QUADRANT

These instruments are variously constructed, and by consequence the apparatus of each kind is somewhat different from those of the others, according to the improvements they have at different times received from several ingenious artists. As all the different kinds of quadrants are circumstantially described, either in printed directions to tile them, or in other books, a particular account of them here might reasonably be esteemed superfluous. It suffices to say that the most useful, as well as the most general, for taking observations at sea is the octant, originally invented by Sir Isaac Newton, .and since that time improved and brought into practice by Mess. Godfrey and Hadley.

It may not however be unnecessary to remark, that the back-observation, which, in many situations, is certainly more accurate and useful than that which is taken in front, is almost totally neglected by our observers, under pretence of its being more uncertain, or more liable to error; but really because it is somewhat more difficult to learn. We may venture to affirm however, that no artist, who thoroughly understands the operation, will ever advance so absurd an objection, unless we should doubt the testimony of a multitude of experiments.

Reference Works