DEMAND FOR WOOD. 
295 
remaining trees fit for such uses.* The walnut trees alone 
felled in Europe within two years to furnish the armies of 
* Besides the substitution of iron for wood, a great saving of consump¬ 
tion of this latter material has been effected by the revival of ancient 
methods of increasing its durability, and the invention of new processes 
for the same purpose. The most effectual preservative yet discovered for 
wood employed on land, is sulphate of copper, a solution of which is 
introduced into the pores of the wood while green, by soaking, by forcing- 
pumps, or, most economically, by the simple pressure of a column of the 
fluid in a small pipe connected with the end of the piece of timber sub¬ 
jected to the treatment. Clave (Etudes Forestieres , pp. 240-249) gives an 
interesting account of the various processes employed for rendering wood 
imperishable, and states that railroad ties injected with sulphate of copper 
in 1846, were found absolutely unaltered in 1855 ; and telegraphic posts 
prepared two years earlier, are now in a state of perfect preservation. 
For many purposes, the method of injection is too expensive, and some 
simpler process is much to be desired. The question of the proper time 
of felling timber is not settled, and the best modes of air, water, and steam 
seasoning are not yet fully ascertained. Experiments on these subjects 
would be well worth the patronage of governments in new countries, 
where they can be very easily made, without the necessity of much waste 
of valuable material, and without expensive arrangements for observation. 
The practice of stripping living trees of their bark some years before 
they are felled, is as old as the time of Vitruvius, but is much less followed 
than it deserves, partly because the timber of trees so treated inclines to 
crack and split, and partly because it becomes so hard as to be wrought 
with considerable difficulty. 
In America, economy in the consumption of fuel has been much pro¬ 
moted by the substitution of coal for wood, the general use of stoves both 
for wood and coal, and recently by the employment of anthracite in the 
furnaces of stationary and locomotive steam-engines. All the objections 
to the use of anthracite for this latter purpose appear to have been over¬ 
come, and the improvements in its combustion have been attended with 
a great pecuniary saving, and with much advantage to the preservation of 
the woods. 
The employment of coal has produced a great reduction in the con¬ 
sumption of fire wood in Paris. In 1815, the supply of fire wood for the 
city required 1,200,000 steres, or cubic metres; in 1859, it had fallen to 
501,805, while, in the mean time, the consumption of coal had risen from 
600,000 to 432,000,000 metrical quintals. See Clave, Etudes , p. 212. 
I think there must be some error in this last sum, as 432 millions 
of metrical quintals would amount to 43 millions of tons, a quantity which 
