150 On the Meteors of 13th November, 1833. 
tance towards the earth, according to the laws of falling bodies. The 
atmosphere may either be considered as terminating at the height of 
fifty miles, oras being, beyond that limit, sorare, asto afford no sensible 
resistance to the descent of bodies; for, at this elevation the air would 
be nearly twenty times as rare as it can be made by the best air 
pumps. ‘The question before us then is, what velocity would a body 
acquire in falling from a point 2238 miles above the earth, to within 
Sifty miles of its surface ? 
If a denote any distance from the center of the earth, and z a less 
distance from the same center, r the radius of the earth, and m the 
space passed through in 1” at the surface, then the velocity acquired 
in falling through a@—z« will be given by the following formula.* 
16.1 X2188 
5280 x 6194 x 4006 
Hence it appears, that the meteors entered the earth’s atmosphere 
with a velocity more than ten times greater than the maximum velo- 
city of a cannon ball, and about nineteen times that of sound. We 
shail find reason to believe that these bodies were, in many instan- 
ces, of great magnitude ; and the immediate consequence of the fall- 
ing of a body with this prodigious velocity must be, a powerful con- 
densation of the air before it, thus retarding its progress, and pro- 
ducing also a great evolution of heat. 
We may call to mind here, what is known respecting the density of 
the air at different elevations. At the height of seven miles above 
the surface, the air becomes four times as rare as at the surface, and 
this rarefaction increases in the same ratio as the height is increased, 
according to the following law : 
i 
That is, V=7912/ \i =a miles. 
Heights, 7 14 Sy Wiha cha yl lyre) 42 49 
Densities, } TS Tt @56 02a) aoe creme 
Hence, at the height of twenty one miles, the air is sixty four 
times as rare as at the surface ; and at the height of forty nine miles, 
16384 times as rare. It follows that three fifths of all the air contain- 
ed in the atmosphere, is within four miles of the earth. 
* See Vince’s Fluxions, Pr. XL. Ex. 5. Young’s Mech. Art. 116. 
t It is worthy of remark, that the velocity of the Weston meteor, as estimated 
by Dr. Bowditch, was three anda half miles per second. (Mem. Amer. Acad. 
r11. 134.) 
