Description

Standing 15 inches tall on three numbered conical feet, this instrument is very unusual in construction and signature.

5 inch (6 inches with bezel) silvered compass signed “Newton, late Willm. Wilton, St. Day, Cornwall”, engine divided into four 90 degree quadrants, and again in complete 360 degree ring with vernier reading to 3″ seconds (scale 0-60) of arc. 8 cardinal points and original cover. Compass dial is perfect-no oxidation. Underside rack and pinion for full rotation and sliding locking bar for the compass needle. Surmounted by a 7 inch arc (half circle), engine divided from 0-180 degrees in both directions (also feet and 6th’s of a fathom) and geared to the upper plate to accommodate the smaller alidades. No telescope for this model but a second 6 inch pair of sighting alidades to the ends of the compass plate (alidade cross hairs replaced with thread but will include black horsehair for the purist). There are three intact bubble levels. Spotty oxidation to all horizontal surfaces from dampness. All vertical surfaces are 100% intact lacquer.

The entire assembly packs into a mahogany case 9 x 9 x 5 inches, with both hooks, lock and key. Weight 5 kg. (12 pounds).

The Lean’s dial was developed (invented) by Joel Lean, a Cornish mine manager for easy reading of elevations inside and outside of mines. The Cornwall mines were almost exclusively using this sophisticated device for plane table surveying.

William Wilton (II)  w.1830-51, died in 1859 and his stock was marketed in London by Edward Newton from 1859 onward. The engraved half circle “Wilton, St. Day” would date this instrument to 1860 as it is old stock.