Origins
Cooper Hewitt lamp, 1903
Charles Wheatstone observed the spectrum of an electric discharge in mercury vapor in 1835, and noted the ultraviolet lines in that spectrum. In 1860, John Thomas Way used arc lamps operated in a mixture of air and mercury vapor at atmospheric pressure for lighting.[3] The German physicist Leo Arons (1860–1919) studied mercury discharges in 1892 and developed a lamp based on a mercury arc.[4] In February 1896 Herbert John Dowsing and H. S. Keating of England patented a mercury vapour lamp, considered by some to be the first true mercury vapour lamp.[5]
The first mercury vapor lamp to achieve widespread success was invented in 1901 by American engineer Peter Cooper Hewitt.[6] Hewitt was issued U.S. Patent 682,692 on September 17, 1901.[7] In 1903, Hewitt created an improved version that possessed higher color qualities which eventually found widespread industrial use.[6] The ultraviolet light from mercury vapor lamps was applied to water treatment by 1910. The Hewitt lamps used a large amount of mercury. In the 1930s, improved lamps of the modern form, developed by the Osram-GEC company, General Electric company and others led to widespread use of mercury vapor lamps for general lighting.
https://en.wikipedia.org/wiki/Mercury-vapor_lamp