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DYNAMICAL GEOLOGY 
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and ending with Suess the contractional hypothesis finds many 
adherents. 
Although the expansion theory of Hutton, the theory of isostasy 
of Dutton, the theory of extensive crust-slide of Reyer, and the 
theory of upheaval of Rothpletz cannot be expected completely 
to replace the contractional hypothesis they especially serve to 
call attention to some of its shortcomings. There are still graver 
objections than those mentioned to the contractional theory of 
orographic and continental genesis. These appear as direct re¬ 
sults of practical experiment in the laboratory. 
In laboratory experimentation on curved prisms, like sectors 
of the earth, with bands to take the place of gravitational control, 
and under conditions analogous to retardation of the earth’s rota¬ 
tion, there is reproduced to a nicety all of those larger structural 
features of the crust such as the oceanic basins, the continental 
arches, the cordilleran corrugations, and the orographic foldings. 
Effects of tangential creeping which many mountain structures 
display thus appear to be not due necessarily to results of the 
earth’s contraction, but to direct cumulative release arising from 
secular retardation of the earth’s rotation. 
On this new basis, with the force and rate of retardation, and 
the amount of crustal shortening capable of exact expression by 
mathematical equation, a ready means is provided for realizing 
not only something of Elie de Beaumont’s fantastic dream of 
orographic symmetry, but for guaging in units of human time the 
age of every mountain uplift, for determining within very narrow 
limits in like terms the periodicity of every diastrophic movement, 
and for evaluating in years not only the span of every era, per¬ 
iod, epoch and stage of stratigraphic record since life began, but 
stratigraphic chronology long antedating the life record itself. 
Keyks. 
Continental Dynamics. There is a definition of continent other 
than the one usually accepted. In it the hydrosphere is left out 
of consideration and the definition is no longer a geographic one. 
The facial expression of the globe is then an effect of our earth 
with a land area only. A condition is premised analogous to that 
of our waterless moon. 
Genetically the oceans serve merely to obscure the larger tec- 
