In the country surrounding Padua, in Italy, there are several basaltic
columns, similar to those of the Giant’s Causeway, although less
magnificent in appearance. About seven miles in a southern direction
from that city, is a hill named Monte Rosso, or the Red mount, which
presents a natural range of prismatic columns, of different shapes and
sizes, placed in a direction nearly perpendicular to the horizon, and
parallel to each other, nearly resembling that part of the Giant’s
Causeway, called the organs.
At an inconsiderable distance is another basaltine hill, called _Il
monte del Diavolo_, or the Devil’s hill, along the sides of which
prismatic columns are arranged in an oblique position. This causeway
extends along the side of the vale beneath, with nearly the same
arrangement of the columns as is displayed on the hill. Although the
columns of both these hills are of the simple, or unjointed kind, still
they differ very remarkably from each other in many respects, but
principally in their forms, and in the texture and quality of their
parts. Those of the Monte del Diavolo commonly approach a circular form,
as nearly as their angles will allow; which is also observable in the
columns of the Giant’s Causeway and of most other basaltic groups. On
the contrary, those of Monte Rosso assume an oblong or oval figure. The
columns of the former measure, one with the other, nearly a foot in
diameter, varying but little in their size; while those of the latter
present a great variety in their dimensions, the diameter of some of
them being nearly a foot, and that of others scarcely three inches:
their common width may be estimated at six or eight inches. They differ,
therefore, very considerably in size from those of the Giant’s Causeway,
some of which measure two feet in width. The length of the columns of
the Monte del Diavolo can not be ascertained, as they present only their
summits to the view: their remaining parts are deeply buried in the
hill, and in some places entirely covered. Those of Monte Rosso, as far
as they are visible, measure from six to eight or ten feet in hight; an
inconsiderable size when compared with the hight of those of the Giant’s
Causeway. The columns of these groups display, however, all the
varieties of prismatic forms, which are observable in those of the
latter, and other similar groups. They are usually of five, six or seven
sides; but the hexagonal form seems chiefly to prevail.
The texture and quality of these columns are not less different than
their forms. Those of the Monte del Diavolo present a smooth surface,
and, when broken, appear within of a dark iron-gray color, manifesting
also a very solid and uniform texture; in which characters they
correspond with the columns of the Giant’s Causeway, and those of most
other basaltic groups. But the columns of Monte Rosso are in these
respects very different, having not only a very rough (and sometimes
knotty) surface, but displaying likewise, when broken, a variegated
color and unequal texture of parts. They are commonly speckled, more or
less distinctly, and resemble an inferior sort of granite, of which
Monte Rosso is itself formed, and which serves as a base to the range of
columns in question. It is, in general, not quite so hard as the alpine
and oriental granites, and is sometimes even friable. This species of
granite abounds in France, where large tracts of it are to be seen in
Auvergne, and the adjoining regions. But it is still more common in
Italy, seeing that, besides Monte Rosso, the bulk of the Euganean hills,
of which that is a part, principally consists of it; and these hills
occupy a considerable tract in the plains of Lombardy. It is also common
in the Roman and Tuscan states; and of this substance the mountain close
to Viterbo, on the road to Rome, is entirely composed. The columns of
Monte Rosso appear, therefore, of a different character from any
hitherto described by mineralogists, who mention those only of an
uniform color and texture. But the great singularity here is, that such
a range of prismatic columns should be found, bedded as it were, in a
mass of granite, and composed nearly of the same substance. An instance
of this kind, relative to any other causeway, is not recorded; and this
circumstance seems to render that of Monte Rosso, in one respect at
least, more curious and singular than the celebrated Giant’s Causeway is
known to be, from the regular articulation of its columns. It is
certain, that the basaltic group of Monte Rosso is not only highly
curious in itself, but interesting on account of the great light it
throws on the origin of granites in general.
It is likewise remarkable, that the columns in the two groups of Monte
Rosso and Monte del Diavolo, preserve respectively the same position,
nearly parallel to each other; which is not usually the case in basaltic
groups. For, although the principal aggregate of which the Giant’s
Causeway is formed, stands in a direction perpendicular to the horizon,
still other small detached groups of columns also appear on the eminence
above, assuming by their position different degrees of obliquity. Among
the numerous basaltic hills of Auvergne and the adjoining regions, in
France, phenomena which seem to abound in those provinces more than in
any other part of Europe, and, perhaps, of the known globe, nothing is
more common than to see the columns of the same group lying in all
possible directions, as irregularly almost as the prisms in a mass of
common crystal. Nor is this variety of position so observable in single
columns as in whole masses or ranges of them, that often present
themselves on the same hill, disposed in different strata or stages, as
it were, one above the other, many of them assuming very different, and
even opposite directions. The columns of the Monte del Diavolo are
bedded in a kind of volcanic sand, by which, in many parts of the hill,
they are entirely covered: it is probable, however, that they repose
beneath on a base of basaltic rock of a similar nature. Nothing is more
common, in the provinces of France, above mentioned, than to see
insulated basaltic hills almost exclusively composed of different layers
of columns, which present themselves in stages, one above the other,
often without any other stratum between them, resembling in some
measure, if the comparison can be allowed, a huge pile or stack of cleft
wood. Although the columnar crystallization of Monte Rosso is the only
one yet known or described, in a mass of granite, still other groups of
columns have elsewhere been met with, which are equally of a
heterogeneous substance or texture, however they may otherwise differ
from those of Monte Rosso, as well as from the common basalts.
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