1792* ^ the effect of voater on 7nachinery. 251 



But manj particulars must be adverted to, before 

 \ve can ascertain whether that water can be so ap- 

 plied, as to produce the greatest effect pofsible. 



We fhall, for the present, lose sight of the water 

 entirely, and, for the sake of illustration, we fhall sup- 

 pose that a number of equal weights could, by some 

 magical powers, be hooked upon the wlieel at a cer- 

 tain place as it turns round, and taken off again in 

 the same way below. 



On this supposition we fhall easily perceive, that 

 the same weight will produce a much more power- 

 ful effect upon one part of the wheel, than upon ano- 

 ther part of it. Let A, B, C, D fig. i. represent 

 a wheel moveable upon its pivot P ; and let the se- 

 veral dots upon one side of it, represent a number of 

 equal weights, affixed in the manner above mention- 

 ed to one side of the wheel. I would observe : 



In xht first place, that the weights at A, and C, 

 can have no .tendency whatever to produce any mo- 

 tion in the wheel; because the one being perpen- 

 dicularly above, the pivot, and the other acting per- 

 pendicularly below it. they can have no tendency to 

 move it to either side. 



Each of the weights a, and h, however, will have 

 a tendency to move the wheel in a certain degree ; 

 because they are placed a little towards one side of 

 the center ; but their moving power will still be 

 small, because they act only upon a radius of small 

 length when compared with that at B. Mathema- 

 ticians have long ago ascertained, that the power of 

 any given weight, acting on a lever, is always in pro- 

 portion to the length of that lever ; so that, suppo- 



TOL. xi. X I 2 \ 



