lolth a View to Irrigation. 203 



in the construction of dams. In Holland and Germany 

 they are very commonly employed for this purpose. A 

 course of large fascines is first laid, the length of the fascines 

 being in the direction of the current, and each in as close 

 contact as possible with its neighbours : upon this a second 

 course is laid transversely, strong pickets are driven through 

 these two courses to connect them together, and the heads 

 of these pickets are wattled together so as to make a kind 

 of hurdle-work, which serves to connect the whole more 

 completely into one mass ; these layers of fascines are then 

 continued in the same manner, each course being picketed 

 to those below, and the pickets connected at top with hurdle 

 work, until the dam has attained the proper height. Very 

 large rivers, with a great depth of water, have been success- 

 fully dammed up and their courses changed by works con- 

 structed in this manner. Where the water is deep, gabions 

 loaded with stones, square wicker baskets, filled with stone, 

 &c., have been used to form the foundation of the dam ; 

 and upon* this a superstructure, as before described, has 

 been raised. 



The above are a few of the most simple and of the readiest 

 modes of constructing dams ; modifications may of course 

 be made to any extent : two or more of these plans may be 

 combined in the construction of a single dam — as, for instance, 

 the sides of a dam when the water is shallow may be made 

 according to figure 1, and the centre part with cribs, as in 

 figure 5, 



The flank of the dam should be secured by being let into 

 the bank and puddled in front, and the earth or rubbish 

 which is thrown in front should be carried up the river 

 against the bank to a greater distance than at other points. 



As a general rule, the sides of a dam should be first 

 constructed and the abutments made good ; — serious 

 accidents have occurred from a neglect of this precaution. 



