without proof. In the chapter which treats of
river-deltas and the dispersion of sediment by currents, and in the
description of reefs of coral now growing over areas many hundred miles
in length, I shall have opportunities of convincing the reader of the
danger of hasty generalizations on this head.

In regard to the imagined universality of particular rocks of ancient
date, it was almost unavoidable that this notion, when once embraced,
should be perpetuated; for the same kinds of rock have occasionally been
reproduced at successive epochs; and when once the agreement or
disagreement in mineral character alone was relied on as the test of
age, it followed that similar rocks, if found even at the antipodes,
were referred to the same era, until the contrary could be shown.

Now it is usually impossible to combat such an assumption on geological
grounds, so long as we are imperfectly acquainted with the order of
superposition and the organic remains of these same formations. Thus,
for example, a group of red marl and red sandstone, containing salt and
gypsum, being interposed in England between the Lias and the Coal, all
other red marls and sandstones, associated some of them with salt, and
others with gypsum, and occurring not only in different parts of Europe,
but in North America, Peru, India, the salt deserts of Asia, those of
Africa--in a word, in every quarter of the globe, were referred to one
and the same period. The burden of proof was not supposed to rest with
those who insisted on the identity in age of all these groups--their
identity in mineral composition was thought sufficient. It was in vain
to urge as an objection the improbability of the hypothesis which
implies that all the moving waters on the globe were once simultaneously
charged with sediment of a red color.

But the rashness of pretending to identify, in age, all the red
sandstones and marls in question, has at length been sufficiently
exposed, by the discovery that, even in Europe, they belong decidedly to
many different epochs. It is already ascertained, that the red sandstone
and red marl containing the rock-salt of Cardona in Catalonia is newer
than the Oolitic, if not more modern than the Cretaceous period. It is
also known that certain red marls and variegated sandstones in Auvergne
which are undistinguishable in mineral composition from the New Red
Sandstone of English geologists, belong, nevertheless, to the Eocene
period; and, lastly, t