Though in the nineteenth century the old sources of power continued in use, their relative importance changed greatly. The windmill remained in use for drainage purposes. Because of their limited power, windmills were soon displaced in industry by steam engines, which came to the fore very rapidly, but were not unchallenged. The eighteenth-century experiments with electricity in laboratories and salons had soon led to research into the possibilities of storing electricity. The famous Leyden jar, invented simultaneously in 1745 by a German Lutheran pastor and a Dutch scientist, van Musschenbroek, gave little more than a flash of "static" electricity when discharged.

A regular supply of electricity was obtained by Volta, when he designed a plate form of substitute for the Leyden jar in 1775. This was gradually improved until it became a true "voltaic pile" or battery. As early as 1800 Nicholson and Carlisle used it to accomplish the first decomposition of water by electrolysis, making electricity do work for the first time. These piles or batteries consisted of two different metals or surfaces in a solution of a chemical. They transformed chemical energy into electrical energy. The old voltaic pile with its copper and zinc plates was not improved until Daniell produced his battery in 1836. Grove followed with a new type in 1839 and in 1842 Bunsen invented his carbon-zinc cell. However, the electromotive force of these cells was rather small, and large batteries had to be used to produce electric phenomena. Thus Davy used 2,000 cells to produce an electric arc in 1808. In 1850 Robert Hunt calculated that electrical power was still 25 times as expensive as steam power.

Unfortunately, when producing electrical energy these batteries were gradually destroyed because the zinc plate was eaten away in the chemical process. In the meantime, another form of transforming energy into electricity had been discovered--the dynamo. It was, however, still important to have some way of storing electrical energy. For this purpose the storage battery, using lead plates immersed in dilute sulfuric acid (designed by Gaston Plante in 1859) was a decided improvement. Clark in perfecting his standard zinc-mercury cell in 1873 contributed much to the proper understanding of batteries. This knowledge enabled Faure in 1880 to develop his openwork grid for battery plates, which reduced the weight of the storage battery considerably. Correns then designed the present form of battery grids in 1888.

By this time the battery had become sufficiently light and economical to be used by William Morrison of Des Moines to operate an electric automobile in 1891. It had also become adaptable enough to be installed in a hydroelectric plant to meet peak-load requirements ( Hartford, Conn. 1896). But the sulfuric acid in the batteries still remained a serious drawback, preventing, for example, its use in submarines. Hence Edison turned his fertile brain to the subject and in 1908 he began marketing his "nickel-alkaline" storage battery, which though much lighter, stronger, and more durable, had a lower voltage than the Plante battery.

The answer to the problem of converting mechanical energy into electricity (the generator) and of converting electricity back into mechanical energy (the motor) was derived from a single experiment that is known to every schoolboy. In 1820 the Danish professor Hand Oersted discovered by accident that a current flowing in a wire caused a nearby compass needle to swing at right angles to the wire. It meant that there was some relation between magnetism and electricity. Oersted rightly supposed that both a magnet and an electric current build up a "field of force" and that the two can act upon one another. Until then, every scientist had believed that all physical phenomena could be described in terms of gravitational attraction, but now apparently a new physical force had been discovered.

This discovery created a great sensation in academic circles, and only a few months later the French physicist Arago was able to prove that a needle in a coil through which an electric current was flowing became magnetized. This "induced magnetism" was permanent in steel, but wrought iron cores lost their magnetism rapidly. The "electric solenoid" was thus a new means of making a magnet. Ampere was another French physicist who was highly interested in Oersted's experiments, which he repeated, showing that two parallel wires carrying current in the same direction attract each other, but that if the currents flow in opposite directions the wires repel each other. The ampere, unit of current strength, was named in his honor.

Unfortunately Ampere's essays were far in advance of his contemporaries and were so highly mathematical in nature as to be largely unintelligible to many of them. This, combined with the chaotic state of terms referring to electrical phenomena, caused academic interest to subside for a time. The popular demonstrations of William Sturgeon, who constructed the first electromagnet in 1825, also aroused much attention in general circles, but little progress could be expected from that quarter.

It took several years for these new phenomena to bear fruit. The American, Joseph Henry, revealed in 1831 a series of remarkable facts. He discovered the phenomenon of electrical induction and applied it to transform magnetism into electricity. He had constructed the first electric motor in 1829, discovered the principle of the "step-down" and "step-up" transformer, and demonstrated a telegraphic instrument using a one-mile length of wire. Unfortunately his discoveries, though published in Silliman's Journal and known to most scientists of the day, did not have the effect they deserved.

Faraday was luckier in this respect. He, too, had pondered and experimented for several years on these phenomena, and in the same year as Henry he discovered the means of transforming magnetism into electricity. A coil connected with a galvanometer and a coil connected with a battery wound on  the same cylinder of wood formed the first instrument he used. When he closed or opened the circuit of the second coil, a current was induced in the first coil, as indicated by a reading of the galvanometer. The same phenomena was observed when the wooden cylinder was replaced by an iron ring. Faraday discovered that moving a magnet in and out of a coil also induced a current in the coil. He went on to construct a 12inch copper disk which rotated between the poles of a horseshoe magnet. A wire taken from the shaft and one taken from a brush rubbing the edge of the disk were made to form a circuit in which an induced current could be detected.

These demonstrations before the Royal Institution in April, 1832, created quite a sensation. When one of the visitors asked Faraday what use this new toy had, he is said to have replied, "What is the use of a newborn child?" It was soon proved that the newborn child was a lusty infant. The coil and magnet contained the principle of the generator, wherein mechanical energy is transformed into electric current, as well as the principle of the motor, which transforms electrical energy into mechanical energy.

The generator or dynamo was therefore understood in principle at least by 1832, but many obstacles stood in the way of constructing a practical working model that could serve as a source of power. One of these was the lack of properly insulated electric wire. When Morse was perfecting his first telegraph in 1837, the only insulated wire available on the market was that used by milliners for the skeleton of the "skyscraper" bonnets then worn by fashionable ladies in New York. Other inventors had to go through the tedious process of winding silk thread around copper wires by hand. . .