C.—GEOLOGY. 65 
Elie de Beaumont, in accordance with the geographical and geological 
information available between 1820 and 1850, unfortunately adopted 
as the basis of his fold and fracture pattern for the earth the pentagonal 
network, which had to him the recommendation of its possession of a high 
degree of symmetry. 
The most obvious fact in the map of the world is that it has no such 
highly developed symmetry as Elie de Beaumont’s system. The pattern 
is in better accordance with the facts adopted by Lowthian Green, the 
tetrahedral arrangement of land and water, with the continents upraised 
at the antipodes to the oceanic depressions, just as on a tetrahedron the 
projecting coigns are antipodal to a face, of which the middle is nearer 
the centre, or from the point of view of gravity, is lower than the edges 
and the coigns. The development of this plan is natural, since by it the 
crust of the earth would most easily adapt itself to the smaller space into 
which it is compressed by the shrinkage of the internal mass. 
I endeavoured to show in 1899 (Geogr. Journ., vol. XII, pp. 225-40) 
that Lowthian Green’s theory agrees both with the existing distribution of 
ocean and continent, and with geological history, as it explains the 
alternation of the slow subsidence of the ocean floors and of crustal storms 
during which fold-mountain chains are raised by lateral compression ; it 
also explains the alternate emergence of the lands as the ocean basins are 
enlarged by the sinking of their floors and submergence of the lands by 
the world-wide advance of the sea due to the shallowing of the oceans 
when the spheroidal form is recovered after the tetrahedral deformation 
has exceeded the stability of the crust. 
Elie de Beaumont’s elaborate classification of mountains has collapsed ; 
for although the foundations were sound, the girders of his superstructure 
were not. Knowledge of the history and structure of mountain chains 
was then inadequate and much of it was erroneous. Mountain chains are 
not straight like crystal edges, but bend in long curves around resistant 
blocks. Their trend is no test of their age. Moreover, a great mountain 
chain is not all built at one episode ; the Alps are due to uplifts that have 
happened from at least the Lower Jurassic to the Upper Kainozoic. 
Lowthian Green, working on the same foundation of a contracting globe, 
built a structure that was more stable as it was in fuller agreement with 
the map of the world. If the earth had been a spheroid of revolution and 
its crust homogeneous, mountain ranges might have developed with 
the high symmetry of the pentagonal network; but the numerous 
irregularities in the form and strength of the crust have led to its deforma- 
“tion by fewer faces and have produced a mountain system and arrangement 
of land and water which is tetrahedral and not pentagonal. 
5. Mountain STRUCTURE. 
Elie de Beaumont’s system was built upon the mountain chains ; and 
his conception of their structure was defective; he regarded them as 
symmetrical ridges and he failed to appreciate the contribution to the 
Association in 1842 by Henry Darwin Rogers which laid the foundation 
of the modern theory of mountain formation. Rogers had early in the 
history of the Association rendered it a medium of co-operation between 
1931 F 
