SMALL WATER SUPPLIES. 



level of the water flowing therein under ordinary 



circumstances. The angle 

 should be noted. To 

 calculate the velocity in 

 such a channel, let H be 

 the same as before, i the 

 hydraulic slope of the 

 water surface, and N a 



FIG. 46. 



coefficient. 



Then N - 4/cosec + 



tan 



and V = 



r8n 



N 



41*6 + 



00281 \ 



sn 



I 4- 



N 



(10) 



(11) 



S being the length in which the water surface falls 

 one unit, that is to say if the fall is 5 ft. per mile, 

 S= 5280^ 5= 1056, and so on. In order to avoid a 

 repetition of the use of the above formulae a list of 

 velocities for given values of H, S, N, and /, etc., will 

 be found in most engineers' pocket-books. 



We now pass on to the flow of water in pipes 

 which are under pressure, that is, they are full and 

 there is a pressure on the upper surface of the in- 

 terior due to the water. For working hydraulic 

 rams, high fall turbines, pelton wheels for pumping 

 purposes, and also conveying water from reservoirs, 

 etc., pipes are used. 



These pipes which we are going to consider are 

 pipes for supply of water for domestic or power pur- 

 poses ; they will usually be made of cast iron or some- 

 times of welded or riveted steel, and are assumed to 

 be running quite full under pressure, Now if we 



