Graphometer - Brass - 1850-1900

Very handsome antique brass graphometer.

19th century.
Good condition.
As found.
Bears an ink mark.

The graphometer is an old instrument for angular measurement. Mounted on a ball joint, it allows one to “take” angles between objects located in the same plane. It is an instrument for geodesy and topography.

It was invented by Philippe Danfrie, the elder rather than the younger, in 1597, if we are to believe the patent letters issued by Henry IV in 1606 and his will1. This semicircle bearing alidades and pinnules would be widely used for over 150 years. It would be succeeded by the eyeglass graphometer, around the 1760s.