CHAPTER XI. 
ON THE FELLING OF OAK IN SPRING AND WINTER. 
THE bark of the Oak tree contains a substance called 
tannin, which is of considerable value, and is used in the 
preparation of leather. Therefore, in order to secure 
this tannin in its greatest quantity, it is the practice to 
fell, or cut down, the trees in the spring of the year, 
when the sap is rising. Under other circumstances, the 
trees would have been cut in the winter, while the sap 
was down and ina quiescent state—a period which has 
been almost universally recognised as the best for felling, 
as it is considered to ensure a better quality, and to be 
conducive to the greater durability of the timber. The 
value of the bark, however, generally overrides this 
consideration, since, although the weight in proportion 
to the contents of the timber will vary according to 
circumstances of growth, it is always thought profitable 
to save it, and, viewed under the commercial aspect, 
it is not likely to be disregarded. 
The quantity of tannin contained in the bark of the 
Oak, as ascertained by Sir Humphry Davy, varies as 
follows, viz.: In Coppice Oak it is 32; middle sized, 29 
and Oak cut in the autumn, 21 per cent. 
The timber and bark merchants variously estimate 
the quantity of bark to the contents of the timber; and 
no doubt there is a very considerable difference in the 
