The waters of some springs and lakes have a petrifying, and others an incrusting quality. The former is impregnated with extremely fine silicious particles, which penetrate the pores of the substances immersed in them, and change their nature. This property is possessed by Lough Neagh. The Danube and the Pregel have also the same quality, but in a less degree. The waters which possess the incrusting property operate in a more rapid and manifest manner, by depositing the earthy particles they hold in solution, on the surfaces of bodies submitted to their action. This effect is produced by both hot and cold springs, particularly by the former. The matter deposited is usually calcareous, but in the instance of the Great Geyser it is silicious.
Waters holding salt in solution, or muriated waters, as they are commonly called, are perhaps the most common of all; but they are rarely found in a state of purity. Among the Uralian and Carpathian mountains, they are frequent, and in general in the zone comprised between the parallels fifty and thirty north latitude. More to the north they are rarely found; farther toward the south crystallized salt is abundant in certain regions, as in the great desert of Africa; but we find only a few salt springs there.
CHAPTER VIII.—CAVERNS.
THE most celebrated cave in the United States, is that in Rockingham county, Virginia, known by the name of Madison’s Cave. It is in the heart of a mountain, about two hundred feet high, which is so steep on one side, that a person standing on the top, might easily throw a pebble into the river which flows round the base; the opposite side of it is, however, very easy of ascent, and on this side the path leading to the cavern runs, excepting for the last twenty yards, when it suddenly turns along the steep part of the mountain, which is extremely rugged, and covered with immense rocks and trees from top to bottom. The mouth of the cavern, on this steep side, about two thirds of the way up, is guarded by a huge pendant stone, which seems ready to fall every instant; it is impossible to stoop under it and not reflect with a degree of awe, that, were it to drop, nothing could save you from perishing within the dreary walls of that mansion to which it affords an entrance. The description which follows, is from the Travels of Mr. Weld.
‘Preparatory to entering, the guide, whom I had procured from a neighboring house, lighted the ends of three or four splinters of pitch pine, a large bundle of which he had brought with him: they burn out very fast, but while they last are most excellent torches. The fire he brought along with him, by the means of a bit of green hickory wood, which, when once lighted, will burn slowly without any blaze, till the whole is consumed.
‘The first apartment you enter is about twenty-five feet high, and fifteen broad, and extends a considerable way to the right and left, the floor ascending toward the former; here it is very moist, from the quantity of water continually trickling from the roof. Fahrenheit’s thermometer, which stood at sixty-seven degrees in the air, fell to sixty-one degrees in this room. A few yards to the left, on the side opposite to you on entering, a passage presents itself, which leads to a sort of anti-chamber, from whence you proceed to the sound room, so named from the prodigious reverberation of the sound of a voice or musical instrument on the inside. This room is about twenty feet square; it is arched at the top, and the sides of it as well as of the apartment which you first enter, are beautifully ornamented with stalactites. Returning from hence into the anti-chamber, and afterwards taking two or three turns to the right and left, you enter a long passage about thirteen feet wide, and, perhaps, about fifteen feet in height, perpendicularly; but if it was measured from the floor to the highest part of the roof obliquely, the distance would be found much greater, as the walls on both sides slope very considerably, and finally meet at the top.
‘This passage descends very rapidly, and is, I should suppose, about sixty yards long. Towards the end it narrows considerably, and terminates in a pool of clear water, about three or four feet deep. How far this pool extends, it is impossible to say. A canoe was once brought down by a party for the purpose of examination, but they said, that after proceeding a little way the canoe would not float, and they were forced to return. Their fears most probably led them to fancy so. I fired a pistol with a ball over the water, but the report was echoed from the after part of thecavern, and not from the part beyond the water, so that I should not suppose the passage extended much farther than could be traced with the eye. The walls of this passage consist of a solid rock of limestone on each side, which appears to have been separated by some convulsion. The floor is of a deep sandy earth, and it has repeatedly been dug up for the purpose of getting salt-petre, with which the earth is strongly impregnated. The earth, after being dug up, is mixed with water, and when the grosser particles fall to the bottom, the water is drawn off and evaporated; from the residue the salt-petre is procured. There are many other caverns in this neighborhood; and also farther to the westward in Virginia; from all of them great quantities of salt-petre are thus obtained. The gunpowder made with it, in the back country forms a principal article of commerce, and is sent to Philadelphia in exchange for European manufactures.
‘About two thirds of the way down this long passage just described, is a large aperture in the wall on the right, leading to another apartment, the bottom of which is about ten feet below the floor of the passage, and it is no easy matter to get down into it, as the sides are very steep and extremely slippery. This is the largest and most beautiful room in the whole cavern; it is somewhat of an oval form, about sixty feet in length, thirty in breadth, and in some parts nearly fifty feet high. The petrifactions formed by the water dropping from above are most beautiful, and hang down from the ceiling in the form of elegant drapery, the folds of which are similar to what those of large blankets or carpets would be, if suspended by one corner in a lofty room. If struck with a stick, a deep hollow sound is produced, which echoes through the vaults of the cavern.
‘In other parts of this room the petrifactions have commenced at the bottom, and formed in pillars of different heights; some of them reach nearly to the roof. If you go to a remote part of this apartment, and leave a person with a lighted torch moving about amidst these pillars, a thousand imaginary forms present themselves, and you might almost fancy yourself in the infernal regions, with spectres and monsters on every side. The floor of this room slopes down gradually from one end to the other, and terminates in a pool of water, which appears to be on a level with that at the end of the long passage; from their situation, it is most probable that they communicate together. The thermometer which I had with me stood in the remotest part of this chamber, at fifty-five degrees. From hence we returned to the mouth of the cavern, and on coming to the light it appeared as if we had really been in the infernal regions, for our faces, hands, and clothes were covered with soot from the smoke of the pine torches which are so often carried in. The smoke from the pitch-pine is particularly thick and heavy. Before this cave was much visited, and the walls blackened with smoke, its beauty, I was told by some of the old inhabitants, was great indeed; for the petrifactions on the roof and walls are all of a dead white kind.’