FLOATING. 



395 



the wood floatiiif^ in a stream (terminal "booms), or to divert it 

 into a side-channel (lateral booms), and it must he considered, 

 secondly, what steps may he taken to reduce the pressure on 

 booms and prevent them from breaking. 



i. T('rt)ii)i(tl Booms. 



Terminal booms, intended to stop all the wood floating in a 

 stream, are erected either transversely or obliquely across a 

 stream, the former being termed straight and the latter oblique 

 booms. Booms may run in a broken line, or be arranged so that 

 a quantity of floating 



wood may be collected and Fig. 236. 



taken away from the 

 boom. 



Straight booms are 

 chiefly found on streams 

 with a slight fall and 

 where sudden floods are 

 not to be feared. They 

 have to resist severe pres- 

 sure, and wherever large 

 sweeps of wood are floated 

 should be strongly con- 

 structed. 



Oblique booms are com- 

 moner both in the case of 

 lateral and terminal booms, 

 they have naturally a 

 greater length in propor- 

 tion to the breadth of 

 the stream than straight 

 booms, and the longer 

 they are, the better able 

 are they to withstand the 



pressure of the floating wood and floods. Most booms are not 

 straight, but have a broken line of contour ; and many booms, 

 and some of the most important ones, collect and retain for 

 some time a large quantity of the floating wood. The boom 



