II.] ITS PROPERTIES AND VARIETIES. 27 



The weight of equal volumes of different woods 

 differs more than is commonly supposed, and there are 

 certain details to be considered in employing weight 

 as a criterion which have not always been sufficiently 

 kept in mind. 



A cubic foot of " seasoned " timber of the Indian 

 tree Hardwickia binata weighs about 80 Ibs. to 84 

 Ibs., while a cubic foot of Bombax malabaricum may 

 weigh less than 20 Ibs., and all gradations are possible 

 with various timbers between these or even greater 

 extremes. If we keep in mind the structure of wood, 

 it is evident that the weights of equal volumes of 

 merely seasoned timber will yield only approximate 

 results. For even if the seasoning, weighing, &c., 

 are effected in a constant atmosphere, woods which 

 differ in " porosity" and other properties will differ 

 in the extent to which they absorb moisture from 

 damp air or give it up to dry air. 



In our climate, timber which is felled in April or 

 May, generally speaking, contains much more water 

 than if felled in July and August : it is, in fact, no 

 uncommon event to find that about half the weight, or 

 even more, of a piece of recently felled timber is due 

 to the water it contains. If this water is driven off by 

 heat, and the piece of wood thoroughly dried, the 

 latter will be found to weigh so much less, but it 



