Moving Force. 221 
But there appears to be a material inconsis- 
tency in this application of the prevailing 
theory. For, there is in fact no difference in 
kind between this case and the 8th case which 
we have before examined; although in that 
case there is, according to the theory, no force 
expended in driving the cylinder into the ball 
of clay. I do not see how this inconsistency 
can possibly be removed, but by adopting 
Mr. Sméaton’s explanation of the collision of 
non-elastic bodies. 
I am aware that many object to the compa- 
rison of changes of figure with changes of 
motion, as effects of force. Our knowledge 
ef both, however, appears to be acquired by 
the same means.—They are both produced by 
pressure acting through some portion of space; 
and there appears to be no difficulty in esti- 
mating the forces by which they are produced 
' hy the same measure. 
Of all the various terms that have been 
adopted in explaining the phenomena which 
we have been examming, none has been so 
uniformly used with the same meaning as the 
word pressure. All our notions of force 
appear to be derived from pressure, as it is 
perceived by the sense of touch. By balancing 
and comparing all other pressures with that of 
gravity, we obtain a common measure of 
