Description

An important mountain surveying plane table alidade in fine condition-18th century-French/English?

The brass beam is 4 x 42 cm. long terminating at one end with a pair of sighting vanes (horse hairs intact) set at right angles and being 15 cm. tall with a wonderful “fleur-de-lys” upper (Gothic trefoil arch?) and held in place by numbered (with dots ….), hand cut and threaded thumb screws to the numbered plate positions. The other end with an unusual semi-circular sighting vane (16 cm. in height), also held in place by numbered screws to the base plate, surmounted by decorative upper section.  Used for mountain or mine surveying, it is the perfect design for steep inclines while working on a plane surveying table. Possibly used by the French in the Napoleonic wars, mapping through the Pyrenees prior to the war of 1813. A rare survivor of which I have never seen another in 40 years.