the Luminiferous Ether. 229 



case, although by the compression we do increase the density, 

 yet we increase the elasticity in the same proportion, and 

 consequently the velocity remains unchanged. Also, if we 

 adopt this view, we must have the entire surface of a body 

 composed of its own molecules : there must be no spaces ; or 

 the imprisoned ether would escape and assume the elasticity 

 and density of the ether of the surrounding body. We thus 

 arrive at the conclusion that, for refraction to be accounted for, 

 we must assume that the elasticity of the ether is different in 

 different bodies, and that this difference is due to the proximity 

 of the ether particles to the different molecular arrangements 

 of bodies. In this assumption, it is needless to state, we make 

 a departure from all known facts. We know of no substance 

 whose elasticity is altered by the proximity of another body. 

 Slightly altering the words of Sir John Herschel, if we accept 

 this explanation we are running counter to all the analogies 

 which the observation of nature affords. 



Again, although the ether in a certain sense is a most pow- 

 erful substance, capable of entering into all bodies, and of 

 vibrating with enormous velocity, yet chemically it is a most 

 inert substance. In no way can we cause it to chemically 

 combine with any other body. Although in intimate con- 

 nexion with the molecules and atoms of all, it chemically 

 affects none. In this property, also, our hypothetical medium 

 is peculiar ; no substance in nature refuses to combine with 

 some one or more other substances. 



The difficulties which one experiences in accepting the 

 ether, owing to certain experiments, are varied and nume* 

 rous. We will consider some of these. A common experi- 

 ment in acoustics is to place an alarm under an exhausted re- 

 ceiver and to receive no sound when the air is withdrawn. 

 This simple experiment is difficult to explain ; for we must re- 

 member that, although the air is withdrawn, the ether remains. 

 Why d oes this ether not take up the vibrations of the sounding 

 body and transmit them ? It cannot be because the vibrations 

 producing sound are too slow ; for an unlimited elastic medium 

 is capable of vibrating in any way. The water of the ocean trans- 

 mits a long rolling wave as readily as the minutest ripple, and 

 the minutest ripple as easily as the shortest sound-wave. It will 

 not suffice to say that the ether does take up the vibration and 

 carry it on to the sides of the receiver, but that here it is unable 

 to throw the molecules of the glass into vibration, and hence 

 the sound cannot reach the external air, because according to 

 theory the ether is contained in the glass. There is, in fact, 

 no break in the line of communication of the ether particles 

 outside with those in the inside of the receiver. What pre- 

 vents the vibrations being taken up and transmitted ? 



