ogic time, in some cases depressing the land, and in others
causing the sea-bottom to protrude beyond its surface. Considering
the inelastic character of its materials, the protuberance of the Alps
could hardly have been pushed out without dislocation and fracture;
and this conclusion gains in probability when we consider the
foldings, contortions, and even reversals in position of the strata in
many parts of the Alps. Such changes in the position of beds which
were once horizontal could not have been effected without dislocation.
Fissures would be produced by these changes; and such fissures, the
advocates of the fracture theory contend, mark the positions of the
valleys of the Alps.

Imagination is necessary to the man of science, and we could not
reason on our present subject without the power of presenting mentally
a picture of the earth's crust cracked and fissured by the forces
which produced its upheaval. Imagination, however, must be strictly
checked by reason and by observation. That fractures occurred cannot,
I think, be doubted, but that the valleys of the Alps are thus formed
is a conclusion not at all involved in the admission of dislocations.
I never met with a precise statement of the manner in which the
advocates of the fissure theory suppose the forces to have
acted--whether they assume a general elevation of the region, or a
local elevation of distinct ridges; or whether they assume local
subsidences after a general elevation, or whether they would superpose
upon the general upheaval minor and local upheavals.

In the absence of any distinct statement, I will assume the elevation
to be general--that a swelling out of the earth's crust occurred here,
sufficient to place the most prominent portions of the protuberance
three miles above the sea-level. To fix the ideas, let us consider a
circular portion of the crust, say one hundred miles in diameter, and
let us suppose, in the first instance, the circumference of this
circle to remain fixed, and that the elevation was confined to the
space within it. The upheaval would throw the crust into a state of
strain; and, if it were inflexible, the strain must be relieved by
fracture. Crevasses would thus intersect the crust. Let us now
enquire what proportion the area of these open fissures is likely to
bear to the area of the unfissured crust. An approximate answer is all
that is here required; for the problem is of such a character as to
render minute