FLOATING AND RAFTING 



365 



The cribs are filled with rock to anchor them firmly. A common 

 method of attaching the boom sticks to the cribs is to drive a 

 pile in the center of the crib. After a large iron ring has been 

 loosely fitted over this pile the boom is fastened by a chain to 

 the ring, and as the water rises and falls the ring is slipped up 

 and down with the chain. Where piling is used instead of cribs 

 a nest of three or four are driven together and bound with 

 chains or cable. 



Storage booms are usually taken in and the chains repaired 

 after the drive is over. They are replaced early in the spring, as 

 soon as the ice leaves the stream. 



The capacity of storage booms varies with the size and length 

 of timber handled. The following table ^ shows the area in 

 acres required to store spruce logs of several sizes and lengths, 

 and also the number of boom logs required to impound given 

 quantities of timber when the logs are forced into a compact 

 body by the current of the stream, all sticks floating on the 

 surface. 



Blodgett rule. 



The average storage capacity of medium-sized white pine and 

 yellow pine logs is approximately 250,000 feet per acre. 



Sorting Equipment. — The main feature is the sorting jack 

 where logs are separated and deflected into the storage pockets 

 downstream. The usual type of sorting gap consists of two op- 

 posite rafts or bracket booms placed from 30 to 50 feet apart and 

 connected by an elevated runway on which the sorters stand 

 and separate the logs by marks as they pass under them. 

 There are many forms of gaps governed by the amount of work 

 ' Boom Areas, by A. M. Carter, Forestry Quarterly, Vol. X, No. i, p. 15. 



