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spaces, and strange subterranean noises likewise heard over
nearly equal areas, yet few cases are on record of volcanoes,
very far distant from each other, bursting out at the same
moment of time. In this instance, however, at the same
hour when the whole country around Concepcion was
permanently elevated, a train of volcanoes situated in the
Andes, in front of Chiloe, instantaneously spouted out a
dark column of smoke, and during the subsequent year
continued in uncommon activity. It is, moreover, a very
interesting circumstance, that, in the immediate neighbourhood,
these eruptions entirely relieved the trembling ground,
although at a little distance, and in sight of the volcanoes,
the island of Chiloe was strongly affected. To the northward,
a volcano burst out at the bottom of the sea adjoining
the island of Juan Fernandez, and several of the great chimneys
in the Cordillera of central Chile commenced a fresh
period of activity. We thus see a permanent elevation of
the land, renewed activity through habitual vents, and a
submarine outburst, forming parts of one great phenomenon.
The extent of country throughout whioh the subterranean
forces were thus unequivocally displayed, measures 7 0 0 by
400 geographical miles. From several considerations, which
I have not space here to enter on, and especially from the
number of intermediate points whence liquefied matter was
ejected, we can scarcely avoid the conclusion, however
fearful it may be, that a vast lake of melted matter, of an
area nearly doubling in extent that of the Black Sea, is
spread out beneath a mere crust of solid land.
The elevation of the land to the amount of some feet
during these earthquakes, appears to be a paroxysmal movement,
in a series of lesser and even insensible steps, by
which the whole west coast of South America has been
raised above the level of the sea. In the same manner,
the most violent explosion from any volcano is merely one
in a series of lesser eruptions : and we have seen that both
these phonomena, which are in so many ways related, are
parts of one common action, only modified by local circumstances.
With respect to the cause of the paroxysmal
convulsion in particular portions of the great area which
is simultaneously affected, it can be shown to be extremely
probable, that it is owing to the giving way of the superincumbent
strata, (and this giving way probably is a consequence
of the tension from the general elevation) and their
interjection by fluid rock—one step in the formation of a
mountain chain. On this view we are led to conclude, that
the unstratified mass forming the axis of any mountain,
has been pumped in when in a fluid state, by as many
separate strokes as there were earthquakes. For instance,
in the case of Concepcion, during the few months subsequent
to the great shock, upwards of three hundred
tremours of the ground were felt, each of which indicated a
fresh fracture, and injection of the fluid stone. It is a case
precisely analogous to what happens in all bad eruptions,
which are invariably followed by a succession of smaller
ones : the difference is, that in the volcano the lava is
ejected, while in the formation of a mountain chain it is
injected. This view of the extremely gradual elevation of
a line of mountains, will alone explain the difficulty (which,
as far as I am aware, has never been attempted to he solved)
of the axis consisting of rock which has become solid under
the pressure of the superincumbent strata, while yet these
same strata, in their present inclined and vertical positions,
cannot possibly cover more than a small portion of that