236 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
A number of interesting cross-sections were shown to illustrate 
the great increase in growth that results from heavily thinning 
a wood of oak or beech a few years before the final felling 
(Lichtungszuwachs). On the section a zone of a certain colour 
(e.g., red) represents the growth made by the tree, during say 
ten years, before being isolated, while outside this the timber 
formed since the wood was thinned may be artificially stained 
green. The annual increment due to the admission of light 
is usually very great, and is often as much as 20 per cent., 
that is to say, a tree of 30 cubic feet may, in three years, have 
attained to about 50 cubic feet. 
A number of cones formed of sections, two inches thick, taken 
every metre (3°3 feet) along an average stem, are shown illustra- 
tive of the yield of different species under different conditions. 
Thus, a beech-wood 131 years old in Spessart has an average 
height of 115 feet, and carries 7835 cubic feet per acre, quarter- 
girth measure. An average oak from a forest in Spessart (over 
200 years old) is shown in section, the height being 119 feet, 
and the volume per acre, quarter-girth measure, 10,325 cubic 
feet. A spruce-wood, 60 years old, in the Bayrischer Wald is 
similarly represented, the average height being 86 feet, and the 
contents per acre 5820 cubic feet, quarter-girth measure. 
The export and import timber-trade for the whole German 
Empire is represented graphically, and shows that whereas in 
1880 the imports amounted to less than two million tons, valued 
at less than four million pounds, in 1904 they exceeded five 
million tons, valued at nearly twelve million pounds sterling. 
During the same period the export in timber fell from 830,000 
tons, valued at a little over two million pounds, to 323,000 tons, 
of a value slightly exceeding one million pounds. ‘Thus it is 
seen that, even with its gigantic forest wealth, Germany’s timber 
imports greatly exceed the exports. 
An interesting section of the Exhibition is concerned with the 
display of products chemically prepared from wood. In 1889 
it was discovered that the cellulose prepared from spruce timber 
could be made to furnish an excellent artificial silk, not so 
elastic and strong as the real article, but superior to it in lustre. 
The annual production is now estimated at over two million 
pounds’ weight, valued at 15s. per pound. It is now largely 
used in upholstery and for making ties and other articles of 
apparel. 
