322 



HYDRAULICS AND ITS APPLICATIONS 



D'Aubuisson on the Wesser. Here the mean slope of the bed was 2*33 

 feet per mile = '000141, and the depth before introducing the dam was 

 2*46 feet. The effect of the darn in raising tho surface level was apparent 

 for 4'33 miles up-stream. 



In a second series of observations on the Werra, the following results 

 were obtained. 



Mean depth H = I'l feet ; width = 80 feet ; fall = 3'88 feet per mile. 



FIG. 142. 



A dam 15*66 feet in height was placed across the stream, and the height 

 of water over the sill was found to be 1*13 feet. 



The following table indicates the observed and calculated depths, and 

 rises in surface level at points above the dam. 



In these calculations the value of /has been taken as "02. 



As an example of the effect of a drop in the bed of a stream in pro- 

 ducing an increased velocity at points up stream, consider the same 

 stream as before to have a fall at some point in its length (Case 1 (&)), 

 and suppose that this causes a lowering of the surface just above the fall 

 through a depth of 6 inches. 



