y furnaces
were condensed into a liquid form, we may here inquire what would be
the result, upon the mass, of a further reduction of temperature. It
is generally assumed that in the cooling of a liquid globe of mineral
matter, congelation would commence at the surface, as in the case of
water; but water offers an exception to most other liquids, inasmuch
as it is denser in the liquid than in the solid form. Hence ice floats
on water, and freezing water becomes covered with a layer of ice,
which protects the liquid below. With most other matters, however,
and notably with the various mineral and earthy compounds analogous to
those which may be supposed to have formed the fiery-fluid earth,
numerous and careful experiments show that the products of
solidification are much denser than the liquid mass; so that
solidification would have commenced at the centre, whose temperature
would thus be the congealing point of these liquid compounds. The
important researches of Hopkins and Fairbairn on the influence of
pressure in augmenting the melting-point of such compounds as contract
in solidifying are to be considered in this connection.

"It is with the superficial portions of the fused mineral mass of the
globe that we have now to do; since there is no good reason for
supposing that the deeply seated portions have intervened in any
direct manner in the production of the rocks which form the
superficial crust. This, at the time of its first solidification,
presented probably an irregular, diversified surface from the result
of contraction of the congealing mass, which at last formed a liquid
bath of no great depth surrounding the solid nucleus. It is to the
composition of this crust that we must direct our attention, since
therein would be found all the elements (with the exception of such as
were still in the gaseous form) now met with in the known rocks of the
earth. This crust is now everywhere buried beneath its own ruins, and
we can only from chemical considerations attempt to reconstruct it. If
we consider the conditions through which it has passed, and the
chemical affinities which must have come into play, we shall see that
these are just what would now result if the solid land, sea, and air
were made to react upon each other under the influence of intense
heat. To the chemist it is at once evident that from this would result
the conversion of all carbonates, chlorides, and sulphates into
silicates, and the separation o