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.

    125/280 (page 99)
    the barometer, at different places, and amongst others, at Zurick, in Switzerland, in latitude 47° N. and at Marseilles, in France, latitude 43° 15’ N : the former place is more than 400 yards above the level of the sea ; it was found that the annual range of the barometer was the same at each place, namely, about 10 lines ; whilst at Genoa, in latitude 44° 25’ N. the annual range was 12 lines, or 1 inch; and at Paris, latitude 48° 50’ N. it was about 1 inch 4 lines. In the same memoir it is related, that I. Lavax made observations, for ten days together, upon the top of S¢. Pilon, a mountain near Mar- seilles, which was 960 yards high, and found that when the barometer varied 22 lines at Marseilles, it varied but 1% upon St. Pilon. Now had it been a law, that the whole atmosphere rises and _ falls with the barometer, the fluctuations in any elevated barometer would be to those of another barometer below it, nearly as the absolute heights of the mer- curial columns in each, which in these instances were far from being so. Hence then it may be inferred, that the fluctuations of the barometer are occasioned chiefly by a variation in the density of the lower regions of the air, and not by an alter- nate elevation and depression of the whole super- incumbent atmosphere. How we conceive this fluctuation in the density of the air to be effected, and in what manner the preceding general facts relative to the variation of the barometer may be accounted for, is what we shall now attempt to explain.