168 M. A. de la Rive on Glacier^-. 



the emersioi) of t])e formations which most recently appeared, 

 should unceasingly perpetuate itself, evaporation being in- 

 sufficient to disperse it, inasmuch as it would in its turn 

 produce as much more rain as it, the humidity, was itself 

 considerable ; and since, moreover, the winds could not in 

 this matter change the condition of the atmosphere, seeing 

 that the humidity alike prevailed throughout. It results, 

 then, as a necessary consequence, that ere the conditions in 

 which the vast amount of ice has been produced undergoes 

 any modification, a certain absolute quantity of meteoro- 

 logical water should disappear. Well, then, it is not diffi- 

 cult to discover in a novel phenomenon which developed 

 itself upon the whole of the emerged portion of the surface 

 of the earth, which was unoccupied by ice and snow, a por- 

 tion too, by much the most extensive, a cause of a gradual 

 absorption of the water which impregnated these strata, and 

 thereby saturated the neighbouring strata of the superim- 

 posed atmosphere. This phenomenon is that of the vegeta- 

 tion, which, of necessity would by degrees manifest itself upon 

 the new soil which would be exposed to the light, and which 

 would develope itself with a rapidity which would increase 

 to the epoch of man's appearance, who, in spreading over the 

 surface of the earth, would again contend with this exten- 

 sion, which hitherto had been unchecked throughout the 

 vegetable kingdom. 



According to the experiments and the calculations of M. 

 Chevandier, one hectare (about two acres) of forest annually 

 absorbs of oxygen and hydrogen a quantity equivalent to 

 1800 kilogrammes of water, a result which has been obtained 

 by the chemical analysis of wood which was perfectly dry ; 

 for there can be no question concerning the hygrometric 

 water which plants absorb and emit, nor concerning that 

 which the sap, the leaves, and generally the humid portions 

 of trees absorb. On the other hand, a cubic metre (yard) of 

 air at the temperature of 10 degrees, contains, when it is 

 saturated with moisture, 10 grammes of water ; consequently, 

 one hectare of forest consumes during one year the quantity 

 of water which would saturate, at the temperature of 10", a 

 stratum of atmospheric air of one hectare of surface, and of 



