212 On the Measure of 
ous quantities according to the positions of the 
rod; it cannot be questioned that the quantity | 
of force must remain the same, under all 
positions of the rod—While the motion con-— 
tinues uniform there certainly can be no vari- 
ation of the force. Yt appears, therefore, (as 
I have before observed p. 173) that Sir Isaac 
Newton understood, that unequal quantities of 
motion might be derived from the same quan- 
tity of force. It must be acknowledged that, 
from some expressions of Sir Isaac Newton, 
in alluding to this and some other cases, it 
might appear—if these expressions are taken 
individually without reference to his eeneral 
doctrines, that he supposed a variation of 
force to take place in this case. That suppo- 
sition has been noticed by M. Bernoulli with a 
degree of unfortunate asperity peculiar to 
himself, and very inconsistent, it must be con- 
fessed, with the character by which philoso- 
phical discussions ought to be distinguished, 
From the context, however, it is obvious, 
that Sir Isaac Newton could not mean the 
casual expressions in question to be strictly 
apphed as relating to variation of force in the 
cases which he mentions. For, if they canbe 
so applied, they must be indiscriminately ap~ 
plied to cases which have no resemblance to 
each other, The force which is expended in 
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