PHYSICAL AND LITERARY. 75 



fed; and therefore this body, before its 

 motion be totally fubdued, muft afcend 

 four times the height that it afcends 

 when thrown upwards with the fingle ve- 

 locity and fingle force. 



But the argument, which the Leibnit- 

 fians truft moft to, is founded upon ex-^ 

 periments of the falling of balls upon 

 clay, or other foft body j where it is efta- 

 blifhed, that ihe impi effions rnade, are in 

 proportion to the heights from whence the 

 balls are let fall, and confequently to the 

 fquares of the velocities. From thefe ex- 

 periments it is inferred, that the forces 

 mult alfo be as the fquares of the veloci- 

 ties ; it being taken for granted, that the 

 impreflions made upon the clay muft be 

 the meafure of the forces or momenta, of 

 which they are faid to be the immediate 

 and dire(5l efFedls. The error of this rea- 

 foning is of the fame kind with the for- 

 mer. The retardation of the motion of a 

 body falling through a reiifting medium 

 is not the effe(5l of gravity, and therefore 

 cannot be the meafure of its force. It is 

 the meafure of the refiftance of the me- 

 dium, 



