Graphometer with suspension ring – Butterfield Paris, 17th century
Butterfield’s early graphometer. After the graphometer, also called semicircle, with transversal vernier, the one with double degree division followed. The mainscale reads from 0 – 180 degrees on the outer edge and 180-0 derees on the inner edge, both anticlockwise. The compass also has a double clockwise degree division. Pair of sights on the semi-circle diameter. In the early ones the name of Butterfield is centrally engraved above the compass. Later species had the name applied to one of the arms. The suspension ring on top makes it possible to measure angles in the vertical plane as well. A special feature of this graphometer is that Butterfield’s name is also engraved in the bottom plate of the compass.
D: 20.5 cm
Signed: Butterfield À Paris
Condition: perfect, original patin