ACTION OF CARBONIC ACID ON THE SOIL. -----------------------------------+-----------+--------+------------ | _No. 1, | | | Without |_No. 2, | _No. 3, _Substances soluble in water, etc._| Artificial| Common | Air and | Supply of | Air | Carbonic | Air._ | Added._|acid added._ -----------------------------------+-----------+--------+------------ Mineral matters | 2.04 | 3.71 | 4.99 Potash | 0.07 | 0.17 | 0.14 Soda | 0.17 | 0.23 | 0.28 Organic matters | 2.76 | 4.32 | 2.43 | | | Weight of Crops | 5.89 | 10.49 | 12.35 -----------------------------------+-----------+--------+------------ It will be seen from the above that air alone exercised nearly as much solvent effect as the mixture of air with one-fourth its weight of carbonic acid; this is doubtless, in part due to the fact that the air, upon entering the soil rich in humus, caused the abundant formation of carbonic acid, as will be presently shown must have been the case. It is, however, probable that organic acids (crenic and apocrenic,) and nitric acid were also produced (by oxidation,) and shared with carbonic the work of solution. It is almost certain, that the acids of peat exert a powerful decomposing, and ultimately solvent effect on the minerals of the soil; but on this point we have no precise information, and must therefore be content merely to present the probability. This is sustained by the fact that the crenic, apocrenic and humic acids, though often partly uncombined, are never wholly so, but usually occur united in part to various bases, viz.: lime, magnesia, ammonia, potash, alumina and oxide of iron. The crenic and apocrenic acids (that are formed by the oxidation of ulmic and humic acids,) have such decided acid characters,--crenic acid especially, which has a strongly sour taste--that we cannot well doubt their dissolving action.