An historical and philosophical account of the barometer, or weather-glass ... And a modest attempt from thence made towards a rational account and probable judgement of the weather / By Edw. Saul, A.M.

  • Saul, Edward, 1677-1754.
Date:
1730
Catalogue details

Licence: Public Domain Mark

Credit: An historical and philosophical account of the barometer, or weather-glass ... And a modest attempt from thence made towards a rational account and probable judgement of the weather / By Edw. Saul, A.M. Source: Wellcome Collection.

    22/112 (page 10)
    is equal to the Preflure of the Air with¬ out. The very fame EffeQ: is clearly fhew’d, and undeniably proved, by placing the Tube of a Barometer, with its Ciftern of Mercury, in the Air Pump ; for fo long as the Air within the Receiver continues in its natural State, the Mercury will keep up to the fame Height; but when the Pump is working, and the Air exhaufting, the 'Mercury will gradually fubfide in the Tube, ’till it comes to near the fame Level with that in theBafon. Open the Communication with the external Air, and let it by De¬ grees into the Receiver* and then the Mercury will gradually rife up again in the Tube, and recover its former Height. And thus, as often as you repeat the Experi¬ ment, the Mercury will alternately fall, or rife in Proportion as the Preflure of the Air is diminilh’d by Pumping it out, or renew’d by the Re-admiffion of it. T o this I fhall only add a more eafy and obvious Experiment, viz. that of pouring Water upon the Mercury in the Ciftern, rais'd for this Purpofe to the Height of two or three Inches; for as the Water is heavier than the Air, it will to a greater Degree increafe the Preffure upon the ftag- nant Mercury> and in the Confequence of it, raife that in the Tube proportionably higher. Draw off the Water by a Pipe,