in North America. From data, which may found a tolerable conjecture, we suppose the highest peak to be about four thousand feet perpendicular, which is not a fifth part of the height of the mountains of South America, nor one-third of the height which would be necessary in our latitude to preserve ice in the open air unmelted through the year. The ridge of mountains next beyond the Blue Ridge, called by us the North mountain, is of the greatest extent; for which reason they were named by the Indians the endless mountains. A substance supposed to be Pumice, found floating on the Mississippi, has induced a conjecture that there is a volcano on some of its waters; and as these are mostly known to their sources, except the Missouri, our expectations of verifying the conjecture would of course be led to the mountains which divide. the waters of the Mexican Gulf from those of the South Sea ; but no volcano having ever yet been known at such a distance from the sea, we must rather suppose that this floating substance has been erroneously deemed Pumice. QUERY V. Its Cascades and Caverns? The only remarkable cascade in this country is that of the Falling Spring in Augusta. It is a water of James' river where it is called Jackson's river, rising in the warm spring mountains, about twenty miles south west of the warm spring, and flowing into that valley. About three-quarters of a mile from its source it falls over a rock two hundred feet into the valley below. The sheet of water is broken in its breadth by the rock, in two or three places, but not at all in its height. Between the sheet and across dry. This cata the rock, at the bottom, you may walk ract will bear no comparison with that of Niagara as to the quantity of water composing it; the sheet being only twelve or fifteen feet wide above and somewhat more spread below; but it is half as high again, the latter being only one hundred and fifty-six feet, according to the mensuration made by order of M. Vaudreuil, Governor of Canada, and one hundred and thirty according to a more recent account. In the lime-stone country there are many caverns of very considerable extent. The most noted is called Madison's Cave, and is on the north side of the Blue Ridge, near the intersection of the Rockingham and Augusta line with the south fork of the southern river of Shenandoah. It is in a hill of about two hundred feet perpendicular height, the ascent of which, on one side, is so steep that you may pitch a biscuit from its summit into the river which washes its base. The entrance of the cave is, in this side, about two-thirds of the way up. It extends into the earth about three hundred feet, branching into subordinate caverns, sometimes ascending a little, but more generally descending, and at length terminates, An eye draught of Madison's cave on a scale of 67 feet to the inch. The arrows show where it descends or ascends. in two different places, at basons of water of unknown extent, and which I should judge to be nearly on a level with the water of the river; however, I do not think they are formed by refluent water from that, because they are never turbid; because they do not rise and fall in correspondence with that in times of flood or of drought; and because the water is always cool. It is probably one of the many reservoirs with which the interior parts of the earth are supposed to abound, and yield supplies to the fountains of water, distinguished from others only by being accessible. The vault of this cave is of solid lime-stone, from twenty to forty or fifty feet high; through which water is continually percolating. This, trickling down the sides of the cave, has incrusted them over in the form of elegant drapery; and dripping from the top of the vault generates on that and on the base below, stalactites of a conical form, some of which have met and formed massive columns. Another of these caves is near the north mountain, in the county of Frederic, on the lands of Mr. Zane. The entrance into this is on the top of an extensive ridge. You descend thirty or forty feet, as into a well, from whence the cave extends, nearly horizontally, four hundred feet into the earth, preserving a breadth of from twenty to fifty feet, and a height of from five to twelve feet. After entering this cave a few feet, the mercury, which in the open air was 50°, rose to 57° of Fahrenheit's thermometer, answering to 11° of Reaumur's, and it continued at that to the remotest parts of the cave. The uniform temperature of the cellars of the observatory of Paris, which are ninety feet deep, and of all subterraneous cavities of any depth, where no chemical agencies may be supposed to produce a factitious heat, has been found to be 10° of Reaumur, equal to 54° of Fahrenheit. The temperature of the cave above mentioned so nearly corresponds with this, that the difference may be ascribed to a difference of instruments. At the Panther gap, in the ridge which divides the waters of the Crow and the Calf pasture, is what is called the Blowing Cave. It is in the side of a hill, is of about one hundred feet diameter, and emits constantly a current of air of such force as to keep the weeds prostrate to the distance of twenty yards before it. This current is strongest in dry, frosty weather, and in long spells of rain weakest. Regular inspirations and expirations of air, by caverns and fissures, have been probably enough accounted for by supposing them combined with intermitting fountains; as they must of course inhale air while their reservoirs are emptying themselves, and again emit it while they are filling. But a constant issue of air, only varying in its force as the weather is drier or damper, will require a new hypothesis. There is another blowing cave in the Cumberland mountain, about a mile from where it crosses the Carolina line. All we know of this is, that it is not constant, and that a fountain of water issues from it. The Natural Bridge, the most sublime of nature's works, though not comprehended under the present head, must not be pretermitted. It is on the ascent of a hill, which seems to have ⚫ been cloven through its length by some great convulsion. The fissure, just at the bridge, is, by some admeasurements, two hundred and seventy feet deep, by others only two hundred and five. It is about forty-five feet wide at the bottom and ninety feet at the top; this of course determines the length of the bridge, and its height from the water. Its breadth in the middle is about sixty feet, but more at the ends, and the thickness of the mass, at the summit of the arch, about forty feet. A part of this thickness is constituted by a coat of earth, which gives growth to many large trees, The residue, with the hill on both sides, is one solid rock of lime-stone. The arch approaches the semi-elliptical form; but the larger axis of the ellipsis, which would be the cord of the arch, is many times longer than the transverse. Though the sides of this bridge are provided in some parts with a parapet of fixed rocks, yet few men have resolution to walk to them, and look over into the abyss. You involuntarily fall on your hands and feet, creep to the parapet, and peep over it. Looking down from this height about a minute, gave me a violent head-ache. If the view from the top be painful and intolerable, that from below is delightful in an equal extreme. It is impossible for the emotions arising from the sublime to be felt beyond what they are here; so beautiful an arch, so elevated, so light, and springing as it were up to heaven! the rapture of the spectator is really indescribable! The fissure continuing narrow, deep, and straight, for a considerable distance above and below the bridge, opens a short but very pleasing view of the North mountain on one side and the Blue Ridge on the other, at the distance each of them of about five miles. This bridge is in the county of Rockbridge, to which it has given name, and affords a public and commodious passage over a valley which cannot be crossed elsewhere for a considerable disThe stream passing under it is called Cedar-creek. It is a water of James' river, and sufficient in the driest seasons to turn a grist-mill, though its fountain is not more than two miles above.* tance. QUERY VI. A notice of the mines and other subterraneous riches; its trees, plants, fruits, &c. I knew a single instance of gold found in this State. It was interspersed in small specks through a lump of ore of about four * Don Ulloa mentions a break, similar to this, in the province of Angaraez, in South America. It is from sixteen to twenty-two feet wide, one hundred and eleven feet deep, and of 1.3 miles continuance, English measure. Its breadth at top is not sensibly greater than at bottom. But the following fact is remarkable, and will furnish some light for conjecturing the probable origin of our natural bridge. "Esta caxa, ó cauce está cortada en péna viva con tanta precision, que las desigualdades del un lado entrantes, corresponden á las del otro lado salientes, como si aquella altura se hubiese abierto expresamente, con sus bueltas y tortuosidades, para darle transito á los aguas por entre los dos morallones que la forman; siendo tal su igualdad, que si llegasen á juntarse se endentarian uno con otro sin dextar hueco." Not. Amer. ii. § 10. Don Ulloa inclines to the opinion that this channel has been effected by the wearing of the water which runs through it, rather than that the mountain should have been broken open by any convulsion of nature. But if it had been worn by the running of water, would not the rocks which form the sides, have been worn plain? or if, meeting in some parts with veins of harder stone, the water had left prominences on the one side, would not the same cause have sometimes, or perhaps generally, occasioned prominences on the other side also? Yet Don Ulloa tells us, that on the other side there are always corresponding cavities, and that these tally with the prominences so perfectly, that, were the two sides to come together they would fit in all their indentures, without leaving any void. I think that this does not resemble the effect of running water, but looks rather as if the two sides had parted asunder. The sides of the break, over which is the natural bridge of Virginia, consisting of a veiny rock which yields to time, the correspondence between the salient and re-entering inequalities, if it existed at all, has now disappeared. This break has the advantage of the one described by Don Ulloa in its finest circumstance; no portion in that instance having held together, during the separation of the other parts, so as to form a bridge over the abyss. |