r 2° ] 
fame time, in feparating the cohering parts from each 
other, produce an effeCt in proportion to the fquare 
of the velocity. 
Into which way of thinking I was firft led from 
the following obfervations ; that a chord, which 
would bear a very ftrong pull, might eafily be broken 
by giving it a fudden jerk ; as alfo that the weight of 
a hammer did not contribute fo much in driving 
a nail, as the quicknefs of the motion given it by 
the driver. 
In order to make a further difcovery, whether or 
no this my fuppofition was really founded in nature j 
I determined firft to make experiments on fuch foft 
bodies as have a confiderable degree of cohefion ; 
and then to try thofe bodies, when dried and re- 
duced to powder, and by that means deprived of 
their cohefion ; which experiments, when compared 
with each other, would, I flattered myfelf, give me 
an infight into this intricate affair, and at the fame 
time difclofe that beautiful fimplicity, which nature 
obferves in all her operations. 
My apparatus for making the experiments confifts 
of four balls exactly fpherical, two iron branches, 
and a fmall lead ciftern^ 
The balls are each of them two inches in diameter ; 
two are of brafs, and two of box- wood ; one of 
each fort is folid, and the other hollow ; that which 
is hollow is only half the weight of the folid one. 
and may be opened by. means of a fcrew in the 
middle. 
The iron branches are to give the balls their pro- 
per directions j they have each of them a fmall brafs 
pully in the fore part, and in the. hind. part a kind of 
i hook, 
