2o6 the effects, qf water on machinery. Oct. IC- 



the general notion seems to prevail, that the greatest 

 reliance ought to be placed on its pow.er when acting 

 by its impetus^ and the effects that might result from 

 its power as a dead weight are disregarded. 



By an accurate set of experiments, conducted with 

 great, care by Mr Smeaton, the ingenious mechani- 

 cian, and recorded in the Philosophical Transactions 

 many years ago, this notion has been proved to be 

 ill founded ; for he has demonstrated in the most sa- 

 tisfactory manner, that, in all cases, the same quan- 

 tity of water will produce a much greater effect with 

 the same height of fall, if made to act by its dead 

 weight than by its impetus. 



The difference of power when applied in these two 

 ways, is always great ; but in some cases it is nearly 

 infinite. Where the stream of water, for example, 

 is small, and the height very great, the power of 

 that water,, if properly applied, by its dead weightt, 

 may be sufficient to overcome a greater resistance 

 than any machinery could bear ; while, by its impe- 

 tus, it qould be nothing ; the whole body of water in 

 that way being broken by the air, and difsipated. 



In a wheel constructed upon the common prin- 

 ciples adopted in this country, with float boards, or 

 A A's, fixfjd on the circumference of the wheel, a 

 ■great part of the impetus is lost by the motion of the 

 wheel ; so that, on this account, the slower the 

 wheel is made to move, the greater will the effect of 

 the water be upon it. 



A great part of the power of the water acting by 

 its dead weight is, in this case also, lost by the water 



