John Churchman and the Longitude Problem

Abstract

In the early days of ocean navigation the problem of finding longitude, apart from the crude methods of dead reckoning, commanded considerable attention until practical solutions were found at mid-eighteenth century. In the initial phase of Atlantic voyaging it was realized that variation changes with longitude. This led to the suggestion that the crucial problem of east-west navigation might be solved from variation observations. Under an Act of Parliament (12 Anne, cap.xv) of 1714, which provided for a handsome monetary prize for the ‘discovery of the longitude’, a committee known as the Board of Longitude was formed. The Board continued, until its dissolution in 1828, to examine proposals for improving navigation after the principal problem had been solved. The 1714 Act led to numerous proposals from cranks and crackpots as well as men of science, and many of these proposals concerned ‘longitude by variation’. John Churchman, a land-surveyor and citizen of Philadelphia, communicated with the Board of Longitude on his scheme for finding longitude by variation for seventeen years from 1787 to 1804. During this time he persisted, with unshaken faith, that he had solved the problem. This paper deals with Churchman's proposals with special reference to his correspondence with the Board of Longitude.