barometer
Date: circa 1920
Inventory Number: DW0641
Classification: Barometer
Subject:
Maker: C. F. Casella & Co. Ltd. (founded 1905)
User: Institute of Geographical Surveying, Harvard University (circa 1930)
User: Institute of Geographical Exploration (1929 - 1952)
User: Department of Geology and Geography, Harvard University ? (1890 - 1961)
Cultural Region:
Place of Origin:
City of Use:
Dimensions:
NOT AVAILABLE
Description:
This instrument is a precision barometer, designed similarly to Fortin barometers, but with an added magnifying lens at the cistern level for precise adjustment.
A long glass tube is encased in black metal, and connects to a cistern of mercury at the bottom of the instrument. The height of the mercury in the cistern is adjustable by the metal screw underneath. The magnifying lens here allows for added precision.
The thermometer scale, below the barometric scale, runs from 260-325 °A, and 15-125 °F.
The barometric scale above reads from 890-1110mb, and 26.3-32.9 inches.
A long glass tube is encased in black metal, and connects to a cistern of mercury at the bottom of the instrument. The height of the mercury in the cistern is adjustable by the metal screw underneath. The magnifying lens here allows for added precision.
The thermometer scale, below the barometric scale, runs from 260-325 °A, and 15-125 °F.
The barometric scale above reads from 890-1110mb, and 26.3-32.9 inches.
Signedbelow barometric scale: CASELLA / LONDON
Inscribedon side: SCHOOL OF GEOGRAPHY HARVARD UNIVERSITY;
on thermometer scale: ABSOLUTE, and FAHR;
above barometric scale: 3289 / H.R.
on thermometer scale: ABSOLUTE, and FAHR;
above barometric scale: 3289 / H.R.
FunctionA 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. The added precison lens allows for more accurate adjustment of the mercury level. A reading is then is taken on the scale, at the the point to which the mercury rises due to the balancing of its weight with the pressure of the surrounding air. 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.
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.
Historical AttributesOwned by Alexander Hamilton Rice, founder of the Institute of Geographical Exploration, Harvard University. Used by the Harvard School of Geography.
ProvenanceBought from the Geography Building in 1959.