Geological Results of the Earth's Contraction. 183 
greatly denuded, and has almost wholly lost the wave-like features, 
which are so distinct in the stratified beds of rock. | 
The principal peculiarity of these plications to which we would 
now ask attention, is the following ;—ihe greater abruptness of 
the northwestern slope of each fold, in connection with the dimi- 
nution of the undulations to the northwestward: and it will be 
our endeavor to show that this peculiarity, and the irregularities 
which exist, are necessary results of the action of a force laterally 
everted.* 
This point may hardly require a formal demonstration ; yet as 
other explanations have been offered, we propose to present it in 
etail. I 
brief detail. In the following figure the folds are represented 
for convenience of illustration, angular at summit. 
Fig. 7. 
DOnd Aye ae 
BEX [A ee ee - 
an C D EE F Gh ad x 
_Let AX represent a bed of stratified clay and sand, in alterna- 
ting layers, say a thousand feet thick and many miles long; the 
material either not at all indurated or imperfectly so. 
Suppose the force to be exerted from the left against A, in a 
ction varying very little from horizontality. 
_ Resistance to this force will proceed from gravity, each vertical 
square yard pressing with a weight in the case supposed, of one 
ed from the propelling force or thrust o poring rea of molten material beneat 
43 pee > 
operating force, as determined by the greater dislocations to the southeast, t y 
say (p. 517), “ the progressive rise of the whole belt towards the side which an- 
ciently lay near the shore of the Appalachian ocean, accords entirely with the be- 
lief that ander the now rent and dislocated margin of the chain there was av 
Prof. W. W. Mather, in his remarks on the secular agin ao the earth, 
(this Journal, xlix, 284,) accounts for the foldings and for the steeper northwest 
on the ground of “a paroxysmal elevation and the action of inertia, this 
Paroxysmal elevation, as he urges, arising from a change in the rapidity of the 
Poly 8 rotation consequent on an abrupt change of capes anally Nee 
. sy : : “ y : any time ome mo 
praauiita a ) He says, p. 299 clinapcgechonge x y tin Te a dale Sessa 
reference to the steeper northwest slopes, (p- 
oF a mountain mass one mile in height; it W 
this increased distance would be 3:1415+24 miles, or feet greater per hour 
than that which it had before its elevation. Inertia therefore would cause the 
mass at the top to press to the westward with a force pr oned to its 
the above mentioned velocity.” 
