This accounts for the very scanty traces to be found in America of
the secondary deposits; for the Permian, Triassic, and Jurassic beds,
instead of being raised to form successive shores, along which their
deposits could be accumulated in regular sequence, as had been the case
with the Azoic, Silurian, and Devonian deposits in the northern part of
the United States, were constantly sinking, so that the Triassic settled
above the Permian, the Jurassic above the Triassic, and so on, each set
of strata thus covering over and concealing the preceding one. Though we
find the stratified rocks of these periods cropping out here and there,
where some violent disturbance or the abrading action of water has
torn asunder or worn away the overlying strata, yet we never find
them consecutively over any extensive region; and it is not till the
Cretaceous and earlier Tertiary periods that we find again a regular
succession of deposits around the shores of the continent, marking its
present outlines. It is, then, in Europe, where the sequence of their
beds is most complete, that we must seek to decipher the history of the
middle geological ages; and therefore, when I meet my readers again,
it will be in the Old World of civilization, though more recent in its
physical features than the one we leave.
Pages:
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264