Notes on the Properties of Wood. 107 
strength and external protection. There being between 
those wires and the non-strengthened conductor, a 
thickness of 5-16ths of an inch of insulating medium and 
jute yarn, which adds little to its strength, it is evident 
that the material strength of the envelope, thus applied 
concentrically away from the conductor, is insufficiently 
and wrongly applied. 
As a consequence, the new Atlantic cable, although 
nearly four times more bulky and heavy than Allan’s 
cable for the same distance and depth, is upwards of 54 
times weaker, 50 per cent. dearer to construct, considerably 
more difficult to handle and carry, and will probably cost 
three times more to ship, pay out, and submerge. 
It must, therefore, be acknowledged, that the fact of 
uniting the above-named advantages, in a small cable, is 
the achievement of a great desideratum, which constitutes 
Allan’s valuable, and not sufficiently appreciated invention, 
deserving of better encouragement by all interested in 
deep sea telegraphy, which means the civilized world. 
NOTES ON THE PROPERTIES OF WOOD. 
Y wood we understand the substance of trees—viz., 
timber, which is that portion of a tree between the 
rind and the marrow, as also to distinguish the heart from 
the sapwood. The inner structure of trees is the founda- 
tion of all the peculiarities of grain of the wood. It is 
alike in all European and foreign trees. If, with the assist- 
ance of a powerful magnifying glass, we examine a cross 
section, we see on the outer surface of the section, first, the 
back and cambium, next the sapwood, then the heartwood, 
and in the centre the marrow. From the centre radiate, 
the rind thin lines, which being crossed by rings, take the 
appearance of the cob-web of a spider. By these rings we 
are enabled to arrive at the age of a tree, one being added, 
neatly every year. This rule cannot always be followed 
out in its integrity, owing to, in some instances, the August 
sap forming a second ring in the same year, by this reason, 
the age of a large tree becomes very doubtful if it be esti- 
mated by its yearly rings. These rings have a close con- 
nection with the development of the leaves, for when found 
K 2 
