A very good altazimuth compass-clinometer by Casella retailed by Henry Hughes & Son c1870

Altazimuth constructed in oxidised and lacquered brass, the main body enclosing a floating azimuth circle (compass), the upper surface marked with cardinal and intercardinal points, jewelled suspension, the circumference marked in degrees (to be viewed through eyepiece), sliding lock and pause button. The clinometer with eccentric weighted circular silvered and die struck dial carrying the retailer’s details, “H. Hughes & Son, London,” the upper face marked over a semi circle in degrees with opposing scales 0°–90° and divided to 1°, the circumference (to be viewed through eyepiece) with replicated scales. Composite or possibly black wood steadying handle. Optical train consisting of eyepiece with push-pull focus for scales and sight line, the telescope with similar arrangement and including removable neutral density filter for brighter conditions.

Presented in its original leather over timber, blue velvet and silk lined case, twin swinging hook type fasteners.

Condition: In very much better than average condition, both compass and clinometer working correctly with all functions free and serviceable. The optical train clean and bright. The compass easily finds north and the clinometer responds accurately to angle change. Some minor deterioration noted to clinometer dial silvering. Externally maintaining much original finish, some minor losses and points of oxidation.

The transport case the subject of re-construction and conservation, but remaining essentially original.

Comments: A really lovely piece, particularly so as it all works and works well. Often scales are badly deteriorated, but in this case they remain clear and easily readable.

This is an instrument that is occasionally seen and might be considered scarce – good ones essentially are very hard to find, particularly with the original handle. Very much a collector’s piece.

Casella’s Pocket Altazimuth combines a sighting telescope with a magnetic compass for determining bearings, and a pendulum (or wheel) clinometer for determining vertical inclinations. Small, compact, and accurate, it was said to be especially useful for travelers and military surveys.

Louis Casella introduced the form in 1864, noting that is was “improved and modified by the kind assistance of Francis Galton, F.R.S.” The reference is to Francis Galton, (1822-1911), a Fellow of the Royal Society of London, whose work ranged over a number of fields. The extract and image are taken from Casella’s catalogue of 1871.