Part 6

The incandescent lamp, or electric lighting by incandescence, underwent a somewhat longer evolution at the hands of inventors than the arc lamp, owing to the difficulty of finding a substance suitable for the production of the necessary glow. The discovery of such substance may be accredited to Edison more fully than to any other. The incandescent or glow lamp is a glass bulb from which the air is exhausted. There passes into the bulb a filament of carbon, which, after a turn or two inside the bulb, passes out at the end through which it entered. When a current from a voltaic battery is sent through this carbon filament, it brings it, in the absence of oxygen within the bulb, to a high white heat without combustion. The portion of this high white heat which is radiated is the light-giving energy of the incandescent lamp. Metal filaments were at first tried in the bulb, but they quickly burned out. Carbon filaments were at length found to be the only ones capable of resisting the heat. They moreover had the advantage of cheapness, and of greater radiating energy than metals. Many substances, such as silk, cotton, hair, etc., were used in the preparation of the carbon filaments, but it was found that strips cut from the inside bark of the bamboo gave, when brought to a white heat by an electric current and then properly treated, the most tenacious and best conducting carbon filament.

The quality of light produced by an incandescent lamp is a gentler glow than that produced by the arc lamp, and in color more nearly resembles the light of gas or the oil lamp. The incandescent light speedily became for the home, hotel, hall, and limited covered area what the arc light became for the street and railway station, and, if anything, the former outstripped the latter in the extent and value of the industry it gave rise to.

In the arc lamp, the carbon pencils have to be renewed daily. In the incandescent lamp, the carbon filament, though very delicate, may last for quite a time, because incandescence takes place in the absence of oxygen. If the favor in which the electric light is held, and the great extent of its use, rested solely on the question of cheapness of production, such question would give rise to interesting debate. And, indeed, the debate would continue, if the question were the superior fitness of electric lighting for lighthouses and like service, where extreme brilliancy does not seem to penetrate a thick atmosphere as effectively as the more subdued glow of the oil lamp. But the debate ceases when the question is as to the beauty and efficiency of the electric light in the home, street, station, mine, on shipboard, and the thousand and one other places in which it has come to be deemed an essential equipment. In all such places the question of economy of production and use is subordinate to the higher question of utility and indispensability.

VII. ELECTRIC LOCOMOTION.

The dawn of the nineteenth century saw, as vehicles of locomotion, the saddled hackney, the clumsy wagon, the ostentatious stage-coach, the primitive dearborn, the lumbering carriage, the poetic “one-hoss shay.” The universal energy was the horse. A new energy came with the application of steam, and with it new vehicular locomotion,—easier, swifter, stronger, for the most part cheaper, rendering possible what was hitherto impossible as to time and distance.

This signal triumph of the century may not have been eclipsed by the introduction of subsequent locomotive changes, but it was to be supplemented by what, at the beginning, would have passed for the idle dream of a visionary. The horse-car came, had its brief day, and went out with all its inconveniences, cruelties, and horrors before, in part, the traction-car, and, in part, the rapidly revolutionizing energy of electricity.

[Illustration: ELECTRIC LOCOMOTIVE.]

The first conception of a railway to be operated by electricity dates from about 1835, when Thomas Davenport, of Brandon, Vt., contrived and moved a small car by means of a current from voltaic cells placed within it. In 1851, Professor Page, of the Smithsonian Institution, ran a car propelled by electricity upon the steam railway between Washington and Baltimore, but though he obtained a high rate of speed, the cost of supplying the current by means of batteries—the only means then known—prohibited the commercial use of his method.

With the invention of the dynamo as an economic and powerful generator of electricity, and also the invention of the motor as a means of turning electrical energy to mechanical account, the way was open, both in the United States and Europe, for more active investigation of the question of electric-car propulsion. Between 1872 and 1887, different inventors, at home and abroad, placed in operation several experimental electric railways. Few of them proved practical, though each furnished a fund of valuable experience. An underground electric street railway was operated in Denver as early as 1885; but the one upon the trolley plan, which proved sufficiently successful to warrant its being called the first operated in the United States, was built in Richmond, Va., in 1888. It gave such impetus to electric railway construction that, in five years’ time, enormous capital was embarked, and the new means of propulsion was generally accepted as convenient, safe, and profitable.

The essential features of the electric railway are: (1.) The track of two rails, similar to the steam railway, (2.) The cars, lightly yet strongly built. (3.) The power-house, containing the dynamos which generate the electricity. (4.) The feed-wire, usually of stout copper, running the length of the tracks of the system, and supported on poles or laid in conduits. (5.) The trolley-wire over the centre of the track, supported by insulated cross-wires passing from poles on opposite sides of the tracks, and connected at proper intervals with the feed-wire. (6.) The trolley-pole of metal jointed to the top of the car, and fitted with a spring which presses the wheel on the end of the pole up against the trolley-wire with a force of about fifteen pounds, and which also serves to conduct the electricity down through the car to the motor. (7.) The motor, which is suspended from the car truck, and passes its power to the car axle by means of a spur gearing. The power requisite for an ordinary trolley-car is about fifteen horse-power. The speed of trolley-cars is regulated in cities to from five to seven miles per hour, but they may be run, under favorable conditions, at a speed equal to, or in excess of, that of the steam-car.

As a means of city transit, and of rapid, convenient, and economic intercourse between suburban localities and rural towns and villages, the electric traction system ranks as one of the greatest wonders of the century. The speed with which it found favor, the enormous capital it provoked to activity, the stimulus it gave to further study and invention, the surprising number of passengers carried, go to make one of the most interesting chapters in electric annals. The end of the century sees thousands of these electric roads in existence; a comparatively new industry involving over $100,000,000; a passenger traffic running into the billions of people; a prospect that the trolley will succeed the steam-car for all utilizable purposes within the gradually extending influence of cities and towns upon their rural surroundings.

In speaking of the passing of the horse-car and its substitution by the trolley, a distinguished writer has well said: “Humanity in an electric-car differs widely from that in the horse-car, propelled at the expense of animal life. It is more cheerful, more confident, more awake to the energy at command, more imbued with the subtlety and majesty of the propelling force. The motor confirms the ethical fact that each introduction of a higher material force into the daily uses of humanity lifts it to a broader, brighter plane, gives its capabilities freer and more wholesome play, and opens fresh vistas for all possibilities. We applaud Franklin for seizing the lightning in the heavens, dragging it down to earth, and subjugating it to man. Let this pass as part of the poetry of physics. But when ethics comes to poetize, let it be said that electricity as an applied force lifts man up toward heaven, quickens all his appreciations of divine energy, draws him irresistibly toward the centre and source of nature’s forces. There is no dragging down and subjugation of a physical force. There is only a going out, or up, of genius to meet and to grasp it. Its universal application means the raising of mankind to its plane. If electricity be the principle of life, as some suppose, what wonder that we all feel better in an electric-car than any other? The motor becomes a sublime motive. God himself is tugging at the wheels, and we are riding with the Infinite.”

[Illustration: ELECTRIC RAILWAY. THIRD RAIL SYSTEM.]

Enthusiasts say the trolley is only the beginning of electric locomotion, and that there is already in rapid evolution an electric system which will supersede steam even for trunk-line purposes. In vision, it presumes a speed of one hundred and twenty-five miles an hour instead of forty; greater safety, cleanliness, and comfort; and what is most momentous and startling, an economy in construction and operation which will warrant the sacrifice of the billions of dollars now invested in steam-railway properties. The proposition is not to sacrifice the steam-railway track, but to add to it a third rail, which is to carry the electric current. Then, by means of feed-conduits alongside of the track, and specially constructed electric locomotives and cars, the system is supposed to reach the practical perfection claimed for it. Experiments with such an electrical system, made upon branch lines of some of our trunk-line railways, as the Pennsylvania, New York Central, and New Haven & Hartford, give much encouragement to the hypothesis that it may become the next great step in the evolution of electrical science.

Another means of electric propulsion was provided by the investigations of Planté, which resulted in his invention of the “accumulator” or “storage battery,” in 1859. His battery consists of plates of lead immersed in dilute sulphuric acid. By the passage of an electric current through the acid, it is electrolytically decomposed. By continuing the current for a time, first in one direction and then in another, the lead plates become changed, the one at the point where the current leaves the cell taking on a deposit of spongy lead, and the one at the point where the current enters the cell taking on a coating of oxide of lead. When in this condition, the battery is said to be stored, and is capable of sending out an electric current in any circuit with which it may be connected. After exhausting itself, it can be re-stored or re-charged in the same way as at first. Faure greatly improved on Planté’s storage battery in 1880, by spreading the oxide of lead over the plates, thus greatly reducing the time in forming the plates. Subsequently, further improvements were made, till batteries came into existence capable of supplying a current of many hundred amperes for several hours. One of the first practical uses to which the storage battery was put was in the propulsion of street-cars; but its weight proved a drawback. It was found better adapted for the running of boats on rivers, and, in the business of water-freightage for short distances, has in many instances become a rival of steam. It found one of its most interesting applications in helping to solve the problem of the _automobile_, or “horseless carriage,” either for pleasure purposes or for street traffic. In this problem it has, at the end of the century, an active rival in compressed air; but as the “horseless carriage” is rapidly coming into demand, means may soon be found to utilize the strong and persistent energy of the storage battery, without the drawback found in its great weight.

VIII. THE X RAY.

An astounding electrical revelation came during the last years of the century through the discovery of the X, or unknown, or Roentgen ray. A hint of this discovery was given by Faraday during his investigation of the effect of electric discharges within rarefied gases. He also invented the terms _anode_ and _cathode_, both of which are in universal use in connection with instruments for producing the X rays; the anode being the positive pole or electrode of a galvanic battery, or, in general, the terminal of the conductor by which a current enters an electrolytic cell; and the cathode being the negative pole or electrode by which a current leaves said cell.

Geissler followed Faraday with an improved system of tubes for containing rarefied gases for experimentation. He partially exhausted his tubes of air, introduced into them permanent and sealed platinum electrodes, and produced those wonderful effects by the discharge obtained by connecting the electrodes with the terminals of an electric machine or induction coil, which from their novelty and beauty became known as Geissler effects, just as his tubes became known as Geissler tubes. In the attenuated atmosphere of the Geissler tube, the current does not pass directly from one platinum point or electrode to the other, but, instead, illuminates the entire atmospheric space. When other gases are introduced in rarefied form, they are similarly illuminated, but in colors corresponding to their composition. In his further experiments, Geissler noted that the gases in the tube behaved differently at the anode, or positive terminal, and the cathode, or negative terminal. A beautiful bluish light appeared at the cathode, while the anode assumed the same color as the illuminated space in the tube. It was also noted that after the electric discharge within the tube, there remained upon the inner surface of the glass a fluorescent or phosphorescent glow, which was attributed to the effect of the cathode.

[Illustration: GEISSLER’S TUBES.]

This brought the study of the _cathode_ rays into prominence, and through the investigations of Professor William Crookes, in 1879 and afterwards, a conclusion was reached that a “Fourth State of Matter” really existed. He perfected tubes of very high vacuum, by means of which he showed that molecules of gas projected from the cathode moved freely and with great velocity among one another, and so bombarded the inner walls of the tube as to render it fluorescent.

Subsequently, Hertz showed that the cathodic rays would penetrate thin sheets of metal placed within the tube or bulb; and soon after, Paul Lenard (1894) demonstrated that the cathodic ray could be investigated as well outside of the tube or bulb as within it. He set an aluminum plate in the glass wall of the bulb opposite the cathode. Though ordinary light could not penetrate the aluminum plate, it was readily pierced by the cathodic rays, to a distance of three inches beyond its outside surface. With these rays, thus freed from their inclosure, he produced the same fluorescent effects as had been noted within the bulb, and even secured some photographic effects. These cathodic rays produced no effect on the eye, which proved their dissimilarity to light. Lenard showed further that the cathodic rays outside of the tube could be deflected from their straight course by a magnet, that they might pass through substances opaque to light, and that in so passing they might cast a shadow of objects less opaque, which shadow could be photographed. Now Professor Roentgen came upon the scene. He had been conducting his experiments in Germany, along the same lines as Lenard, and had reached practically the same results as to the penetrative, fluorescent, and photographic effects of the cathodic rays. But he had gone still further, and, in 1896, fairly set the scientific world aflame with the announcement that all the effects produced by Lenard in the limited space of a few inches could also be produced at long distances from the tube, and with sufficient intensity to depict solid substances within or behind other substances sufficiently solid to be impermeable by light. Professor Roentgen claims that his X ray is different from the cathodic ray of Lenard and others, because it cannot be deflected by a magnet. This claim has given rise to much controversy respecting the real nature of the X ray, a controversy not likely to end soon, yet one full of inspiration to further investigation.

[Illustration: SCIAGRAPH OR SHADOW PICTURE.

By X Ray process.]

The essential features of the best approved apparatus designed to produce the X ray and to secure a photograph of an invisible object, are: (1.) A battery or light dynamo as a generator of the electric current, accompanied, of course, by the necessary induction coil, which should be so wound as to give a spark of at least two inches in length in the tube where a picture of a simple object, as a coin in a purse, is desired; a spark of four inches in length where pictures of the bones of the hands, feet, or arms are desired; and a spark of from eight to ten inches in length where inside views of the chest, thighs, or abdomen are desired. (2.) The second essential is the glass tube. The one in common use is the Crookes tube, usually pear-shaped, and resting upon a stand. Into it is inserted two aluminum electrodes or disks, the one through the smaller end of the tube being used as the cathode, and the one from below and near the large end being used as the anode. (3.) A fluoroscope with which to observe the conditions inside the tube necessary to the production of the X ray, to decide upon its proper intensity, and to establish the proper degree of fluorescence. The favorite fluoroscope for this purpose is the one invented by Edison. It is in the form of a stereopticon, in which is a dark chamber after the manner of a camera. In front are two openings, admitting of a view within of both eyes. At the opposite, and greatly enlarged, end is a screen which is rendered fluorescent by means of a new substance (tungstate of calcium) discovered by Mr. Edison after some eighteen hundred experiments. Such is the power of this fluoroscope that it may be used as an independent instrument in cases of minor surgery to locate bullets or other objects buried in the flesh, even before a photograph has been taken. (4.) The photographic plate, which is prepared with a sensitized film and mounted in a frame as in ordinary photography. Upon this film the object to be photographed is laid, say, for instance, the human hand, care being taken to have the film or plate at a proper distance from the Crookes tube. Current is now turned into the tube, the X ray is developed, the film is exposed to its effects, and the result is a negative showing the interior structure of the hand,—the bones or any foreign object therein. This negative is developed as in ordinary photography.

The discovery and application of the X ray has proved of immense value in medicine and surgery. By its means the physician is enabled to carry on far-reaching diagnoses, and to ascertain with certainty the whole internal structure of the human body. Fractures, dislocations, deformities, and diseases of the bones may be located and their character and treatment decided upon. In dentistry, the teeth may be photographed by means of the X ray, even before they come to the surface, and broken fangs and hidden fillings may be located. Foreign objects in the body, as bullets, needles, calculi in the bladder, etc., may be localized, and the surgery necessary for their safe removal greatly simplified. The beating of the heart, movement of the ribs in respiration, and outline of the liver may be exhibited to the eye. It has been boldly suggested that in the X ray will be found an agent capable of destroying the various bacilli which infest the human system, and become germs of such destructive diseases as cholera, yellow fever, typhoid fever, diphtheria, and consumption. Even if this be speculative as yet, there is still room for marvel at the actual results of the discovery of the X ray, and its future study opens a field full of the grandest possibilities.

IX. OTHER ELECTRICAL WONDERS.

The novel idea of keeping time by means of electricity originated quite early in the century, and culminated in two kinds of electric clocks, one moved directly by the electric current, the other moved by weights or springs, but regulated by electricity. The former have the advantage of running a very long time without attention, but as it is impossible to keep up an unvarying electric current, they are not so accurate as the latter in keeping time. Though the latter are popularly called electric clocks, they are really only clocks regulated by electricity, and in such regulation the electric current comes to be a most important agent, as is proved at all centres of astronomical and other observations, as at Greenwich and Washington. At such centres the astronomical time-keeper is set up so as to run as infallibly as possible. This central time-keeper, say at Washington, is electrically connected with other clocks, at observatories, signal-service stations, railway stations, clock-stores, city halls, etc., throughout the country. Should any of these clocks lose or gain the minutest fraction of time as compared with that of the central time-keeper, the electric current corrects such loss or gain, and so keeps all the clocks at a time uniform with one another and with the central one. Electrical devices are also often attached to individual clocks, as those upon city hall towers and in exposed places, for the purpose of meeting and correcting inequalities of time occasioned by weather exposure, expansion and contraction by heat and cold, etc.

The fatherhood of the very useful and elegant arts of electrotyping and electroplating is in dispute. Daniell, while perfecting his battery, noticed that a current of electricity would cause a deposit of copper. In 1831, Jacobi, of St. Petersburg, called attention to the fact that the copper deposited on his plates of copper by galvanic action could be removed in a perfect sheet, which presented in relief, and most accurately, every accidental indentation on the original plates. Following this up, he employed for his battery an engraved copper plate, caused the deposit to be formed upon it, removed the deposit, and found that the engraving was impressed on it in relief, and with sufficient firmness and sharpness to enable him to print from it. Jacobi called his discovery galvanoplasty in the publication of his observations in 1839. It was but a step from this discovery to the application of the electrotyping process to the art of printing. A mould of wax, plaster, or other suitable substance is made of an engraving or of a page of type. This mould is covered with powdered graphite (black lead) so as to make it a conductor of electricity. It is then inserted in a bath containing a solution of sulphate of copper. An electric current is passed through the bath, and the copper is deposited on the mould in sufficient quantity to give it a hard surface capable of offering greater resistance in printing than the types themselves, and also of producing a clearer impression. In electroplating, practically the same principle is employed. The bath is made to contain a solution of water, cyanide of potassium, and whatever metal—gold, silver, platinum, etc.—it is designed to precipitate on the article to be electroplated. The current is then passed through the bath, and the article—spoon, knife, fork, etc.—to be electroplated receives its coating of gold, silver, German silver, platinum, or whatever has been made the third agent in the bath.