189U-91.] THE LUMINIFEROUS ETHER. 95 



explanation of this he held to be that electricity, like light, was due to 

 the undulatory vibrations of the medium which is beyond question 

 necessary for the propagation of light. This fact is at the foundation of 

 Maxwell's electro-magnetic theory of light which is no doiibt destined to 

 play no unimportant part in the development of the true Theory of 

 Energy. Thus by considering in succession all the so-called natural 

 forces it will be seen that they are all simply manifestations of an 

 unchangeable amount of indestructible energy. Every form of energy 

 is capable of being transformed by suitable manipulations into all its 

 other forms without in any case involving any increase or decrease in 

 che total quantity of energy. But, while the quantity of energy in the 

 universe is invariable, yet by virtue of laws of which we have a 

 particular instance in Clausius' Second Main Principle of the Mechanical 

 Theory of Heat, the amount of available energy is being constantly 

 exhausted. This is simply another method of saying that no known 

 natural processes are perfectly reversible. In the transformation of these 

 various forms of energy into one another the ether plays, as at once 

 follows from what has been said above, an important part. 



Then not only does the ether convey light from the sun to the earth 

 but also from the remotest visible star. Indeed the functions performed 

 by it are so varied and of such a nature that this mysterious ether must 

 pervade not only all interstellar but also into intermolecular and inter- 

 atomic space 



Not only does the existence of the ether explain the fact of the propa- 

 gation of light from the sun and stars to the earth, but it also very clearly 

 explains all the other known phenomena of light. As pointed out by 

 Sir Wm. Thomson, all these properties come out as a matter of course 

 from the dynamical consideration of the subject. So much so that any 

 one not knowing these phenomena would have discovered them in work- 

 ing out the matter dynamically. He would have discovered anomalous 

 dispersion, fluorescence, phosphorescence, etc. Indeed, Sir Wm. Thom- 

 son says that he never heard of anomalous dispersion till " he found it 

 lurking in the formulas," and as a consequence he very pertinently 

 remarks that the dynamical treatment which discovers what is afterwards 

 verified by experiment, is a very important piece of dynamics. We have 

 then the observed and ascertained facts which are explained by the 

 existence of the ether, and there being no other known method of 

 accounting for the facts, we conclude that the ether is a reality and not 

 the. creation of scientific imagination. 



Having thus proved the existence of the ether, and having pointed out a 

 few of the functions fulfilled by it, let us briefly consider some of its more 



