expansion and contraction of timber, &c, §71 
three and a half per cent, in drying. Both were, subsequently, 
several times subjected to various degrees of temperature and 
moisture, and each expanded nearly in the same degree that 
it had contracted, the form of the one remaining ver)^ nearly 
permanent, and that of the other constantly changing. 
A beech and an ash tree, each somewhat exceeding twenty 
inches in diameter, were felled in the end of January (at 
which time the buds of both had become sensibly enlarged ) 
and a transverse section of about an inch in thickness, and 
necessarily of a circular form, was immediately cut off from 
the trunk of each, near its base. An incision was then at- 
tempted to be made with a saw from the bark to the medulla, 
directly in the line of the convergent cellular processes, with 
the expectation that these, on each side, would expand, and 
impede the action of the saw. The result was just what I 
had anticipated, and longbefore the saw approached near the 
medulla, it became so strongly compressed that my assistant 
could scarcely move it. A much thinner saw, which I had 
in readiness, was then employed ; and the incision, which was 
kept open by a wedge, was extended to the medulla. The 
wedge w^as then withdrawal, and the opposite sides of the 
division instantly came in contact with great force. A second 
incision, similar to the preceding, was then made to com- 
mence at the bark, about an inch distant from the preceding, 
and to terminate, like that, at the medulla ; by which means, 
a wedge of wood, an inch square at the bark, and ending in 
an edge at the medulla, and ten inches in length, was wholly 
detached. This, nevertheless, did not quit its position, being 
retained in it by the expansion of the wood from which it had 
been separated. 
N n 
MDCCCXVII. 
