towards producing, on the continents, many of the wonderful phsnomena wliich excite
our astonishment.
As all these facts and data, of which the number might be considerably augmented,
are now generally established, I purpose making use of them to explain my ideas on
the formation of the Lake of Geneva, and the valleys which there terminate, as well as
to account in what manner the immense blocks of granite, or primitive rock, have
found their way to the summit of most of the calcareous mountains which now screen
it, and with which they have not the least affinity; and I can safely say, that, the more I
have observed the structure of the different mountains situate between the Pennine
Alps and the lake, including the Saleve, Mont Sion, the Vouaches, the Jura, Jorat,
and the major part of those which serve it as a barrier, the more have I been confirmed
in my opinion, that, after the crystallisation of their nuclei, of which the different forms
and directions had already traced the greatest part of our valleys, the subterraneous
fires or volcanoes that afterwards existed, as also the cavcms and fissures naturally
formed during that crystallisation, were soon after, in great part, totally covered by the
successive sediments of the sea, at the time of its retreat; so that the surface, which
extended from the summit of the Alps to the last chain of the Jura, may be considered
as having presented or formed one entire, inclined, and irregular, or undulated surface,—
though not, however, sufficiently irregular to prevent the sea, in one of its retreats,
from carrying from the summit of the primordial chain the immense masses of
granite or compound stones. See. which it had, as it were, detached, and then deposited
in the places where they are now found; or, in other words, where the force of
impulsion, at first given by the current of the sea, was obliged to yield to that of gravity
and friction.
Admitting, therefore, this supposition, the surprise ceases with respect to the finding
such huge masses of primitive rock at so great a distance and elevation as they now
are, and not only isolated, but absolutely lying on mountains so totally foreign to them
in composition and structure, as the Salgve, the Jura, along the lake, on the hills of
Cerdon, before observed, and even in the neighbourhood of Lyons; for soon after, a
number of valleys having been apparently formed by the crush of the vaulted roof of
the before-mentioned subterraneous caverns, as also by the causes stated in the tenth
article and following data, the greatest part of these same blocks were necessarily, or
unavoidably, left on the summit of those calcareous mountains formed by the new-made
It
valleys: it is therefore no unreasonable supposition to conclude, that most of the valleys
which terminate near the lake may have been thus formed, as well as the mountains of
the extensive basin itself, to judge by the different directions exhibited in the strata of
the mountains which now skirt it on all sides, as also by their structure, abruptness, and
the enormous calcareous rocks which cover their basis,—in fine, by the very great analogy
that exists in the construction of most of the hills, which serve as its internal dike.
From these suppositions and facts, I am therefore again induced to conclude, that
the lake may have once formed an extensive cavern, or caverns, of which the vaulted
roof suddenly gave way, from some of the causes before mentioned, or else by the
expansive force of a fluid, occasioned by some subterraneous fires j for, as already
noticed, all bodies expanding with heat, and the limits of that force of expansion
being there undetermined, it gradually increased, until it became superior to the incumbent
weight of the vault, which it so distended as to occasion its explosion.
I t is also probable, that the focus of these subterraneous fires may have lain between
Evian and Lausanne, and that the seiches, or subterraneous air, before described, as
likewise the water-spouts (electrical phsnomena), which now and then appear on the
lake, may be found to derive their origin from some remains of the same expansive
fluid, which, even at the present epoch, still escapes from its deepest galleries or
recesses, though covered by the detached fragments of the original vaulted roof, sinceimbedded
in the successive sediments of the sea, after having precipitated itself into
the new-created gulf. The same circumstances also appear to have given birth to the
greater part of the inferior hills which screen the lake, and are entirely composed of
primitive and secondary productions, united by a calcareous cement.
As to the lake itself, the form of which is at present that of an irregular crescent, it
appears to have been originally (that is, at the time when the waters of the sea no
longer covered the summits or tops of the Jura and Saleve) that of a scalene triangle,
of which the Jura might be considered as having formed one of the sides, tending in a
direction nearly from south-west to north-east; while the mountains of Berne and Frcyburg
formed the second, from north-east to south-south-east; and those of the Saleve,
\'^oirans, and a part of the mountains in the duchy of Chablais, the third, from southsouth
east to south-west.
There is also every reason to suppose that the Rhine, at that remote period, may
likewise have served as the drain to that extensive lake, and that the two valleys