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.

    45/112 (page 33)
    9. I n mifty, or foggy Weather, (if it be of any Continuance) the Glafsis common¬ ly obferv’d to Hand very high ; becaufe the the Air is ufually then perfectly Hill and calm, and preffes with its full perpendicular Weight upon the ftagnant Mercury, without any Interruption, or Abatement. The learned Dr. Wallis is of Opinion, that the Mills and Vapours hanging thus in the Air, add to, and encreafe its Preffure : Which, no doubt, is true in general; becaufe the colledlive Body of the Air and Vapours taken together, muft be of greater Weight than the Air alone. And, upon this Account, not only in milly, but in dark, fettled, calm Weather, (when the Vapours are raifed and fupported at a very great Height; and fo equally and copioufly difperfed, that the Sky appears uniformly thick and hazy in ail Quarters ; without the the lead Gleam of Sunfhine breaking through, or any Cloud diilinftly form’d in any Part of the Hemiff here:) In fuch a denfe State of the Atmafphere, the Weight of it is greatly encreas’d ; and the Height of the Mercury raifed by it, is ufually near 30 Inches. B u t as foon as this State of the Atmof- phere changes, either by the Wind rifing, the Sun breaking out, or both together difperf- ing the Hemiffhere of Vapours* and forming many of them into large Clouds, failing F above;