FLOATING. 



395 



By supplying booms with sluice-gates, they may be improved 

 considerably; but this necessarily pre-supposes sufficient 

 strength to withstand the 

 pressure of the wood and 

 water. Sluice-gates are 

 specially valuable in the 

 case of large booms with 

 masonry supports. By 

 regulating the supply of 

 water, the front of the 

 boom may be covered 

 more uniformly with 

 floating w r ood, so that 

 when the sluices are 

 opened the greater part of 

 it may become stranded, 

 or can be brought to land 

 easily. In the case of 

 long booms, it is highly 

 advantageous, by opening 

 first one sluice-gate and 

 then another, to drive 

 the wood in front of 



portions of the boom 

 hitherto free from it ; 



7. Lateral l;o<>m. 



and, finally, by opening all the sluice-gates to bring in the tail 

 of the sweep of the wood. 



of the Pressure on a 



Attempts should be made in every possible way to reduce 

 the pressure on a boom ; this object may be secured in 

 various ways, by constructing booms on weirs, by means of 

 channels for waste water, channels to remove sand, sluice- 

 gates, etc. 



Generally lateral booms are placed on a weir, which supports 

 part of the water-pressure and reduces the fall of the stream 

 and the pressure on the boom. Nearly all large booms which 

 are intended to strand the wood, or to serve as lateral booms, 



