in the lighting of trains, and in the
ignition and starting of gasoline engines. As an adjunct of the
gas-driven automobile, it renders the starting of the engine independent
of muscle and so makes possible the general use of the automobile by
women as well as men.

The dynamo brought into service not only light and power but heat; and
the electric furnace in turn gave rise to several great metallurgical
and chemical industries. Elihu Thomson's process of welding by means
of the arc furnace found wide and varied applications. The commercial
production of aluminum is due to the electric furnace and dates from
1886. It was in that year that H. Y. Castner of New York and C. M. Hall
of Pittsburgh both invented the methods of manufacture which gave to
the world the new metal, malleable and ductile, exceedingly light,
and capable of a thousand uses. Carborundum is another product of the
electric furnace. It was the invention of Edward B. Acheson, a graduate
of the Edison laboratories. Acheson, in 1891, was trying to make
artificial diamonds and produced instead the more useful carborundum, as
well as the Acheson graphite, which at once found its place in industry.
Another valuable product of the electric furnace was the calcium carbide
first produced in 1892 by Thomas L. Wilson of Spray, North Carolina.
This calcium carbide is the basis of acetylene gas, a powerful
illuminant, and it is widely used in metallurgy, for welding and other
purposes.

At the same time with these developments the value of the alternating
current came to be recognized. The transformer, an instrument developed
on foundations laid by Henry and Faraday, made it possible to transmit
electrical energy over great distances with little loss of power.
Alternating currents were transformed by means of this instrument at
the source, and were again converted at the point of use to a lower and
convenient potential for local distribution and consumption. The first
extensive use of the alternating current was in arc lighting, where the
higher potentials could be employed on series lamps. Perhaps the chief
American inventor in the domain of the alternating current is Elihu
Thomson, who began his useful career as Professor of Chemistry and
Mechanics in the Central High School of Philadelphia. Another great
protagonist of the alternating current was George Westinghouse, who was
quite as much an improver and inventor as a manufacturer of machinery.
Two other invento