RAFTING. 409 



rafts. A quantity of wood firmly bound together is termed a 

 raft-section, and a number of sections form a raft. 



1, Uaf ting -Channels. 



In order that rafting may be possible, it is generally necessary 

 that the water in a stream should flow uniformly and gently, 

 with only a slight fall. In well-regulated rafting-channels a 

 smaller head of water is required than in mere floating-channels, 

 but the depth must not be less than 2 or 2| feet. Although 

 rafting may be done more favourably on the lower courses of 

 streams and large placid rivers,* yet higher mountain-torrents are 

 sometimes thus utilized. In such cases, however, where the 

 channel is full of rocks and boulders and has a considerable fall, 

 a larger head of water is required than for floating, for unless 

 the rafts are carried over all obstacles in the water, they will be 

 stranded and broken-up. 



Li the latter case, therefore, artificial supplies of water are 

 requisite, and both reservoirs and weirs placed along the stream 

 are employed to increase the head of water. The latter are 

 either sunken weirs with a long wooden wall in the middle of 

 which there is a passage which may be closed, or stone over- 

 flow-weirs are used. 



Reservoirs are not so valuable for rafting as for floating, as 

 they do not concentrate the water in a certain part of the rafting 

 channel. On the other hand, this may be done efl"ectively by 

 placing weirs at short distances apart along a channel, when the 

 water can accumulate between any two weirs to the height 

 required by a raft. 



Wherever the sections and rafts are made-up in powerful 

 streams, a side-channel or basin is required wide enough for the 

 logs to be turned and placed alongside one another. In smaller 

 streams this is best secured by constructing weirs at places with 

 shelving banks. In the upper portion of rafting-channels the 

 rafts may be made-up in the bed of the stream at any suitable 

 place with shallow water. It has been already remarked that 



* In 1883, araft consisting of 11 sections, each containing 500 logs, and 800 feet 

 long, was towed 600 miles from St. John in New Bmuswiek to New York iu ten 

 days by two powerful steam- tugs. 



