[ S'S ] 
For fince all Men agree, that the Force of the Body- 
being the fame, the Velocity mud alfo be the fame; 
the Force being increafcd or diminifhed, the Velocity 
muft be fo alfo, what can be more natural or pro- 
per than to take the Velocity for the Meafure of 
the Force? 
Several other things might be advanced to (hew 
that this Definition agrees beft with the common 
popular Notion of the Word Force. If two Bodies 
meet diredly with a Shock, which mutually de- 
ftroys their Motion without producing any other 
fenlible Effcd, the Vulgar would pronounce, with- 
out Hefitation, that they met with equal Force and 
fo they do, according to the Meafure of Force above 
laid down : For we find by Experience, that in this 
Cafe their Velocities are reciprocally as their Quan- 
tities of Matter. In Mechanics, where by a Machine 
two Powers or Weights are kept in equilibrto , the Vul- 
gar would reckon that thefe Powers ad with equal 
Force, and fo by this Definition they do. The 
Power of Gravity being conftant and uniform, any 
one would expect that it fhould give equal Degrees 
of Force to a Body in equal Times, and fo by this 
Definition it does. So that this Definition is not 
only clear and fimple, but it agrees beft with the 
Ufe of the Word Force in common Language, and 
this I think is all that can be defired in a Defi- 
nition.. 
But if you are not fatisfied with laying it down 
as a Definition, that the Force of a Body is as its 
Velocity, but will needs prove it by Demonftration 
or Experiment j I muft beg of you, before you take 
one Step in the Proof, to let me know what you 
Y y y mean 
