( lU ) 
“ Fall made Pits in the Tallow, that were precifely 
“ equal : the Ball of one Pound, from the Beginning 
“ of its Fall, till it came to reft, going through a Space 
exprefs’d by the Number two, produc’d an Effed: 
“ equal to that, which the two Pound Ball did pro- 
duee, in falling thro’ a Space exprefs’d by the Num- 
“ ber one. It follows therefore, that we may look 
“ upon it as a fettled Truth, That the adive Forces 
“ (vires vivas') of falling Bodies are then equal, when' 
“ their proper Weights are in a reciprocal Ratio of 
“ the Spaces, which the faid Bodies defcribe by their 
“ Fall. And becaufe thefe Spaces are in the fame Ra- 
tio^ as the Squares of the Numbers exprefling tlie Ve- 
” locities *, it appears by the Experiment, that the 
adive Force (vim vivam) of the falling Body, is 
“ that which is made up of the Body itfelf, multiplied 
“ into the Space defcribed in the Fall, or into the 
Squareof the Number, that exprelfes the Velocity of 
the Body, at the end of the Motion. This Experi- 
“ ment I did not only make once, but feveral rimes, 
“ changing the Balls, the Diftances, and the Body on 
^ which they fell ^ as for example, making ufe of Clay, 
“ or of foft Wax : and notwithftanding thefe various 
“ ways of trying the Experiments, the Effeds were 
** conftantly the fame j which made me eahly con- 
“ elude, that there was always the fame Reafon in Na- 
ture for this Phenomenon. 
Thus far Rolenus^ whofe Miftake lies in this j that 
he eftimates the Force of the Stroke of the falling Balls, 
by the Deptlv of the Impreflion made in* the Tallow, 
Clay, Wax, or any yielding Subftance. Bur we muft 
confider, that when two Bodies move with-equal Farces, 
but different Velocities, that, which moves the fwifteft, 
muft make the deepeft Impreflion, whilft the floweft 
