CHAPTER X. 



EUROPEAN TIMBERS — (Continued). 



ON THE TENSILE STRENGTH, OR DIRECT COHESION, 

 AND STRENGTH UNDER COMPRESSION OF BRITISH 

 OAK. 



The tensile experiments are somewhat difficult to carry- 

 out, and therefore only specimens Nos. i to 6, Table IX., 

 were tested from the log referred to at page 102. They 

 varied from 2,240 to 5,320 lbs., giving a mean strength 

 of 3,837 lbs. to the square inch, the wood next to the 

 pith or centre proving to be the strongest, as with the 

 transverse test. The gradations of strength, taking 

 No. I as unity or foo, give No. 2 as '82 ; No. 3, 785 ; 

 No. 4, •81; No. 5, "475; and No. 6, -42, the tensile 

 strength of the inner wood of this tree being therefore 

 about 58 per cent, greater than the outer. 



Instances of weakness, both transversely and tensilely, 

 similar to those which are given in Table IX., are not 

 unfrequent, and may occur, as before stated, in good- 

 looking specimens of any species of timber : and this, 

 again, serves to show that it would be unsafe to arrange 

 the various parts of any construction according to the 

 highest calculated strength of any timber to be 

 employed. 



Further tensile experiments were made on six speci- 

 mens of British Oak saved from the pieces experimented 



