From the Rare Book and Special Collections Division Title: An explanation of the magnetic atlas, or variation chart, hereunto annexed : projected on a plan entirely new, by which the magnetic variation on any part of the globe may be precisely determined, for any time, past, present, or future : and the variation and latitude being accurately known, the longitude is of consequence truly determined / by John Churchman, late land surveyor for the district of the counties of Delaware and Chester, and for part of Lancaster and Berks, Pennsylvania. - [Catalog record]
