PINETUM BRITANNICUM. 
|A> 
12 
it shrinks in bulk one-seventieth part in drying. But the weight of all wood varies according to the 
age of the tree from which it is taken, and also according to the rapidity of its growth and the 
nature of the locality in which it has been grown. Consequently, no absolute dependence can be placed 
upon the results obtained from such experiments. But perhaps the data which deserve most attention 
are those given in Brown’s “Forester,” pp. 630, 635, in tables composed by Mr Rait, the forester at 
Castle Forbes, Aberdeenshire, embodying the results of many years’ labour and study in experiments on 
the subjedt. These tables include Farch, Scots Fir, and Spruce, also Oak, Ash, Elm, and various other 
deciduous trees; but confining ourselves to the Spruce, we find that the weight per cubic foot of a tree 
35 years old is nearly the same as that of one 50 years old, but considerably more than that of one 90 
years old—the exafif figures of the rough or unmanufactured tree being the following; viz., first, according 
to the mode of measurement in common use (one-fourth of the girth squared and multiplied by the length); 
and second, by the more accurate mode of measurement, which would be nearly correct were the tree 
exactly cylindrical (one-fifth of the girth squared and multiplied by twice the length) :— 
Rough or Unmanufactured. 
Manufactured. 
Age. 
By First Measurement. 
By Second Measurement. 
Inch Boards. 
Scantlings. 
Heart Wood. 
Sap Wood. 
Bark on. 
Bark off. 
Bark on. 
Bark off. 
Green. 
Dry. 
Green. 
Diy. 
Green. 
Dry. 
Green. 
Dry. 
Y ears. 
35 
lb. 
7 \\ 
lb. 
lb. 
58f 
lb. 
55i 
lb. 
lb. 
lb. 
52| 
lb. 
m 
lb. 
32 
lb. 
26 f 
lb. 
6l 
ib. 
28 
50 
74 i 
5 H 
55 
5^ 
261 
47-54 
271-28* 
3 if-37H 
24^-2 8 f 
62*-63 
26-27 
90 
64 
57 
50 
444 
43f 
31* 
391- 
331 
32| 
28| 
6 2* 
341 
From this table it will be seen that in the rough state there is a decrease of weight with age: the 
weight of the manufactured timber giving similar results while the wood is green, but the reverse 
when it is dry. The little dependence which can be placed upon this data, however, cannot be more 
forcibly illustrated than by the weights of the heart wood and sap wood taken separately, the sap 
wood being, as might be expedted, heavier than the heart wood, and lighter when dry than when 
green; while the relative proportions of weight of young and old recorded in the first nine columns 
have wholly disappeared, or even been reversed, these shewing a decrease of weight with age ; the last 
four shewing an increase. 
The bark answers for tanning, but is inferior for this purpose to that of the Farch, but equal to 
that of the Silver Fir, and superior to that of the Scots Fir. If the tree is wanted for its bark it should 
be felled in May, as the bark then separates most readily from the wood. If for its timber, it should be 
cut in winter. 
Burgundy pitch is made from the sap of this tree, and is the gum or resin melted and clarified. In 
the forests where its collection is made a matter of trade, the plan is, early in spring (before the sap begins 
to ascend), to cut out, at about i\ feet from the ground, on the smooth side of the tree, a long narrow slip 
of bark about 3 feet long, by 1 or i\ inches wide, going down to the sap wood, but not penetrating it. 
In about eighteen months (for it accumulates very slowly) the slit so made will be found full of the gum, 
which is scraped out, and the sides of the groove are in the following spring again pared or made raw, so 
that a fresh bleeding may take place. This may be repeated five or six times, by which time the tree will 
probably die. Some authors say that the timber of trees which have been so treated is still as good as 
ever for fuel, and may even be used for construction ; but Duhamel, Hartig, and most others, say that it 
utterly destroys the tree, and if repeated sufficiently often, will end in so exhausting it as to make the wood 
not even fit for fuel. This seems the more reasonable view. 
Excellent cordage is made of the fibres of the roots both of this and the Scots Fir in Norway and 
Sweden ; and, judging from the specimens exhibited at the Great Fondon Exhibition of 1862, these ropes 
are not inferior in tenacity and strength to the best ropes made of hemp or other materials. The mode in 
which 
