460 
lowing up the pyrolignite with an infusion of 
nutgalls or oak-bark, the mass of the wood is 
penetrated with ink, which presents a black, 
blue, or grey colour, according to circumstances; 
a solution of another salt of iron succeeded by 
one of prussiate of potash will cause a precipitate 
of prussian blue in the wood, &c.; in short, by 
the numerous reactions of this kind with which 
chemistry is familiar, a great variety of colours 
_ may be obtained.—Among the number of useful 
properties communicated to wood by impregna- 
tion with saline solutions, that of being rendered 
little apt to combustion ought not to be omitted. 
M. Gay-Lussac was the first who thought of ren- 
dering vegetable tissues incombustible by means 
of saline impregnations. By incombustible, we 
are not to understand unalterable by a red heat; 
for every one must see that the protecting power 
of no salt can extend so far as this; but tissues 
which take fire very readily, and burn with great 
rapidity, cease from giving any flame and merely 
smoulder after they have been impregnated with 
certain salts; they take fire with difficulty, go 
out of themselves, become charred, and are inca- 
pable of propagating fire. And this is exactly 
what happens with wood which has been pro- 
perly charged: it burns, and is reduced to ashes 
with extreme slowness, so that two huts exactly 
alike, built one of charged wood, and the other 
of ordinary wood, having been set fire to at the 
same moment, the latter was already burned to 
the ground, when the interior of the former. was 
scarcely charred. 
“The ingenious process of impregnating wood 
by the way of vital inspiration is not without 
certain objections. In the first place, it can 
only be performed at those periods of the year 
when the sap is in motion, and the trees are 
covered with their leaves. This time, however, 
is limited to a few months of the year, and the 
usual practice being to fell timber in the winter, 
wont and usage are opposed to cutting down 
trees in the spring and autumn. To meet these 
objections, M. Boucherie engaged in new experi- 
ments, which led him to a means of impregnat- 
ing timber at all seasons, in winter as well as 
spring and autumn, and in a very short space of 
time; this second method is applicable to wood 
that has already been squared as well as to the 
round trunk, provided it has been recently felled. 
To impregnate timber by this process, the logs 
are placed vertically, and the upper extremities 
are fitted with an impermeable sack for the re- 
ception of the saline solution destined to charge 
them; the fluid enters from above, and almost 
at the same moment the sap is seen to begin 
running out below. ‘There are some woods 
which include a large quantity of air in their 
tissues; in this case the flow does not go on 
until this air has been expelled; once begun, it 
goes on without interruption. The operation is 
terminated when the fluid, which drips from the 
lower part, is of the same nature as that which 
TIMBER. 
is entering above. In my opinion this method 
must be preferable to that by aspiration. In the 
second mode of proceeding, in fact, we accom- 
plish our object by a true displacement; almost 
the whole of the sap is expelled, and the saline 
solution introduced has only to subdue or neu- 
tralize the very small quantity of soluble organic 
matter which may remain adhering to the woody 
tissue. By accomplishing such a displacement 
by means of simple water we should undoubtedly 
obtain results favourable to the preservation of 
timber, inasmuch as we should have freed it 
from almost the whole of those matters which 
are regarded as the most alterable themselves, 
and the first cause of rotting in timber. The 
rapidity with which the fluid introduced is sub- 
stituted for the sap which it displaces, and the 
quantity of this expelled sap which may be read- 
ily collected, exceeds any thing that could have 
been imagined before making the experiment ; 
thus the trunk of a beech tree about 524 feet in 
length by 333 inches in diameter, and consequently 
forming a cube of somewhat more than 294 feet, 
gave in the course of 25 hours upwards of 330 
gallons of sap, which were replaced by about 350 
gallons of pyroligneous acid. The liquid which 
penetrates in this way acts so effectually in dis- 
placing the sap, that M. Boucherie says we can 
readily procure or extract by its means the sac- 
charine, mucilaginous, resinous, and coloured 
juices contained in trees. It would, perhaps, be 
possible, and I beg to suggest this idea to colo- 
nial planters, to apply the method of displace- 
ment to the extraction of the colouring matters 
of dye-woods. The trade in dye-woods does not 
extend beyond localities favourably situated for 
exportation, so that at a certain distance from 
the shores of the ocean, or the banks of rivers, it 
is found absolutely impossible to carry on a trade, 
the material of which is so heavy and bulky as 
timber. The greater number of the colouring 
matters found in wood being soluble, it is pos- 
sible to export them in the state of extract. 
Various attempts of this kind have already been 
made; and if they have not been successful, the 
obvious cause of this lies in the method which 
has been followed, and which has hitherto con- 
sisted in treating the wood reduced to chips by 
means of boiling water, and then reducing the 
coloured solution obtained; but it is obvious 
that in the remote forests of America, or of Africa, 
where all mechanical means are wanting, nothing 
but failure could attend upon such a procedure, 
By the method of M. Boucherie, the main diff- 
culties appear to be got over; there is nothing 
more to be done, in fact, than to get the trees 
into the state of logs, and these are generally 
readily transportable, after which one or more 
evaporating pans seem all that are further ne- 
cessary.” 
The common method of determining the cubic 
contents of a rough piece of timber, whether 
stem or branch, is to take the mean of its girth 
menietss 
