the Luminiferous ^Ether. 415 



millions of millions of degrees Fahrenheit above the standard 

 temperature ; but such a wave is transmitted in the aether 

 although its temperature is far less than has ever been pro- 

 duced by artificial means. 



3. The ratio of the elasticity to the density in the aether is 

 exceedingly large compared with the same ratio in air. The 

 temperature of air being taken at 60° F. and the aether at 20° 

 F. ; absolute, the ratio is, with sufficient accuracy, 



/980,000,000\ 2 Q 1A11 , 

 ( 1090 ) -8x10" nearly, 



4. The specific heat of the aether is, at least, many million 

 times that of air, or of any other known gas. 



5. The atmosphere is of variable density, elasticity, and 

 temperature, while the aether is well-nigh isometric throughout 

 space in regard to each of these elements. 



6. A molecule of aether is well-nigh infinitesimal compared 

 with one of air. 



7. Air is attracted to a planet with such a relative force, 

 that its extreme height is only a few miles. 



8. The ratio of the density to the elasticity of the aether is 

 constant; but in the atmosphere, on account of the decrease 

 of temperature with the elevation, the density decreases less 

 rapidly than the elasticity, as may be seen by comparing 

 the first part of equation (35) with equation (33) : we have 



S I e 

 sr= 6 - -• 

 <>o e 



On this account a wave would be propagated with less velocity 

 in the higher regions of the atmosphere than in the lower, 

 while a wave in the aether has a sensibly uniform velocity 

 throughout space. 



The question may arise, May not the resistance of the aether 

 drag away the remote molecules of the atmosphere, and so 

 scatter them in space along the path of the earth's orbit ? 

 Assuming that the atmosphere is moving with the earth 

 through space at the rate of 20 miles per second (which 

 exceeds the actual velocity), and that the resistance of the 

 aether is. measured in the same manner as for fluids, we have 



for the resistance Ji — kwa^- y where v is the velocity of a 



molecule of air, a is meridian section, to the weight of a unit 

 of volume of the aether, and k a coefficient depending upon 

 the form of the body. Making & = 1, which is greater than its 



