126 OUR FORESTS AND WOODLANDS 
timber is in general more likely to be profitable. 
In oak coppice the crop should be as full as 
possible, and it should be kept free from admix- 
ture of other growth, whether hardwoods or soft- 
woods, except in those places that show themselves 
unsuitable for the oak. The rotation in which 
the coppice can be worked, and consequently the 
number of compartments and the area to be cut 
over, vary greatly according to the soil, the situa- 
tion, and the local climate. The best rotation is 
that which will enable each fall to be made just 
at the age when the smooth bark, the ‘ pipe-bark’ 
of the oak-stubbs, begins to become rough and 
fissured, because, after that, it contains less tannin 
than before. In favourable situations, with good 
soil and a warm southern exposure, the usual 
rotation is about fifteen or sixteen years, though 
varying of course from about twelve to eighteen 
years according to special circumstances; but a 
longer rotation is necessary for less productive 
soils and a cooler climate. 
For coppice woods the Durmast or sessile oak 
yields on the whole better returns in bark, and 
straighter and more vigorous shoots than the 
English or pedunculate oak. 
