Mr. Knight on the different qualities , &c. 157 
of my workmen permitted me to have done without danger to 
them, and it was then suffered to remain standing. The other 
tree was felled, and, in the usual manner, immediately stript 
of its bark ; and the trunk was then removed to a situation 
in which it was securely protected from the sun and rain. 
The following winter, in December, the other tree (which 
still retained life) was felled, and its trunk immediately placed 
in the same situation with that of the other tree ; pieces of 
each, selected from similar parts, have been subjected to the 
following experiments at different subsequent periods. 
Small blocks, of similar form and size, were taken from 
the alburnum of each tree ; and after these had ceased to lose 
weight, in a very warm and dry situation, the specific gravity 
of each was ascertained ; when that of the alburnum of the 
spring-felled tree was found to be o , 666 , and that of the same 
substance of the winter-felled tree to be 0,565, taking the 
average of several pieces of each. I had anticipated a loss 
of weight to about this amount in the alburnum of the winter- 
felled tree, having inferred, from former experiments, that 
it must have given out a large quantity of matter in the spring 
and early part of the summer, to form the leaves and young 
shoots, which quantity could not have been restored to it 
during the summer, on account of the descending current of 
sap through the bark having been wholly intercepted. 
Small blocks of equal weight of the alburnum of each 
tree were divided by cleaving into thin pieces ; and these, 
after having become perfectly dry, were suspended together 
during ten days, in a somewhat damp room ; when 1000 
grains of the alburnum of the spring-felled tree were found 
to have gained 162 grains, and an equal weight of that of the 
mdcccxx. Y 
