Peter Cooper Hewitt

Peter Cooper Hewitt
Peter Cooper Hewitt holding his mercury vapor rectifier
Born	(1861-05-05)May 5, 1861 New York City, New York, U.S.
Died	August 25, 1921(1921-08-25) (aged 60) Paris, France
Nationality	American
Alma mater	Columbia University School of Mines
Known for	Arc discharge lamp, mercury-arc valve
Notable awards	Elliott Cresson Medal (1910)

Peter Cooper Hewitt (May 5, 1861 – August 25, 1921) was an American electrical engineer and inventor, who invented the first mercury-vapor lamp in 1901. Hewitt was issued U.S. Patent 682,692 on September 17, 1901. In 1903, Hewitt created an improved version that possessed higher colour qualities which eventually found widespread industrial use.

Hewitt was born in New York City, the son of New York City Mayor Abram Hewitt and the grandson of industrialist Peter Cooper. He was educated at the Stevens Institute of Technology and the Columbia University School of Mines.

In 1901 he invented and patented a mercury-vapor lamp; a gas-discharge lamp that used mercury vapor produced by passing current through liquid mercury. His first lamps had to be started by tilting the tube to make contact between the two electrodes and the liquid mercury; later he developed the inductive electrical ballast to start the tube. The efficiency was much higher than that of incandescent lamps, but the emitted light was of a bluish-green unpleasant color, which limited its practical use to specific professional areas, like photography, where the color was not an issue at a time where films were black and white. For space lighting use, the lamp was frequently augmented by a standard incandescent lamp. The two together provided a more acceptable color. Later. in the 1930s. a fluorescent coating (phosphor) was added to the inside of the tube at General Electric, which produced more pleasing white light when it absorbed the ultraviolet light from the mercury. This was the fluorescent lamp, which is now one of the most widely used lamps in the world.