in the recesses of caves, or of animals
which have been carried in for prey, may be drifted along, and mixed up
with mud, sand, and fragments of rocks, so as to form osseous breccias.

In 1833 I had an opportunity of examining the celebrated caves of
Franconia, and among others that of Rabenstein, newly discovered. Their
general form, and the nature and arrangement of their contents, appeared
to me to agree perfectly with the notion of their having once served as
the channels of subterranean rivers. This mode of accounting for the
introduction of transported matter into the Franconian and other caves,
filled up as they often are even to their roofs with osseous breccia,
was long ago proposed by M. C. Prevost,[1047] and seems at length to be
very generally adopted. But I do not doubt that bears inhabited some of
the German caves, or that the cavern of Kirkdale, in Yorkshire, was once
the den of hyaenas. The abundance of bony dung, associated with hyaenas'
bones, has been pointed out by Dr. Buckland, and with reason, as
confirmatory of this opinion.

The same author observed in every cave examined by him in Germany, that
deposits of mud and sand, with or without rolled pebbles and angular
fragments of rock, were covered over with a _single_ crust of
stalagmite.[1048] In the English caves he remarked a similar absence of
_alterations_ of alluvium and stalagmite. But Dr. Schmerling has
discovered in a cavern at Chockier, about two leagues from Liege, three
distinct beds of stalagmite, and between each of them a mass of breccia,
and mud mixed with quartz pebbles, and in the three deposits the bones
of extinct quadrupeds.[1049]

This exception does not invalidate the generality of the phenomenon
pointed out by Dr. Buckland, one cause of which may perhaps be this,
that if several floods pass at different intervals of time through a
subterranean passage, the last, if it has power to drift along fragments
of rock, will also tear up any alternating stalagmitic and alluvial beds
that may have been previously formed. Another cause may be, that a
particular line of caverns will rarely be so situated, in relation to
the lowest levels of a country, as to become, at two distinct epochs,
the receptacle of engulfed rivers; and if this should happen, some of
the caves, or at least the tunnels of communication, may at the first
period be entirely choked up with transported matter, so as not to allow
the subsequent passage of water in th