to be
a principle in our reasoning afterwards, I shall now endeavour to
generalise the subject as much as possible, in order to answer that end,
and, at the same time, to point out the particular method of inquiry.

There are to be found, among the various strata of the globe, bodies
formed of two different kinds of substances, _siliceous_ bodies, and
those which may be termed _sulphureous_ or _phlogistic_. With one or
other, or both of those we substances, every different consolidated
stratum of the globe will be found so intimately mixed, or closely
connected, that it must be concluded, by whatever cause those bodies
of siliceous and sulphureous matter had been changed from a fluid to a
concreted state, the strata must have been similarly affected by the
same cause.

These two species of bodies, therefore, the siliceous and the
sulphureous, may now be examined, in relation to the causes of their
concretion, with a view to determine, what has been the general
concreting or consolidating power, which has operated universally in the
globe; and particularly to show, it has not been by means of any fluid
solution, that strata in general have been consolidated, or that those
particular substances have been crystallized and concreted.

Siliceous matter, physically speaking, is not soluble in water; that is
to say, in no manner of way have we been enabled to learn, that water
has the power of dissolving this matter.

Many other substances, which are so little soluble in water, that their
solubility could not be otherwise detected of themselves, are made to
appear soluble by means of siliceous matter; such is feld-spar, one of
the component parts of rock-granite.

Feld-spar is a compound of siliceous, argillaceous, and calcareous
earth, intimately united together. This compound siliceous body
being, for ages, exposed to the weather, the calcareous part of it is
dissolved, and the siliceous part is left in form of a soft white earth.
But whether this dissolution is performed by pure water, or by means
also of an acid, may perhaps be questioned. This, however, is certain,
that we must consider siliceous substances as insoluble in water.

The water of Glezer in Iceland undoubtedly contains this substance in
solution; but there is no reason to believe, that it is here dissolved
by any other than the natural means; that is, an alkaline substance, by
which siliceous bodies may be rendered soluble in water[5].

[Note 5: This