3 1 6 tht effect of. water on machinery. Ocii 31 . 



with the same degree of velocity, nearlj, that the wa- 

 ter itself, moves. If, theiefore, the float-board of a 

 mill wheel that is moveable upon ks center, be laid 

 acrofs a river, so as to prevent the water from paf- 

 sing, it will operate as a dam, till the water behind 

 ihall rise to such a heig-ht, as, by its prefsure upon 

 the upper side of the float- board, it (hall overcome the 

 whole resistance made bj the machinery. Whe.re- 

 • ever tbis happens, the float-board will be forced to 

 give way and suffer the water to pafs j the succeed- 

 ing float- board will be made to yield in its turn ; and 

 so on, till a rotatory motion be given to the wheel,, 

 that must continue as long as the water fliall coati-- 

 nue to flow with the same degree of force. 



The principle on which machinery might be tur- 

 ned in these circumstances, is so excefsively clear, 

 that many persons will be surprised it never has been 

 carried into practice in this country ; bat when we 

 advert that the power of water, where the fall is con- 

 siderable, is so much greater than where its motion 

 is lefs rapid, we will not be surprised that mankind 

 flaould have _/?rx^ thought of constructing machinery 

 only where a considerable fall could be obtained ; 

 and, when these mills came to be generally used, and 

 the mode of managing water in these circumstances 

 familiar to every body, it would occur at the first 

 glance, thatalargcbody of water, moving slowly, could 

 not be managed with ease in the lame xoay ; and of 

 courselittle attention tosluggifh streams, as amoving 

 power, would be given.. The difliculties which would 

 tlius present themselves, on a superficial view of the. 

 subject, might thus appear to be insurmour. table, when 



