Stoney — On Texture in Media, etc. 403 



by the motions that are going on within the one volume being dif- 

 ferent from those that pervade the other. In every other respect 

 they are as exactly alike as one stationary portion of space is to 

 another. One such portion of space is not another; but it is 

 exactly like it : and there is no limit to this resemblance, however 

 small the portions compared may be. There is no "texture" 

 until there is motion. 



On the other hand, when, in investigating the motions of pon- 

 derable matter, we have occasion to conceive the bodies we are 

 dealing with divided into small portions, it is only if we stop short 

 in our division so that the blocks we form do not fall below a 

 certain size, that we are justified in treating them as resembling 

 one. another. When we thus stop short, the blocks are in reality 

 accumulations of more minute internal motions ; and if we do not 

 stop short, but carry the division sufficiently far, we shall come 

 down upon the individual motions themselves, between which of 

 course the most marked differences would be found. 



It appears to be the same in regard to the luminiferous ether. 

 It is only when we do not subdivide too far, that we are justified 

 in speaking of the blocks as resembling one another. The lumini- 

 ferous ether seems to be a textured medium like ponderable matter. 

 But in the elemental ether — in space itself regarded as movable — 

 there are no such limits. Its portions, however small, resemble 

 one another with mathematical exactness \{p) except so far as there 

 may be different motions prevailing within those portions. 



It thus appears that the distinction between different parts, 



(p) Empty coreless vortices involve the hypothesis of a medium that is discon- 

 tinuous and has boundaries ; or else (in the case of some coreless vortices) of a medium 

 which obeys two laws of motion, one for the part of the medium that is interned on 

 one side of a closed vortex sheet, and another for the rest of the medium. Now, it 

 seems very improbable that the objectively existing elemental ether — space under its 

 kinematical aspect — is of either of these kinds ; and, accordingly, it is improbable that 

 empty coreless vortices can be any part of real nature. This is a kind of objection 

 which may raise an improbability, even a great improbability ; but we should be rash 

 to rely on it as finally decisive, for the reality of things is not limited by our way of 

 conceiving them. 



The objection, such as it is, would not lie against the presence in nature of coreless 

 vortices lined with a vortex-sheet and filled in with a part of the medium devoid of 

 rotational motion ; but such vortices would, in some respects, behave differently from 

 empty coreless vortices. 



