, there is no modernly discovered practical motive power but what has been found less expensive both as to time and money than horse power. But the cable for this purpose is now in turn everywhere yielding to electricity, the great motor next to steam. The overhead cable system for the transportation of materials of various descriptions in carriers, also run by a central motor, is still very extensively used. The cable plan has also been tried with some success in the propelling of canal boats.
Canals, themselves, although finding a most serious and in some localities an entirely destructive rival in the railroad, have grown in size and importance, and in appliances that have been substituted for the old-style locks. The latest form of this device is what is known as the pneumatic balance lock system.
It has been said by Octave Chanute that “Progress in civilisation may fairly be said to be dependent upon the facilities for men to get about, upon their intercourse with other men and nations, not only in order to supply their mutual needs cheaply, but to learn from each other their wants, their discoveries and their inventions.” Next to the power and means for moving people, come the immense and wonderful inventions for lifting and loading, such as cranes and derricks, means for coaling ships and steamers, for handling and storing the great agricultural products, grain and hay, and that modern wonder, the grain elevator, that dots the coasts of rivers, lakes and seas, receives the vast stores of golden grain from thousands of steam cars that come to it laden from distant plains and discharges it swiftly in mountain loads into vessels and steamers to be carried to the multitudes across the seas, and to satisfy that ever-continuing cry, “Give us this day our daily bread.”
CHAPTER IX.
ELECTRICITY.
In 1900 the real nature of electricity appears to be as unknown as it was in 1800.
Franklin in the eighteenth century defined electricity as consisting of particles of matter incomparably more subtle than air, and which pervaded all bodies. At the close of the nineteenth century electricity defined as “simply a form of energy which imparts to material substances a peculiar state or condition, and that all such substances partake more or less of this condition.”
These theories and the late discovery of Hertz that electrical energy manifests itself in the form of waves, oscillations or vibrations, similar to light, but not so rapid as the vibrations of light, constitute about all that is known about the nature of this force.
Franklin believed it was a single fluid, but others taught that there were two kinds of electricity, positive and negative, that the like kinds were repulsive and the unlike kinds attractive, and that when generated it flowed in currents.
Such terms are not now regarded as representing actual varieties of this force, but are retained as convenient modes of expression, for want of better ones, as expressing the conditions or states of electricity when produced.
Electricity produced by friction, that is, developed upon the surface of a body by rubbing it with a dissimilar body, and called frictional or static electricity, was the only kind produced artificially in the days of Franklin. What is known as galvanism, or animal electricity, also takes its date in the 18th century, to which further reference will be made. Since 1799 there have been discovered additional sources, among which are voltaic electricity, or electricity produced by chemical action, such as is manifested when two dissimilar metals are brought near each other or together, and electrical manifestations produced by a decomposing action, one upon the other through a suitable medium; inductive electricity, or electricity developed or induced in one body by its proximity to another body through which a current is flowing; magnetic electricity, the conversion of the power of a magnet into electric force, and the reverse of this, the production of magnetic force by a current of electricity; and thermal electricity, or that generated by heat. Electricity developed by these, or other means in contra-distinction to that produced by friction, has been called dynamic; but all electric force is now regarded as dynamic, in the sense that forces are always in motion and never at rest.
Many of the manifestations and experiments in later day fields which, by reason of their production by different means, have been given the names of discovery and invention, had become known to Franklin and others, by means of the old methods in frictional electricity. They are all, however, but different routes leading to the same goal. In the midst of the brilliant discoveries of modern times confronting us on every side we should not forget the honourable efforts of the fathers of the science.
We need not dwell on what the ancients produced in this line. It was a single fact only:—The Greeks discovered that amber, a resinous substance, when rubbed would attract lighter bodies to it.
In 1600 appeared the father of modern electricity—Dr. Gilbert of Colchester, physician to Queen Elizabeth. He revived the one experiment of antiquity, and added to it the further fact that many substances besides amber, when rubbed, would manifest the same electric condition, such as sulphur, sapphire, wax, glass and other bodies. And thus he opened the field of electrodes. He was the first to use the terms, electricity, electric and electrode, which he derived from the word elektron, the Greek name for amber. He observed the actions of magnets, and conjectured the fundamental identity of magnetism and electricity. He arranged an electrometer, consisting of an iron needle poised on a pivot, by which to note the action of the magnet. This was about the time that Otto von Guericke of Magdeburg, Germany, was born. He became a “natural” philosopher, and for thirty-five years was burgomaster of his native town. He invented the air-pump, and he it was who illustrated the force of atmospheric pressure by fitting together two hollow brass hemispheres which, after the air within them had been exhausted, could not be pulled apart. He also invented a barometer, and as an astronomer suggested that the return of comets might be calculated. He invented and constructed the first machine for generating electricity. It consisted of a ball of sulphur rotated on an axis, and which was electrified by friction of the hand, the ball receiving negative electricity while the positive flowed through the person to the earth. With this machine “he heard the first sound and saw the first light in artificially excited electricity.” The machine was improved by Sir Isaac Newton and others, and before the close of that century was put into substantially its present form of a round glass plate rotated between insulated leather cushions coated with an amalgam of tin and zinc, the positive or vitreous electricity thus developed being accumulated on two large hollow brass cylinders with globular ends, supported on glass pillars. Gray in 1729 discovered the conductive power of certain substances, and that the electrical influence could be conveyed to a distance by means of an insulated wire. This was the first step towards the electric telegraph.
Dufay, the French philosopher and author, who in 1733-1737 wrote the Memoirs of the French Academy, was, it seems, the first to observe electrical attractions and repulsions; that electrified resinous substances repelled like substances while they attracted bodies electrified by contact with glass; and he, therefore, to the latter applied the term vitreous electricity and to the former the term resinous electricity. In 1745 Prof. Muschenbroeck of Leyden University developed the celebrated Leyden jar. This is a glass jar coated both inside and outside with tinfoil for about four-fifths of its height. Its mouth is closed with a cork through which is passed a metallic rod, terminating above in a knob and connected below with the inner coating by a chain or a piece of tinfoil. If the inner coating be connected with an electrical machine and the outer coating with the earth, a current of electricity is established, and the inner coating receives what is called a positive and the outer coating a negative charge. On connecting the two surfaces by means of a metallic discharger having a non-conducting handle a spark is obtained. Thus the Leyden jar is both a collector and a condenser of electricity. On arranging a series of such jars and joining their outer and inner surfaces, and connecting the series with an electrical machine, a battery is obtained of greater or less power according to the number of jars employed and the extent of supply from the machine.
The principle of the Leyden jar was discovered by accident. Cuneus, a pupil of Muschenbroeck, was one day trying to charge some water in a glass bottle with electricity by connecting it with a chain to the sparking knob of an electrical machine. Holding the bottle in one hand he arranged the chain with the other, and received a violent shock. His teacher then tried the experiment himself, with a still livelier and more convincing result, whereupon he declared that he would not repeat the trial for the whole Kingdom of France.
When the science of static electricity was thus far developed, with a machine for generating it and a collector to receive it, many experiments followed. Charles Morrison in 1753, in the Scots Magazine, proposed a telegraph system of insulated wires with a corresponding number of characters to be signalled between two stations. Other schemes were proposed at different times down to the close of the century.
Franklin records among several other experiments with frictional electricity accumulated by the Leyden jar battery the following results, produced chiefly by himself: The existence of an attractive and a repulsive action of electricity; the restoration of the equilibrium of electrical force between electrified and non-electrified bodies, or between bodies differently supplied with the force; the electroscope, a body charged with electricity and used to indicate the presence and condition of electricity in another body; the production of work, as the turning of wheels, by which it was proposed a spit for roasting meat might be formed, and the ringing of chimes by a wheel, which was done; the firing of gunpowder, the firing of wood, resin and spirits; the drawing off a charge from electrified bodies at a near distance by pointed rods; the heating and melting of metals; the production of light; the magnetising of needles and of bars of iron, giving rise to the analogy of magnetism and electricity.
Franklin, who had gone thus far, and who also had drawn the lightning from the clouds, identified it as electricity, and taught the mode of its subjection, felt chagrined that more had not been done with this subtle agent in the service of man. He believed, however, that the day-spring of science was opening, and he seemed to have caught some reflection of its coming light. Observing the return to life and activity of some flies long imprisoned in a bottle of Madeira wine and which he restored by exposure to the sun and air, he wrote that he should like to be immersed at death with a few friends in a cask of Madeira, to be recalled to life a hundred years thence to observe the state of his country. It would not have been necessary for him to have been embalmed that length of time to have witnessed some great developments of his favorite science. He died in 1790, and it has been said that there was more real progress in this science in the first decade of the nineteenth century than in all previous centuries put together.
Before opening the door of the 19th century, let us glance at one more experiment in the 18th:
While the aged Franklin was dying, Dr. Luigi Galvani of Bologna, an Italian physician, medical lecturer, and learned author, was preparing for publication his celebrated work, De viribus Electricitatis in Motu Musculari Commentarius, in which he described his discovery made a few years before of the action of the electric current on the legs and spinal column of a frog hung on a copper nail. This discovery at once excited the attention of scientists, but in the absence of any immediate practical results the multitude dubbed him the “frog philosopher.” He proceeded with his experiments on animals and animal matter, and developed the doctrine and theories of what is known as animal or galvanic electricity. His fellow countryman and contemporary, Prof. Volta of Pavia, took decided issue with Galvani and maintained that the pretended animal electricity was nothing but electricity developed by the contact of two different metals. Subsequent investigations and discoveries have established the fact that both theories have truth for their basis, and that electricity is developed both by muscular and nervous energy as well as by chemical action. In 1799 Volta invented his celebrated pile, consisting of alternate disks of copper and zinc separated by a cloth moistened with a dilute acid; and soon after an arrangement of cups—each containing a dilute acid and a copper and a zinc plate placed a little distance apart, and thus dispensing with the cloth. In both instances he connected the end plate of one kind with the opposite end plate of the other kind by a wire, and in both arrangements produced a current of electricity. To the discoveries, experiments, and disputes of Galvani and Volta and to those of their respective adherents, the way was opened to the splendid electrical inventions of the century, and the discovery of a new world of light, heat, speech and power. The discoveries of Galvani and Volta at once set leading scientists at work. Fabroni of Florence, and Sir Humphry Davy and Wollaston of England, commenced interesting experiments, showing that rapid oxidation and chemical decomposition of the metals took place in the voltaic pile.
By the discoveries of Galvani the physicians and physiologists were greatly excited, and believed that by this new vital power the nature of all kinds of nervous diseases could be explored and the remedy applied. Volta’s discovery excited the chemists. If two dissimilar metals could be decomposed and power at the same time produced they contended that practical work might be done with the force. In 1800 Nicholson and Carlisle decomposed water by passing the electric current through the same; Ritter decomposed copper sulphate, and Davy decomposed the alkalies, potash and soda. Thus the art of electrolysis—the decomposition of substances by the galvanic current, was established. Later Faraday laid down its laws. Naturally inventions sprung up in new forms of batteries. The pile and cup battery of Volta had been succeeded by the trough battery—a long box filled with separated plates set in dilute acid. The trough battery was used by Sir Humphry Davy in his series of great experiments—1806-1808—in which he isolated the metallic bases, calcium, sodium, potassium, etc. It consisted of 2000 double plates of copper and zinc, each having a surface of 32 square inches. With this same trough battery Davy in 1812 produced the first electric carbon light, the bright herald of later glories.
Among the most noted new batteries were Daniell’s, Grove’s and Bunsen’s. They are called the “two fluid batteries,” because in place of a single acidulated bath in which the dissimilar metals were before placed, two different liquid solutions were employed.
John Frederick Daniell of London, noted for his great work, Meteorological Essays, and other scientific publications, and as Professor of Chemistry in King’s College, in 1836, described how a powerful and constant current of electricity may be continued for an unlimited period by a battery composed of zinc standing in an acid solution and a sheet of copper in a solution of sulphate of copper.
Sir William Robert Grove, first an English physician, then an eminent lawyer, and then a professor of natural philosophy, and the first to announce the great theory of the Correlation of Physical Forces, in 1839 produced his battery, much more powerful than any previous one, and still in general use. In it zinc and platinum are the metals used—the zinc bent into cylindrical form and placed in a glass jar containing a weak solution of sulphuric acid, while the platinum stands in a porous jar holding strong nitric acid and surrounded by the zinc. Among the electrical discoveries of Grove were the decomposition by electricity of water into free oxygen and hydrogen, the electricity of the flame of the blow-pipe, electrical action produced by proximity, without contact, of dissimilar metals, molecular movements induced in metals by the electric current, and the conversion of electricity into mechanical force.
Robert Wilhelm Bunsen, a German chemist and philosopher and scientific writer, who invented some of the most important aids to scientific research of the century, who constructed the best working chemical laboratory on the continent and founded the most celebrated schools of chemistry in Europe, invented a battery, sometimes called the carbon battery, in which the expensive pole of platinum in the Grove battery is replaced by one of carbon. It was found that this combination gave a greater current than that of zinc and platinum.
A great variety of useful voltaic batteries have since been devised by others, too numerous to be mentioned here. There is another form of battery having for its object the storing of energy by electrolysis, and liberating it when desired, in the form of an electric current, and known as an accumulator, or secondary, polarization, or storage battery. Prof. Ritter had noticed that the two plates of metal which furnished the electric current, when placed in the acid liquid and united, could in themselves furnish a current, and the inventing of storage batteries was thus produced. The principal ones of this class are Gustave Planté’s of 1860 and M. Camille Faure’s of 1880. These have still further been improved. Still another form are the thermo-electric batteries, in which the electro-motive force is produced by the joining of two different metals, connecting them by a wire and heating their junctions. Thus, an electric current is obtained directly from heat, without going through the intermediate processes of boiling water to produce steam, using this steam to drive an engine, and using this engine to turn a dynamo machine to produce power.
But let us retrace our steps:—As previously stated, Franklin had experimented with frictional electricity on needles, and had magnetised and polarised them and noticed their deflection; and Lesage had established an experimental telegraph at Geneva by the same kind of electricity more than a hundred years ago. But frictional electricity could not be transmitted with power over long distances, and was for practical purposes uncontrollable by reason of its great diffusion over surfaces, while voltaic electricity was found to be more intense and could be developed with great power along a wire for any distance. Fine wires had been heated and even melted by Franklin by frictional electricity, and now Ritter, Pfaff and others observed the same effect produced on the conducting wires by a voltaic current; and Curtet, on closing the passage with a piece of charcoal, produced a brilliant light, which was followed by Davy’s light already mentioned.
As early as 1802 an Italian savant, Gian D. Romagnosi of Trent, learning of Volta’s discovery, observed and announced in a public print the deflection of the magnetic needle when placed near a parallel conductor of the galvanic current. In the years 1819 and 1820 so many brilliant discoveries and inventions were made by eminent men, independently and together, and at such near and distant places, that it is hard telling who and which was first. It was in 1819 that the celebrated Danish physicist, Oersted of Copenhagen, rediscovered the phenomena that the voltaic current would deflect a magnetic needle, and that the needle would turn at right angles to the wire. In 1820 Prof. S. C. Schweigger of Halle discovered that this deflecting force was increased when the wire was wound several times round the needle, and thus he invented the magnetising helix. He also then invented a galvano-magnetic indicator (a single-wire circuit) by giving the insulated wire a number of turns around an elongated frame longitudinally enclosing the compass needle, thus multiplying the effect of the current upon the sensitive needle, and converting it into a practical measuring instrument—known as the galvanometer, and used to observe the strength of currents. In the same year Arago found that iron filings were attracted by a voltaic charged wire; and Arago and Davy that a piece of soft iron surrounded spirally by a wire through which such a current was passed would become magnetic, attract to it other metals while in that condition, immediately drop them the instant the current ceased, and that such current would permanently magnetise a steel bar. The elements of the electro-magnet had thus been produced. It was in that year that Ampère discovered that magnetism is the circulation of currents of electricity at right angles to the axis of the needle or bar joining the two poles of the magnet. He then laid down the laws of interaction between magnets and electrical currents, and in this same year he proposed an electric-magneto telegraph consisting of the combination of a voltaic battery, conducting wires, and magnetic needles, one needle for each letter of the alphabet.
The discoveries of Ampère as to the laws of electricity have been likened to the discovery of Newton of the law of gravitation.
Still no practical result, that is, no useful machine, had been produced by the electro-magnet.
In 1825 Sturgeon of England bent a piece of wire into the shape of a horse-shoe, insulated it with a coating of sealing wax, wound a fine copper wire around it, thus making a helix, passed a galvanic current through the helix, and thus invented the first practical electro-magnet. But Sturgeon’s magnet was weak, and could not transmit power for more than fifty feet. Already, however, it had been urged that Sturgeon’s magnet could be used for telegraphic purposes, and a futile trial was made. In the field during this decade also labored the German professors Gauss and Weber, and Baron Schilling of Russia. In 1829 Prof. Barlow of England published an article in which he summarised what had been done, and scientifically demonstrated to his own satisfaction that an electro-magnetic telegraph was impracticable, and his conclusion was accepted by the scientific world as a fact. This was, however, not the first nor the last time that scientific men had predicted impracticabilities with electricity which afterwards blossomed into full success. But even before Prof. Barlow was thus arriving at his discouraging conclusion, Prof. Joseph Henry at the Albany Institute in the State of New York had commenced experiments which resulted in the complete and successful demonstration of the power of electro-magnetism for not only telegraph purposes but for almost every advancement that has since been had in this branch of physics. In March 1829 he exhibited at his Institute the magnetic “spool” or “bobbin,” that form of coil composed of tightly-wound, silk-covered wire which he had constructed, and which since has been universally employed for nearly every application of electro-magnetism, of induction, or of magneto-electrics. And in the same year and in 1830 he produced those powerful magnets through which the energy of a galvanic battery was used to lift hundreds of tons of weight.
In view of all the facts now historically established, there can be no doubt that previous to Henry’s experiments the means for developing magnetism in soft iron were imperfectly understood, and that, as found by Prof. Barlow, the electro-magnet which then existed was inapplicable and impracticable for the transmission of power to a distance. Prof. Henry was the first to prove that a galvanic battery of “intensity” must be employed to project the current through a long conductor, and that a magnet of one long wire must be used to receive this current; the first to magnetise a piece of soft iron at a distance and call attention to its applicability to the telegraph; the first to actually sound a bell at a distance by means of the electro-magnet; and the first to show that the principles he developed were applicable and necessary to the practical operation of an effective telegraph system.
Sturgeon, the parent of the electro-magnet, on learning of Henry’s discoveries and inventions, wrote: “Professor Henry has been enabled to produce a magnetic force which totally eclipses every other in the whole annals of magnetism; and no parallel is to be found since the miraculous suspension of the celebrated oriental impostor in his iron coffin.” (Philosophical Magazine and Annals, 1832.)
The third decade was now prepared for the development of the telegraph. As to the telegraph in its broadest sense, as a means for conveying intelligence to a distance quickly and without a messenger, successful experiments of that kind have existed from the earliest times:—from the signal fires of the ancients; from the flag signals between ships at sea, introduced in the seventeenth century by the Duke of York, then Admiral of the English fleet, and afterwards James II of England; from the semaphore telegraph of M. Chappe, adopted by the French government in 1794, consisting of bars pivoted to an upright stationary post, and made to swing vertically or horizontally to indicate certain signals; and from many other forms of earlier and later days.
As to electricity as an agent for the transmission of signals, the idea dates, as already stated, from the discovery of Stephen Gray in 1729, that the electrical influence could be conveyed to a distance by the means of an insulated wire. This was followed by the practical suggestions of Franklin and others. But when, as we have seen, voltaic electricity entered the field, electricity became a more powerful and tractable servant, and distant intelligent signals became one of its first labors.
The second decade was also made notable by the discovery and establishment by George Simon Ohm, a German professor of Physics, of the fundamental mathematical law of electricity: It has been expressed in the following terms: (a) the current strength is equal to the electro-motive force divided by the resistance; (b) the force is equal to the current strength multiplied by the resistance; (c) the resistance is equal to the force divided by the current strength.
The historical development and evolution of the telegraph may be now summarized:—
1. The discovery of galvanic electricity by Galvani—1786-1790.
2. The galvanic or voltaic battery by Volta in 1800.
3. The galvanic influence on a magnetic needle by Romagnosi (1802) Oersted (1820).
4. The galvanometer of Schweigger, 1820—the parent of the needle system.
5. The electro-magnet by Arago and Sturgeon—1820-1825—the parent of the magnet system.
Then followed in the third decade the important series of steps in the evolution, consisting of:—
First, and most vital, Henry’s discovery in 1829 and 1830 of the “intensity” or spool-wound magnet, and its intimate relation to the “intensity” battery, and the subordinate use of an armature as the signalling device.
Second, Gauss’s improvement in 1833 (or probably Schilling’s considerably earlier) of reducing the electric conductors to a single circuit by the ingenious use of a dual sign so combined as to produce a true alphabet.
Third, Weber’s discovery in 1833 that the conducting wires of an electric telegraph could be efficiently carried through the air without any insulation except at their points of support.
Fourth, Daniell’s invention of a “constant” galvanic battery in 1836.
Fifth, Steinheil’s remarkable discovery in 1837 that the earth may form the returning half of a closed galvanic circuit, so that a single conducting wire is sufficient for all telegraphic purposes.
Sixth, Morse’s adaptation of the armature and electro-magnet of Henry as a recording instrument in 1837 in connection with his improvement in 1838 on the Schilling, Gauss and Steinheil alphabets by employing the simple “dot and dash” alphabet in a single line. He was also assisted by the suggestions of Profs. Dana and Gale. To which must be added his adoption of Alfred Vail’s improved alphabet, and Vail’s practical suggestions in respect to the recording and other instrumentalities.
To these should be added the efforts in England, made almost simultaneously with those of Morse, of Wheatstone and Cook and Davy, who were reaching the same goal by somewhat different routes.
Morse in 1837 commenced to put the results of his experiments and investigations in the form of caveats, applications and letters patent in the United States and in Europe. He struggled hard against indifference and poverty to introduce his invention to the world. It was not until 1844 that he reduced it to a commercial practical success. He then laid a telegraph from Washington to Baltimore under the auspices of the United States Government, which after long hesitation appropriated $30,000 for the purpose. It was on the 24th day of May, 1844, that the first formal message was transmitted on this line between the two cities and recorded by the electro-magnet in the dot and dash alphabet, and this was immediately followed by other messages on the same line.
Morse gathered freely from all sources of which he could avail himself knowledge of what had gone before. He was not a scientific discoverer, but an inventor, who, adding a few ideas of his own to what had before been discovered, was the first to combine them in a practical useful device. What he did as an inventor, and what anyone may do to constitute himself an inventor, by giving to the world a device which is useful in the daily work of mankind, as distinguished from the scientific discoverer who stops short of successful industrial work, is thus stated by the United States Supreme Court in an opinion sustaining the validity of his patents, after all the previous art had been produced before it:—
“Neither can the inquiries he made nor the information or advice he received from men of science in the course of his researches impair his right to the character of an inventor. No invention can possibly be made, consisting of a combination of different elements of power, without a thorough knowledge of the properties of each of them, and the mode in which they operate on each other. And it can make no difference in this respect, whether he derives his information from books, or from conversation with men skilled in the science. If it were otherwise, no patent in which a combination of different elements is used would ever be obtained, for no man ever made such an invention without having first obtained this information, unless it was discovered by some fortunate accident. And it is evident that such an invention as the electro-magnetic telegraph could never have been brought into action without it; for a very high degree of scientific knowledge and the nicest skill in the mechanic arts are combined in it, and were both necessary to bring it into successful operation. The fact that Morse sought and obtained the necessary information and counsel from the best sources, and acted upon it, neither impairs his rights as an inventor nor detracts from his merits.”—O’Reilly vs. Morse, 5 Howard.
The combination constituting Morse’s invention comprised a main wire circuit to transmit the current through its whole length whenever closed; a main galvanic battery to supply the current; operating keys to break and close the main circuit; office circuits; a circuit of conductors and batteries at each office to record the message there; receiving spring lever magnets to close an office circuit when a current passes through the main circuit; adjusting screws to vary the force of the main current; marking apparatus, consisting of pointed pieces of wire, to indent dots and lines upon paper; clockwork to move the paper indented; and magnet sounders to develop the power of the pointer and of the armatures to produce audible distinguishable sounds.
It was soon learned by operators how to distinguish the signs or letters sent by the length of the “click” of the armature, and by thus reading by sound the reading of the signs on paper was dispensed with, and the device became an electric-magnetic acoustic telegraph.
What is known as the Morse system has been improved, but its fundamental principles remain, and their world-wide use constitute still the daily evidence of the immense value of the invention to mankind.
Before the 1844 reduction to practice, Morse had originated and laid the first submarine telegraph. This was in New York harbour in 1842. In a letter to the Secretary of the United States Treasury, August 10, 1843, he also suggested the project of an Atlantic telegraph.
While Henry was busy with his great magnets and Morse struggling to introduce his telegraph, Michael Faraday was making those investigations and discoveries which were to result in the application of electricity to the service of man in still wider and grander fields.
Faraday was a chemist, and Davy’s most brilliant pupil and efficient assistant. His earliest experiments were in the line of electrolysis. This was about 1822, but it was not until 1831 that he began to devote his brilliant talents as an experimentalist and lecturer wholly to electrical researches, and for a quarter of a century his patient, wonderful labours and discoveries continued. It has been said that “although Oersted was the discoverer of electro-magnetism and Ampère its expounder, Faraday made the science of magnets electrically what it is at the present day.”
Great magnetic power having been developed by passing a galvanic current around a bar of soft iron, Faraday concluded that it was reasonable to suppose that as mechanical action is accompanied by an equal amount of reaction, electricity ought to be evolved from magnetism.
“It was in 1831 that Faraday demonstrated before the Royal Society that if a magnetized bar of steel be introduced into the centre of a helix of insulated wire, there is at the moment of introduction of the magnet a current of electricity set up in a certain direction in the insulated wire forming the helix, while on the withdrawal of the magnet from the helix a current in an opposite direction takes place.
“He also discovered that the same phenomenon was to be observed if for the magnet was substituted a coil of insulated wire, through which the current from a voltaic element was passing; and further that when an insulated coil of wire was made to revolve before the poles of a permanent magnet, electric currents were induced in the wires of the coil.”—Journal of the Society of Arts.
On these discoveries were based the action of all magneto-dynamo electric machines—machines that have enabled the world to convert the energy of a steam engine in its stall, or a distant waterfall, into electric energy for the performance of the herculean labours of lighting a great city, or an ocean-bound lighthouse, or transporting quickly heavy loads of people or freight up and down and to and fro upon the earth.
As before stated, Faraday was also the first to proclaim the laws of electrolysis, or electro-chemical decomposition. He expressed conviction that the forces termed chemical affinity and electricity are one and the same. Subsequently the great Helmholtz, having proved by experiment that in the phenomena of electrolysis no other force acts but the mutual attractions of the atomic electric charges, came to the conclusion, “that the very mightiest among the chemical forces are of electric origin.”
Faraday having demonstrated by his experiments that chemical decomposition, electricity, magnetism, heat and light, are all inter-convertible and correlated forces, the inventors of the age were now ready to step forward and put these theories at work in machines in the service of man. Faraday was a leader in the field of discovery. He left to inventors the practical application of his discoveries.
Prof. Henry in America was, contemporaneously with Faraday, developing electricity by means of magnetic induction.
In 1832, Pixii, a philosophical instrument-maker of Paris, and Joseph Saxton, an American then residing in London, invented and constructed magneto-machines on Faraday’s principle of rendering magnetic a core of soft iron surrounded with insulated wire from a permanent magnet, and rapidly reversing its polarity, which machines were used to produce sparks, decompose liquids and metals, and fire combustible bodies. Saxton’s machine was the well-known electric shock machine operated by turning a crank. A similar device is now used for ringing telephone call bells.
Prof. C. G. Page of Washington and Ruhmkorff of Paris each made a machine, well known as the Ruhmkorff coil, by which intense electro-magnetic currents by induction were produced. The production of electrical illumination was now talked of more than ever. Scientists and inventors now had two forms of electrical machines to produce light: the voltaic battery and the magneto-electric apparatus. But a period of comparative rest took place in this line until 1850, when Prof. Nollet of Brussels made an effort to produce a powerful magneto-electric machine for decomposing water into its elements of hydrogen and oxygen, which gases were then to be used in producing the lime light; and a company known as “The Alliance” was organized at Paris to make large machines for the production of light.
We have seen that Davy produced a brilliant electric light with two pieces of charcoal in the electric circuit of a voltaic battery. Greener and Staite revived this idea in a patent in 1845. Shortly after Nollet’s machine, F. H. Holmes of England improved it and applied the current directly to the production of electric light between carbon points. And Holmes and Faraday in 1857 prepared this machine for use.
On the evening of December 8, 1858, the first practical electric light, the work of Faraday and Holmes, flashed over the troubled sea from the South Foreland Lighthouse. On June 6, 1862, this light was also introduced into the lighthouse at Dungeness, England. The same light was introduced in French lighthouses in December, 1863, and also in the work on the docks of Cherbourg. At this time Germany was also awake to the importance of this invention, and Dr. Werner Siemens of Berlin was at work developing a machine for the purpose into one of less cost and of greater use. Inventors were not yet satisfied with the power developed from either the voltaic battery or the magneto-electric machine, and continued to improve the latter.
In 1867, the same year that Faraday died, and too late for him to witness its glory, came out the most powerful magneto-electric machine that had yet been produced. It was invented by Wilde of London, and consisted of very large electro-magnets, or field magnets, receiving their electric power from the “lines of force” discovered by Faraday, radiating from the poles of a soft iron magnet, combined with a small magneto-electric machine having permanent magnets, and by which the current developed in the smaller machine was sent through the coils of the larger magnets. By this method the magnetic force was vastly multiplied, and electricity was produced in such abundance as to fuse thick iron wire fifteen inches long and one-fourth of an inch in diameter, and to develop a magnificent arc light. Quickly succeeding the Wilde machine came independent inventions in the same direction from Messrs. G. Farmer of Salem, Mass., Alfred Yarley and Prof. Charles Wheatstone of England, and Dr. Siemens of Berlin, and Ladd of America. These inventors conceived and put in practice the great idea of employing the current from an electro-magnetic machine to excite its own electric magnet. They were thus termed “self-exciting.” The idea was that the commutator (an instrument to change the direction, strength or circuit of the current) should be so connected with the coils of the field magnets that all or a part of the current developed in the armature would flow through these coils, so that all permanent magnets might be dispensed with, and the machine used to excite itself or charge its own field magnets without the aid of any outside charging or feeding mechanism.
Mr. Z. Gramme, of France, a little later than Wilde made a great improvement. Previously, machines furnished only momentary currents of varying strength and polarity; and these intermittent currents were hard to control without loss in the strength of current and the frequent production of sparks. Gramme produced a machine in which, although as in other machines the magnetic field of force was created by a powerful magnet, yet the armature was a ring made of soft iron rods, and surrounded by an endless coil of wire, and made to revolve between the poles of the magnet with great rapidity, producing a constant current in one direction. By Faraday’s discovery, when the coil of the closed circuit was moved before the poles of the magnet, the current was carried half the time in one direction and half in the other, constituting what is called an alternating current. Gramme employed the commutator to make the current direct instead of alternating.
Dynamo-electric machines for practical work of many kinds had now been born and grown to strength.
In addition to these and many other electrical machines this century has discovered several ways by which the electricity developed by such machines may be converted into light. I. By means of two carbon conductors between which passes a series of intensely brilliant sparks which form a species of flame known as the voltaic arc, and the heat of which is more intense than that from any other known artificial source. II. By means of a rod of carbon or kaolin, strip of platinum or iridium, a carbon filament, or other substance placed between two conductors, the resistance opposed by such rod, strip, or filament to the passage of the current being so great as to develop heat to the point of incandescence, and produce a steady white and pure light. Attempts also have been made to produce illumination by what is called stratified light produced by the electric discharge passing through tubes containing various gases. These tubes are known as Geissler tubes, from their inventor. Still another method is the production of a continuous light from a vibratory movement of carbon electrodes to and from each other, producing a bright flash at each separation, and maintaining the separations at such a rate that the effect of the light produced is continuous. But these additional methods do not appear as yet to be commercially successful.