64 SECTIONAL ADDRESSES. 
because his conclusions are not based upon any a priori reasoning, but on 
the evidence of facts; and also, because, in part, they are in accordance 
with my own observations.’ 
But the principles of Elie de Beaumont and Lyell are not essentially 
inconsistent. Lyell repeatedly remarked that the intensity of the forces 
has varied in the past as it does locally to-day. He insisted that the 
forces were the same although they may at times have been spent. A 
lull lasts until the force has regained fresh energy. A volcano has a con- 
tinuous history, although it may be dormant between its eruptions. The 
orogenic episodes are the culmination of long accumulated stresses. The 
Jurassic and Cretaceous disturbances in the Alps were the preliminary 
movements to the convulsions of the Middle Kainozoic. 
Elie de Beaumont’s episodes of world-wide mountain formation were 
not due to the sudden application of an extraneous force but to a long 
continued stress that was relieved by quick changes during the restoration 
of stability to the deformed crust. Sedgwick called these episodes 
‘catastrophes’; but they are as much the result of continuously acting 
agencies as the eruptions of a volcano and the quiet processes of the 
dormant intervals. 
Conybeare** was more critical of Elie de Beaumont’s theory. He 
recognised that some facts support it, but others are inconsistent. He 
objected to describing the Urals and the American Cordillera as parallel,” 
and to reference to the axes of folds as if they were mathematically 
straight ; and he held that the correlation of English folds by parallelism 
is unsatisfactory. f 
K. Boué and other French geologists were more severe in their 
criticisms ; they represented the view that mountain uplifts happened at 
distinct periods as not new, and the original part of the theory, on which 
rested the synchronism of distant mountains, as not true. 
he de Beaumont’s work, from his ‘ Recherches sur quelques unes des 
révolutions de la Surface du Globe ’ in 1828, to his ‘ Systéme de Montagnes ’ 
(3 vols., 1852), laid the foundations of the modern study of the general 
plan of the earth. His two fundamental principles were that the main 
movements in the earth’s crust are due to its compression owing to the 
shrinkage of the internal mass, and that the collapse of the crust determines 
the main features in the relief of the globe. The shrinkage is probably 
due more to closer packing of the constituents than to cooling. The 
argument has constantly been advanced that the contraction of the earth 
cannot have been sufficient to have caused mountain folding ; it has also 
been claimed that the earth is expanding and not shrinking, and has 
been growing hotter instead of cooler. That the main folding of the 
crust has been due to compression that at first acted on every part of the 
earth of which we have evidence and later was confined to special belts 
seems one of the most certain of geological facts. 
*4 Phil. Mag. n.s., 1832, pp. 118-26 ; 1834, pp. 404-14. 
25 Elie de Beaumont’s theory has been often misjudged owing to his use of the term 
parallel in its original sense of side by side, and not as restricted by mathematical 
usage. It was objected that though mountain lines along the parallels of latitude 
are parallel, those along the meridians are not. Elie de Beaumont applied the term 
to lines parallel to a great circle or along great circles that intersect at a pole and to 
parallels drawn in reference to a pole elsewhere than at the two existing poles. 
