ATMOSPHERE. That region of the air next to the earth, which receives the vapours and exhalations, and is terminated by the re fraction of the sun's light ; sometimes it signi iro the whole ambient air.
The pressure of the atmosphere on thewhole surface of the earth is said to be equivalent to that of a globe of lead of sixty miles in diame ter. Admitting therefore the surface of a man's body to be about 15 square feet, and the pressure about 15 lb. on a square inch, it is computed that a man must sustain 32,400 lb., or nearly 14 tons and a half weight; but the difference in the weight sustained in different states of the atmosphere may be as much as a ton and a half. The density of the atmosphere is not the same in all parts ; for it decreases in proportion to the height, and, as is suppos ed, in this proportion : that the density decreas es geometrical progression as the heights increase; whence the comparative density of the air at the several corresponding heights has been calculated as follows : Height in Miles. No. of times rarer.
0 1 3 and a half . . . . . 2 7 4 14 16 21 64 28 256 35 ... 1021# and pursuing this calculation, it has be puted that a cubic inch of the air we reathe would be so much rarefied at the height of 600 miles, that it would fill a sphere equal in di ameter to the orbit of Saturn. The tempera ture of the atmosphere likewise diminishes as the distance from the earth increases, though, as it should seem, in a leas ratio. M. de Sams; sure found that, by ascending from Genera to Chamonni, a height of 347 toises, Reaunier's thermometer fell 4 degrees 2 minutes, and that on ascending from thence to the top of Mount Blanc, 1941 toises, it fell 20 degrees 7 minutes.