30 PRESENT-DAY RATIONALISM 



former question of the two? We start with the hitherto 

 accepted beh"ef in the universal existence of ether, im- 

 ponderable and immaterial, pervading all space and all 

 material objects. Prof. Dolbear says that from experi- 

 ments in a vacuum " one is led to infer that matter is not 

 the agent that transmits light". Hence the universal 

 ether is hypothecated to account for the transmission of 

 the waves of light, magnetism, electricity and gravitation. 



" Ether is not atomic in structure, presents no friction 

 to bodies moving through it, and is not subject to the 

 law of gravitation, it does not seem proper to call it 

 ' matter '. We might speak of it as a ' substance ' if 

 we want another word than its specific name for it. As 

 for myself, I make a sharp distinction between the e^/ier 

 and matter, and feel somewhat confused to hear any one 

 speak of the ether as matter. " ^ 



Similarly, Tait says : " If we adopt Sir W. Thom- 

 son's [Lord Kelvin] supposition that the universe is filled 

 with something which we have no right to call ordinary 

 matter (though it must possess inertia) but which we may 

 call a perfect fluid ; then, if any portions of it have vortex- 

 motion communicated to them, they will remain for ever 

 stamped with that vortex-motion ; they cannot part with 

 it ; it will remain with them as a characteristic for ever, 

 or at least until the creative act which produced it shall 

 take it away again. Thus this property of rotation may 

 be the basis of all that to our senses appeals as matter'^ ^ 



It is thought that " atoms " of matter are made out of 

 ether. 



The artificial manufacture of "vortex-rings" (such as 

 may be sometimes seen in smoke-rings from a tobacco- 



^ Matter, Ether and Motion, p. 35. 



- Lectures on Some Recent Advances in Physical Science, by i'. G. 

 Tait, 1876, p. 294. 



