THEIR GENERAL SHAPE. 
2G5 
taverns in both continents, that several geologists of the 
School of Freyberg have given it the name of cavern-limestone 
(hohlenkalkstein). It is this rock which so often interrupts 
the course of rivers, by engulfing them into its bosom. In 
this also is formed the famous Cucva del Guacharo, and 
the other grottoes of the valley of Caripe. The inuriati- 
ferous gypsum, * whether it be found in layers in the Jura 
or Alpine limestone, or whether it separate these two forma- 
tions, or lie between the Alpine limestone and argillaceous 
sandstone, also presents, on account of its great solubility, 
enormous cavities, sometimes communicating with each 
other at several leagues distance. After the limestone and 
gypseous formations, there would remain to be examined, 
among the secondary rocks, a third formation, that of the ar- 
gillaceous sandstone, newer than the brine-spring formations ; 
but this rock, composed of small grains of quartz cemented 
!\v clay, seldom contains caverns ; and when it does, they are 
not extensive. Progressively narrowing towards their ex- 
tremity, their walls are covered with a brown ochre. 
IV c have just seen, that the form of grottoes depends 
partly on the nature of the rocks in which they are found ; 
but this form, modified by exterior agents, often varies 
even in the same formation. The configuration of caverns, 
i:ke the outline of mountains, the sinuosity of valleys, and 
so many other phenomena, present at first sight only 'irregu- 
larity and confusion. The appearance of order is resumed, 
when we can extend our observations over a vast space 
of ground, which has undergone violent, but periodical and 
uniform revolutions. F rom what I have seen in the moun- 
tains of Europe, and in the Cordilleras of America, caverns 
may be divided, according to their interior structure, into 
three classes. Some have the form of large clefts or cre- 
vices, like veins not filled with ore ; such as the cavern 
ol Kosenmiiller, in Franconia, Eldeu-hole, in the peak of 
Derbyshire, and the Sumideros of Chamaeasapa in IVlcxico. 
Other caverns are open to the light at both ends. These 
are rocks really pierced ; natural galleries, which run 
through a solitary mountain: such are the Hohleberg of 
Uuggendorf, and the famous cavern called Dantoe by the 
* Gypsum of Bottendorf, sa/i/olienyyjit. 
