Page:Voyage in search of La Perouse, volume 1 (Stockdale).djvu/100

90 for between 14° N. lat. and the Equator, in the pace contained between 23° and 26° W. long. the difference had not been more than 3°, or from 14° to 11°; whilt in the ame extent of outh latitude, between 26° and 30° W. long. the compas varied eight degrees to the eat, or from 11° to 3°. Might not the vicinity of the coat of Brazil be one of the principal caues of this difference?

The mallet variation oberved was that of 1° 50′, in 25° S. lat. and 29° W. long. It cannot be doubted that the change of ituation with repect to longitude has a much greater influence upon the variation of the needle, than change of latitude. The variation increaed enibly in proportion as we advanced farther eatward.

One of our officers who was taking the ditances between the un and moon, in a very incommodious ituation, with a copper extant made by Dollond, the radius of which was a foot in length, dicovered a caue productive of error in the calculations, which one hould hardly have upected. The radii of this intrument, though very heavy, were till o lender as to bend when it was preed with any degree of force againt the breat, whereby the parallelim of the pecula was deranged. The ame effect does not take place with extants made of wood, for their radii, being