Manchester Monoirs, Vol. Iv. {igio). No. 4t- 3 



to engage both divers chymists to learn and relish the 

 notions of the Corpuscular Philosophy, and divers eminent 

 embracers of that to endeavour to illustrate and promote 

 the new philosophy by addicting themselves to the experi- 

 ments and perusing the books of chemists."'' While on 

 this subject, he mentions Descartes and Gassend con- 

 stantly, and other philosophers hardly ever. 



Descartes believed in the existence of atoms, and at 

 the same time he denied that a void could exist. A subtle 

 fluid occupied the space between the atoms, and even per- 

 meated them. Hence the vortex motion which had been 

 set up in the fluid could not but communicate itself to the 

 atoms. An admirable description of the atmosphere, 

 according to the Cartesian theory, is to be found in 

 Boyle's " New Experiments, Physico-Mechanical, touching 

 the Spring of the Air." "The restless agitation of that 

 celestial matter, wherein these particles [of air] swim, so 

 whirls them round, that each corpuscle endeavours to beat 

 off all others from coming within the little sphere requisite 

 to its motion about its own centre . . . their elastical 

 power is made to depend . . . upon the vehement agita- 

 tion . . . which they receive from the fluid ether that 

 swiftly flows between them."" It is remarkably difficult 

 to find in Descartes so good a description of his theory as 

 thi.s.^ 



Descartes' denial that a vacuum could exist, it is 

 plain from this, is not to be taken in the crudest sense. 

 He never meant and never said that space is full of matter 

 of the ponderable kind.'' He meant, surely, that in the 



*• Op. lit., vfil. 2, p. 501. 

 « Op. cii., vol. I, p. 8. 



' CEuvres, ed. by Cousin, vol. 5, p. 159-162, 169-170. 

 ^ Clerk Maxwell might well have emphasised this in his comment on 

 "The Error of Descartes," in " Matter and Motion," article xvi. 



