Page:Philosophical Transactions - Volume 095.djvu/108

94 94 Mr. Knight concerning the State in which

water in which it had heen infused, and had raised its specific gravity to i.ooa. The specific gravity of the water in which the summer-felled wood had, in the same manner, been infused was i.ooi. 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 »ich indsion had been deprived of a larger portion of its concrete or inspissated sap than in other parts of the same tree : and 1 therefore sus- pected that I should find similar effects to have been producecjL by the young annual shoot? and leaves ; and that any gi ve^ weight of the alburnum in their vicinity would be found to coar 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, L poured on each portion an eqyal quantity of boiling water, which. I suffered to remain twenty hours, as in the preceding experir ments : and I then found that in some instances the wood from the lQ>yer, and in others that from the upper parts of the poles^