GROTTO

GROTTO, a large deep cavern or den in a mountain or rock.

Of these there are several remarkable ones in different parts of the world †. The most celebrated one of our own country, is that called Oakley-hole, on the south side of Mendip hills. Its length is about two hundred yards, and its height various; being in some places very low, and in others eight fathoms.

GROTTO is also used for a small artificial edifice made in a garden, in imitation of a natural grotto.

The outskirts of these grottos are usually adorned with rustic architecture, and their inside with shell-work, coral, &c. and also furnished with various fountains and other ornaments.

GROTTO del Cani, a little cavern near Pozzuoli, four leagues from Naples, the steams whereof are of a mephitical or noxious quality; whence also it is called bocca venenosa, the poisonous mouth.

“Two miles from Naples, says Dr Mead, just by the Lago de Agnano, is a celebrated mofeta, commonly called la Grotta del Cani, equally destructive to all within the reach of its vapours.

“It is a small grotto about eight feet high, twelve long, and six broad; from the ground arises a thin, subtle, warm fume, visible enough to a discerning eye, which does not spring up in little parcels here and there, but in one continued stream, covering the whole surface of the bottom of the cave: having this remarkable difference from common vapours, that it does not, like smoke, disperse itself into the air, but quickly after its rise falls back again, and returns to the earth, the colour of the sides of the grotto being the measure of its ascent; for so far it is of a darkish green, but higher only common earth. And as I myself found no inconvenience by standing in it, so no animal, if its head be above this mark, is the least injured. But when, as the manner is, a dog, or any other creature, is forcibly kept below it, or by reason of its smallness cannot hold its head above it, it presently loses all motion, falls down as dead or in

a swoon, the limbs convulsed and trembling, till at last no more signs of life appear, than a very weak and almost insensible beating of the head and arteries; which, if the animal be left a little longer, quickly ceases too, and then the case is irrecoverable; but if snatched out, and laid in the open air, soon comes to life again, and sooner if thrown into the adjacent lake.”

“The fumes of the grotto, the same author argues, are no real poison, but act chiefly by their gravity; else the creatures could not recover so soon; or if they did, some symptoms, as faintness, &c. would be the consequence of it. He adds, that in creatures killed therewith, when dissected, no marks of infection appear; and that the attack proceeds from a want of air, by which the circulation tends to an entire stoppage, and this so much the more, as the animal inspires a fluid of a quite different nature from the air, and so nowise fit to supply its place.

“Taking the animal out while alive, and throwing it into the neighbouring lake, it recovers. This is owing to the coldness of the water, which promotes the contraction of the fibres, and so assists the retarded circulation. The small portion of the air which remains in the vesicle, after every expiration, may be sufficient to drive out the noxious fluid. After the same manner, cold water acts in a deliquium animi: the lake of Agnano has no other virtue in it more than others.”

The steam arising in this grotto was for a long time reckoned to be of a poisonous nature, and thought to suffocate the animals which breathed it. Dr Hales imagined that it destroyed the elasticity of the air, caused the vesicles of the lungs to collapse, and thus occasioned sudden death.—It is now, however, found that this steam is nothing else than fixed air, which from time immemorial hath issued out of the earth in that place in very great quantity, the causes of which cannot yet be investigated from any of the modern discoveries concerning that species of air. It proves pernicious when breathed in too great quantity, by rarefying the blood too much; and hence the best method of recovering persons apparently killed by fixed air, is to apply a great degree of cold all over their bodies, in order to condense the blood as much as possible. This is the reason why the dogs recover when thrown into the lake Agnano, as above-mentioned. See the articles BLOOD, DAMPS, and (the Index subjoined to) MEDICINE.

GROTTO del Serpi, is a subterranean cavern near the village of Sassa, eight miles from the city of Braccano in Italy, described by Kircher thus:

“The grotto del serpi is big enough to hold two persons. It is perforated with several siltular apertures, somewhat in manner of a sieve; out of which, at the beginning of the spring season, issues a numerous brood of young snakes of divers colours, but all free from any particular poisonous quality.

“In this cave they expose their lepers, paralytics, arthritics, and elephantiac patients, quite naked; where, the warmth of the subterranean steams resolving them into a sweat, and the serpents clinging variously all around, licking and sucking them, they become so thoroughly freed of all their vitious humours, that, upon repeating the operation for some time,

Grove. time, they become perfectly restored."

This cave Kircher visited himself; and found it warm, and every way agreeable to the description given of it. He saw the holes, and heard a murmuring hissing noise in them. Though he missed seeing the serpents, it not being the season of their creeping out; yet he saw a great number of their exuviae, or sloughs, and an elm growing hard by laden with them.

The discovery of this cave, was by the cure of a leper going from Rome to some baths near this place. Losing his way, and being benighted, he happened upon this cave. Finding it very warm, he pulled off his clothes; and being weary and sleepy, had the good fortune not to feel the serpents about him till they had wrought his cure.