Shadow Square Graphometer, Circa 1640-60

Interesting brass graphometer, unsigned, but French, of fairly early production around 1640-1660, provided in the center of the semi-circle with a shadow square. The instrument measures 26cm in diameter and 14.3cm in height. The semicircle is divided into two times 180 degrees, all degrees. In the center of the semi-circle a shadow square bears the inscriptions "Umbra Recta" and on its two sides "U[mbra] versa". It is divided four times from 10 to 100 degrees. The mobile alidade carrying a division from 90 to 0, then a short scale 0 to 100. The dermicircle has been cleaned and varnished. The four pinnules were formerly remade in oxidized steel. Part of the ball joint was also previously remade in pink steel: the plate joining the ball joint to its foot and the butterfly screw. Despite these defects and restorations, elegant graphometer, very well divided, nicely engraved and beautifully cut, from the mid-17th century.