178 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
2. The total increment in value is always enhanced by well- 
conducted, careful tending, even when the yield from 
thinnings is not reckoned at compound interest up to the 
time of final clearance. 
3. The final yield of the mature woods is, of course, usually 
smaller in woods that have been freely thinned, but the 
difference in money-value is not so great as the difference 
in volume might indicate, because the value per cubic 
foot is higher on the average ; hence the smaller quantity 
may easily represent the large value, as was especially 
shown (in the investigations) to be the case with spruce 
and oak. 
4. The most favourable effect on the increment in value 
obtainable in young and middle-aged woods is not to be 
achieved by the old system of thinning out only sup- 
pressed and moribund stems, but by slightly interrupting 
the canopy (Hochdurchforstung, a method now borrowed 
from France, where it has long been in practice, and is 
known as éclaircie par le haut), somewhat in the manner 
of a very slight partial clearance to stimulate increment. 
Schwappach’s observations about the thinning of young spruce- 
woods are not, however, allowed to go unchallenged, for Pro- 
fessor Martin (also of the Neustadt-Eberswalde Academy), in the 
course of a very sensible criticism, points out that ‘here can be 
no general rule as regards planting-distance at first and distance 
from stem to stem later on, but that local circumstances must 
always be an important factor in determining what may be the 
most advantageous method of thinning. And that is, of course, 
merely stating a common-sense opinion, for a landowner wanting 
to grow pit-wood will adopt quite a different method from the 
proprietor desirous of providing material for a saw-mill engaged 
principally in turning out boards and planks, etc. 
Following on the five violent gales which in 1904 threw down 
large quantities of timber in the Prussian forests (over 1,250,000 
cubic feet being thrown on the Harz on 17th June 1904), a wide- 
spread storm on the night of 6th January 1905, coming from 
N.W. and N.E. (in different localities), threw over 3,200,000 
cubic feet in the State Forests alone. 
With regard to the fixation of atmospheric nitrogen by the 
humus-layer in woodlands (see Zyansactions for 1904, p. 168), 
