Royal Observatory, Greenwich, the famous English observatory founded by Charles II. in 1675. The first observation was made Sept. 19, 1675. The Director of the Observatory is styled Astronomer Royal, and is under the official control of the Admiralty, but receives his appointment directly from the Prime Minister, and holds office by warrant under the royal sign manual. Longitude is commonly reckoned from here.
Entry from Everybody's Cyclopedia,
1912.