78 THE PROGRESS OF SCIENCE 



form of matter? Fifty years ago, such a 

 suggestion would have been scouted as a revival 

 of the dreams of the alchemists. At present, it 

 may be said to be the burning question of physico- 

 chemical science. 



In fact, the so-called "vortex-ring" hypothesis 

 is a very serious and remarkable attempt to deal 

 with material units from a point of view which is 

 consistent with the doctrine of evolution. It 

 supposes the ether to be a uniform substance, and 

 that the " elementary " units are, broadly speak- 

 ing, permanent whirlpools, or vortices, of this 

 ether, the properties of which depend on their 

 actual and potential modes of motion. It is 

 curious and highly interesting to remark that this 

 hypothesis reminds us not only of the speculations 

 of Descartes, but of those of Aristotle. The re- 

 semblance of the "vortex-rings" to the "tour- 

 billons" of Descartes is little more than nominal ; 

 but the correspondence between the modern and 

 the ancient notion of a distinction between 

 primary and derivative matter is, to a certain 

 extent, real. For this ethereal " Urstoff " of the 

 modern corresponds very closely with the Trpwrr) 

 v\rj of Aristotle, the materia prima of his mnlia- 

 val followers; while matter, differentiated into 

 our elements, is the equivalent of the first stage 

 of progress towards the ea^drr) v\r), or finished 

 matter, of the ancient philosophy. 



it the material units of the existing order of 



