244 SCIENCE PROGRESS 



spacial frame of reference, and extensive modifications will be 

 introduced into the equations of motion for a projectile or a 

 cyclone, — or, for the matter of that, a railway train . That fruitful 

 points of view can be gained by aid of so artificial a procedure 

 is remarkable, but that the scheme of nature is really improved 

 by any such intricate device is almost unthinkable. We have 

 no right to complicate the philosophy of nature, or to confuse 

 metaphysicians with analytical refinements about those pure 

 abstractions space and time, merely because of an admitted 

 practical difficulty about employing material objects for their 

 precise measurement. The real complication belongs to the 

 material objects, and depends on recently discovered properties 

 of matter ; those properties should not be masked, and their 

 study evaded, by arbitrarily complicating the framework of 

 reference. The procedure of Procrustes, who fitted the occupant 

 to the bed instead of vice versa, has in this application some 

 merit. 



Concerning the Newtonian idea of absolute motion : It is in- 

 finitely unlikely that any piece of matter is at absolute rest. For 

 motion is one of the attributes of matter ; no particular velocity 

 is more likely than another ; and only one precise velocity is 

 zero. But on the other hand it is unlikely that the whole 

 ether of space is in a state of locomotion — in any sense that 

 we can attribute to the words. We may venture to assume 

 that the ether of space, if of infinite extent, is at rest : i.e. 

 we may take it as our definition or standard of rest. Strain 

 and stress belong to the ether, not motion. When a piece of 

 matter is strained, i.e. altered in shape or size, the configuration 

 of its particles is altered, they are simply moved into fresh 

 positions, but all stress between them is in the connecting 

 mechanism, i.e. in the ether. Motion is a fundamental property 

 of matter. We have no reason to attribute motion to the 

 continuous medium in which matter moves. For if the ether 

 were moving as a whole, no conception of such movement 

 could be made — nor would it make any difference to anything 

 that happened in it. And it is unnecessary and gratuitous to 

 suppose, without any evidence, that it is streaming in such 

 a way that different parts are going in different directions. 

 Ether is the receptacle of static energy, as matter is of 

 kinetic energy, and the straightforward assumption about it 

 is that it is stagnant except for such intense internal con- 



