162 On. the Measure of 
power was sjfent in the same way, by the 
manner in which it acted upon the wheel; he 
determined to apply the water, in all cases, so 
that it should act more by its weight, and less 
by its impulse; and the advantage gained by 
that improved construction was found to be 
fully equal to his expectations. It was 
afterwards so generally adopted and improved 
upon by himself and by other engineers in this 
country, that although undershot water-wheels 
were, about fifty years ago, the most prevalent, 
they are now rarely to be met with; and 
wherever the economy of power is an object, 
no new ones are made. So that all the points 
in question, as far as they relate to undershot 
water-wheels, although highly important at 
the time when Mr. Smeaton wrote his first 
paper, are now become matters of mere spe- 
culative curiosity, and, in this country at least, | 
they can no longer be of any practical use. 
The question, however, respecting that part 
of the power which is expended in producing 
a change of figure, is highly interesting in 
other points of view, and we shall have occa- 
sion to consider it more fully when we come 
to examine the Gth, 7th, 8th, 9th, 12th, and 
13th cases. 
Dr. Milner, in allusion to Mr. Smeaton’s 
‘yemarks on the theory, observes that, “ It is 
1 
