494 The Lunar Atmosphere (October, 
small about it is its density, as compared with the very 
dense atmosphere of the earth, while its real magnitude and 
mass is immense ; and the mass above equal portions of the 
surface is not so much smaller than on the earth. 
To ascertain what atmosphere is possible on the moon, it 
is necessary that we should express, by means of a few 
simple equations, the conditions any atmosphere would 
have. As, however, the derivation of these equations from 
the known physical laws, with respect to gases, would in- 
volve the application of more complex mathematics, it will 
be dispensed with. Throughout, it may be observed, it is 
assumed that the moon’s atmosphere would be essentially 
similar in composition to the earth’s, with perhaps a much 
larger percentage of carbonic anhydride, which is to be 
expected. 
Let a = the radius of the moon in miles; 
x = any height in miles above the surface ; 
8, Por fo = the density, pressure, and temperature of 
the atmosphere at the lunar surface, and 6, £, ¢ the same at 
height x. 
And put for the constants involved— 
a = 0'000294, multiplied by the density of the lunar 
atmosphere in terms of the standard terrestrial density of 
air ; 
& = 0'003665, the expansion of gases for 1° C. ; 
1, = the height in miles of a column of the lunar atmo- 
sphere of density 5,, at temperature ¢ that would—under 
the action of gravity at the moon’s surface—exert a pressure 
oi7,. Erom this— 
1, = 32°6837 (1+¢7,) miles. 
a 
Finally, for brevity, write 6 for i: 
Then the equations expressing the physical condition of 
the lunar atmosphere may be written— 
ei We pacer =k «= we 
Where ¢ is the base of the natural logarithms— 
—u 
6 = K€ vk, ee Gk ue ee a 
b= $,8, Gaffe a ee 
E--et _ 
rf (rae) CEU roses ee 
ee Pt 
