412 



WOOD TRANSPORT BY WATER. 



be fastened to each log by iron nails or clamps. In this' 

 method the raft-section is a rigid body, and no independent 

 motion is allowed to the individual logs. 



This mode of fastening has the great advantage, that the 

 logs are much less injured by the bore-holes than by the 

 larger holes made in the former case. In that case, the ends* 



of the logs must be sawn off, whilst 

 when the pole is used, the bore- 

 hole can be plugged eventually 

 with a piece of wood and the 

 whole log become utilisable. 



In powerful streams with 

 numerous rapids, as in the river 

 Isar, the poles or planks are 

 sometimes let into the logs. The latter are grooved at their 

 ends, so as to admit the plank, and then fastened to it as 

 before. The raft-section thus fastened is more rigid and 

 stronger than without the groove. In Moravia, only the 



Fig. 274. ^Method of fixing pole. 



Fig 275. Fixing a section by a plank. 



outer logs are grooved, and trenails are used to fix the 

 plank to the logs (Fig. 275). 



The first condition for rafting is that the wood to be rafted 

 is lighter than water, which is the case with all German woods 

 except oak. Whilst, therefore, all other woods may be used 

 alone to form a raft, oakwood must be mixed in rafts with 

 other species which are light and will support it. For this 



* These separate ends of floated logs arc used in many places for paving 

 stables. 



