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FOREST FIRES. 
somewhat retarded by the general humidity of the soil and of 
the beds of leaves which cover it. But in long droughts the su- 
perficial layer of leaves and the dry fallen branches become as 
inflammable as tinder, and the fire spreads with fearful rapid- 
ity, until its further progress is arrested by want of material, 
or, more rarely, by heavy rains, sometimes caused, as many 
meteorologists suppose, by the conflagration itself. 
In the artificial forest the annual removal of fallen or half- 
dried trees and the leaves and other droppings of the wood, 
though otherwise a very injurious practice, much diminishes the 
rapid spread of fires; and the absence of combustible under- 
wood and the greater distance between the trees are additional 
safeguards. But, on the other hand, the comparative dryness 
of the soil, and of any leaves or twigs which may remain upon 
it, and the greater facility for the passage of wind-currents 
through a regularly planted and more open wood, are circum- 
stances unfavorable to the security of the trees against this 
formidable danger. The natural forest, unless isolated and of 
small extent, can be protected from fire only by a vigilance too 
costly to be systematically practised. But the artificial wood 
may be secured by a network of ditches and of paths or occa- 
sional open glades, which both check the running of the fire 
and furnish the means of approaching and combating it.* 
The experience of 1871 ought not to be wholly without value 
as a lesson. It is not possible to estimate the damage by forest 
fires in that disastrous year, in what were lately the North-west- 
ern States, and in Canada, but as the demand for lumber, and, 
consequently, its market price, are rising at a rate higher than 
the interest on capital, in a geometrical ratio, one may almost 
forests are often an insuperable obstacle to the success of attempts to preserve 
the woods or to improve their condition. See, on this subject, ALFRED 
Maury, Les anciens Foréts de la Gaule, chap. xxix. 
* It is stated that in the pine woods of the Landes of Gascony a fire has 
never been known to cross a railway-track ora common road. See Des Jn- 
cendies, etc., dans la Region des Maures in the Revue des Hauax et Foréts for 
February, 1869. Many other important articles on this subject will be found 
in other numbers of the same very valuable periodical. 
