It Is Not The Sulphate 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 decide, whether the swinestone acts as a

Hydrosulphuret, or by means of a bituminous principle.* (* That description of fetid limestone called by the German mineralogists stinkstein is always of a blackish brown colour. It is only by decomposition that it becomes white, after having acted on the surrounding air. The stinkstein which is of secondary formation, must not be confounded with a very white primitive granular limestone of the island of Thasos, which emits, when scraped, a smell of sulphuretted hydrogen. This marble is coarser grained than Carrara (Marmor lunense). It was frequently employed by the Grecian sculptors, and I often picked up fragments of it at the Villa Adriani, near Rome.) Its property of absorbing oxygen gas is known to all the miners of Thuringia. It is the same as the action of the carburetted clay of the gypseous grottoes, and of the great chambers (sinkwerke) dug in mines of fossil salt which are worked by the introduction of fresh water. The caverns of calcareous mountains are not exposed to those decompositions of the atmospheric air, unless they contain bones of quadrupeds, or the mould mixed with animal gluten and phosphate of lime, from which arise inflammable and fetid gases.

Though we made many enquiries among the inhabitants of Caripe, Cumanacoa, and Cariaco, we did not learn that they had ever discovered in the cavern of Guacharo either the remains of carnivorous animals, or those bony breccias of herbivorous animals, which are found in the caverns of Germany and Hungary, and in the clefts of the calcareous rocks of Gibraltar. The fossil bones of the megatherium, of the elephant, and of the mastodon, which travellers have brought from South America, have all been found in the light soil of the valleys and table-lands. Excepting the megalonyx,* a kind of sloth of the size of an ox, described by Mr. Jefferson, I know not a single instance of the skeleton of an animal buried in a cavern of the New World. (* The megalonyx was found in the caverns of Green Briar, in Virginia, at the distance of 1500 leagues from the megatherium, which resembles it very much, and is of the size of the rhinoceros.) The extreme scarcity of this geological phenomenon will appear the less surprising to us, if we recollect, that in France, England, and Italy, there are also a great number of grottoes in which we have never met with any vestige of fossil bones.

Although, in primitive nature, whatever relates to ideas of extent and mass is of no great importance, yet I may observe, that the cavern of Caripe is one of the most spacious known to exist in limestone formations. It is at least 900 metres or 2800 feet in length.* (* The famous Baumannshohle in the Hartz, according to Messrs.

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