380 WOOD TRANSPORT BY WATER. 



cases it may be even worth while to make tunnels for the 

 water to pass, as at Hals, near Passau. 



Artificial floating-canals leading to a timber-depot are of the 

 same nature as the above and sometimes run from one river- 

 basin into another. 



The best known of these artificial floating-canals is that 

 belonging to the Prince of Schwartzenberg, at Krummau, in 

 Bohemia ; it is 35 miles long, of which 600 yards are tunnels 

 leading from the centre of the forests to the river Miihel, 

 which flows into the Danube between Lintz and Passau and 

 brings down the yield of 35,000 acres of forest. 



Whenever a canal is dug, levels must be taken most carefully 

 beforehand ; one in fifty is the best fall, though frequently 

 unattainable. The canal just described has a fall of one in nine 

 for a short distance, and one in the Bavarian forest a fall of 

 one in five. In such places, the bed of the canal must be 

 paved, or terraced, as already described. 



In the latter case, the upper section of the canal is only 4 

 to 5J feet broad, and 1% feet deep ; it brings down very large 

 butts for the saw-mills. It is there constructed of blocks of 

 granite ; lower down, its banks are made of wood, but in 1882 

 the floods proved too much for these wooden constructions. 

 In the lowest section, where there is much more water available, 

 the width of the canal is 10 feet. 



In constructing such canals the chief point is to secure a 

 good supply of water, owing to the snowfall in mountainous 

 regions this can generally be done. The line is then taken, as 

 far as possible, through all adjoining mountain-streams, or it 

 is supplied with water by reservoirs and dams. 



iv. Lateral Booms. 



All streams used for floating have branches either natural or 

 artificial, and arrangements must be made to keep the wood 

 out of such bifurcations, or in certain cases to conduct it into 

 a side-stream. To effect this, lateral booms either floating, 

 or fixed in the bed of the stream, are required. A thoroughly 

 dried spruce-log fastened to the bank of the stream by withes 

 and floating in the water in front of the side-stream will often 

 suffice. 



