3i8 TIMBER AND TIMBER TREES. [CHAP. 



Having in former chapters, treating of the hard- 

 wood trees, adopted the British Oak timber as the 

 standard of quality and fitness for all the purposes of 

 naval and civil architecture, it is proposed to adopt the 

 Dantzic Fir timber — the most important and generally 

 useful of the Firs and Pines — as the standard of com- 

 parison for the soft or white wood class. The author 

 has, therefore, gone more fully into the experiments on 

 this timber than would have been possible with each of 

 the other descriptions. 



The transverse experiments recorded in Table 

 CXXV. were made upon pieces of well-seasoned wood, 

 of good average quality, and in every respect fit to be 

 employed in the best architectural works, their specific 

 gravity ranging from 478 to 673, and averaging 582. 

 Of these specimens the elasticity of one piece was 

 perfect immediately after the weight of 390 lbs. was 

 removed, and in each of the others it was very nearly so, 

 the average of the whole giving only '066 of deflection. 

 All these would probably have recovered their straight- 

 ness if time had permitted of their being left for only 

 a short period prior to proceeding with the breaking 

 strain. 



The strains required to break these specimens varied 

 very much, the minimum being 700 and the maximum 

 970 lbs., the average 876-6 lbs. on pieces of the standard 

 dimensions. The deflections at the crisis of breaking 

 varied from 4' 5 to 6" 15 inches, and averaged 5' 142 

 inches. 



The experiments for determining the direct cohesive 

 strength are, as before stated, somewhat difficult to carry 

 out, even upon the hard woods, but they are infinitely 

 more so on the soft woods, owing to the liability of the 

 pieces to crush in the clamps holding them before the 



