development of the open-hearth process, the birth of the age of steel.
The incandescent electric light was but six years old. For household and street lighting, illuminating gas had been one of the wonders of modern ingenuity until Thomas A. Edison, in 1879, completed the long series of experiments which resulted in his vacuum bulb containing a filament that emitted, when electrified, a light brighter and more serviceable than any hitherto known. Edison's interminably careful methods were exemplified by this most famous of his inventions. He spent years trying out materials for a filament, discarding platinum because of its cost, and almost abandoning carbon because it blew itself to pieces if electrified in contact with air. On discovering that the carbon would burn in a vacuum without destroying itself, he had the problem well-nigh solved. There yet remained a vast amount of detail, however, before perfection could be reached. Hundreds of materials were used for filament before the inventor decided that bamboo was the best. Thereupon he sent men all over the world to find the most superior bamboo. The Japanese variety was chosen after the search had cost $100,000. For years that fiber was used satisfactorily, until it was supplanted by a more economical filament made by squirting a solution of cellulose through glass jets into alcohol. When the alcohol coagulates, the hardened cellulose is carbonized by heat. There can be no doubt that prior to the motor age Edison's incandescent lamp was the invention which most vitally affected the everyday life of the everyday man.
In the autumn of 1885 the first electric street railway
