34 Mr. Knight concerning the State in which 
water in which it had been infused, and had raised its specific, 
gravity to 1.002. The specific gravity of the water in which 
the summer-felled wood had, in the same manner, been infused 
was 1.001. The wood in all the preceding cases was taken 
from the upper parts of the poles, about eight feet from the 
ground. 
Having observed, in the preceding experiments, that the sap 
of the sycamore became specifically lighter when it had con- 
tinued to flow’ during several days from the same incision, I 
concluded that the alburnum in the vicinity of such incision had 
been deprived of a larger portion of its concrete or inspissated 
sap than in other parts of the same tree : and I therefore sus- 
pected that I should find similar effects to have been produced 
by the young annual shoots and leaves ; and that any given 
weight of the alburnum in their vicinity would be found to con- 
tain less extractive matter than an equal portion taken from 
the lower parts of the same pole, where no annual shoots or 
leaves had been produced. 
No information could in this case be derived from the dif- 
ference in the specific gravity of the wood ; because the sub- 
stance of every tree is most dense and solid in the lower parts 
of its trunk : and I could on this account judge only from the 
quantity of extractive matter which equal portions of the two 
kinds of wood would afford. Having therefore reduced to 
pieces several equal portions of wood taken from different 
parts of the same poles, which had been felled in May, I poured 
on each portion an equal quantity of boiling water, which I 
suffered to remain twenty hours, as in the preceding experi- 
ments : and I then found that in some instances the wood from 
the lower, and in others that from the upper parts of the poles., 
