232 Mr. E. H. Cook on the Existence of 



into a black substance. A body is colourless because the power 

 of the ether between its molecules to vibrate is the same 

 as the power of the ether in the surrounding medium to 

 vibrate. A body is black because its ether takes up and re- 

 tains all the vibrations which fall upon it. Thus the vibration 

 of the ether in the black substance must be more powerful 

 than in the colourless. (This also follows because energy cannot 

 be destroyed by the black substance.) Here, then, the vibra- 

 tion of the ether in the colourless chloride of silver has pro- 

 duced a substance containing ether particles vibrating with 

 more energy. In other words, the energy of the vibration in 

 the argentic chloride has been used up in first shaking the 

 atom of silver from the atom of chlorine, and also in causing 

 the ether in the silver and the ether in the chlorine to vibrate. 

 According to the conservation of energy, these energies should 

 be equal. But we find that there is more energy in the black 

 silver than in the chloride ; and consequently we have inequa- 



Kt y- 



The reason assigned for the superior energy of the violet 

 rays is simple and satisfactory if we admit the previous as- 

 sumptions. It is that in consequence of their more rapid vi- 

 bration they are more energetic and thus capable of doing more 

 work. 



In the decomposition of carbonic anhydride effected by light 

 in the presence of chlorophyll, we have another experiment 

 which is difficult of explanation on the ether theory. The 

 vibration of the ether of the carbonic anhydride is unable to 

 effect the decomposition itself; but when brought near to the 

 vibrating ether of the chlorophyll, the decomposition is effected. 

 What is the nature of the action which here takes place ? and 

 what known action is analogous to it ? 



Stating briefly the difficulties in the conception of the ether, 

 we have : — 



(a) The want of any direct evidence. 



(/3) The fact that no ethereal condensation is observed 

 around the celestial bodies. 



(y) The interposition of this substance between the mole- 

 cules of bodies. 



(8) The nature of the action producing a difference of elas- 

 ticity or density in this imprisoned ether. 



(e) The chemical inertness of the ether. 



In addition to these we have from experimental evidence 

 the following : — 



(a) Inability of the ether to take up every species of vibra- 

 tion. 



(/3) Inability to transmit electricity. 



