Moving Force. 167 
measure of the effect when compared with the 
: force by which it is produced. The machine, 
without the moving force, has no power; and 
; , when we speak of the greater or less power of 
_amaachine, we only mean to say that we make 
yy use of a larger or smaller instrument to convey 
the moving force. If we have to let off the 
% __ water from a reservoir, we know that it will be 
Rte emptied in less time through a large -aperture, 
or channel, than through a small one; and just 
i‘ so we know, that bya large and strong ma- 
chine, a given quantity of moving force may 
be conveyed in less time than by a small and 
weak one. But if the whole, or any deter- 
___- Minate portion of the moving force be properly 
o applied, the whole, or proportionate effect, 
must nevertheless be the same, whatever may 
__ be the portion of time oceupied in the opera- 
| tion. | And the same principle holds good in 
the application of the elastic force of steam, or 
of any other moving force, to produce a me- 
chanical effect. 
a In jection, however, to this, the reviewers 
observe as follows :— 
__ “When it is said, for example, that a bushel 
‘of good coals will give to a steam-engine the 
wer required to grind eleven bushels of 
eat, this must always imply a rate of burn- 
ing included within certain limits ; for the fuel 
