ORIGIN AND POUMATION OP SOILS. 139 



(p. 128). Boussingault and Lewy {Memoires de CJiimie 

 Agrk'ole, etc.^p. 369,) liave analyzed the air contained in 

 the pores of the soil, and, as was to be anticipated, found 

 it vastly riclier in carbonic acid than the ordinary atmos- 

 phere. 



The following table exhibits the composition of the air 

 in the soil compared with that of the air above the soil, 

 as observed in their investigations. 



Carbonic acid in 10,000 

 parts of air (by weight). 



Ordinary atinospbeie 6 



Air from sandy subsoil of forest 38 



" " loamy " " " 134 



" " surface-soil " " 130 



" " " " vineyard 146 



" " " " old asparagus bed 123 



" " " " " " newly manured. 333 



" " " " pasture 370 



*' " *' rich in humus 543 



" •' " newly manured sandy field, 



durinir dry weather 333 



" " " newly manured sandy field, 



during wet weather 1413 



That this carbonic acid originates in large part by oxi- 

 dation of organic matters is strikingly demonstrated by 

 the increase in its quantity, resulting from the application 

 of manure, and the supervention of warm, wet weather. 

 It is obvious that the carbonic acid contained in the air 

 of the soil, being from twenty to one hundred or more 

 times more abundant, relatively, than in the common at- 

 mosphere, must act in a correspondingly more rapid and 

 energetic manner in accomplishing the solution and disin- 

 tegration of mineral matters. 



c. The organic acids of the humus group probably aid 

 in the disintegration of soil by direct action, though our 

 knowledge is too imperfect to warrant a positive conclu- 

 sion. The ulmic and humic acids themselves, indeed, do 

 not, according to Mulder, exist in the free state in the 

 soil, but their soluble salts of ammonia, potash or soda, 

 have acid characters, in so far that they unite energetical- 



