252 On the Measure of 
experiment, than conclusions derived from the 
examination of mechanical changes of figure. 
This term, as has been already observed, 
includes every change of figure which requires 
moving force, or pressure acting through some 
portion of space, to produce it. Whether 
it be the repulsion or the cohesion of the inte- 
grant parts of bodies, or the ‘attraction of 
masses to each other, that is to be overcome, 
mechanical change of figure is produced ; and 
we have seen, in various cases which have 
been examined, the uniform relation whick 
subsists between determinable quantities of 
change of figure and the moving forces by 
which they are produced. We find by expe- 
rience, that when a body in motion is retarded 
or brought to rest, either a change of figure is 
produced, or a quantity of moving force, equal 
to that which the body has parted with, is 
communicated to some other body or system 
of bodies. It has been supposed, indeed, that 
A and B, in the case stated, may be brought to 
_ rest without any change of figure being produc- 
ed. That supposition, however, is contradicted 
by universal experience, and in point of fact 
we may, with as much consistency, suppose 
that a body may be put in motion without 
force, as that two bodies moving in opposite 
directions may destroy each other’s motion 
