INDUSTRIAL USES OF WOOD. 



iron. Iron ships are most resisting to storms, of larger 

 burden, easier to repair and more durable than wooden ships. 



As regards the shape, there is a considerable difference 

 between ships intended for the sea, and fresh-water barges : 

 the former are comparatively short compared with their 

 breadth, with keels which run straight from end to end of the 

 ship; whilst all the other lines are of various degrees of 

 curvature. This curved shape is given to ships by means of 

 ribs, which are made partly by joining different pieces of wood, 

 but also by using curved pieces. 



Fresh-water barges have no keels, but a broad flat bottom 

 on which the knee-pieces are fastened at a sharp angle, so 

 that the straight line is much more frequent in their construc- 

 tion than in that of ships. The chief strength in ships consists 

 in the ribs, which are very close together, the outer planking 

 being less important ; in barges the ribs are much further 

 apart, and the planking is of greater importance. 



The demands on wood for building ships and boats depends 

 on the species of wood, its quality, shape and strength. 



2. Species and Quality. 



The wood of teak (Tectona grandis) is used chiefly in ship- 

 building. The preference given to it is due to its large 

 dimensions, its great durability, its being only slightly subject 

 to warp, a matter of great importance owing to the varying 

 degrees of insolation and humidity to which a ship is subject ; 

 teak-wood also is not affected by contact with iron, so that 

 there is no rust such as the tannin in oakwood causes, which 

 loosens bolts fastening iron plates to oaken ribs of ships. 

 Next to teakwood comes oakwood, which must be durable and 

 strong. Only heartwood 'is used, and with broad uniform 

 annual zones, but not broader than 6 mm. (4 to an inch) ; it 

 should be of uniform colour and with a fresh scent of tannin. 



It is uncertain whether the pedunculate or sessile oak yields 

 the best wood for shipbuilding, but most ships are built of 

 pedunculate oak. For the Austrian navy, the wood of the 

 pubescent oak is preferred for ribs ; in Norway, sessile oak is 

 used chiefly. The best oak for shipbuilding is that grown 

 on rich soil and in a warm climate, even the coasts of the 



