A treatise on the aneroid, a newly invented portable barometer. With a short historical notice on barometers in general, their construction and use / By Edward J. Dent.
- Edward John Dent
- Date:
- 1850
Licence: Public Domain Mark
Credit: A treatise on the aneroid, a newly invented portable barometer. With a short historical notice on barometers in general, their construction and use / By Edward J. Dent. Source: Wellcome Collection.
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![Fig. ]. Torricellian Tube. This is the figure of the present tube, as we have it in the Wheel Barometer. After the publication of Torricelli’s experiments in 1645, the field was opened to all philosophers for the practice of every experiment to which the barometer is applicable. Torricelli did not live long to enjoy the fame of his discovery, and died at an early age. To enter into an account of the nume¬ rous experiments of distinguished men with the Torricellian tube, would be extending the limits of this paper beyond the object proposed. It may be suffi¬ cient for us to know that the principle remains precisely the same. By the barometer, we are enabled to determine the pressure of the atmosphere, which is known to be about 15 lbs. pressure on a square inch. This fact is proved when the air is exhausted, by means of an air-pump, from any glass receiver or air-tight box, similar to the vacuum- vase of the Aneroid. At the earth’s surface, where, from the weight of the atmosphere above it, the air is in a state of the greatest compression, a cubic foot of air weighs 1*2857 oz.; and the higher we ascend, the less dense will it become. The barometer will con¬ sequently fall, as the elasticity of the air is equal to the weight of the atmosphere above it, and they always balance each other. The principle of the Torricellian tube having been](https://iiif.wellcomecollection.org/image/b31912588_0006.jp2/full/800%2C/0/default.jpg)
