Leaving out of consideration infiltrated substances, the reason a cubic foot of one kind of dry wood is heavier than that of another is because it contains a greater amount of wood substance.

~Density~ is merely the weight of a unit of volume, as 35 pounds per cubic foot, or 0.56 grams per cubic centimetre.
~Specific gravity~ or relative density is the ratio of the density of any material to the density of distilled water at 4 deg.
C.( 39.2 deg.

F.).

A cubic foot of distilled water at 4 deg.

C.weighs 62.43 pounds.