66 



THE IMPROVEMENT OF RIVERS. 



Where the channel is to be closed by timber-cribs filled with stone, the general 

 method of construction is the same as described for the building of fixed dams, and 

 care must be taken to prevent the water from cutting under or around the structure. 

 The elaborateness of the precautions will of course depend on the nature of the banks 

 and bed, and the volume of water to be controlled. 



