[ 22 ] 
When the brafs balls, in weight to each other as 
two to one, were let hill on tempered clay, from 
four feet and eight feet refpedtively, the impredions 
made were on various trials found to be equal. 
When the wood balls, being to each other as two 
to one, were let fall from the lame heights, on dried 
clay pulverifed, that from four feet generally made 
the deeper imprelTion. 
When the wood balls were let fall from the lame 
heights on brick-dud;, that from four feet confUntly 
made the deeper imprelTion. 
When the lighter brafs ball was let fall on 
tempered clay, from two feet and eight feet, the 
impredions were to each other as one to four. 
When the lighter wood ball was let fall on dried 
clay pulverifed, from the fame heights, the im- 
predions were (lb far as the eye could judge) nearly 
in the proportion of one to three. 
When the fame ball was let fall on brick -dud:, 
from the like heights, the impredions were not much 
fhort of the proportion of one to two. 
From thefe experiments it plainly appears : Firdr, 
That the impredions made in loft clay are in pro- 
portion to the heights, from whence the balls are 
let fall, conlequently as the fquares of their refpec- 
tive velocities. Secondly, That the impredions, in 
pulverifed clay, recede condderably from that pro- 
portion, being as it were in the medium between 
the lquares of the velocities and the velocities them- 
feives. Thirdly, That the impredions in brick-duft 
are nearly in a fubduplicate proportion of the heights 
from whence the balls are let fall, conlequently vary 
but 
