STRUCTURE OF WOOD, &C. 32$ 



Ligneous parts 0*26489 cubic inch. Sap, &e. in 



Sap 036546 wood ' 



Air V.V . . 0'36965 



1 -ooooo 



From the results of these two experiments, we may con- 

 clude, that the body of a tree contains more sap in the winter 

 than in summer, and more air in summer than in winter. 

 But the following experiments demonstrate the snp to be very 

 disproportionately distributed in the several parts of the same 

 tree, at the same season. 



On the 8th of September, I had a branch, about three inches 

 in diameter, cut from the lime just spoken of, and which issued 

 from the trunk at the height of ten feet above the surface of 

 the earth. From the lower end of this branch, I took a piece 

 of wood, and subjected it to the investigation requisite to ascer- 

 tain its constituent parts. 



Its specific gravity was 70201. The same day, T found the 

 specific gravity of a piece of the trunk of the same tree, to be 

 75820. 



Surprising as this difference appeared, my astonishment was 

 still more excited, on finding that a piece of wood, of three 

 years growth, cut from the upper end of the same branch, 

 where it was but one inch in diameter, had a specific gravity 

 of 85240. 



There was, therefore, much more sap, and less air, in the 

 wood of the upper extremity of the branch, than in the lower, 

 which was nearer to the body of the tree. 



I afterwards examined the young shoots of the current year, 

 in the same tree, as well as in several other species of wood, 

 and uniformly found that the specific gravity of the young 

 wood, that is to say, of the current year, is always considerably 

 greater than that of the same species of wood when grown 

 older. Doubtlessly, because it contains more sap, and less air, 

 than the old wood. 



In the management of experiments for determining the spe- 

 cific gravity of wood of the current year, it is indispensably 

 necessary to take an account of the space occupied by the pith, 

 without which precaution, we shall be led to false conclusions. 



Supplement.— Vol. XXXIV.— No. 160. Z I found 



