tl792« t^J^ effects ofivater on machinery, 207 



ifceing thrown from the A A's, in consequence of their. 

 inclined position, where lower than the axle, upon the 

 edges of the trough in which the wheel moves : for 

 as there must always be a vacant space between the 

 edge of the A A's and that trough, as much water as 

 fills that space, must, in all cases, escape, without ac- 

 ting upon the wheel at all by its dead weight. 



The quantity of water that thus is entirely lost will 

 always be m proportion to the distance between the 

 trough and the wheel. It is therefore of the utmost 

 consequence, if we wifli to lose little power, tha. the 

 the trough be formed with the nicest accuracy, and 

 be made to apply as close to the wheel as can be done, 

 so as not to touch it. 



The lofs that is thus incurred will be greatest, 

 where the velocity of the water is greatest, for 

 a reason that fhall be soon explained ; therefore that 

 lofs will be always in proportion to the height of the 

 fall, other circumstances being equal. 



An opinion at present very generally prevails in 

 this country, that a great deal of power is in all cases 

 gained by encreasing the breadth (I do not mean the 

 diameter) of the wheel. In other words, by making 

 the A A's of greater length than formerly. This o- 

 pinion, however, is extremely erroneous ; for where 

 ever the fall is considerable, a dimunition of power 

 must be the result of this alteration ; and where 

 th,-' wheel is constructed with plain A A's, this lofs, 

 where the fall is great, mav be prodiyious. 



To explain this circumstance, it is only necefsary 

 to remark, that the depth of a stream whic.i uaiis- 

 jnits the same quantity of water in a given time, its 

 breadth continuing the same, diminiilics in propor- 



