1869.] The Ethereal Eypoihesk of Light. 11 



sonorous object, the air does not enter into the object, but the force 

 is transferred to the material particles of the object itself. Blow 

 into the air and you have no sound (except that caused by the com- 

 pression of the air between the lips). The air is transparent or 

 nearly so, to sound. Blow upon a tumbler, and you have a " note." 

 There is a reilection or reaction of part of the force upon the 

 air, and an absorption of the other into the sonorous substance; 

 and, precisely as in the case of Kght, the efiect produced is varied 

 according to the nature of the object upon which the force impinges. 

 Professor Tyndall has shown the close analogies between sound 

 and light in his beautiful work on the former force;* but I 

 cannot help thinking that if he had considered the nature of the 

 " chromatic " scale ui both cases, conjointly with the other resem- 

 blances between the two forces, his views regarding a hypothetical 

 ether circulating within bodies, would have become modified. He 

 attributes the velocity of sound in its passage through substances, 

 to a direct action upon the matter itself; but why not suppose 

 some attenuated gas to be the medium, as sonorous " ether ? " Such 

 a supposition is at once negatived by the fact that whilst the 

 velocity of sound through the rarest of gases is only 4164 feet in 

 a second,! it traverses steel wire at the rate of 16,023 feet per 

 second. The density of a substance does not therefore necessarily 

 impede the passage of soiDtcl (any more than that of mechanical 

 motion), and when the field of operation of the force is changed, 

 and it leaves a rarer form of matter to act upon a denser one, its 

 efiect in the new direction is intensified and its result upon the 

 senses changed. 



So far, then, as the analogies between light and sound, as well 

 as the mere density of bodies, are concerned, we are at least as cor- 

 rect in leaving the " ether " (whatever that may be) at the outside, 

 as in admitting its presence within solid bodies ; and now let us 

 inquire how various substances behave under the influence of light 

 as compared with other forces, which are supposed by the ethereahsts 

 to have the ether for their vehicle everywhere, within as well as 

 without solid objects. 



The following are the conducting or transmitting powers of 

 certain well-known types of matter : — 



Now, when we consider these phenomena along with those referred 



* ' Ou Sound,' p. 4J:. Lougmaus. t Ibid., p. 37. 



