or GROTTA, a large deep cavern or den in a mountain or rock. The word is Italian, grotta, formed, according to Menage, &c. from the Latin crypto. Du Cange observes, that grotta was used in the same sense in the corrupt Latin.
The ancient anchorites retired into dens and grottoes, to apply themselves the more attentively to meditation.
Okey-hole, Elden-hole, Peak's-hole, and Pool's-hole, are famous among the natural caverns or grottoes of our country.
The entrance to Okey-hole, on the south side of Mendip-hills, is in the fall of those hills, which is betel all about with rocks, and has near it a precipitate descent of near twelve fathoms deep, at the bottom of which there continually issues from the rocks a considerable current of water. The naked rocks above the entrance show themselves about 30 fathoms high, and the whole ascent of the hill above is about a mile, and is very steep. As you pass into this vault, you go at first upon a level, but advancing farther, the way is found to be rocky and uneven, sometimes ascending and sometimes descending. The roof of this cavern, in the highest parts, is about eight fathoms from the ground, but in many particular places it is so low, that a man must stoop to get along. The breadth is not less various than the height, for in some places it is five or six fathoms wide, and in others not more than one or two. It extends itself in length about two hundred yards. People talk much of certain stones in it, resembling men and women, and other things; but there is little matter of curiosity in these, being only shapeless lumps of a common spar. At the farthest part of the cavern there is a good stream of water, large enough to drive a mill, which passes all along one side of the cavern, and at length slides down about six or eight fathoms among the rocks, and then preluding through the clefts of them, discharges itself into the valley. The river within the cavern is well stored with eels, and has some trouts in it; and these cannot have come from without, there being so great a fall near the entrance. In dry summers, a great number of frogs are seen all along this cavern, even to the farther part of it; and on the roof of it, at certain places, hang vast numbers of bats, as they do in almost all caverns, the entrance of which is either level, or but slightly ascending or descending; and even in the more perpendicular ones they are sometimes found, provided they are not too narrow, and are sufficiently high. The cattle that feed in the pastures through which this river runs, have been known to die suddenly sometimes after a flood; this is probably owing to the waters having been impregnated, either naturally or accidentally, with lead ore.
Elden-hole is a huge profound perpendicular chasm, three miles from Buxton, ranked among the natural wonders of the Peak. Its depth is unknown, and is pretended to be unfathomable. Cotton tells us he founded 884 yards; yet the plummet still drew. But he might easily be deceived, unless his plummet was very heavy; the weight of a rope of that length might well make the landing of the plummet scarce perceivable.
Peak's-hole and Pool's-hole are two very remarkable horizontal caverns under mountains; the one is situated near Castleton, and the other is just by Buxton. They seem to have owed their origin to the springs which have their current through them; when the water had forced its way through the horizontal fissures of the strata, and had carried the loose earth away with it, the loose stones must fall down of course: and where the strata had few or no fissures, they remained entire; and so formed these very irregular arches, which are now so much wondered at. The water which passes through Pool's-hole is impregnated with particles of limestone, and has incrusted the whole cavern in such a manner that it appears as one solid rock.
In grottoes are frequently found crystals of the rock, stalactites, and other natural conglaciations, and those often of an amazing beauty. M. Homburg conjectures, from several circumstances, that the marble pillars in the grotto of Antiparos vegetate or grow. That author looks on this grotto as a garden, whereof the pieces of marble are the plants; and encourages to shew, that they could only be produced by some vegetative principle. See ANTIPAROS.
At Foligno in Italy is another grotto, consisting of pillars and orders of architecture of marble, with their ornaments, &c. scarcely inferior to those of art; but they all grow downwards: so that if this too be a garden, the plants are turned upside down.
Grotto del Cani, a little cavern near Pozzuoli, four leagues from Naples, the air of which is of a mephitical or noxious quality; whence also it is called bocca velenosa, the poisonous mouth.
"Two miles from Naples (says Dr Mead), just by the Lago de Agnano, is a celebrated mofeta, commonly called la Grotto del Cani, and equally destructive to all within the reach of its vapours. It is a small grotto about eight feet high, twelve long, and fix 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 diffuse 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, 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 convoluted and trembling; till at last no more signs of life appear than a very weak and almost insensible beating of the heart and arteries; which, if the animal be left a little longer, quickly ceases too, and then the case is irrecoverable; but if it be snatched out, and laid in the open air, it 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 in no respect fit to supply its place. Taking the animal out, while yet 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 affords the retarded circulation; the small portion of air which remains in the vesicles, 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 greater virtue in it than others."
The air 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 air is nothing else than fixed air, or carbonic acid gas, which issues from the earth in that place in great quantity.
GROTTO del Serpi, is a subterraneous cavern near the village of Safia, eight miles from the city of Bracciano in Italy, described by Kircher thus: "The grotto del serpi is big enough to hold two persons. It is perforated with several fissural 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 subterraneous 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 vicious humours, that, upon repeating the operation for some 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 feeding 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 Museum leper going from Rome to some baths near this place, Worm. Loosing 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.
Milky Grotto, Crypta Laetea, a mile distant from the ancient village of Bethlehem, is said to have been thus denominated on occasion of the blessed Virgin, who let fall some drops of milk in giving suck to Jesus in this grotto. And hence it has been commonly supposed, that the earth of this cavern has the virtue of restoring milk to women that are grown dry, and even of curing fevers. Accordingly, they are always digging in it, and the earth is sold at a good rate to such as have faith enough to give credit to the fable. An altar has been built on the place, and a church just by it.
is also used for a little artificial edifice made in a garden, in imitation of a natural grotto. The outsides of these grottoes are usually adorned with rustic architecture, and their inside with shell-work, fossils, &c. finished likewise with jets d'eau or fountains, &c.
A cement for artificial grottoes may be made thus: Take two parts of white rosin, melt it clear, and add to it four parts of bees wax: when melted together, add two or three parts of the powder of the stone you design to cement, or so much as will give the cement the colour of the stone: to this add one part of flower of sulphur: incorporate all together over a gentle fire, and afterwards knead them with your hands in warm water. With this cement the stones shells, &c. after being well dried before the fire, may be cemented.
Artificial red coral branches, for the embellishment of grottoes, may be made in the following manner: Take clear rosin, dissolve it in a brafs-pan; to every ounce of which add two drams of the finest vermilion: when you have stirred them well together, and have chosen your twigs and branches, peeled and dried, take a pencil and paint the branches all over whilst the composition is warm; afterwards shape them in imitation of natural coral. This done, hold the branches over a gentle coal fire, till all is smooth and even as if polished. In the same manner white coral may be prepared with white lead, and black coral with lampblack.
A grotto may be built with little expense, of glass, cinders, pebbles, pieces of large flint, shells, mofs, stones, counterfeit coral, pieces of chalk, &c. all bound or cemented together with the above-described cement.