500 ‘The Philippine Journal of Science 1921 
Fic. 10. Apparatus used in testing hardness of timber. 
the dry weight, to give the proportion of moisture, and this is 
usually expressed in per cent of the dry weight. 
SPECIFIC GRAVITY 
Specific gravity is the weight of any given substance divided 
by the weight of an equal volume of pure water at its greatest 
density. 
VARIABILITY IN THE STRENGTH OF TIMBER 
The mechanical properties of the woods tested were found to 
vary greatly, not only of the specimens from different trees of 
the same species, but also of those cut from different portions 
