208 
STALACTITES AKD INCRUSTATIONS. 
tlie Andes. It is by connecting in the mind the primitive, 
secondary, and volcanic rocks, and distinguishing between 
the oxidated crust of the globe, and the interior nucleus, 
composed perhaps of metallic and inflammable substances, 
that we may account for the existence of grottoes every- 
where. They act in the economy of nature as vast reser- 
voirs of water and of elastic fluids. 
The gypseous caverns glitter with crystallized selenites. 
Vitreous crystallized plates of brown and yellow stand out 
on a striated ground composed of layers of alabaster and fetid 
limestone. The calcareous grottoes have a more uniform 
tint. They are more beautiful, and richer in stalactites, in 
proportion as they are narrower, and the circulation of air 
is less free. By being spacious, and accessible to ah’, the 
cavern of C'aripe is almost destitute of those incrustations, 
the imitative forms of which are in other countries objects 
of popular curiosity. I also sought in vain for subterranean 
plants, those cryptogamia of the family of the Usneaceee, 
which we sometimes iind fixed on the stalactites, like ivy on 
walls, when we penetrate for the first time into a lateral 
grotto.* 
The caverns in mountains of gypsum often contain me- 
phitic emanations and deleterious gases. It is not the sul- 
phate of lime that acts on the atmospheric air, but the 
clay slightly mixed with carbon, and the fetid limestone, 
so often mingled with the gypsum. We cannot yet de- 
cide, whether the swinestone acts as a hydrosulphuret, or 
by means of a bituminous principle. t Its property of ab- 
sorbing oxygen gas is known to all the miners of Thuringia. 
It is the same as the action of the carlnu-etted clay of the 
• Lichen t.ophicola was discovered when the beautiful cavern of Rosen- 
miiller in Franconia was first opened. The cavity containing the lichen 
was found dosed on all sides by enormous masses of stalactite. 
t That description of fetid limestone called hy the German minera- 
logists utinkstein is always of a blackish brown colour. It is only by 
decomposition that it becomes white, after having acted on the surround- 
ing air. T lie stinkstein which is of secondary formation, must not be 
confounded with a very white primitive granular limestone of the island 
uf ihasos, which emits, when scraped, a smell of sulphuretted hydrogen. 
This marble is coarser grained than Carrara (Mannor lunense). It was 
frequently employed hy the Grecian sculptors, and I often picked up 
fragments of it at the Villa Adriari, near Rome. 
