ave been discovered either in caves or in lacustrine
deposits; and that not a cave or true lacustrine bed is known belonging
to the age of our secondary or palaeozoic formations.

But the imperfection in the geological record mainly results from
another and more important cause than any of the foregoing; namely, from
the several formations being separated from each other by wide intervals
of time. When we see the formations tabulated in written works, or when
we follow them in nature, it is difficult to avoid believing that
they are closely consecutive. But we know, for instance, from Sir R.
Murchison's great work on Russia, what wide gaps there are in that
country between the superimposed formations; so it is in North America,
and in many other parts of the world. The most skilful geologist, if
his attention had been exclusively confined to these large territories,
would never have suspected that during the periods which were blank and
barren in his own country, great piles of sediment, charged with new and
peculiar forms of life, had elsewhere been accumulated. And if in each
separate territory, hardly any idea can be formed of the length of time
which has elapsed between the consecutive formations, we may infer that
this could nowhere be ascertained. The frequent and great changes in the
mineralogical composition of consecutive formations, generally implying
great changes in the geography of the surrounding lands, whence the
sediment has been derived, accords with the belief of vast intervals of
time having elapsed between each formation.

But we can, I think, see why the geological formations of each region
are almost invariably intermittent; that is, have not followed each
other in close sequence. Scarcely any fact struck me more when examining
many hundred miles of the South American coasts, which have been
upraised several hundred feet within the recent period, than the absence
of any recent deposits sufficiently extensive to last for even a short
geological period. Along the whole west coast, which is inhabited by a
peculiar marine fauna, tertiary beds are so scantily developed, that no
record of several successive and peculiar marine faunas will probably be
preserved to a distant age. A little reflection will explain why along
the rising coast of the western side of South America, no extensive
formations with recent or tertiary remains can anywhere be found, though
the supply of sediment must for ages have been