FLOATING. 



381 



Should the width of the stream be 

 sufficient, a chain of two or 

 more logs (Fig. 252) attached 

 together either by withes or 

 iron rings may be substituted. 

 These are floating booms. Wher- 

 ever a boom has to withstand 

 a great pressure, as, for instance, 

 where numbers of saw-mill 

 butts are being floated, or the 

 floating wood is being driven 

 from the main stream into a 

 bifurcation, a fixed boom 

 (Fig. 253) should be constructed. 

 In this case, piles (m m) are 

 driven into the bed of the 

 stream and are supported by props 



so great that this is not 



. 2:>2. A lateral floating boom. 



(s s). 



Fiir 253. Fixed lateral boom. 



The logs forming 

 the boom are then 

 attached to these 

 piles and close the 

 stream. One row 

 of logs is often 

 insufficient, and 

 then two or more 

 logs are fastened 

 together and 

 placed in front of 

 the piles. Such 

 booms will not, 

 however, stop 

 water -logged 

 wood ; when there 

 is much of this, a 

 more elaborate 

 boom is required, 

 the construction 

 of which will be 

 described further 



on. 



