62 Mayow 



means of which impulses and movements of such kind 

 are kept up. Should any one ask here what it is 

 which perpetually agitates that subtle matter, I answer 

 that it was set in motion when first created and that 

 there is nothing that can hinder its motion. For we 

 must imagine that it has no weight at all to stop 

 its motion, but that it is rather probable that the 

 weight of bodies is due to its impulse. Nor is this 

 subtle matter impeded in its motion by meeting with 

 other bodies, since it must be supposed so thin, and 

 smooth, and solid as either to pass with ease through 

 the pores of bodies or to be reflected with its motion 

 unaffected when it impinges upon their solid particles. 

 For it is impossible that this very subtle matter should 

 strike against any soft body. For softness implies a 

 great number of particles in a loose state of union, 

 but this matter is so fine that it cannot at a time 

 touch several particles, and so can only strike one, 

 and that is hard. 



Let us then suppose that this subtle matter occupies 

 little spaces here and there interspersed among the 

 particles of rigid bodies and sets up its motion of 

 circumgyration in these pores without hindrance of 

 any kind. For it is to be observed that the matter of 

 rigid bodies, of whatever sort it be, was at one time 

 soft, tender, and to some extent fluid, so that the 

 subtle matter was able from the beginning to open 

 out little spaces in which to set up its motion. But 

 now when the rigid bodies are bent and their matter 

 suffers compression, the pores and little spaces of the 

 bent rigid body are necessarily somewhat contracted, 

 so that the subtle matter is unable to describe its 

 circles in these now contracted little spaces, and there- 

 fore it strikes and impels any particles of the rigid 

 body which have been pushed into the spaces where 



