ME. EOBEET MALLET ON VOLCANIC ENEEGY. 
155 
24. The nature of the conception of this force, as more or less clearly shadowed forth 
by geologists, admits of no doubt, as regards French geologists at least, when we consider 
the force of their adopted term soulevement (presumably sublevare, sous-levement , a lift 
by a force from beneath), and, indeed, is pretty evident in the German Aushebmu / ; but 
the English “upheaval” and “elevation” admit of any cloudiness of conception or 
latitude of interpretation. 
25. Peevost’s ideas are scattered through numerous papers, extending over nearly 
twenty years, but are to be found in their most systematic and formal manner in vol. xxxi. 
part ii. of the ‘ Comptes Bendus’ for September 1850, p. 461 et seq., and, at an earlier 
period, in the ‘ Bulletin de la Societe Geologique de France,’ vol. xi. p. 183 et seq. His 
view is this, that, apart from the great deformations which hollowed out the ocean-beds, 
as to which he is not quite so clear, all elevations of the earth’s surface of the nature of 
hills or mountains (in general the rugose contour of its surface) have been produced, 
not by vertical forces directly coming from some unknown deep-seated source, but by 
vertical forces, the* resultants of tangential pressures, acting against each other in hori- 
zontal or nearly horizontal directions, and transversely to the ridges or lines of elevation, 
these tangential pressures originating in the contraction of the earth’s crust by secular 
refrigeration. This view, which the writer believes to be true, has been followed out 
by Dana, the two Bogees in America, by Elie De Beaumont and some other continental 
geologists, by showing how completely the observed facts fall into place and are account- 
able for by it, but oppose themselves to the notion of a vertical primary force. 
26. The Pev. O. Fishee also, in an important paper “ On the Elevation of Mountain- 
chains, and Speculation on the Cause of Volcanic Heat ” (Cambridge Trans, vol. xi. p. iii, 
1868), which the writer had no knowledge of until after the present paper had been written, 
has given support to Peevost’s view, by proving the mechanical adequacy of the tangential 
pressure due to refrigeration to the elevation of the highest mountains of our globe. 
Mr. Fishee’s views in the above paper as to the origin of volcanic heat are entirely 
different from those of the writer as here developed. 
27. Upon Hopkins’s view, all elevated parts must have convex surfaces, and, whether 
continents or ridges steep as the high Alps, must be bombe or dome-like in contour ; they 
must all present the evidences of tension during elevation and in orthogonal directions. 
But the careful geological surveys and sections made since Peevost’s day show that, on the 
whole, the sectional contour of large areas, much less those of continents, are not bombe , 
and that the transverse sections of all mountain-ranges prove their curvatures on opposite 
flanks to be not convex, but concave — a form which is generally the case in the fall of 
the land from all mountain-crests to the sea-level, as is evident by the concave form 
(approaching to something of a curve of the parabolic order) shown by the longitudinal 
section of all large river-courses. 
28. The “ fan-like ” structure of the Alps ( structure en eventail), so well elucidated by 
Favee and Studee, Von Linth, and other Alpine geologists, becomes a conclusive proof 
alone that the forces of elevation have been lateral compressions resolved into the 
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