TIMBER AND TIMBER TREES. 



cavities are too small, or few, or both, in comparison 

 with the solid matter; and why dry wood floats better 

 than freshly cut, " green " or wet wood— there is more 

 air and less water in the former. 



Although the so-called specific gravity of fresh, or of 

 dried wood, is so misleading a value, as usually quoted, 

 nevertheless it is possible to obtain some information of 

 a very interesting nature if we carefully compare a suffi- 

 ciently large number of determinations. 



For instance, by determining the average specific 

 gravity of a number of pieces of the same wood when 

 fresh cut, and then repeating the process after the pieces 

 are seasoned, we obtain at least an insight into the 

 quantity of liquid water which the fresh wood con- 

 tained. If we add determinations of the specific gravity 

 of the same wood thoroughly dried, at i io° C, we can 

 form some ideas of the distribution of the water in each 

 piece. Of course corrections have to be made for the 

 shrinkage of the pieces, and an ingenious but simple 

 instrument, called a xylometer or wood-measurer, has 

 been invented for the purpose of such investigations. 



Botanists have taken some trouble to have such 

 measurements carefully carried out, and often repeated, 

 since a good deal depended on a knowledge of the 

 distribution of the water and the air (or other gases) in 

 wood from various trees, and from different parts of the 

 same tree. 



Thus, if the weight of a given piece of wood, 

 measuring loo cubic centimeters when fresh from the 

 tree, is found to be 85 grams, and that of the same 

 piece, perfectly dry, is 35 grams, then we know that the 

 fresh piece of wood contained altog-ether 50 grams of 

 water, which we expelled as vapour. 



The weight of the solid dry wood being 35 grams,. 



