Early Aneroid Barometer by Casella No 669 c.1864

A scarce and very good cased aneroid barometer with thermometer by Louis Casella, Maker to the Admiralty, no. 669 c1864.   Aneroid barometer having 4¼” silvered, engraved and engine divided stepped dial, the upper part with barometric scale calibrated in inches of mercury with a range from 27” – 31” divided down to 1/100ths, the inset with standard meteorological terms and signed “L. Casella, Maker to the Admiralty,” the lower part marked “London” and serial no. “669” with “Compensated.” Semi-circular thermometer, the register calibrated in degrees Fahrenheit with a range from 30° - 120°, fine blued steel pointer, bevelled glass, fine bezel-set index. High quality Vidie pattern movement driven from a single 2¾” nickel alloy capsule tensioned on a C spring, static mass to spindle. All contained within a substantial lacquered brass drum form case. Presented in its original black leather over timber, crimson silk and velvet lined case, snap closure on a button release.   Condition: The subject of a full service, conservation, and calibration under laboratory conditions. The movement working well across the standard barometric range 28” – 31”, see dynamic pressure test. It should be noted that instruments of this age often fail to register pressures at the lower range - this is normal. Generally about crisp overall, the dial clean and bright with good definition, small mark to centre. The brass case retaining much original lacquered finish, some oxidation and losses, minor convex dent at lower part of side. The travel case structurally sound, the leather replaced to front upper and lower, the velvet re-dyed, the silk remaining original.   Comments: These early aneroid instruments are really hard to find with this completeness including the travel case. Surviving in above average condition, this is a very good example from a maker we consider to be amongst the very best.