Notes on the State of Virginia (1853)/Query 05
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 20 miles Southwest of the Warm Spring, and flowing from that valley. About three quarters of a mile from its source, it falls over a rock 200 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 rock at the bottom you may walk across dry. This cataract will bear no comparison with that of Niagara, as to the quantity of water composing it; the sheet being only 12 or 15 feet wide above, and somewhat more spread below; but it is half as high again, the latter being only 156 feet, according to the mensuration made by order of M. Vaudreuil, Governor of Canada, and 130 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 200 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 300 feet, branching into subordinate caverns, sometimes ascending a little, but more generally descending, and at length terminates 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 which yield supplies to the fountains of water, distinguished from others only by its being accessible. The vault of this cave is of solid lime stone, from 20 to 40 or 50 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 Frederick, on the lands of Mr. Zane. The entrance into this is on the top of an extensive ridge. You descend 30 or 40 feet, as into a well, from whence the cave then extends, nearly horizontally, 400 feet into the earth, preserving a breadth of from 20 to 50 feet, and a height of from 5 to 12 feet. After entering this cave a few feet, the mercury, which in the open air was at 50°, rose to 57° of Farenheit'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 90 feet deep, and of all subterranean cavities of any depth, where no chymical agents may be supposed to produce a factitious heat, has been found to be 10° of Reaumur, equal to 54½° of Farenheit. 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 Cow and the Calf Pasture, is what is called the Blowing Cave. It is in the side of a hill, is of about 100 feet diameter, and emits constantly a current of air of such force, as to keep the weeds prostrate to the distance of 20 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 reserviors 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 dryer 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, 270 feet deep, by others only 205. It is about 45 feet wide at the bottom, and 90 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 60 feet, but more at the ends, and the thickness of the mass at the summit of the arch about 40 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 semi-axis which gives its height. 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 headache. This painful sensation is relieved by a short but pleasing view of the Blue Ridge along the fissure downwards, and upwards by that of the short hills, which, with the Purgatory Mountain, is a divergence from the North Ridge; and descending then to the valley below, the sensation becomes delightful in the 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 continues deep and narrow, and following the margin of the stream upwards, about three-eighths of a mile, you arrive at a lime stone cavern, less remarkable however for height and extent than those before described. Its entrance into the hill is but a few feet above the bed of the stream. 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 distance. The stream passing under it is called Cedar Creek. It is a water of James River, and sufficient in the dryest seasons to turn a grist mill, though its fountain is not more than two miles above.
[Note.—This description was written after a lapse of several years from the time of my visit to the bridge, and under an error of recollection which requires apology, for it is from the bridge itself that the mountains are visible both ways, and not from the bottom of the fissure, as my impression then was. The statement therefore in the former editions needs the corrections here given to it.August 16, 1817.]
- See Map No. 1, App. iv.
- Bouguer mentions a cascade of two or three hundred toises height of the Bogota, a considerable river passing by Santa Fé. The cataract is vertical, and is about 15 or 16 leagues below Santa Fé.—Bouguer, xci. Buffon mentions one of 300 feet at Terni, in Italy. 1. Epoques, 470.
- See Map No. 2, App. iv.
- See Musschenbroek, § 2,604.
- Don Ulloa mentions a break similar to this in the province of Angaraez, in South
America. It is from 16 to 22 feet wide, 111 feet deep, and of 1.3 miles continuance,
English measures. 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
murallones que la forman; siendo tal su igualdad, que si llegasen á juntarse se
endentarían uno con otro sin dexar 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 plane? 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.
Another is mentioned by Clavigero: “Il ponte di dio. Cosi chiamano un vasto volume di terra traversato sul profondo fiume Atoyaque presso al villaggio Moleaxac, cento miglia in circa da Messico verso Scirocco, sopra il quale passano comodamente icarri e le carrozze. Si puo credere, che sia stato un frammento della vicina montagna, da qualche antico tremuoto strappato.” Storia del Messico, L. 1., § 3.