regions, to have an opportunity of gratifying their
curiosity by obtaining a sight not only of the superficial strata of
remote eras, but also of the contemporaneous nether-formed rocks. Having
recognized, therefore, in such mountain-chains some ancient rocks of
aqueous and volcanic origin, corresponding in character to superficial
formations of modern date, they will regard any other class of ancient
rocks, such as granite and gneiss, as the _residual phenomena_ of which
they are in search. These latter rocks will not answer the expectations
previously formed of their probable nature and texture, unless they wear
a foreign and mysterious aspect, and have in some places been fused or
altered by subterranean heat; in a word, unless they differ wholly from
the fossiliferous strata deposited at the surface, or from the lava and
scoriae thrown out by volcanoes in the open air. It is the total
distinctness, therefore, of crystalline formations, such as granite,
hornblende-schist, and the rest, from every substance of which the
origin is familiar to us, that constitutes their claim to be regarded as
the effects of causes now in action in the subterranean regions. They
belong not to an order of things which has passed away; they are not the
monuments of a primeval period, bearing inscribed upon them in obsolete
characters the words and phrases of a dead language; but they teach us
that part of the living language of nature, which we cannot learn by our
daily intercourse with what passes on the habitable surface.

CHAPTER XIII.

UNIFORMITY IN THE SERIES OF PAST CHANGES IN THE ANIMATE AND INANIMATE
WORLD.

Supposed alternate periods of repose and disorder--Observed facts in
which this doctrine has originated--These may be explained by
supposing a uniform and uninterrupted series of changes--Threefold
consideration of this subject; first, in reference to the living
creation, extinction of species, and origin of new animals and
plants; secondly, in reference to the changes produced in the
earth's crust by the continuance of subterranean movements in
certain areas, and their transference after long periods to new
areas; thirdly, in reference to the laws which govern the formation
of fossiliferous strata, and the shifting of the areas of
sedimentary deposition--On the combined influence of all these modes
and causes of change in producing breaks and chasms in the chain of