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.

    31/280 (page 5)
    still adhered to the maxim were reduced to great difficulties, and forced to have recourse to various unmeaning subtilties, to get rid of the vacuum; whilst many began to question the truth of the maxim itself. At length it was clearly proved, from the instance in question, and from other phenomena, that the maxim was contradictory to the laws of nature; the suspension of the mercury in the barometer was attributed to its true cause, the weight of the air; and the space at the top of the tube was ascertained to be nearly a perfect vacuum, or space void of matter. This discovery, as it led to that of the air pump, and other impor- tant ones, is justly regarded as one of the greatest in the last century. Torricelli, the inventor of the barometer, ob- served, that if it was suffered to stand for a length of time, the height of the mercury in the tube was perpetually varying, though its whole range did not exceed 2 inches at that place; it was further noticed, that this variation seemed to have some affinity to the weather, the quicksilver being gen- erally low in windy and rainy weather, and high in serene and settled weather, which circumstance procured the instrument the name of weather-glass. This discovery promised to be of the utmost im- portance to mankind, by enabling them to foresee those changes in the atmosphere, the knowledge of which was so interesting to them; and the most sanguine expectations were entertained on the sub- ject. The experience of a century and a half has