(4i)' 2 55 



apply himself intellectually to another so as to demon- 

 strate coincidence as regards the possession of reason. 

 If, therefore, you hold our president to be reasonable, 

 it is because he behaves as if he were reasonable. As 

 in the case of the ether, beyond the "as if" you cannot 

 go. Nay, I should not wonder if a close comparison of 

 the data on which both inferences rest caused many re- 

 spectable persons to conclude that the ether had the 

 best of it. 



This universal medium, this light-ether as it is called, 

 is a vehicle, not an origin of wave motion. It receives 

 and transmits, but it does not create. Whence does it 

 derive the motions it conveys ? For the most part from 

 luminous bodies. By this motion of a luminous body I 

 do not mean its sensible motion, such as the flicker of a 

 candle, or the shooting out of red prominences from the 

 limb of the sun. I mean an intestine motion of the 

 atoms or molecules of the luminous body. But here a 

 certain reserve is necessary. Many chemists of the 

 present day refuse to speak of atoms and molecules as 

 real things. Their caution leads them to stop short of 

 the clear, sharp, mechanically intelligible atomic theory 

 enunciated by Dalton, or any form of that theory, and 

 to make the doctrine of multiple proportions their intel- 

 lectual bourne. I respect the caution, though I think it 

 is here misplaced. The chemists who recoil from these 

 notions of atoms and molecules accept without hesita- 

 tion the undulatory theory of light. Like you and me 

 they one and all believe in an ether and its light-pro- 

 ducing waves. Let us consider what this belief in- 

 volves. 



Bring your imaginations once more into play and 

 figure a series of sound waves passing through air. 



