Fortin-type mercury barometer
Date1870-1910
Inventory Number1998-1-0288
ClassificationBarometer
Subject
Maker
L. G. Tower
Cultural Region
Place of Origin
Dimensions102 x 4.4 x 4.4 cm (40 3/16 x 1 3/4 x 1 3/4 in.)
Material
DescriptionMercury barometer with a wooden cistern and a metal outer casing. The mercury tube is now missing, and the thermometer and cistern are both broken. The cistern is held in place by metal screws, and there is a larger metal screw coming out from the bottom of the cistern. There is a metal knob between the thermometer and the barometric scale, and a silvered metal cap at the top, with a small metal loop.
Overall, the barometer is in poor condition.
The barometric scale has interval markings but no corresponding numbers to the side.
Thermometer scale from -30 to 170 °F, with "Freezing," (32) "Temperate," (between 60 and 70) "Blood Heat," (98) and "Scalding" (15) marked.
Overall, the barometer is in poor condition.
The barometric scale has interval markings but no corresponding numbers to the side.
Thermometer scale from -30 to 170 °F, with "Freezing," (32) "Temperate," (between 60 and 70) "Blood Heat," (98) and "Scalding" (15) marked.
Signedon side: L.C. TOWER / ROCHESTER / N.Y.
FunctionA device for measuring atmospheric pressure. During use, the screw could be used to adjust the mercury level in the cistern, and perhaps also to empty the cistern into the tube during transportation. The small brass hoop at the top would have been used to hang the instrument from a tripod, or from a wall mounting.
The height of the mercury in the cistern would then have been set to a standard height, at which point, the air pressure would balance with the weight of the mercury such that it would form a column in the tube of a particular height. A measurement could then be taken on the scale of the height of the column. For a more precise measurement of values between those of the main scale, the sliding vernier, adjustable by the center screw, could be used.
The presence of the thermometer was also important for calibrating the instrument to temperatures other than that of the standard.
The height of the mercury in the cistern would then have been set to a standard height, at which point, the air pressure would balance with the weight of the mercury such that it would form a column in the tube of a particular height. A measurement could then be taken on the scale of the height of the column. For a more precise measurement of values between those of the main scale, the sliding vernier, adjustable by the center screw, could be used.
The presence of the thermometer was also important for calibrating the instrument to temperatures other than that of the standard.
The W. M. Welch Scientific Company
Date: 1934-1950
Accessories: black wood case
Object number: 1998-1-0205
