Art. X. Remarks on the Mineralogy and Geology of the the Northwestern part of the State of Virginia, and the Eastern part of the State of Tennessee.
Art. X. Remarks on the Mineralogy and Geology of the Northwestern part of the State of Virginia, and the Eastern part of the State of Tennessee. By Mr. John H. Kain, of Tennessee.
The most prominent as well as the most beautiful feature of this country, is that succession of mountain and valley, ridge and vale, which we meet with in traversing its surface. The grand range of Alleghany mountains enters Virginia about the 39th degree of north latitude; and, pursuing a southwestern course, spreads out upon the east end of Tennessee, and terminates near the southern boundary line of that state, in the Alabama territory; and about the 34th parallel of north latitude. In this view are included the Blue Mountains, the North Mountains, the Allegheny, (properly so called) the Cumberland, Clinch, Iron, and Smoky mountains, together with a variety of smaller mountains, spurs, and ridges, all running parallel to each other, from the northeast to the southwest; and all, I believe I may say, covered with forests, and presenting to the eye of the naturalist a most interesting field for speculation and improvement.
With a few exceptions, the geologist meets with none of those remarkable appearances which indicate the changes and convulsions which have been wrought by time, the great enemy of nature. Occasionally we are presented with a view of a sublime precipice, formed by a section which a river appears to have made for itself through an opposing mountain; and the large masses of ruins, which lie scattered around such a place, seem, to the imagination of the solitary traveller, the historical records of commotions, awful even in retrospect. Most commonly, however, the mountains seem to have lain for ages in undisturbed repose; and the streams of water, when they have crossed them, have sought an easy passage through the ravines, which do not so often divide a mountain, or ridge, at right angles, as wind between the ends of two opposing spurs, which pass each other, gradually declining into the champaign country at their mutual base. Through this whole extent of country we rarely meet with any remarkable falls of water; the obvious reason of which is, that the rocks are so soft that they are easily worn down to the level of the beds of rivers. But shoals, or shallows, are frequent, and are formed by beds of rounded sandstone, spread out into a broad base, over which the water often rushes with no small violence and noise.
The mountains are generally, though not always, sterile, and produce nothing but forest trees; but the valleys are, with hardly an exception, rich, and productive of every variety of "grass and herb yielding seed, and fruit-tree yielding fruit." Nor are they less favoured in the mineral kingdom; possessing the greatest abundance of all the most useful and necessary minerals, of which we shall now proceed to speak in order.
All the country included under the boundaries mentioned above, with the exception of some primitive ranges of mountains on the southeastern side, is apparently transition. This, it will be seen by a reference to Mr. Maclure's excellent map, will extend the boundary of his transition class considerably farther northwest, and make it include Cumberland Mountain and all East Tennessee. This would be evident from comparing the northwestern part of Virginia, which Mr. Maclure has included in his transition tract with all East Tennessee. Every mineralogist must observe the identity of the minerals of the two countries as well as that of their stratification and general formation. The limestone in the valleys, and the sandstone on the mountains, lie in strata which make an angle of from 25 to 45 degrees with the horizon. The limestone bears the impressions of shells, but rarely, if ever, of vegetables, and contains beds of hornstone, but not of flint, or what can properly be called flint.
The rock which lies in the lowest valleys, and often rises into pretty high hills, and is seen forming bluffs on the banks of the rivers, is limestone: it is of a dark blue, approaching to a gray, as it is exposed to the air, and often appearing quite white. Its fracture is compact in one direction; in another it is more or less slaty in its structure. It is interspersed with veins of the crystallized carbonate of lime, more or less perfect, and of a pure but opaque white. Another variety of this limestone, not so abundant, is that which is white and red, having the white and red spots intimately mingled. Its structure is similar to the other kind.
Lying in beds of this limestone, parallel to, and imbedded in, its strata, is a stone, which, from its globular form, its hardness, and its colour, has been usually mistaken for flint. On comparing it with the flint of chalk-beds, we find it much less translucent, its colour darker, and its hues duller; and its rough and irregular fracture, compared with the easy, smooth, and conchoidal cleavage of the true flint, decides it to be hornstone. It is found also forming considerable distinct beds on the hills; and is seen in detached pieces, and irregular pebbles, covering many of the ridges.
Alternating with the beds of limestone, and possessing the same formation, is a soft clay slate. Soapstone is found in it.
As soon as we ascend the mountains, we meet with a slaty sand-stone of various compactness, as it possesses more or less iron, often forming an excellent iron ore. A variety of this iron ore has been lately turned to a good use, in the manufacture of a red paint, near Knoxville, Tennessee. Different varieties of this sandstone possess different qualities. It is converted by the inhabitants into millstones, grindstones, and whetstones. Interspersed among the sandstone of the mountains we often find very beautiful and interesting specimens of hornstones, assuming a resemblance to all the silicious stones, from the chalcedony to the jasper. In this extensive range of mountains, many other minerals exist, of which we shall treat more particularly hereafter. The limestone, slate, and sandstone, as far as the writer's knowledge extends, so to speak, form the country; the limestone and clay slate dipping under the sandstone. Gypsum, coal, sulphate of barytes, &c. are found in these, and we shall now speak of their localities.
Gypsum.—This valuable mineral production exists in Washington County, Virginia, 20 miles north of Abingdon, in the vicinity of Saltville. It is similar, in every respect, to the plaster of Nova Scotia, and devoted by the farmers of that part of Virginia, and Tennessee, to similar purposes.
Coal is said to exist in immense quantities in the Cumberland Mountain. A bed of it is wrought near Knoxville, Tennessee. It is of an excellent quality; but wood is so abundant that it is used only in forges.
Sulphate of Barytes.—This mineral is found in Bottetourt County, Virginia, near Fincastle; and in Sevier County, Tennessee.
Hard Carbonates of Lime.—Stalactitical concretions abound in all the caves so often described as existing in this country. Those of Virginia are more perfectly crystallized than those of Tennessee. Under the head of hard carbonates should be mentioned an extensive bed or vein in Montgomery County in the State of Virginia, near the seat of Colonel Hancock. It appears to have been formed in a chasm, in the common limestone of the country, by a calcareous deposition which resembles, exactly, in all its characters, the calcareous concretions which are found forming in the caves of the country. The whole bed may, in fact, be regarded as a cave which has been filled up in the progress of time, by this curious process. Its width is various, from two feet to ten, or more, extending along the side of a very steep ridge, for at least 50 yards, and it is said to be continued seven miles farther.
The silicious carbonate of lime may be worth distinguishing from the common limestone. It is found in a bed near Colonel Hancock's, and was supposed to be gypsum. It phosphoresces beautifully; it is white, and confusedly crystalline in its structure, and much harder than the common limestone. Indeed the limestone generally, on the east of the Alleghany, is somewhat harder than that on the west.
Lead.—There are several localities of this mineral. A mine of it is wrought near New River, 15 miles from Wythe, Virginia. Another locality of the ore of lead is said to have been discovered in Granger County, Tennessee, on land belonging to General Cocke. It exists also, very near the surface, on the plantation of the Rev. Mr. Craighead, near Nashville; which, however, is out of our boundary.
Other metallic ores are said to have been found among these mountains, and particularly those of gold and silver; but the accounts are vague and uncertain, and not to be credited.
The numerous Caves of this country present attractions to every, the least curious, traveller; and, in an eminent degree, to the mineralogist. They are crevices, or large chasms, probably worn in the rocks by the passage of water. This will, at first view, perhaps appear a bold assertion; but if it be recollected that they occur only in limestone, which is a soft rock, and (under certain circumstances,) soluble in water; that the rocks bear every mark of having been worn by water; and that streams of water are always found in them, it will not appear an improbable hypothesis. It is by no means difficult to believe that a stream, after having worn such a chasm as a cave presents, in the solid rock, may have found another channel; and, forsaking the old, have left room for nature to display some of her most beautiful works. A description of one of these caves will be a description of all; and we shall select Wier's Cave, in Rockingham County, Virginia, as it is the most curious of any with which we are acquainted.
The entrance of the cave is narrow and difficult. When the cave was first discovered, the passage into it was impeded by stalactites, which had formed perpendicular columns across it; but these are now removed. As we advance, our course is at first horizontal, but we soon descend fifteen or twenty feet by a ladder, and find ourselves in a large echoing cavern. Stalactites of a silvery whiteness are suspended from above, and pillars of stalagmites are rising around us. Ledges of rocks form our floor, and the uneven walls are incrusted over with a beautiful brown spar, which is sometimes suspended from the canopy in thin, shining, and translucent sheets. In passing on over the rugged rock of our pathway, our attention is divided between a care for our safety, and an admiration of the surrounding wonders.
Proceeding on through a narrower crevice in the rocks, we are soon introduced into other apartments, differing in shape and size from the first, but resembling it in the irregularity of its walls, floor, and covering, and in the calcareous incrustations and concretions, which, assuming a thousand fantastic shapes, and displaying a sparkling lustre, the more vivid as the light is stronger, give to this whole grotto the power of charming every beholder.
The cave is a mile and a half in extent, and extremely irregular in its course and shape. Its perpendicular height varies from three to forty feet, and its breadth from two to thirty. Its dividing branches are numerous, forming a great variety of apartments. The blue limestone appears frequently enough to satisfy us that it is the groundwork of the whole; but it is almost every where covered with incrustations of the hard carbonates. These hang from the arched vault above in clusters, and often reach the ground, forming massive columns. Stalagmites again rise from the floor like so many statues; the irregular sides of the ledges of rocks are often incrusted over with white crystals of the carbonate of lime, and have the appearance of banks of salt: at times we seem to walk on diamond pavements; again our footway is of rounded pebbles, and seems the bed of a river which had deserted its channel. Often we pass small streams of water; and the water is continually dripping from the ends of the stalactites, the echoing sound of which, when it drops, forms the only interruption to the profound silence which reigns throughout the cavern.
To give an idea of the diversified shapes which these concretions assume in the progress of their formation, (and they are constantly forming,) would be impossible. Suffice it to say, that there is scarcely any thing on earth to which they may not be supposed to form a resemblance; and yet, in fact, they are unlike any thing but themselves.
It is generally known that the earth in these caves contains the nitrates of lime, and potash, and other salts. The numerous caves which have been found in the Cumberland mountains and other parts of Tennessee, have been very productive of the nitrate of potash. In the investigation of the causes which have given origin to these salts, it may be recollected, that wild animals burrow in these caves; that when pursued by the hunter, they make them the places of their retreat, and probably die there; that the aborigines have made them a place of burial; and that the streams of water which flow through them in wet weather, carry with them not only great quantities of leaves but many other vegetable productions.
The natural bridge is celebrated as one of the greatest curiosities of the world. Viewed by a geologist, it would probably be considered as a cave (so to speak) unroofed in all but one place. It seems improbable that if the ravine had been made by a convulsion, which had split and separated the rock to the distance of fifty or sixty feet, any part of it, and particularly so large a mass as that which forms the bridge, should have been left, without exhibiting any marks of violence. The rock is limestone. It is known that this rock wears away rapidly under the attrition of water; and the supposition does not appear improbable, that, in the lapse of ages, so large a creek as that which flows below the bridge, may have worn as deep a ravine as that which now strikes us with so much surprise, In short, may not a cave have been originally formed where the ravine is now, and the pending portion of it have fallen in at every place except that which now forms this celebrated natural curiosity?
Mineral Springs.—The mineral springs of this region are numerous and diversified. Chalybeate springs are promiscuously scattered over the whole of it; and springs impregnated with sulphuretted hydrogen are quite common. Salt springs and licks are found more in the western than the eastern range of mountains. That which was first wrought by William King, is well known. The salt here is associated with gypsum. In the same range of mountains, farther to the southwest, there are now several other salt-works, and also one to the west, on Goose Creek, in Kentucky, which has been very productive.
The Warm Springs.—These springs are situated in a country which presents many attractions to the travelling geologist; and much light, it is hoped, will yet be thrown on the geology of our country, by a more minute and accurate examination of it than has yet been made.
The warm springs ooze through the sand on the south bank of the French Broad river, in the mountains which divide the state of Tennessee from her parent state, about the 36th parallel of latitude. The temperature of the water is about 95° of Fahrenheit.
On the opposite side of the river from the springs is a geological curiosity. A limestone rock is seen dipping under the sandstone which forms the country. Limestone is nowhere else to be seen within six miles of this place. In this limestone rock is a cave similar to others already described.
Paint Rock, in the vicinity of the Warm Springs, is interesting on many accounts. It is a bold precipice on the bank of French Broad river. At this place the river passes with a very rapid current directly across the course of a mountain, which terminates abruptly, and forms the precipice on the north bank of the river. On looking at the rock, the opposite end of the mountain, and the ruins around it, the mind is insensibly carried back to the contemplation of some dreadful commotion in nature, which probably shook these mountains to their bases.
The rock is composed of a clay slate; and it is here again remarkable, that this stone is not to be seen in any other place within some miles. It has received its name from some red paintings, (probably left on it by the Indians,) which have the appearance of hieroglyphics.
To conclude. It will be seen from the above observations, that this country presents a vast field of most interesting research, and claims the attention of every traveller who is interested at all in geological inquiries. If what has been said will at all contribute to the enlargement of the general stock of our knowledge on these subjects, the writer will be much gratified; and it is his sincere wish, that the accuracy of his remarks may be tried, and his mistakes corrected, by the researches of succeeding travellers.