Knock, knock
Who’s there?
Merry.
Merry who?
Merry Christmas!
Mercury vapour lampIn 1901, the first U.S. patents for a mercury vapour lamp were issued to inventor Peter Cooper Hewitt of New York City (Nos. 682,692-99). These eight patents covered the design of an elongated vacuum tube fitted with a mercury electrode at one end and an iron electrode at the other end. Light was produced when an electric current passed through the mercury vapour. However, it was a garish blue-green colour, lacking any red light. The lamps were subsequently manufactured by the Cooper Hewitt Electric Company in New York City, in Dec 1902. They were an important forerunner of today's fluorescent lights.« |
