413 
We must carefully discriminate between material of the type, and material 
illustrating the optimum of the species ; the two may exhibit a good deal of difference. 
The physical properties of timber vary greatly according to environment, timbers 
rapidly growing under " soft " conditions, i.e., those which favour great bulk, may be 
very different to those in which the conditions are harder. Coloured plates bringing 
these differences out admirably as regards Oak and Spruce are to be found in Fisher 
(Schlich's) " Manual of Forestry," v, Plates 1 and 2 (1896). Fisher does not actually 
employ the term " optimum," and the first important work on timbers in which I find 
it is " Traite d'Exploitation Commerciale des Bois" (by Arphonse Mathey, Paris, 1906), 
p. 43, certain passages of which are offered in translation : 
2. Influence of the place of origin and position (station). 
Law. Things being equal in regard to the soil, there is one region and one alone (italics as in original) 
which realises the optima conditions giving to the wood of each forestry species its maximum of specific 
weight, hardness, elasticity, cohesion, &c., that is to say, its maximum of utility. This region is the natural 
habitat of the species taken into consideration. When this natural habitat forms a belt or zone of country 
it is in the middle of this zone that the wood is best ; it is in the centre if the area forms a circumference. 
At this time when exotism is the rage in the forestry world it is good to enlighten the public as to the 
value of the products which are delivered to it products which commerce, rightly distrustful, buys 
cheap, but sells again as dear as possible to ignorant customers. It is the consumer who pays finally the 
expenses of the venture. 
Let us now see, from the point of view of the value of the wood, how certain species behave in their 
natural and artificial habitat. And, for that, let us consult the diagram of Dr. Gayer below : 
Artificial position IIF colder than the natiiral position. 
Natural position IF colder than the optimum. 
I optimum. 
II C warmer than the optimum. 
Artificial position III warmer than the natural position. 
If the law enunciated above is true for each species, the weight of the wood ought to decrease 
from I to II, then from II to III. At the same time the breadth of the rings ought to become larger or 
smaller. Or, let us put it this way : 
Decreases in weight 
, /(a) From I (optimum) to IF (colder than optimum). 
\(&) From I (optimum) to II C (warmer than optimum). 
2 ((a) From IP" (colder than optimum) to III 1 ' (colder than natural). 
\(b) From IF (warmer than optimum) to IIF (warmer than natural). 
Facts. (1 ) In Germany the area of the oak extends over IF, except in the plains of the Rhine, 
where the climate is near to the optimum. By cultivation this species has been introduced as far as IIF. 
In a general way the breadth of the rings increases with the heat, and the increases diminish regularly 
from IIF to IIF. Let us see how the specific weight varies. In the Spessart (a large forest in Germany, 
between Wurzburg and Aschaffenburg Rees Encyclop.) (IF) the wood of the adult oak, dried in the open 
air, has a specific weight of 50. In the plains of the Rhine the specific weight attains 74. 
(2) The Larch was introduced more than a century ago into IF in Germany and into 
IIF in Denmark. In these two artificial positions the growth is extraordinarily rapid, but the wood is 
lighter. Its specific weight there is only 45, while it attains 80 in its natural position. 
(3) The Spruce Fir [Epicea (Abies or Picea ezcelsa)] in i ts natural position (I and IF) has 
a specific weight of 45; introduced into IIF, its weight becomes lower, drops to 38 and 41. In the Alpine 
forests (of boundary) (IF), the specific weight varies between 40 and 42 ; that is to say, it is always inferior 
to the figure found for the natural position. In France the Spruce Fir cultivated in III c is still lighter 
and softer, its wood cracking like glass ; it is only suitable for the making of papier-mache. 
