Attitude and Longitude

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  Article taken from "Backsights" Magazine published by Surveyors Historical Society

ATTITUDE AND LONGITUDE

by David Alan Grier

Where is the center of the known universe? For those of us who believe the world revolves around American politics, we suppose the point by which all else is reckoned hovers somewhere above the Capitol dome, or perhaps over the West Lawn.

But it turns out there was a time when Washingtonians had a less metaphorical claim to being the center of the world: It was called the American Meridian, a geographical line that separated the Eastern and Western hemispheres. To residents of Foggy Bottom, the American Meridian had a more prosaic name: 24th Street NW.

Congress authorized the meridian in the Naval appropriations bill for 1849 and directed that it pass through the central dome of the U.S. Naval Observatory, a facility then located on a small bluff at 24th and D NW.

Prior to that year, American navigators tended to use either the French meridian at Paris or the British meridian at Greenwich to measure longitude. Meridians were expensive ventures for governments - to make them anything other than a defiant gesture of political independence, a government needed to publish an annual almanac giving the positions of the stars relative to the meridian. Adm. Charles Henry Davis, the first director of the American Almanac, estimated that the British government spent between $16,000 and $17,000 preparing its version (which, trust us, was a considerable sum in those days).

As it turned out, few navigators adopted the American Meridian, as they owned charts that gave distances relative to Paris, or London, rather than 24th Street NW. Davis recognized that navigators continued to require Greenwich star tables and included them in the American Almanac.

The stellar tables for the American Meridian were used, but by surveyors, not navigators. By 1849 teams of surveyors and mappers were moving steadily across the American West. For them, measuring distances to a line that lay across a broad ocean was inconvenient at best, and at worst introduced errors into their surveys. Davis noted that the "difficulty of making absolute determinations of longitude increases as the place is more remote."

As a result, those great square boundaries of the Western states are all figured in appealing round numbers from the American Meridian at 24th Street. The eastern border of Wyoming is exactly 27 degrees west of 24th Street, that of Arizona is 32 degrees west, the Utah-Nevada border is 36 degrees west.

The United States abandoned the American Meridian in 1884, when it accepted the meridian at Greenwich as the international standard.

The Naval Observatory moved to its current site on Massachusetts Avenue in 1893, taking with it the telescopes that had been used to measure the stars above the meridian. The original naval observatory site is now the location of the Naval Surgery command. The old buildings, including the abandoned telescope domes, can be clearly viewed from the roof of the Kennedy Center and from the Roosevelt Bridge. Drivers traveling on that bridge may believe that they are leaving Virginia and entering the District, but in fact, they are moving from the Western American Hemisphere into the Eastern by crossing the meridian at 24th Street.

- Washington, DC Insiderís Guide, The Washington Post, Feb. 6, 2000

 

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