ancient rocks containing potash, soda,
magnesia, etc., occurring in most soils, and that at the same time it
liberates silica from these rocks; and lastly, that lime is one of the
substances found uniformly and in considerable quantity in the ashes of
plants, that therefore its application may be beneficial simply as
furnishing a material indispensable to the substance of a plant.

These explanations are no doubt good as far as they go, but experience
furnishes many facts which cannot be explained by any one, or all, of
these suppositions. Lime, we all know, does much good on soils abounding
in organic matter, and so it frequently does on soils almost destitute
of it. It may liberate potash, soda, silica, etc., from clay soils, but
the application of potash, soda, and silica has little beneficial effect
on the soil, and therefore we cannot account for the action of lime on
the supposition that it renders the potash, soda, etc., of the soil
available to plants. Furthermore, lime effects great good on soils
abounding in salts of lime, and therefore it cannot be that it operates
as a source of lime for the structure of the plant.

None of the existing theories, therefore, satisfactorily account for the
action of lime. Prof. Way's views are most consistent with the facts of
practical experience; but they are confessedly hypothetical; and his
more recent investigations do not confirm the idea that lime acts
beneficially by converting the soda silicate into the lime silicate.

Thus, six soils were treated with lime water until they had absorbed
from one and a half to two per cent of their weight of lime. This,
supposing the soil to be six inches deep, would be at the rate of about
300 bushels of lime per acre. The amount of ammonia in the soil was
determined before liming, after liming, and then after being exposed to
the fumes of carbonate ammonia until it had absorbed as much as it
would. The following table exhibits the results:

----------------------------+------+------+------+------+------+------
|No. 1.|No. 2.|No. 3.|No. 4.|No. 5.|No. 6.
----------------------------+------+------+------+------+------+------
Ammonia in 1,000 grains | | | | | |
of natural soil | 0.293| 0.181| 0.085| 0.109| 0.127| 0.083
Ammonia in 1,000 grains | | | | | |
of soil after liming | 0.169| 0.102| 0.040| 0.050| ... | 0.051