CHAPTER X. 
ON THE TENSILE STRENGTH, OR DIRECT COHESION, 
AND VERTICAL STRENGTH OF BRITISH OAK. 
The tensile experiments are somewhat difficult to carry 
out, and therefore only specimens Nos. I to 6, Table VII., 
were tested from the log referred to at page 53. They 
varied from 2,240 to 5,320 lbs., giving a mean strength 
of 3>837 ^s. the sc l uare 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. 1 as unity or roo, give No. 2 as -82 ; No. 3, 785 ; 
No. 4, *81; No. 5, '475 5 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 VII., 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 
upon, and referred to in Tables V. and VI. They appear 
