be examined be, for instance, feldspar; this substance,
taken alone, even when reduced to the finest powder, requires for
its solution to be treated with an acid for weeks or months; but if
we first mix it with quick-lime, and expose the mixture to a
moderately strong heat, the lime enters into chemical combination
with certain elements of the feldspar, and its alkali (potass) is
set free. And now the acid, even without heat, dissolves not only
the lime, but also so much of the silica of the feldspar as to form
a transparent jelly. The same effect which the lime in this process,
with the aid of heat, exerts upon the feldspar, it produces when it
is mixed with the alkaline argillaceous silicates, and they are for
a long time kept together in a moist state.

Common potters' clay, or pipe-clay, diffused through water, and
added to milk of lime, thickens immediately upon mixing; and if the
mixture is kept for some months, and then treated with acid, the
clay becomes gelatinous, which would not occur without the admixture
with the lime. The lime, in combining with the elements of the clay,
liquifies it; and, what is more remarkable, liberates the greater
part of its alkalies. These interesting facts were first observed by
Fuchs, at Munich: they have not only led to a more intimate
knowledge of the nature and properties of the hydraulic cements,
but, what is far more important, they explain the effects of caustic
lime upon the soil, and guide the agriculturist in the application
of an invaluable means of opening it, and setting free its
alkalies--substances so important, nay, so indispensable to his
crops.

In the month of October the fields of Yorkshire and Oxfordshire look
as it they were covered with snow. Whole square miles are seen
whitened over with quicklime, which during the moist winter months,
exercises its beneficial influence upon the stiff, clayey soil, of
those counties.

According to the humus theory, quick-lime ought to exert the most
noxious influence upon the soil, because all organic matters
contained in it are destroyed by it, and rendered incapable of
yielding their humus to a new vegetation. The facts are indeed
directly contrary to this now abandoned theory: the fertility of the
soil is increased by the lime. The cerealia require the alkalies and
alkaline silicates, which the action of the lime renders fit for
assimilation by the plants. If, in addition to these, there is any
decaying organic matt