158 COHESION OF SOLIDS. 



lowers in great doubt whether he had any settled 

 opinion on the subject. In the first edition of 

 the Principia, he maintained that universal space 

 is a vacuum ; or that it ivas void of all sensible 

 matter, and that the ultimate particles of bodies 

 are endowed with inherent forces, or powers of at- 

 traction and repulsion. 



That he afterwards renounced the vacuum of 

 space and the self motive power of a toms, is evident 

 from the scholium which he added to the second 

 edition of the Principia, his letter to Boyle, and 

 from the whole tenor of the Opticks in each of 

 which, he maintains the existence of an exceed- 

 ingly subtile, active, and elastic aether as pervad- 

 ing universal space and the pores of all bodies 

 that it was the cause of cohesion, capillary at- 

 traction, and of the force by which menstruums 

 dissolve solids in fine, that it was the moving 

 power of nature. 



It is also universally known, that he regarded 

 light as a material substance, capable of being 

 attracted and repelled by gravitating matter; 

 which alone is sufficient to prove, that he had 

 abandoned the hypothetical vacuum of space. 

 He further supposed that light and common mat- 

 ter were convertible into each other an hypo- 

 thesis which I shall endeavour to show hereafter 

 by an appeal to nature, and the most decisive 

 experiments, is susceptible of positive demon- 

 stration. 



Considering the almost unbounded influence 



