Signedplaque mounted on side: J. & H.J. GREEN N.Y. 2531
Inscribedsticker on bottom of cistern: David P. Wheatland
FunctionA portable device for measuring atmospheric pressure. The mercury level in the cistern can be adjusted by the screw, allowing for the emptying of the cistern for transportation. When in use, the small zeroing pointer on the cistern indicates where the height of the mercury should be. Then a reading is taken on the scale, at the the point to which the mercury rises. The sliding vernier, adjustable by the center screw allows for more precise measurement of values which are between those marked on the main scale.
The small hoop on top would have been used to hang the barometer from a tripod or from a wall mounting.
The thermometer would have been used to correct the readings for temperatures that varied from the standard.
ProvenanceBought by David Wheatland from Geography building, Harvard, February 1959.
Related WorksOn Henry James Green: On James Green: Middleton, W. E. Knowles. The History of the Barometer. Johns Hoptins Press, Baltimore: 1964, pg. 343-50