CXXll 
APPENDIX. 
sufficient with a very little practice to enable the variation to be assigned for 
every point of the compass, without a reference to tables or to computation, 
and with quite as much accuracy as was necessary for the practical purposes 
of navigation, which, as the compass was not referred to in surveying, the 
position of all lands being determined by astronomical bearings, was, in fact, 
its only use on board. 
