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.

    104/280 (page 78)
    Sir George Suucksuren’s letter to Col. Roy, (Philosophical Transactions, Vol. 68.) will serve to give my readers an idea in what manner the baro- meter is made subservient to the purpose; and also how the height of mountains, &c. may be ascertained by means of the barometer.—In order to understand the use of the table, it should be observed, that two persons are to take cotemporary observations, upon two barometers and thermome- ters, one person having one of each at the bottom of the mountain, and the other at the top. THE TABLE. EXPLANATION. : fbate This table gives the number of feet Ze in a column of the atmosphere, equi- valent in weight to a like column of 32 | 86.85 35 |87.49| quicksilver toth of an inch high, when 40 | 88.54 the barometer stands at 30 inches, for 50 | 90.66 | every 5° of temperature from 32 to 80.* For any other height of the barometer 60 | 92.77 ' 65 | 93.82! it will be in the inverse ratio of that ae eae height to 30.—Let 4d=the mean height 80 | 96.99| of the two barometers, in inches; a= the difference of the two, in tenths of an inch; 0 = the number of feet, per table, corresponding to the mean height of the two thermometers ; x = the height of the mountain, in feet: then, we shall ae = 4, the height required. have this theorem, * From the table it appears, that, in round numbers, every 30 yards of elevation reduces the height of the mercury in the barometer +'o of an inch, near the earth’s surface.