countenance to that which supposes water the
chief instrument in consolidating strata.

The formation of salt at the bottom of the sea, without the assistance
of subterranean fire, is not a thing unsupposable, as at first sight
it might appear. Let us but suppose a rock placed across the gut
of Gibraltar, (a case nowise unnatural), and the bottom of the
Mediterranean would be certainly filled with salt, because the
evaporation from the surface of that sea exceeds the measure of its
supply.

But strata of salt, formed in this manner at the bottom of the sea, are
as far from being consolidated by means of aqueous solution, as a bed of
sand in the same situation; and we cannot explain the consolidation of
such a stratum of salt by means of water, without supposing subterranean
heat employed, to evaporate the brine which would successively occupy
the interstices of the saline crystals. But this, it may be observed, is
equally departing from the natural operation of water, as the means for
consolidating the sediment of the ocean, as if we were to suppose
the same thing done by heat and fusion. For the question is not,
If subterranean heat be of sufficient intensity for the purpose of
consolidating strata by the fusion of their substances; the question is,
Whether it be by means of this agent, subterranean heat, or by water
alone, without the operation of a melting heat, that those materials
have been variously consolidated.

The example now under consideration, consolidated mineral salt, will
serve to throw some light upon the subject; for, as it is to be shown,
that this body of salt had been consolidated by perfect fusion, and
not by means of aqueous solution, the consolidation of strata of
indissoluble substances, by the operation of a melting heat, will meet
with all that confirmation which the consistency of natural appearances
can give.

The salt rock in Cheshire lies in strata of red marl. It is horizontal
in its direction. I do not know its thickness, but it is dug thirty or
forty feet deep. The body of this rock is perfectly solid, and the salt,
in many places, pure, colourless, and transparent, breaking with a
sparry cubical structure. But the greatest part is tinged by the
admixture of the marl, and that in various degrees, from the slightest
tinge of red, to the most perfect opacity. Thus, the rock appears as if
it had been a mass of fluid salt, in which had been floating a quantity
of marly substance, not u