126 On the Strength, Durability, and Value 
named from the dust or bloom which always covers the sessile 
leaves. 
It is a common opinion that this tree sheds its bark an- 
nually : it is, however, only the outer layer which dries and 
peels off in long strips at certain periods. ‘This casting of 
the outer bark does not take place upon the young plants 
during the persistence of the sessile leaves: when it falls 
from the tree, the next layer is left perfectly smooth, of a 
bright buff colour, which soon changes to a leaden gray, or 
ash of different hues. In some trees the outer bark comes off 
in short dry curled chips, from which the trunk seems never 
free : this does not, however, appear to be the case in those 
of large size. 
The bark upon the full-grown tree is very compact, and of 
a woody fibrous texture, in which the layers are not readily 
distinguished. The piece upon the table is from a tolerably- 
sized tree, and though scarcely an inch in thickness is com- 
posed of 49 layers: the section of the outer one is always 
green, which arises, no doubt, from the action of light. 
The alburnum, or sapwood, is seldom more than an inch in 
thickness; but the sap appears to ascend through a small 
portion of the inner wood also. ‘The concentric layers of the 
inner wood or spine differ considerably ; but from the means 
of a number of measurements an average may be taken of 
about +; of an inch, at which rate a tree six feet in diameter 
in the medium butt would require 4832 years to attain that 
size. Much, however, depends upon the position, and other 
circumstances. Timber from the hills is of much closer 
grain, and therefore of better quality than that grown in the 
ravines or gullies; and in this respect it resembles the oak 
and other timber trees. 
Unlike the Oak, the Gum is stronger when dry than when 
ereen, which must be occasioned by the greater shrinking of 
the latter during the period of seasoning. Much attention is 
