OF SOLIDS AND LIQUIDS. 231 



tlum, effluere speciem immateriatam corporis 

 ipsius, cui specie! et vis prensandi, et lux, luci 

 vero et calor et color, quodlibet ex suo fonte 

 derivatum, inhaereant nee enim uspiam est 

 species ilia, nisi in opposite et occurrente cor- 

 pore, lucis quidem in ejus superficiei opaca ; 

 virtu tis vero motrica in tota corpulentia : in 

 spatio vero interrnedio inter solera et superfi- 

 ciem, non est, sed fuit." (Epist. Astron.) It is 

 not here easy to annex any clear ideas to our 

 author's meaning ; in what manner this imma- 

 terial image of the sun acts upon the planet to 

 bring it towards the sun (vis prensandi) he has 

 not explained. He speaks of the cause as an 

 immaterial active body ; as a divine mind ; as 

 the mind of man ; and by its action retaining 

 the planets in their orbits. 



" The only hypotheses which have met with 

 any advocates amongst philosophers, are those 

 of DES CAHTES, Sir I. NEWTON, and I. BER- 

 NOUILLI. Des Cartes attempted to account 

 for the motions of the planets, by supposing 

 them to be carried round the sun in vortices. 

 But Sir I. Newton, besides his other argu- 

 ments against this theory, very justly observes, 

 that the free motioos of comets in all direc- 

 tions, and their being subject to the same laws 

 which the planets are, destroy, at once, the 

 hypothesis of vortices. Sir I. Newton accounts 

 for gravitation in the following manner. He 



