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 by 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.