ean, as in the case of the
primitive rocks by their own crystallization from a fluid state, but
that they have been altered in their positions by actions of a character
totally distinct from that by which they were originally formed.

This inference is still further confirmed by the great and sudden
changes of level that are frequently to be seen in similar strata,
faults, as they are styled by miners, in which the same bed has its
level sometimes changed hundreds, nay even thousands of feet. These
faults, if in greatest abundance in the more ancient rocks, are to be
found even in the newest, and sometimes affect several formations
incumbent on each other, of ages the most different. Thus, then, we have
distinct and conclusive evidence, that as we inferred from theory, the
solid crust of the globe has been shattered and fractured repeatedly,
and at all the different epochs of its history. This fracturing and
cracking we have shown, must, in conformity with strict mechanical laws,
have been attended with the rise of the molten liquid from beneath,
which ought in some cases to have formed veins and dykes, in the places
where the fractures occurred. It is however possible, that the rise of
the fluid from beneath, may not have taken place where the pressure
occurred; but it would then have been compelled by hydrostatic pressure,
to issue at some other point, breaking and tearing the weaker parts of
the solid crust, in order to afford itself a vent.

The latter class of phenomena are still in action, and we have evident
traces of their occurrence in all the different stages of the world's
existence; of the former it will also be seen there is conclusive
evidence.

The visible effects of a subterranean heat, are most frequently met with
at the present day in the form of volcanoes. Of these, there are not
only a great number in activity, but there are still more that have been
certainly active since the last great change that the surface of the
earth has undergone.

That part of the great group of mountains which we have before
described, which lies in the new continent, contains many active
volcanoes, and others but recently extinct. Terra del Fuego, as its very
name imports, is the seat of many; Chili has several; in Peru are to be
noted Arequipa, Pichinca, and Cotapaxi; while Chimborazo is obviously
one that has become extinct at a period not remote. Passing the Isthmus
of Panama, we find the volcanoes of Guatimala and