Casella Mine Surveying Aneroid Joins the Collection
A precision eight-inch mine surveying aneroid by C. F. Casella & Co. Ltd., London, made around 1950, has been added to the collection. Built for barometric levelling underground, it reads to 0.01 inHg and combines a deep convex beryllium bronze capsule, a full-disc anti-parallax mirror and a movable reading lens.
A Mine Surveying Aneroid Barometer by C. F. Casella & Co. Ltd. of London, dating from around 1950, has been added to the collection. Not a weather glass but a geodetic instrument: it reads to 0.01 inHg over a single revolution of the pointer, with a movable magnifier and a full-disc anti-parallax mirror to make such fine divisions usable underground.
Its most unusual feature is the aneroid capsule, whose deeply convex beryllium bronze diaphragms give it a tall, vase-like profile — a design that buys travel in order to keep the lever amplification low, and with it the influence of friction and backlash.
The full description and detailed photographs are on the item page.