396 



WOOD TRANSPORT BY WATER. 



are of this nature. Channels for waste water are artificial 

 cuts, which branch-off from the main stream above the boom, 

 returning into the stream below it. Thus a certain portion of 

 the water is led away from the boom, which has, therefore, 

 less pressure to withstand. Fig. 268 represents such a channel, 



Fig. 268. Side channel taking 

 pressure off a boom. 



Fig. 269. Floating-channel with 

 sand-grating. 



which is supplied at its outlet (m) with a lateral boom and 

 sluice-gates and sub-divides below into several branches (b I b). 

 If the terminal boom were also in a side-channel, which has 

 besides the advantage of a weak current, its utility may be 

 increased further by smaller channels taken from above the 

 iHtom and returning into the othor below it. 



