Notes on the Properties of Wood. 109 
porous as the rootwood. This is frequently the case with 
the branches of the trees. Therefore, if we have to select 
between two oaks, we shall choose the one with the broader 
yearly rings, because, in a cubic foot of the same, we shall 
have a larger quantity of wood than in the other. Should 
it happen that a whole forest produces trees with wide 
yearly rings, and another, trees with smaller rings, then 
arises the question whether the former is caused by the 
damp condition of the soil, in which case the wood in the 
first will be more porous and loose than in the latter. It is 
necessary therefore, that we take into consideration the 
specific weight as well as the broadness of the rings, and 
if found to correspond, then we may conclude that the 
timber is sound. Wood which has rings of more than six 
mil. wide for a section of some inches should not be used: 
in building. Trees which have grown in clammy or marsh 
soil furnish bad timber. 
More regularity in the width of the rings from the centre 
towards the bark is found in the Pine. The process 
depends much upon the position of the tree and the sur- 
rounding influences. In the Leafwoods, a greater variety 
in the rings is to be found ; but these, as well as the Pines, 
have that same feature in common, that the rings increase 
towards the bark, and that close to the latter they decrease 
again. The number of branches influence the width of 
the rings in their position. It is hardly necessary to remark 
that the assertion that the rings are wider on the south 
side of a tree than those on the north side is devoid of 
truth. 
The bark is of very great importance toatree. It acts 
as a protective band for the distribution of the sap, and Is, 
therefore, necessary for the formation of the yearly rings, 
If it gets damaged or split at a certain place, it will be 
observed that the next following ring increases considerably 
at this wound. There is no rule without an exception, and 
we have it exemplified in the case of the almond-tree, 
(Amygdalus), which bends hollow in the place where the 
bark has been damaged. 
In some trees destruction commences with the ripening 
of the wood, as with the Canadian Poplar (Populus), and 
the Willows (Salix), which begin to darken in the centre, 
and by their smell indicate their decay. The sapwood of 
hardwood trees is not of much use, never lasting for any 
period, and when used, only serving to introduce destruc- 
tive organs into the better wood, 
