210 ANTIENT METAPHYSICS. Book 11. 



pot, the Rem of the plant will neverthelefs bend itfelf, and grow up- 

 ward, even though a welgtit be appended to keep it down. It 

 appears, theretore, to be certain, that there is in nature a motion up- 

 ward as well as downward ; fuch as cannot be accounted for from 

 any material impulfe, or mechanical caule, of any kind. 



The third rectilineal motion I {hnll mention is, that by which bo- 

 dies move toward one another. This, as well as gravitation, or the 

 motion of bodies to a centre, is called, in the language of our modern 

 philolophy, attraction ; a very improper name for it, as I Ihall take 

 occafion afterwards to obferve. It is a motion unknown to Ariftotle, 

 and to all the antient philalophers, as far as I know ; but, by later 

 experiments, it is certainly known to exift in nature. And chemiftry, 

 particularly, exhibits to us wonderful examples of it ; from which it 

 appears, that bodies, by this movement, fometimes unite themfelves to 

 one kind of body, and then, finding another that they like better, they 

 go to that other, and incorporate themfelves with it. This is what is 

 called, in chemical language, eleciive attra^ion^ by which the parti- 

 cles of matter appear to chufe and prefer one kind of body to another. 

 And, indeed, in fuch kinds of movement, mind is, 1 think, vifible, 

 even to the mod vulgar and ignorant. 



This kind of movement appears to me to be the principle of cohe- 

 fion in bodies, by which all the different kinds of natural bodies are 

 formed and difcriminated one from another. The effedt of this prin- 

 ciple is mofl vifible in the common chemical experiment of the folu- 

 tion of falts of different kinds in water ; for, when the water is evapo- 

 rated, all the feveral particles of the different falts range themfelves, 

 as it were, under their proper flandards, and unite to form cryilals of 

 the feveral kinds. And, in this manner, I imagine the homogeneous 

 particles of all the different bodies in the univerle have united to form 

 thofe bodies. 



The 



