54 
OROGENY AND EARTH’S ROTATION 
of sediments. This view is, indeed, a direct, although contra¬ 
dictory, application of J. F. W. Hershel’s principle which 
ascribes weight of accumulating sediments as the chief cause of 
local down-sinking of the earth’s crust. 
In the Appalachians the great thickness of sediments at once 
lent color to its important role in mountain-building as urged by 
Hall. Although the convolutions of these mountains were man¬ 
ifestly not due to waves which once traversed the liquid interior 
of the earth, as the Rogers fancied, they were of such a nature 
that it was possible to calculate the amount of lateral compression 
involved in the process. In emphasizing the importance of the 
action of a horizontally acting force in orographic genesis all other 
factors were lost sight of; and the possibility of the phenomenon 
being a mere shadow of the real cause did not receive consideration. 
So attractive has proved the American idea of Appalachian 
structure that it has been the subject of elaborate and repeated 
laboratory reproduction. Flexing experiments of Reyer,^^ Ca- 
dell,^® Willis,^® Poulcke,^^ and others, that have been so widely 
applauded, have not been on the whole so really expressive of 
orographic mechanics as they have been fancied to be, since they 
have proved to be merely examples of crushing, or pressure, 
phenomena in which the internal mass movement has been made 
visible. Although the necessary inference has been that the re¬ 
sults represent conditions analogous to those of a contracting crust 
of a cooling globe several of the most essential factors have been 
omitted; since the shot overburden represents nothing more than 
an additional layer of sediment rather than a force affecting 
crumpling. Then, again, there has been coincidence of directions 
of compression and greatest resistence; whereas in nature the 
former is represented by the chord of an arc represented by the 
latter. Under these diverse conditions the tectonic effects must 
be fundamentally distinct. Of course, in the simple compression 
trials, no such thing as tectonic effect in a rotating body is pos¬ 
sible. Latest experiments in tectonic adjustment take into ac¬ 
count all of these essential and initial factors, whereas all ques¬ 
tions arising out of assumed secular refrigeration are entirely 
eliminated. 
13 Proc. Geol. Soc., Pondon, Vol. II, p. 548, 1837. 
14 Geol. u. Geol. Exper., Haft I. 
15 Trans. Roy. Soc., Edinburg, Vol. XXXVI, p. 337, 1888. 
16 Thirteenth Ann. Kept. U. S. Geol. Surv., p. 241, 1894. 
17 Compte Rendu Cong. Geol. Inter., Xlle Sess., Canada, p. 835, 1914. 
