6 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
soil, where, unless special means are taken to prevent the 
absorption of water, the timber rapidly becomes very wet. 
The American experimenters suggested a standard of dryness 
of 12 per cent. for comparing different sets of observations, and 
they found in their experiments that timber in such a condition 
of dryness was on an average about 75 per cent. stronger than 
timber which was quite “green,” that is, filled with the natural 
sap. 
485 
40,000 
8.000 
Fil Ge) 
6000 
FULL LINE, TIMBER UNDERGOING DRYING 
CONPRESSION STRENGTH PER SQ. (NCH 
7 
DOTTED LINE, TINBER RE -ABSORBING (MO/STUPRE 
MOISTURE IN WOOD, PER CENT 
O° to 20 30 40 50% 
Before leaving this question of the influence of sap or moisture 
on the strength of wood, I may mention that the American 
research dealt also with the effect of “bleeding,” as it is called, 
or tapping the long-leaf (pitch) pine (Pinus palustris, Mill.) for 
its turpentine. It was commonly held that this process con- 
siderably weakened the timber, and also affected its durability. 
The investigation conducted by the Forest Department of 
the United States, with a very large number of tests, showed, 
fairly conclusively, that there was no marked effect produced 
by previous “bleeding” of the tree on the mechanical properties 
