onception been formed of the forces and interior movements brought
necessarily into operation by the secular cooling of the globe,
geologists could scarcely have failed to see that their notion as to the
way and direction in which the forces producing elevation have actually
acted could not, if arising from refrigeration, be those which they have
almost universally supposed, namely--some force acting vertically
upwards, _i.e._, radially from the centre of the sphere. Had geologists
only looked at Nature with open eye, they must have seen that mountain
ranges, and elevations generally (exclusive of volcanic cones),
presented circumstances absolutely incompatible with their having been
thrust up by any force _primarily_ acting in the direction of a radius
to the spheroid.

Yet this is the erroneous notion of the mechanism of elevation which to
the present hour prevails amongst geologists, so far as they in general
have framed to themselves any distinct idea of such mechanism at all.

Thus, only to cite two examples from recent authors of justly high
reputation. Lyell says of the probable subterranean sources, whether of
upward or downward movement, when permanently uplifting a country, and
in reference to the crumpling of strata on mountain flanks by lateral
pressure, it would be rash to assume these able to resist a power of
such stupendous energy, "_if its direction, instead of being vertical_,
happened to be oblique or horizontal." This is somewhat vague--and I
trust I do not mistake or misrepresent the illustrious author--yet it
is the most explicit expression I can find in the "Principles of
Geology" as to his notion of the primary direction of elevatory force
(Edit. 10, Vol. I., p. 133). That Mr. Scrope's idea is that only of
primary radial or vertical direction of such forces, is apparent on
inspecting his Diagram No. 64 ("Volcanoes," p. 285), and in the use of
the words, "an axial wedge of granite," which, on the next page, we find
is "liquefied granite;" and if we read on to page 294, and refer also to
pages 50 and 51, I believe there can be no doubt that _vertical_ or
_direct up-thrust_ is the author's notion of the primary direction of
all forces of elevation. The true nature of these forces was, however,
clearly seen and most justly stated by Constant Prevost ("Compt. Rend.,"
Tome XXXI., 1850, and "Bulletin de la Societe Geolog. de France," Tome
II., 1840) as consisting, not in forces of some unknown origin ac