Part IV.] 
PRUNING AND THINNING. 
229 
the current of sap. These protuberances will, 
indeed, in the course of time almost entirely 
disappear, because, if equals are annually added 
to unequals, in the course of time apparent, 
though not absolute equality, will result; and 
this does take place in the annual deposit of new 
layers of wood and bark over the stem and these 
protuberances. But each of these protuberances 
creates a piece of dead, disunited wood, which 
is in general nearly, if not perfectly rotten. 
This system of pruning, as far as it goes, makes 
flaws in timber, and disunited knots, similar to 
the leaving dead branches on trees. These flaws 
are discovered only in the saw-pit, or by the 
searching augur, and the blame is laid on prun¬ 
ing generally; whereas pruning living branches 
close to the stem prevents the very evils which 
it is accused of creating. If a dead branch and 
the stem are cut longitudinally where they join, 
though the whole branch may have dried in in 
the form of a cone as far as the central pith of 
the tree, still there is a perfect unison of the 
dead wood of the branch with the living wood 
of the stem, and the junction of each new annual 
growth of the stem and the branch will be per¬ 
fectly visible as long as the branch lived. But 
from where the branch died each annual growth 
Q 3 
