The simplest facts of electro-magnetism, upon which much of the later electrical developments depend, remained entirely unknown until near the close of the first quarter of the nineteenth century. Magnetism itself, as exemplified in loadstone or in magnetized iron or steel, had long before been consistently studied by Dr. Gilbert, of Colchester, England, and in 1600 his great work, _De Magnete_, was published. It is a first example, and an excellent one, too, of the application of the inductive method, so fruitful in after-years. The restraints which a superstitious age had imposed upon nature study were gradually removed, and at the beginning of the century just past occasional decided encouragement began to be given to physical research. It was this condition which put into the hands of Humphry Davy, of the Royal Institution, in London, at the opening of the century, a voltaic battery of some 250 pairs of plates. With this a remarkably fruitful era of electric discovery began. In 1802 Davy first showed the electric arc or “arch” on a small scale between pieces of carbon. He also laid the foundation for future electro-chemical work by decomposing by the battery current potash and soda, and thus isolating the alkali metals, potassium and sodium, for the first time. This was in 1807, and the result was not only to greatly advance the youthful science of chemistry, but to attract the attention of the world to a new power in the hands of the scientific worker, electric current. A fund was soon subscribed by “a few zealous cultivators and patrons of science,” interested in the discovery of Davy, and he had at his service in 1801 no less than 2000 cells of voltaic battery. With the intense currents obtained from it he again demonstrated the wonderful and brilliant phenomenon of the electric arc, by first closing the circuit of the battery through terminals of hardwood charcoal and then separating them for a short distance. A magnificent arch of flame was maintained between the separated ends, and the light from the charcoal pieces was of dazzling splendor. Thus was born into the world the electric arc light, of which there are now many hundreds of thousands burning nightly in our own country alone.