ORIGIN AND FORMATION OF SOILS. 139 
(p. 128). Boussingault and Lewy (Mémoires de Chimie 
Agricole, etc., p. 369,) have analyzed the air contained in 
the pores of the soil, and, as was to be anticipated, found 
it vastly richer 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), 
6 
Ordinary atmosphere............ cece cece ceee eee 
Air from sandy subsoil of forest..............c0006 38 
EES Noam SE iad saan awe aera 14 
& ‘surface-soil “cess iesscaveoe eaves 130 
es ee * vineyard............0e eee 146 
She oe ss “ old asparagus bed....... 122 
it] cr be “ce a“ [Ts newly manured. 233 
eis AEE as © pastOre sc seas ceive vee se 270 
SS OEE as rich in humus...........665 543 
a as newly manured sandy field, 
during dry weather....... 333 
Berets “ 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- 
