280 On the Velocity of Water Wheels. 



tional quantities of water ufed by the old mill, nothing more 

 was neeetlary than to meal u re the time the water took to 

 rife to a certain height in that pond ; and accordingly, on 

 the tlrft of May 1798, I made the experiments noted in the 

 following table: 



The firft and fecond experiments were made with the mill 

 at its common velocity; the third and fourth at nearly half 

 that velocity. 



The time which the mill required to ufe the fame quantity 

 of water in theie experiments may be taken in round num- 

 bers ; the proper velocity at 7 minutes, and half that velocity 

 at 15 minutes. 



1h. remit of thefe experiments approaches very nearly to 

 that of 1796. The difference mav be accounted for by the 

 fmall degree of leakage which muft have taken place at the 

 iluices on the lower end of the pond; and the time being 

 greater in the third and fourth experiments, the leakage 

 would, ot'cpurfg, be greater. 



Mr. Smeaton ' and others have proved, in a very fatisfac- 

 tory manner, that u the mechanical power wh ch muft be 

 emplo\ed in giving different degrees of velocity to the fame 

 body mutt be as the fquare of that velocity " But it appears 

 to me that the refult of the above experiments may be eafily 

 reconciled to this propofition by conlidering what Mr. Smea- 

 ton favs immediately afterwards: — " If the converfe of this 

 propofition (fays he) did not hold true, viz. that if a body 

 in motion, on being flopped, would not produce a mecha- 

 nical effect equal or proportional to the fquare of its velocity,, 

 or. to the mechanical power employed in producing it, the 

 effect would not correfrond with its producing caufe." Nov/, 

 it is to be obferved, that Mr. Smeaton's experiments were 

 made on the velocity of heavy bodies free Jromjrittion and 



* See Smeaton on Mills, p. 18. 



other 



