A prominent factor in the electrical art is the Storage Battery, Secondary Battery, or Accumulator, as it is variously called. A storage battery acts upon the same general principle as the ordinary galvanic or voltaic battery in giving forth electrical current as the correlated equivalent of the chemical force, but differs from it in this respect, that when the elements of a primary battery are used up, the battery is exhausted beyond repair. With the storage battery, it may be regenerated at will by simply subjecting it to an electric current from a dynamo. The dynamo stores up in this battery its electric force by converting it into chemical force, which is imprisoned in chemical compounds that are formed while the power of the dynamo is being applied. These chemical compounds are, however, in a condition of unstable chemical equilibrium, which is undisturbed so long as the poles of the storage battery are not connected, but when connected through a circuit, the instability of the chemical compounds asserts itself, and in passing back to a condition of normal equilibrium the disruption gives off the correlative equivalent of electric current stored up in it by the dynamo.Probably the earliest suggestion of a storage battery is by Ritter in 1812, in his “secondary pile.” This device consisted of alternate discs of copper and moistened card, and was capable of receiving a charge from a voltaic pile and of then producing the physical, chemical, and physiological effects obtained from the ordinary pile. The first storage battery of importance, however, was made by Gaston PlantÉ in 1860, which consisted of leaden plates immersed in a 10 per cent. solution of sulphuric acid in water. In Fig. 64 is shown a modification of the PlantÉ type of storage battery, composed of a series of plates shown on the left. Each of these plates is built up, as shown in detail in Fig. 65, of lead strips corrugated and arranged in layers alternately with flat strips, within perforated leaden cases. The corrugation of the leaden laminÆ gives greater superficial area, and the alternation of flat and corrugated strips keeps them properly spaced, so the sulphuric acid solution may penetrate and act upon the same. Each plate section has a rod to connect it with its proper terminal. When the charging current is applied, the positive lead plate becomes covered with lead peroxide (PbO₂) and finely divided metallic lead is deposited on the negative plate. When the battery is being discharged the peroxide of lead gives up one of its atoms of oxygen to the spongy metallic lead deposited on the other plate, and both plates remain coated with lead monoxide (PbO).

The most important development of the storage battery was made by Camille A. Faure, in 1880 (U.S. Pat. No. 252,002, Jan 3, 1882). In the early part of 1881 there was sent from Paris to Glasgow a so-called “box of electric energy” for inspection and test by Sir William Thomson, the eminent electrician. It was one of the first storage batteries of M. Faure. The illustration, Fig. 66, shows a battery of this type in which the lead plates covered with red lead (Pb₃O₄) replace the plain lead plates in the PlantÉ cell. The action of the battery is that when a current of electricity is passed into the same, the red lead on one plate (the negative) is reduced to metallic lead, and that on the other is oxidized to a state of peroxide (PbO₂). These actions are reversed when the charged cell is discharging itself. The elements of this battery consist of alternate layers of sheet lead, and a paste of red oxide of lead. These are immersed in a 10 per cent. solution of sulphuric acid in water. Many minor improvements have been made in the storage battery, covered by 716 United States patents, most of which relate to cellular construction for holding the mass of red lead in place. The most notable are those of Brush, to whom many patents were granted in 1882 and 1883.

The storage battery finds many important applications. For furnishing current for the propulsion of electric street cars it has proved a disappointment, on account of the vibrations to which it is subjected, and the great weight of the lead, which in batteries of suitable capacity runs up into many thousands of pounds. The storage battery finds a useful place, however, for equalizing the load in lighting and power stations, and is there brought into action to supplement the engine and dynamo during those hours of the day when the tax or load is greatest. It is also used to keep up electrical pressure at the ends of long transmission lines; for telegraphing purposes; for isolated electric lighting; for boat propulsion; the propulsion of automobile carriages; and in all cases where a portable source of electric current would find application. The great growth of automobile carriages in the past year has greatly stimulated the output of storage batteries. One large company (The Electric Storage Battery Company), manufactured and sold storage batteries for the year ending June 1, 1899, to the amount of $2,387,049.91, and there are many other manufacturers.

Electric Welding was invented by Prof. Elihu Thomson, of Lynn, Mass., and patented by him August 10, 1886, No. 347,140-42, and July 18, 1893, No. 501,546. It is useful for the making of chains, tools, carriage axles, joining shafting, wires, and pipes, mending bands, tires, hoops, and lengthening and shortening bolts, bars, etc. For electric welding a current of great volume or quantity, and very low electro-motive force, is required. Thus a current of from one to two volts, and one to several thousand amperes, is best suited. Referring to Fig. 67, the current from the dynamo is conducted to one binding post of the commutator 3, which is arranged to send the current through one-sixth, one-third or one-half of the primary wire P of a transformer or induction coil. The other binding post of the commutator 3 extends to one terminal of an isolated primary coil 4, and the other terminal of this coil connects with the dynamo. The coil 4 is provided with a switch to regulate the amount of current. The rods to be welded are placed in clamps C C', C being connected with one terminal of the secondary conductor S, and the movable clamp C' with the other. When the current is turned on C' is moved so as to project one of the surfaces to be welded against the other, and as they come in contact they heat and fuse together, as shown at W. Larger apparatus has been devised to weld railroad joints on the roadbed, and for other applications.

The generation of electricity for commercial purposes is almost entirely dependent upon the dynamo, as this is cheaper than the voltaic battery. The dynamo, however, must be energized by a steam engine. The direct production of electric energy by the combustion of coal would be the ideal method. A process invented by Edison (Pat. No. 490,953, Jan. 31, 1893), is interesting as an effort in this direction, and is presented in Fig. 68. A carbon cylinder D is suspended in an air-tight vessel B, and is surrounded by oxide of iron F, the whole being placed above a furnace. The temperature being raised to a point where the carbon will be attacked by the oxygen, carbonic oxide and carbonic acid will be formed, which are exhausted by the suction fan E. A constant current of electricity is given off from the two electrodes through the wires, the metallic oxide being reduced and the carbon consumed.

Electrical Navigation began with Jacobi, who made the first attempt on the Neva in 1839. He used voltaic apparatus consisting of two Grove batteries, each containing sixty-four pairs of cells, but little progress was made in this field until the secondary battery was perfected. In 1881 Mr. G. TrouvÉ made an application of the storage battery and electric motor to a small boat on the Seine. The electric motor, which was located on top of the rudder, as seen in Fig. 69, was furnished with a Siemens armature connected by an endless belt with a screw propeller having three paddles arranged in the middle of an iron rudder. In the middle of the boat were two storage batteries connected with the motor by two cords that both served to cover the conducting wires and work the rudder. Electric launches have in later years rapidly gained in popularity. Visitors to the Chicago fair will remember the fleet of electric launches, which afforded both pleasure and transportation on the water, at that great exposition, and to-day every safe harbor has its quota of these silently gliding and fascinating pleasure crafts. Fig. 70 is a longitudinal section and a general view of one of these launches.

Electro-plating is one of the great industrial applications of electricity which had its origin in, and has grown into extensive use in, the Nineteenth Century. It originated with Volta, Cruikshank, and Wollaston in the very first year of the century. In 1805 Brugnatelli, a pupil of Volta, gilded two large silver medals by bringing them into communication by means of a steel wire with the negative pole of a voltaic pile and keeping them one after the other immersed in a solution of gold. In 1834 Henry Bessemer electro-plated lead castings with copper in the production of antique relief heads. In 1838 Prof. Jacobi announced his galvano-plastic process for the production of electrotype plates for printing. In the same year he superintended the gilding, by electro-plate, of the iron dome of the Cathedral of St. Isaac at St. Petersburgh, using 274 pounds of ducat gold. In 1839 Spencer described an electrotype process and carried the date of his operations back to September, 1837. In 1839 Jordan also describes an electro-plating process. In 1840 Murray used plumbago to make non-conducting surfaces conductive for electro-plating. In 1840 De Le Rive made known his process of electro-gilding, employed by him in 1828, and in the same year (1840) De Ruolz took out a French patent for electro-gilding, and in the following year formed electro deposits of brass from cyanides of zinc and copper. In 1841 Smee employed his battery for electro-plating with various metals. In 1844 there were published the electro-plating experiments of Dancer, made in 1838. In 1847 Prof. Silliman imitated mother-of-pearl by electro-plating process.

In the last half of the century the production of electrotype plates for printing in books, and for the production of rollers for printing fabrics, and the extensive art of electro-plating with gold, silver, nickel and copper, has grown to enormous proportions, but the fundamental principles have not materially changed. The dynamo, however, has generally supplanted the voltaic battery in this art. The deposition of silver and gold on baser metals not only increases the ornamental effect, but prevents oxidation. Silver plated goods for the table and articles of vertu are to be found everywhere. Nickel is employed for cheaper ornamental effect, and copper finds a large application for electrotypes for printing and for coating iron castings as a protection against rust. In Fig. 71, which shows the interior of an electro-plating establishment, the dynamo is shown on the right connected by wires with two horizontal rods running along the wall and across the various tanks containing the plating solution. On the tanks are rods supporting the articles to be plated, which are suspended in the solution. Similar rods support the opposite electrodes of the tank. Wires connect these rods to the rods on the side of the wall, and to the opposite poles of the dynamo.

The electric pen of Edison, brought out in 1876 (U.S. Pat. No. 196,747, Nov. 6, 1877), is one of the simple applications of electricity, which for a number of years was in quite general use for making manifold copies of manuscript. In the illustration, Fig. 72, this is shown. It comprises a stylus b reciprocated in a tube a by the vibratory action of an armature k over the poles of an electro-magnet, supplied with a suitable current and vibrating contacts l h. The stylus was rapidly reciprocated, and as the operator traced the letters on the paper, the stylus produced a continuous trail of punctures which permitted the paper to be used as a stencil to make any number of copies. It has, however, been rotated out of existence by manifolding carbon paper, and the almost universal use of the typewriter.

Electricity in Medicine.—The superstitious mind is prone to resort to mysterious agencies for the cure of diseases, and for many years men of no scientific knowledge whatever have been employing this seductive instrumentality for all the ills that flesh is heir to. That it has valuable therapeutic qualities when rightly applied no intelligent person will doubt, and it is unfortunate that for the most part it has been in the hands of charlatans who sell their wares, and rely upon a faith-cure principle for the result. Still there have been intelligent experimenters in this field, and it is one of much promise for further research.In the first century of the Christian Era (A. D. 50) Scribonius Largus relates that Athero, a freedman of Tiberius, was cured of the gout by the shocks of the torpedo or electric eel. In 1803 M. Carpue published experiments on the therapeutic action of electricity. The discovery of induction currents by Faraday in 1831 brought a new era in the medical application of electricity, in the use of what is known as the Faradaic current. The first apparatus for medical use, which operated on this principle, was made by M. Pixii in France, and the first physician who employed such currents was Dr. Neef, of Frankfort. The medical battery is a well-known and useful adjunct to the physician’s outfit. Electric baths are also common and effective modes of applying the electric current. An early example of such a device is shown in the U.S. patent to Young, No. 32,332, May 14, 1861. The electric cautery and probe are also scientific and useful instruments. The cautery consists of a loop of platinum wire carried by a suitable non-conducting handle, with means for constricting the white hot loop of wire about the tumor or object to be excised. It was invented in 1846 by Crusell, of St. Petersburgh. A form of the electric cautery is shown in Fig. 73, in which a is the platinum wire loop whose branches slide through guide tubes, the ends being attached to a sliding ring B. The current enters through the wire at the binding posts at the end of non-conducting handle A, and heats the platinum loop, a, red hot. The loop, a, being around the object to be excised, is constricted by drawing down the handle ring B.

Of the various applications of electricity in body wear and appliances there is scarcely any end. There are patents for belts without number, for electric gloves, rings, bracelets, necklaces, trusses, corsets, shoes, hats, combs, brushes, chairs, couches, and blankets. Patents have also been granted for electric smelling bottles, an adhesive plaster, for electric spectacles, scissors, a foot warmer, hair singer, syringes, a drinking cup, a hair cutter, a torch, a catheter, a pessary, gas lighters, exercising devices, a door mat, and even for an electric hair pin and a pair of electric garters.Electrical Musical Instruments include pianos, banjos, and violins, all of which are to be played automatically by the aid of electrical appliances. In the illustration, Fig. 74, is shown a modern electrical piano. A small electrical motor 1, run by a storage battery or electric light wires, turns a belt 3, and rotates pulley 4 and a long horizontal cylinder 5 running beneath the keyboard. Above this cylinder is the mechanism that acts upon the keys. It consists of a series of brake shoes which, when brought into frictional contact with the cylinder 5, are made to act on small vertical rods which bring down the keys just as the fingers do in playing. The selection of the proper keys is made by a traveling strip of paper perforated with dots and dashes representing the notes, which strip of paper passes between two metal contact faces, which are terminals of an electric battery. When the contacts are separated by the non-conducting paper the current does not flow, but when the contacts come together through the perforations the current is completed through an electro-magnet, and this is made to bring the proper brake shoe into position to be lifted by the cylinder 5, which rotates constantly.

Electro-blasting.—In 1812 Schilling proposed to blow up mines by the galvanic current. In 1839 Colonel Pasley blew up the wreck of the “Royal George” by electro-blasting. On Jan. 26, 1843, Mr. Cubitt used electro-blasting to destroy Round Down Cliff, and in our own time the extensive excavations in deepening the channel and removing the rocks at Hell Gate, from the mouth of New York harbor, was a notable operation in electro-blasting, and doubtless owes its success largely to the electric current employed.

Only the briefest mention can be made of the induction coil and the electrical transformer, of electric bells and hotel annunciators, of electric railway signalling, and electric brakes, of electric clocks and instruments of precision, of heating by electricity, of electrical horticulture, and of the beautiful electric fountains. These, however, all belong to the Nineteenth Century, and include interesting developments.

Electro-chemistry and the electrolytic refining of metals represent also, in the applications of electricity, a large and important field, more fully treated under the chapters devoted to chemistry and metal working.