CHEMICAL INFLUENCE OF THE FOREST. 1S) 
of hail-storms in the neighborhood of Saluzzo and Mondovi, 
the lower part of the Valtelline, and the territory of Verona 
and Vicenza, is probably to be ascribed to a similar cause.* 
Chemical Influence of the Forest. 
We know that the air in a close apartment is appreciably 
affected through the inspiration and expiration of gases by 
plants growing in it. The same operations are performed on 
a gigantic scale by the forest, and it has even been supposed 
that the absorption of carbon, by the rank vegetation of earlier 
geological periods, occasioned a permanent change in the con- 
stitution of the terrestrial atmosphere.t To the effects thus 
produced are to be added those of the ultimate gaseous decom- 
position of the vast vegetable mass annually shed by trees, and 
of their trunks and branches when they fall a prey to time. 
But the quantity of gases thus abstracted from and restored 
to the atmosphere is inconsiderable—infinitesimal, one might 
* Le Alpi che cingono (Italia, i., p. 877. See ‘‘On the Influence of the 
Forest in Preventing Hail-storms,” a paper by Becquerel, in the J/émuoitres de 
v Académie des Sciences, vol. xxxv. The conclusion of this eminent physicist 
is, that woods do exercise, both within their own limits and in their vicinity, 
the influence popularly ascribed to them in this respect, and that the effect is 
probably produced partly by mechanical and partly by electrical action. 
+ ‘‘ Long before the appearance of man, . . . . they [the forests] had 
robbed the atmosphere of the enormous quantity of carbonic acid it contained, 
and thereby transformed it into respirable air. Trees heaped upon trees had 
already filled up the ponds and marshes, and buried with them in the bowels 
of the earth—to restore it to us, after thousands of ages, in the form of bi- 
tuminous coal and of anthracite—the carbon which was destined to become, 
by this wonderful condensation, a precious store of future wealth.”—CLAvs, 
Etudes sur V Economie Forestizre, p. 13. 
This opinion of the modification of the atmosphere by vegetation is con- 
tested. 
Mossman ascribes the great luxuriance and special character of the Austra- 
lian and New Zealand forests, as well as other peculiarities of the vegetation 
of the Southern hemisphere, to a supposed larger proportion of carbon in the 
atmosphere of that hemisphere, though the fact of such excess does not 
appear to have been established by chemical analysis.—MossMAn, Origin of 
the Seasons, Edinburgh, 1869. Chaps. xvi. and xvii, 
