Lapidaries' COMPASSES, a piece of wood in form of the shaft of a plane, cleft at top, as far as half its length; and with this the angles, &c., of jewels and precious stones are measured. There is in the cleft a little brass rule, fastened at one end by a pin, but so that it may be moved in the manner of a brass level. With this kind of square lapidaries take the angles of the stones, laying these on the shaft as they cut them.