THE IMPROVEMENT Of RIVERS. 



trestles were made in the form of a St. Andrew's cross, of bar iron, about i J inches hy 



2 inches. On the Sa6ne, on the pass of 

 the He Barbe dam, the trestles were about 

 13 feet high, and made of channel-irons 

 about 2J inches wide. On the Kanawha 

 River the pass and weir trestles are 16 

 feet 9 inches and 1 1 feet 9 inches high 

 respectively. They are built in the 

 shape shown in Fig. 16, DC on the 

 pass being composed of two 4-inch 9-lb. 

 channels and all the other members of 

 one channel of similar size. On the 

 weir, DC is formed of a 3-inch 9-lb. 

 I beam, and the other members are of a 

 single 3 -inch 6-lb. channel. The trestles 

 are all 8 feet apart. 



The trestles of La Mulatiere dam, near 

 Lyons, are 9.8 feet apart, in the form of 

 a St. Andrew's cross, and carry a steam- 

 engine with which the dam is operated. Each member consists of a single channel- 

 iron, sJ inches wide. Their height is a little over 22 feet, and the width of base n feet 

 6 inches. 



Wickets Strain on Horse and Prop. To find the maximum strains on a wicket 

 of the Chanoine type we will assume the water to be flowing over the top to a depth d, 

 and that there is no water below. In practice d may vary from o to i$ feet (see Fig. 17). 

 Let H = depth of water on sill in feet; 

 d = depth of overflow in feet; 

 w = width of wicket in feet ; 

 P = total of pressure of water; 

 Q = that part of P acting at B ; 

 5 = strain in prop; 

 T= " " horse; 

 , @, j- = angles of inclination as shown ; 



k = distance from base to center of pressure; 

 /- ' " " support. 



Then P = w X H sec a X 62} Ibs. X (-- + d\ 



The distance k may be found by considering P as composed of a rectangle and 

 a triangle of pressures (Fig. 18), thus: 



p - p' + p" _ dwH secaX 62* ILs. + wH sec . X 62 J Ibs. 



