416 On the Luminiferous ^Ether. 



actual value, and a= ^17 feet, which, again, is in excess of 



the true area, it; the value in equation (10), we find that 

 2 1 11 



R= W± x 10" x ( 20 x 5280 ^ • Wl = W 6 of a pound nearly# 



The attractive force of the earth for a molecule of air is given 

 in equation (28), and hence the attraction of the earth for a 

 molecule of air will exceed 500,000 times the resistance of the 

 aether ; hence the molecules accompany the earth in its orbit 

 as certainly as does the moon, and are more rigidly bound to 

 it than is its satellite. 



The Kinetic energy of a molecule of air at standard con- 

 ditions is about 



\ • 32-2xl 8 7xl0^ 16 °° 2= I^ f°°t-pound; 

 and of the aether, according to our results, about 



\ • 22^o(273,000 x5280) 2 = jJ^g foot-pound; 



which results are nearly the same ; but in a pound of the 

 aether there is some 100,000,000,000 times the Kinetic energy 

 of a pound of air. 



Considering the terrestrial atmosphere as equivalent to one 

 of uniform density and 5J miles high, each of whose mole- 

 cules has a mean square velocity of 1600 feet per second, and 

 the aether of uniform density each of whose molecules has the 

 mean square velocity of 286,000 miles per second, a rough 

 approximation shows that the Kinetic energy of the aether in 

 a sphere whose radius is 92,000,000 miles (nearly the distance 

 of the earth from the sun) will be only about 100,000 times 

 that in our atmosphere. 



The mean free path of a molecule of gas as given by 

 Loschmidt is 



, combined volume of the molecules 



volume of the gas x \ the diameter of a molecule' 

 and by Maxwell, 



p v p y\ 



(the last member of which we have added), in which p is the 

 density of the gas, fi the coefficient of internal friction, and v 

 the velocity whose square is the mean of the squares of the 

 actual velocities of the molecules. In regard to the aether, 

 these equations contain at least three unknown quantities, Z, 

 fi, and the diameter of a molecule, and hence they cannot be 



