CHEMICAL INFLUENCE OF THE FOREST. 153 



storms in the neighborhood of Saluzzo and Mondovi, the lower 

 pai-t of the Valtelline, and the territory of Verona and Yicenza, 

 is probably to be ascribed to a similar cause.* 



CJierrdcal InjUience of the Forest, 



We know that the air in a close apartment is appreciably af- 

 fected 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 ab- 

 sorption of carbon, by the rank vegetation of earher geological 

 periods, occasioned a permanent change in the constitution of the 

 terrestrial atmosphere, f To the effects thus produced, are to be 

 added those of the ultimate gaseous decomposition 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 in- 

 considerable — ^infinitesimal, one might almost say — in comparison 

 with the ocean of air from which they are drawn and to which 

 they return ; and though the exhalations from bogs, and other 



* Le Alpi che dngono V Italia, \., p. 377. See " On the Influence of the For- 

 est in Preventing Hail-storms," a paper by Becquerel, in the Memoires de VAcad- 

 emie 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 in- 

 fluence popularly ascribed to them in this respect, and that the effect is prob- 

 ably produced partly by mechanical and partly by electrical action. 



f "Long before the appearance of man, .... they [the forests] had rob- 

 bed 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 bitu- 

 minous coal and of anthracite — the carbon which was destined to become, by 

 this wonderful condensation, a precious store of future wealth." — Clave, 

 Etudes 8ur I'Economie Foresti^re, 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 Australian 

 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 atmos- 

 phere 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. 

 7* 



