Chap. XVII. ANTIENT METAPHYSICS. 2ti 



The /o«r/^ kind of recStillneal motion, and which appears alfo to 

 have been unknown to the antients, but is now univerfally acknow- 

 ledged, is the oppofite of what is called attraciion^ and therefore is de- 

 noted by the name of repulfiQn'^\ by which bodies, inllead of moving 

 towards one another, move a contrary way, and, as it were, fiy from one 

 another. What the influence of this principle of nature is, and whether 

 it be as univerfal as the influence of the other principle laft mentioned, 

 is not, I believe, well known; but l am told that there is a philofopher 

 now in Geneva, Le Sage^ I think, is his name, who is^ writing a 

 book to prove, that all the phaenomena of nature, which Sir Ilaac 

 Newton has explained by attraftion^ may be as well or better ex- 

 plained by repulfion, 



Thefe are all the redilineal motions which are conftant and uniform 

 in nature. The next kind of motion mentioned by Ariftotle is the 

 circular motion, which he afcribes to the celeflial bodies, and which 

 he no doubt fuppofed to be exactly circular^ but which, by later difco- 

 veries, is found to be elliptical. It is, however, true, that it is a mo- 

 tion of the circular kind, in fo far as it revolves into itfelf. And i be- 

 lieve it is likewife true, as Ariftotle fuppofes, that it is peculiar to the 

 ccleftial bodies : At leaft, we have not hitherto difcovered any other 

 bodies that move regularly and conftantly in fuch a line. 



The laft kind of motion that Ariftotle mentions, Is what is 

 betwixt the other two, that is, what is neither in a ftraight line, 



D d 2 nor 



* As both attraflion and repulfion feem to have been unknown to the antients, 

 there is one divifion of fimpie or uncompounded motion made by Ariilotle, which is 

 not compleat. That motion, fays he, is either to a centre, /rom a centre, or round ;i 

 centre ; Lib i. de Coelo, cap. 2. For that motion, by which bodies attract or repel 

 one another, is a fimple rcdilineal motion, but none of thefe three. 



