Description

Quality Mathematics in the mid-18th Century, English, mid 18th century, signed “F. Watkins, London,” of thin brass 6-1/4″ x 1-3/4″ (16 x 4.5 cm) decorated both sides with running leaf tip design. The front has gently beveled edges, and is exquisitely engraved with a rectangular protractor (divided every half-degree) and with scales of equal parts with transversals for interpolation. The reverse has further chart scales, and complex scales for calculation (Cho, Lat, Sin, In Me, Tan, Hou, E P, Rum, Lon, Sec, Sec Continued, and Tan Continued). Very fine condition.