92 Mr. Knight concerning the State in which 
less rapidity of its growth. These sources of error might ap- 
parently have been avoided by cutting off, at different seasons, 
portions of the same trunk or branch: but the wound thus 
made might, in some degree, have impeded the due progress 
of the sap in its ascent, and the part below might have been 
made heavier by the stagnation of the sap, and that above 
lighter by privation of its proper quantity of nutriment. The 
most eligible method therefore, which occurred to me, was to 
select and mark in the winter some of the poles of an oak 
coppice, where all are of equal age, and where many, of the 
same size and growing with equal vigour, spring from the 
same stool. One half of t hepoles which I marked and num- 
bered were cut on the 31st of December, 1803, and the 
remainder on the 15th of the following May, when the leaves 
were nearly half grown. Proper marks were put to distinguish 
the winter-felled from the summer-felled poles, the bark being 
left on all, and all being placed in the same situation to dry. 
In the beginning of August I cut off nearly equal portions 
from a winter and summer-felled pole, which had both grown 
on the same stool ; and both portions were then put in a 
situation, where, during the seven succeeding weeks, they 
were kept very warm by a fire. The summer-felled wood was, 
when put to dry, the most heavy ; but it evidently contained 
much more water than the other, and, partly at least, from 
this cause, it contracted much more in drying. In the begin- 
ning of October both kinds appeared to be perfectly dry, and 
I then ascertained the specific gravity of the winter-felled 
wood to be o .679, and that of the summer-felled wood to be 
0.609 ; after each had been immersed five minutes in water. 
This difference of ten per cent, was considerably more than 
