Historical Notes on the Deviation of the Compass

Few historians of the magnetic compass carry their story beyond the period of the birth of ocean avigation. To those interested in this fascinating instrument here are, however, many interesting lines of enquiry to be traced in the centuries which followed. These notes are the result of an attempt to investigate the beginnings of just one branch of progress. During the Sixteenth, Seventeenth, and Eighteenth Centuries, when there were many who tried to solve the problem of finding the longitude at sea, one of the favorite methods proposed was the use of the variation of the compass. Of those who proposed this method one of the last was Ralph Walker, a resident of Jamaica, who, in the year 1793, traveled to England* to lay his proposals before the Board of Longitude. It is not intended here to discuss his variation theory but to point out that, in addition to producing this theory, he designed a compass to enable the variation to be observed with greater accuracy at sea. This compass was sent. for trial in It. M. Ships Invincible, Glory, and Lynx• and it was this trial in the Glory which introduced her master, Murdo DownieJ:, to fame among those who have written on the magnetic compass. In his report on Walker's compass Downie wrote [see 1 of "Authorities quoted" at end of paper]: