Mr. smeaton on Mechanic Power , 
the overfhot mills, if it were poflible to fet afide all fric- 
tion, refinance from the air, &c. fee p. 130. 
The velocity alio of the wheel, which, according to 
M parent’s determination, adopted by desaguliers 
an maclaurin, ought to be no more than one-third of 
t at of the water, varies at the maximum in the above- 
mentioned experiments of table 1. between one third 
and one half; but in all the cafes there related, in which 
the moft work is performed in proportion to the water ex- 
pended, and which approach the neareft to the circum- 
ltances of great works, when properly executed, the 
maximum lies much nearer to one half than one third - 
one half feemingtobe the true maximum, if nothing were 
loft by the reft fiance of the air, the fcattering of the water 
carried up by the wheel, and thrown off by the centri- 
fugal force, & c. all which tend to diminifh the effedt 
more, at what would be the maximum if thefe did not 
take place, than they do when the motion is a little 
flower. 
Finding- thefe matters, as well as others, to come out 
in the experiments, fo very different from the opinions 
and calculations of authors of the firft reputation, who 
reafonmg according to the Newtonian definition, muff 
have been led into thefe errors fromawant of attending to 
the proper collateral circumftances ; I thought it very ma- 
terial, efpecially for the practical artift, that he fhould 
make ufe of a kind of reafoning in which he fhould not 
be fo liable to miftakes; in order, therefore, to make this 
matter perfedtly clear to myfelf, and poffibly fo to others, 
I refolved 
