the earth, consists in this; that nature applies heat
under circumstances which we are not able to imitate, that is, under
such compression as shall prevent the decomposition of the constituent
substances, by the separation of the more volatile from the more fixed
parts. This is a circumstance which, so far as I know, no chemist
or naturalist has hitherto considered; and it is that by which the
operations of the mineral regions must certainly be explained. Without
attending to this great principle in the mineralizing operations
of subterraneous fire, it is impossible to conceive the fusion and
concretion of those various bodies, which we examine when brought up to
the surface of the earth.]

The only question, therefore, which it concerns us to decide at present,
is, Whether those operations of extreme heat, and violent mechanic
force, be only in the system as a matter of accident; or if, on the
contrary, they are operations natural to the globe, and necessary in the
production of such land as this which we inhabit? The answer to this is
plain: These operations of the globe remain at present with undiminished
activity, or in the fullness of their power.

A stream of melted lava flows from the sides of Mount Aetna. Here is a
column of weighty matter raised from a great depth below, to an immense
height above, the level of the sea, and rocks of an enormous size
are projected from its orifice some miles into the air. Every one
acknowledges that here is the liquefying power and expansive force of
subterranean fire, or violent heat. But, that Sicily itself had been
raised from the bottom of the ocean, and that the marble called Sicilian
Jasper, had its solidity upon the same principle with the lava, would
stumble many a naturalist to acknowledge. Nevertheless, I have in my
possession a table of this marble, from which it is demonstrable, that
this calcareous stone had flowed, and been in such a state of fusion and
fluidity as lava.

Here is a comparison formed of two mineral substances, to which it is of
the highest importance to attend. The solidity and present state of the
one of these is commonly thought to be the operation of fire; of the
other, again, it is thought to be that of water. This, however, is not
the case. The immediate state and condition of both these bodies is now
to be considered as equally the effect of fire or heat. The reason of
our forming such a different judgment with regard to these two subjects