No. 105.] 233 



rod ; to find the quantity of water that will flow In it. It will fall 

 320 inches in a mile ; the perimeter in contact with the water will 

 be, six inches on the bottom and four inches at each side = l4 

 inches ; the area of the section will be 6 times 4 = 24, which di- 

 vided by 14, the perimeter, gives 1.7 = the hydraulic mean depth. 

 Then by applying the above rule, 



y =1 . 23 v/320xl .7 = 1. 23x7 .4 = 9.1 inches, the velocity per se- 

 cond, or about one gallon per second, or one hogshead per minute. 

 In practice, considerable allowance must be made for rough and 

 uneven sides and bottom, which would tend to retard the current. 

 In larsfer channels, the calculation would be more accurate. 



