°PHYSICALano LITERARY. 67 
ftruggle with, has but half the time in any 
_ given {pace to produce its effect; and there- 
fore this body, before its motion be totally 
fubdued, muft afcend four times the height 
that it afcends when thrown upwards with 
the fingle velocity and fingle force. 
- Bur the argument which the Leibnishans 
truft moft to, is founded upon experiments of 
the falling of balls upon clay, or other foft 
body ; where it is eftablifhed, that the im- 
preffions made, are in proportion to the 
heights from whence the. balls are let fall, 
and confequently to the fquares of the velo- 
cities. | From thefe experiments it is inferred, 
that the forces muft alfo be as the fquares of 
the velocities; it being taken for granted, 
that the impreffions made upon the clay muft 
be the meafure of the forces or momenta, of 
_ which they are faid to be the immediate and 
ee 
direct effets. The error of this reafoning is 
of the fame kind with the former. The re- 
tardation of the motion of a body falling 
through a refitting medium, is not the effect 
of gravity, and therefore cannot be the mea- 
“fure of its force. It is the meafure of the re- 
fiftance of the medium, becaufe it is the effect 
of that refiftance. All the world knows, that 
when bodies move through a fluid, or any 
foft 
