230 On the, Measure of 
The practical application of this principle 
is exemplified in a variety of imstances.—In 
driving piles—if the weight of the ram be very 
- small in proportion to that of the pile, a great 
part of its moving force is expended in bruis- 
ing the pile, and the progress of the pile into 
_ the earth is very small. The heavier the ram 
is in proportion to the pile, the greater is the 
progress of the pile, by the application of the 
same quantity of moving force.—On the other 
hand, if the object be to produce a change of 
figure in the substance which is struck, in 
hammering iron for example, if the anvil be 
light in proportion to the hammer, the intend- 
ed effect is not produced in the same degree 
as when the anvil, or the mass which is struck, 
is heavy in proportion to the hammer which 
strikes it. * 
If a non-elastic body strike a non-elastic 
<—,07. But these two quantities are as 
den 
ies shea) ASE" 
] Fear hence it appears that the fractional part of the 
moving force found in the motion of the bodies after colli- 
sion is , consequently the part which is spent in pro- 
A+B 
ducing change of figure is remy 
* Examples of moving force similar to these are referred 
to by Mr. Leslie, in his excellent work on heat, p. 128, 
He explains them however on different principles. 
