Meteorological observations and essays / By John Dalton.

  • John Dalton
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: Meteorological observations and essays / By John Dalton. Source: Wellcome Collection.

    237/280 (page 211)
    It will be perceived that the principle we have adopted in the Essay on the variation of the Baro- meter is, that an equality of elasticity in two verti- cal columns of air, will, in great part, counteract an inequality in their weight. To illustrate this posi- tion: suppose a cylindric vessel of indefinite length were filled with hydrogen gas, and placed perpen- dicular to the ground plane, having no communi- cation with the atmosphere; suppose then that a small hole were made in the side of said vessel, at a point where the elasticities of the two gases were equal. A communication being now opened, an intercourse would immediately commence ; but this would not be occasioned by the specifically heavy gas rushing into the light gas, nor the light gas into the heavy gas, exclusively. The two gases, having equal elastic forces, would, by virtue of those forces, be diffused through each other slowly and gradually, according to the law which I have pointed out in another Essay—that of one gas being as a vacuum to another in regard to their mutual diffusion. The application of this principle, in accounting for a temporary existence of a warm vapoury volume of atmosphere, supporting itself against heavier but colder volumes of atmosphere on the right and left of it, is too obvious to be insisted upon. Of all the phenomena of meteorology, there is none more difficult to explain, than those relating to the fluctuations of the pressure of the atmo-