All of the volcanic rocks, without exception, are composed of
mixtures of various portions of the above-named minerals, which
in their composition show substances of high importance to agri-
culture, but inasmuch as the single substances are united in them
to each other, forming as a whole, a silicate of indifferent charac-
ter, like sand, they can form in this condition nothing but a poor
soil, which in no way can answer the demand which the plants
require from it. These substances only require to be liberated, to
exercise in full their influence on the quality of the soil; from a
light and sandy soil of small depth, would then at once arise a
soil containing a sufficient quantity of clay to become tenacious
and binding, a sufficient quantity of Peroxyd of Iron to exercise
an attractive influence on atmospheric ingredients, on heat, &c.,
and finally of alkalies and soluble silicic acid, which are direct
nourishments for plants. We know that by the influence of
air and water, all of these substances will be decomposed, the
manner of which has been shown already and indeed, the quan-
tity of sand, clay, oxyd of iron and lime on one side, and soluble
substances on the other, which we find in these soils already in a
liberated condition, indicates in what degree the disintegration of
them has advanced during past ages. But as this process goes
on very slowly, the agricultural question therefore arises, by what
means this process of disintegration can be quickened; and here
theory as well as practical experience gives us at once the reme-
dies which are required.

We know by experience made on many localities, the geological
character of which was similar to that of the soils under considera-
tion, that the action of water-slaked lime on them, was always ac-
companied by a wonderful success in relation to their culture. This
success is also well sustained by a theoretical contemplation of the
properties of water-slaked lime, as far as they are brought into action.
Water-slaked lime is an hydrate of the oxyd of calcium mixed with
carbonate of lime, the proportion of which depends on the length
of time during which the former compound was exposed to the
air, and into which, finally, it will be totally transformed. The
hydrate of the oxyd of calcium is remarkable for its great affinity
to silicic acid, as it exists in silicates, viz: in its combination with
alkalies, oxyd of aluminum, (clay) or iron; in consequence of

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