Moving Force. 161 
It was chiefly in this last consideration that 
he found the prevailing theory to be defective ; 
for, according to that theory, as it is applied 
in explaining the collision of bodies, there can 
be no force spent in producing change of 
figure: and it is very remarkable, that no 
succeeding writer has, as far as I can learn, 
paid any attention to this circumstance. 
However much Mr. Smeaton’s valuable ob- 
servations may have been disregarded by 
authors, they have not been lost to practical 
men. Before the publication of the paper 
which I have been endeavouring to defend, 
several mills had been constructed under Mr. 
Smeaton’s direction, in which his chief object 
was to apply the water so that less of its force 
should be expended in producing change of 
figure, and consequently more of its force be 
communicated to the wheel. Although he had 
obtained by his experiments results which 
were “more than double of what is assigned 
by the theory,” yet by comparing the effective 
with the real head, he found that nearly' 
half the power was, in many instances, spent 
in producing a change of figure in the water, 
before it reached the wheel; and still finding 
(as stated above in the second observation) 
that more than half of what remained of the 
x 
