[ l 9 ] 
To which I muft farther add, that fome of the 
moft learned and zealous advocates for time being 
taken into the account, have not agreed among 
themfelves whether it be in a direct or reciprocal 
proportion of the velocity a . 
Thofe who, on the contrary, infill that the force 
of percuflion is in proportion to the fquares of the 
velocity, finding from experiment that in foft bodies 
the velocity after percuflion falls fhort of this 
eflimate, would make us believe, that in com- 
prefling the parts of thofe bodies, a certain degree 
of force muft neceffarily be loft, which, being added 
to what remains after percuflion, will fufliciently 
confirm the truth of their dodlrine. 
To this I reply, that the parts of foft bodies are, 
indeed, removed out of their places by the ftroke, 
and that fome motion is loll in the impinging body, 
being communicated to the parts of the foft body 
it llrikes upon j but thefe parts cannot lofe their mo- 
tion any other way, than by communicating it to 
other parts, or by the force accruing to the whole 
How then are thefe different effeds to be accounted 
for, and in what manner are they to be deduced from 
the fame caufe ? This diverfity of appearances, I have 
for fome time fufpeded, might proceed from the 
nature of cohefion : that while the force of percuflion 
produced an effed on the whole mafs of matter 
which receives the ftroke, in proportion to the 
velocity of the impinging body j it might, at the 
a Dr. Pemberton, Philofophical Tranfa&ions, N° 371. p. 57. 
Dr. Clarke, Philofophical Tranfadions, N° 401. p. 382. 
D 2 fame 
