cters and value, but
they have not hitherto proved very successful; and the result of more
recent chemical investigations has not been such as to encourage a
farther attempt. We have not at present data sufficient for the purpose,
nor, if we had, would it be possible to arrange any soil in its class
except after an elaborate chemical examination. The only classification
at present possible must be founded on the general physical characters
of the soil; and the ordinary mode followed in practice of dividing them
into clays, loams, etc. etc., which we need not here particularize,
fulfils all that can be done until we have more minute information
regarding a large number of soils. Those of our readers who desire more
full information on this point are referred to the works of Thaer,
Schuebler, and others, where the subject is minutely discussed.

FOOTNOTES:

[Footnote I: Transactions of the Highland and Agricultural Society, vol.
vi., p. 317.]

CHAPTER VI.

THE IMPROVEMENT OF THE SOIL BY MECHANICAL PROCESSES.

Comparatively few uncultivated soils possess the physical properties or
chemical composition required for the production of the most abundant
crops. Either one or more of the substances essential to the growth of
plants are absent, or, if present, they are deficient in quantity, or
exist in some state in which they cannot be absorbed. Such defects,
whether mechanical or chemical, admit of diminution, or even entire
removal, by certain methods of treatment, the adaptation of which to
particular cases is necessarily one of the most important branches of
agricultural practice, as the elucidation of their mode of action is of
its theory. The observations already made with regard to the characters
of fertile soils must have prepared the reader for the statement that
these defects may be removed, either by mechanical or chemical
processes. The former method of improvement may at first sight appear to
fall more strictly under the head of practical agriculture, of which the
mechanical treatment of the soil forms so important a part, and that
their improvement by chemical means should form the sole subject of our
consideration in a treatise on agricultural chemistry. But the line of
demarcation between the mechanical and the chemical, which seems so
marked, disappears on more minute observation, and we find that the
mechanical methods of improvement are frequently dependent on chemical
principles; and those whic