| 
. 
OF THE MORE DISTURBED ZONES OF THE EARTH’S CRUST. 443 
usually, though not always, by some sudden difference of dip, that we are en- 
abled to detect the presence and the magnitude of the dislocation. 
It seems also necessary, on this occasion, to explain the effects of those great 
longitudinal obliquely-dipping faults, when they occur directly in the anticlinal and 
synclinal axis planes, which are their occasional positions. The same forward 
upward-sliding, just described as having occurred where the fracture is between 
the anticlinal and synclinal curves, must have taken place where it has coincided 
with these, and as the movement must necessarily have been in the same direc- 
tion, lifting, that is to say, the lower strata cut by the fault, upon the edges of 
higher and higher beds, in the forward propulsion of the Fig. 2. 
flat side of the broken wave, we have no difficulty in un- 
derstanding how fractures in these positions, as well as 
in the other already spoken of, must have given rise to 
that very common phenomenon of the dipping of newer 
formations under older ones in plicated and dislocated 
countries, like the Alps and Appalachians. This puzzling 
feature of stratification, long an enigma to geologists, can, 
I conceive, be explained upon no other analysis than that 
which is here given, namely, the oblique folding of undu- 
lated strata,—the obliquity of the planes of the faults, . |... Pilla: (eerste 
either coincident with, or parallel to, obliquely dipping axis Ractioh atoning: Raehpland of frac- 
planes,—and the forward upward thrust of the uninverted driven forward upon the inverted. 
upon the inverted broken strata, through a tremendous tangential force incident to 
a wave motion. 
EXEMPLIFICATION OF THE LAWS OF FLEXURE, BY THE PHENOMENA OF SOME OF THE 
UNDULATED ZONES OF EUROPE. 
Belgium and the Rhenish Provinces—Embracing in one view the undulated 
districts of Southern Belgium, the Rhenish Provinces, the Westphalian coal-field, 
the Ardennes, the Hundsruck, Taurus, and Hartz ranges, as described and mapped 
_ by M. Dumont and other geologists, we can discern most distinctly all the phe- 
Tlomena of flexure and of dislocation of the strata, here indicated as charac- 
teristic of the structure of the Appalachians. We there perceive a wide zone of 
crust undulations having its strata most invaded by igneous rocks, and most 
ruptured and metamorphosed, along its south-eastern side, and displaying its 
most ancient sedimentary formations in a state of close plication, with innu- 
merable inversions of the dip, imparting to wide tracts one uniform parallel incli- 
nation towards the south-east. Crossing the zone north-westward, we enter 
newer and newer strata, until we come to the undulated coal-field of Westphalia 
or Belgium, our traverse taking us from the non-fossiliferous formations, at the 
very base of the Paleeozoic system. In whatever meridian we make our section, 
VOL. XXI. PART II. 6D 
