The Graduation of Compass Cards

Extract

I recently received from a correspondent on the other side of the Atlantic a request for information concerning the graduation of compass cards. I compiled the following notes which may be of some interest to readers of the Journal. I must, however, point out that to a great extent they are based on examination of compasses and cards in museums and on my own experience. It may well be that readers, especially those from other countries, may be able to supplement or correct my statements. Any such information would be most welcome.