SHIP- AND BOAT-BUILDING. 



131 



firewood. Such knees last 10 years in barges. Beechwood 

 may also be so used in the interior of vessels. In Saxony use 

 is made of the lower part of a spruce stem with a strong root 

 attached, which may be 15 to 20 feet long, and 7 to 10 inches 

 thick. 



It is difficult to give the proper dimensions for compass-timber 

 used in shipbuilding, but the longer and thicker, the more 

 valuable they are ; 10 inches diameter, and 15 to 20 feet length 

 represent the minimum dimensions. When used for barges 

 and boats the diameter of knee-pieces may go down to 4 inches. 



Long, straight pieces of timber are used for keels, but are 

 chiefly sawn into planks for the inner, or outer, casing of vessels, 

 and even larger sizes are required than for compass-timber : 

 lengths below 24 to 30 feet, and a diameter of less than a foot at 

 the smaller end, are not permissible. Only in the case of planks 

 for barges are much smaller sizes used. 



Figs. 38 and 39 show different sections of a shij) where the curved 

 pieces are used. 



Fig. 38. 



Longitudinal section of a ship. (After Boppu.) 



(b) Mast- and Spar-Wood. — Wood for masts, booms, and 

 spars should be perfectly straight, as cylindrical as possible, and 

 when required for large ships, of the largest possible dimensions. 



K 2 



