B68-524 SURVEYOR'S GRAPHOMETER. This superb instrument strongly resembles James Lilley's 1857 patent, but it isn't signed and, unlike Lilley's patent (and typical graphometers), it is based on a quarter circle rather than full semicircle. The quarter circle has a 6" radius and gridlines for calculating areas. There two arms, one fixed and 11" long and the other adjustable and 13", both with sighting vanes and tally counters. The instrument be mounted horizontally, with a Jacob's staff socket, and oriented with a trough compass and level, or it can be used vertically to measure altitudes. Each part has the same assembly number (103) indicating that it was probably manufactured. Beautifully made with original, never polished patina. From the collection of Chuck Morgan. Good+ 400-800