This is a cylindrical instrument, 5.5 inches in diameter. The silvered face is marked “SIGNAL SERVICE U.S. ARMY / L. CASELLA / MAKER TO THE ADMIRALTY & ORDNANCE / LONDON / COMPENSATED / 2634 / ‘FOR ISSUE’ / NO 21.” The scale around the circumference of the face extends from 17 to 22 inches of mercury, graduated in tenths; another scale indicates altitudes from below 10,000 to above 15,000 feet.
This was probably made after 1870 when the Signal Service was charged with organizing a national weather service. And it was probably made before the establishment of the U.S. Weather Bureau, as a civilian agency, in 1890.
Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.