140 THE OAK 



the difference would hold if sufficiently numerous com- 

 parisons were made. 



(5) Swelling may be regarded as complementary to 

 shrinkage. It has been found that it oak wood is 

 allowed to absorb water until thoroughly saturated it 

 will increase from 0-13 to 0'4 per cent, in length, and 

 be distended radially from 2 -66 to 3 -9 per cent., or tan- 

 gentially 5 -59 to 7*55 per cent., according to age and 

 condition, young wood swelling more than old. It has 

 also been found that the total volume increased from 5*5 

 to 7*9 per cent., and the weight from 60 to 91 per cent., 

 on complete saturation. 



(6) Elasticity and Tenacity. Oak is very elastic, 

 and easily bent if steamed, and it does not readily 

 splinter. When pulled in a direction parallel to the 

 length of the structure the absolute tenacity = 2 -23 to 

 14*51 kgr. i.e. it took a pull equal to this weight per 

 1 sq. mm. of section to pull the wood asunder. 



The limit of elasticity corresponds to a load of 2 '72 

 to 3 '5 kgr., according to various authorities, the speci- 

 men lengthening ^g-^th in the former case. 



The modulus of elasticity is given as 826 to 1,030 

 kgr., and the breaking limit as 4 -66 to 6' 85. 



When the pull is in a direction across the length of 

 the fibres, the results differ according as the load is 

 applied so as to act radially or tangentially. 



When acting radially the modulus of elasticity is 

 given as 188'7 kgr., and the breaking limit as 0-582 kgr. 



When acting parallel to a tangent the modulus of 



