A very interesting Hutchinson’s Improved Surveying Aneroid barometer altimeter chassis no 6704 movement no 6699 by Callaghan, London for Stanley c1880

Aneroid pocket barometer having 1¾” diameter silvered and die struck dial, bi-directional bezel operated altimetric scale calibrated in feet, divided to 20ft with full scale deflection +/- 1,000ft. Inner barometric scale calibrated in inches of mercury having a range from 26” – 31” and divided to 1/10th”. Blued steel pointer under bevelled glass. Conventional Vidi pattern movement driven from a single 1” capsule tensioned on a C spring. Contained in a drum form case, the bezel with engine turned finish, side extension short grip, the verso with calibration port.

Complete with its original black leather over timber, green silk and velvet lined case, snap closure on a button release.

Condition: The subject of a full mechanical overhaul, conservation and calibration under laboratory conditions. The movement working well with well above average accuracy across the standard barometric range, see performance chart. Generally good, the dial crisp, clean and vibrant. The leather case structurally sound, showing signs of light wear. The release button a replacement.

Comments: Perhaps one of the most interesting instruments yet disassembled, confirming much of what had previously been conjecture. The movement is certainly the work of Callaghan – the only maker known that struck serial numbers into the cock. “Stanley” has been inscribed in the lower case almost certainly to identify this piece as an order for W.F. Stanley.

It has been clear, even obvious, from analysis of these instruments, that many were manufactured by entities not shown on the dials, that indeed major scientific instrument makers, famous in their own right for the construction of a myriad of instruments dedicated to other disciplines, ‘bought in’ specialist instruments from other makers. This is almost certainly one such example.
It is likely that the construction of Hutchinson’s improved aneroid was licensed to several makers, evidenced by the conformity in dial design and engraving. It is known that William Callaghan made many other types of aneroid instruments mostly signed by the maker – however, he also built the barometer movements for the majority of weather stations, the lion’s share of which bear the names of other scientific instrument makers or retailers.

Callaghan along with JH Steward, Louis Casella and Adie, was at the forefront of English making in the 19th century, producing instruments comparable with, and in many cases superior to, anything produced anywhere else in the world.