Art. II. On the Geology, Mineralogy, Scenery, and Curiosities of Parts of Virginia, Tennessee, and the Alabama and Mississippi Territories, &c.

Art. II. On the Geology, Mineralogy, Scenery, and Curiosities of Parts of Virginia, Tennessee, and the Alabama and Mississippi Territories, &c. with Miscellaneous Remarks, in a letter to the Editor. By the Rev. Elias Cornelius.

To Benjamin Silliman, Professor, &c.

SIR, Having recently returned from a tour of considerable extent in the United States, I avail myself with pleasure of the first leisure moment, to communicate, agreeably to your request, some facts, relative to the Mineralogy and Geology of that part of the country through which I passed.

INTRODUCTORY REMARKS.

Before doing this, you will permit me to premise, that in consequence of my limited acquaintance with these branches of Natural Science, and the still more limited time, which other and important concerns allowed me to devote to the subject, I can do little more than give a general description. What my eye could catch, as I travelled from one country and wilderness to another, preserving occasionally a few of the most interesting specimens, was all I could do. The specimens you have received. The narrative I am about to give, is drawn principally from the notes which were taken on the journey, and will be confined to a simple statement of such facts as were either observed by myself, or derived from good authority. Their application to preconceived theories, I leave to those who have more leisure and disposition for speculation than myself.

A description of a few natural and artificial curiosities which came under particular notice, will not, I trust, be thought an improper digression. The whole is committed to your disposal; and if it shall add but one mite to the treasury of American Natural History, I shall be gratified, and rejoice to have made even this small remuneration for your unwearied efforts, to impart to one, formerly your pupil, a love for Natural Science.

The Author's Route.

My route was in a line nearly direct from Boston to New-Orleans; passing through the principal cities to Washington; thence, diagonally, through Virginia, East Tennessee, and the northwestern angle of Georgia; in a western course through the north division of the Territory of Alabama, to the northeastern boundary of the State of Mississippi; and thence in a line nearly southwest to Natchez. From this last place I descended the river Mississippi to New-Orleans. On my return I frequently varied from this course, and had increased opportunities for surveying the country. In both instances I passed through the countries belonging to the Cherokee, Chickesaw, and Choctaw tribes of Indians, and travelled among them, in all, about one thousand miles.

Geology of Virginia.

As others have described more minutely and accurately than I can, the country north of Virginia, I shall begin with a few remarks on the geological character of that State. It is there that the traveller, in passing from the Atlantic to the interior, crosses successively the most important formations of the earth, from the most recent alluvial to the oldest primitive. For a considerable distance from the coast, the country is alluvial. It then assumes an older secondary formation[30]—and sandstone and puddingstone are frequent. This is the character of the District of Columbia, and indeed of a great part of the valley of the Potomac.

Sandstone of the Capitol, &c.

In this valley, and adjacent to the river, is found the sandstone of which the President's house, and the Capitol are constructed. It is composed of fine silicious grains, is easily wrought, and from its colour, has the appearance at a small distance of white marble.

Beautiful Breccia.

It is also in the valley of this river, and not far from its famous passage through the Blue Ridge, that immense quarries of beautiful Breccia have been opened. This rock was first brought into use by Mr. Latrobe, for some years employed by the government as principal architect. It is composed of pebbles, and fragments of silicious and calcareous stones of almost every size, from a grain, to several inches in diameter, strongly and perfectly cemented. Some are angular, others rounded. Their colours are very various, and often bright. Red, white, brown, gray, and green, are alternately conspicuous, with every intermediate shade. Owing to the silicious stones which are frequently imbedded through the mass, it is wrought with much difficulty; but when finished, shows a fine polish, and is unquestionably one of the most beautifully variegated marbles, that ever ornamented any place. It would be difficult to conceive of any thing more grand than the hall of the Representatives, in the Capitol, supported as it is by twenty or thirty pillars formed of the solid rock, and placed in an amphitheatrical range; each pillar about three feet in diameter, and twenty in height. Some idea of the labour which is employed in working the marble may be formed from the fact, that the expense of each pillar is estimated at five thousand dollars. The specimens in your possession, are good examples of its general structure, but convey no adequate idea of its beauty.

Petrifaction of Wood.

It will be proper to notice in this place, a petrifaction of wood which is found on the road from Washington to Fredericksburgh, 16 miles from the latter, and four miles north of the court-house in Stafford county. It is remarkable for its size, rather than for any singularity in the composition. It was found by digging away the earth on the side of the road, and appears to have been the trunk of a considerable tree. It is firmly fixed in the ground, and penetrates it obliquely; how far has not yet been ascertained. At the time I saw it about two feet had been exposed. The diameter is about eight inches. Its colour is white, sometimes resembling that of wood. The fibres are well preserved, and so is the general structure. It is much to be desired, that some one would clear it from its bed, and give it entire to one of our mineralogical cabinets.

Geological Features.

Next to the alluvial and secondary formations, as you pass to the west and northwest, are to be found ranges of granite and shistose, and other primitive rocks; interspersed with these may be seen sandstone, clay, slate, quartz, and limestone. Granite ranges were particularly seen in the neighbourhood of Fredericksburgh, crossing the Rappahannock; and in Orange and Albemarle counties, extending nearly to the Blue Ridge. Great quantities of quartz and quartz rock, sometimes covering with their fragments the sides of hills, are frequent. Another, and more interesting rock in the same connexion, is found in Albemarle county. For some time I doubted to what class to refer it. But from its resemblance to the rocks of the east and west mountains near New-Haven, I ventured to call it trap or whinstone. It becomes more abundant as you approach the Blue Ridge, and the granite disappears. On the sides and summit of the mountain, its appearance is more decidedly that of greenstone. In crossing the southwest mountain, the range to which Monticello belongs, and distant from the Blue Ridge about 25 miles, I observed the same rock. Whether this opinion is just, you will be able to decide from the specimens which have been forwarded.

Blue Ridge.

I have repeatedly named the Blue Ridge. It is the first of those long and parallel ranges of mountains, called the Alleghany; and constitutes one of the most prominent features in the geology of the United States. Its height I cannot determine with accuracy. Probably it would not average more than one thousand feet. Its base may extend in diameter from one to two miles; and yet such is the influence it has on the climate, that vegetation on the eastern, is usually two weeks earlier than on the western side. And what is remarkable, this difference obtains, on the former side at least, until you arrive within a few hundred yards of the summit. I crossed the mountain in two places, distant from each other one hundred miles, but observed nothing essentially different in their mineralogy. At one of them called the Rockfish-Gap, on the road from Charlotteville to Staunton, I spent a few hours, and brought away specimens of all the varieties of minerals which I could find. These have been submitted to your inspection. Among them, you will, I think, see greenstone, epidote, and slate more or less allied to the first. These are the most common rocks, and excepting the second, are usually stratified. The epidote is generally associated with quartz, and sometimes is imbedded in it. In some instances it has a porphyritic appearance, and is very beautiful. In others, it is coated with small filaments of a greenish asbestos. Other minerals were found, whose nature I could not so easily determine. I regret exceedingly, that I cannot furnish you with a more complete description of this interesting mountain. That its character is peculiar, or different from the country on either side of it, must be obvious to the most superficial observer. Its principal rock does indeed bear a resemblance to the trap or whinstone of Albemarle county, and yet I think you will say it is not the same. One fact of importance cannot be mistaken; this mountain constitutes the great dividing line between the granite and limestone countries. For you no sooner reach its western base, than the greenstone and epidote disappear; and limestone pervades the country for hundreds of miles in every direction. In all the distance from this mountain to New-Orleans, I did not find a single specimen of granite, or greenstone. This may appear singular, since Mr. Maclure and Professor Cleaveland have a granite range on their maps, immediately west of the Blue Ridge; and even that mountain is on those maps, in some parts of it, covered with the granitic tinge. This may be true. I can answer for only two points of it, and for that part of the country beyond, lying near the main road to Tennessee. In this route I descended almost the whole length of the great valley included between the Blue Ridge on the east, and the north mountain on the west. But in no instance did I meet with specimens of granite; nor west of the Blue Ridge with any prevailing rock but limestone. I know of no reason why the Blue Ridge should not be regarded as the first great dividing line between the granite and limestone countries. The change in the geological formation is so sudden and striking, that it would be difficult for the most careless traveller with his eyes open, not to observe it. The face of nature, he cannot but perceive, wears a different aspect; the air is more cool and lively; even the water which he drinks possesses new properties perceptible to his taste. The inhabitants no longer speak of their "sandstone water;" but every where he hears of "limestone water." Indeed for 800 miles in the direction which I travelled, he tastes no other water. Every spring and every rivulet, is strongly impregnated with carbonate of lime. The vessels in which it is prepared for culinary use, soon become lined with a white calcareous crust. Nor is its taste the only inconvenience experienced by the traveller unaccustomed to it. It often injures the health of a stranger, and covers the surface of the body with cutaneous eruptions.

Limestone country in inclined Strata.

The geological observer has now entered upon a very interesting field. Its great extent, and its wonderful uniformity, give new facilities to investigation. Two divisions of it seem to have been made in nature.

The first is that which includes the limestone lying in INCLINED STRATA. This division extends from the Blue Ridge, to the Cumberland mountain in East Tennessee, a distance in the direction of my route of 500 miles. Of course it includes all the ranges, five in number, of the Alleghany mountains. The strata lie in a course northeast and southwest, the same as the general course of the mountains. The angle which they make with the horizon is very variable, from 25° to 45°. The colour of the rock varies from blue, and pale blue, to gray, or grayish white, frequently it presents a dull earthy appearance. The fracture is more or less conchoidal. Sometimes the rock assumes a different character, and the fracture is uneven, and the texture firm. This last is distinguished from the former, not only by the fracture, but by the colour. It is usually spoken of by the inhabitants as the gray limestone, the colour of the other being usually of a bluish cast. It differs from that also by being less brittle, and possessing the quality denominated by stonecutters, "tough." In consequence of this, and its enduring heat better, it is more frequently used in building than the other. This variety of limestone is not uncommon. Its colour is not always gray, sometimes it is a reddish brown, and sometimes white. Immense quantities of it, possessing either a grayish or reddish brown colour, are found in the vicinity of Knoxville, East Tennessee. One range of it is crossed by every road, passing to the south and east of Knoxville. Its appearance is that of some variegated marbles; white veins penetrate it, and wind through it in every direction. Whether any part of it has a texture sufficiently fine and firm to be wrought to advantage, is yet to be determined. To the eye of a superficial observer, there are many indications that it has. A specimen of very fine white marble, resembling the Italian white, was shown me in Augusta county, Virginia, which was found 15 miles from Staunton, where there is said to be a considerable quantity of it.

Limestone country in Horizontal Strata.

The second great division of the limestone country extends, on the route which I took, two hundred miles from the Cumberland mountain, and others associated with it southwest, as far as the Dividing Ridge, which separates the waters flowing into the Tennessee from those which proceed direct to the gulf of Mexico. The grand circumstance which distinguishes the limestone of this division from that already described, is this, ITS STRATA ARE HORIZONTAL. Frequently immense piles may be seen forming bold precipices, but always in horizontal layers, differing in thickness, from a few inches to many feet. How far this arrangement extends to the west and north, I have not yet been able to learn. Travellers always speak of the limestone rocks in West Tennessee and Kentucky as flat, from which circumstance I conclude that the Cumberland mountain forms for a considerable distance at least, the eastern boundary. I have observed but three other particulars in which the strata of the horizontal differ from those of the inclined limestone.

1. Its colour is not so strongly marked with the bluish tinge.

2. It is not so commonly penetrated with white veins of a semicrystallized carbonate of lime; nor is it so frequently associated with the uneven fractured species.

3. Petrifactions are oftener found in it.

I will here take the liberty to suggest, whether in our maps of geology, some notice should not be taken of this very important division in the limestone country. Such a division exists in fact; nature has made it; and if geology depends on nature for its only legitimate inductions, there can be no reason why a feature so prominent as this, should be overlooked. I shall not undertake to account for their difference: but would not every geological theorist consider them as distinct formations?[31]

Cumberland Mountain.

The Cumberland mountain, which forms a part of this dividing line, is itself a singular formation. It belongs to the class called "Table mountains." Its width varies from a few miles, to more than fifty. Its height is not perceptibly different from that of the Blue Ridge. It forms a circuit, in a shape somewhat resembling a half moon. Winding to the southwest, it keeps a course north of the Tennessee river, in some places nearly parallel with it; passes a few miles to the southeast of Huntsville in the Alabama Territory, and not long after terminates. At one part, over which I crossed, the mountain is eighteen miles wide. This is about 150 miles southwest of Knoxville, a little north of the 35th degree of N. Lat. I had not ascended the mountain more than halfway, before I found sandstone begin to intermingle with limestone strata. As I drew near the summit, the limestone disappeared entirely, and sandstone prevailed in abundance, with no other mineral associated until I reached the western descent, where I met bold precipices of horizontal limestone, reaching from the base to the summit. I examined several sandstone rocks while crossing the mountain, found them usually imbedded in the earth, generally with flat surfaces, of a fine grain, and strong texture. The colour is usually a reddish brown, or grayish red. The specimen which you have received is a good example. I crossed this mountain in the vicinity of Huntsville, not less than one hundred miles southwest of the place above-mentioned, and found it not wider than mountains commonly are. Its height had also become less, and horizontal limestone in regular strata prevailed in every part.

Although this mountain forms a part of the dividing line which has been mentioned, it does not exclusively so: for the Rackoon mountain, which crosses the Tennessee river, at the place so well known by the name of "the Suck," and the Look-Out mountain, which terminates abruptly about 6 miles to the left of "the Suck," form an acute angle with the Cumberland, and are composed of horizontal strata of limestone. Thus it would appear the line which divides the two kingdoms of this rock, is nearly north and south, inclining perhaps a few points to the east and west.

Scenery.

And here I cannot forbear pausing a moment to call your attention to the grand and picturesque scenery which opens to the view of the admiring spectator. The country is still possessed by the aborigines, and the hand of civilization has done but little to soften the wild aspect of nature. The Tennessee River, having concentrated into one mass, the numerous streams it has received in its course of three or four hundred miles, glides through an extended valley with a rapid and overwhelming current, half a mile in width. At this place, a group of mountains stand ready to dispute its progress. First, the "Look-Out," an independent range, commencing thirty miles below, presents, opposite the River's course, its bold and rocky termination of two thousand feet. Around its brow is a pallisade of naked rocks, from seventy to one hundred feet. The River flows upon its base, and instantly twines to the right. Passing on for six miles further it turns again, and is met by the side of the Rackoon mountain. Collecting its strength into a channel of seventy yards, it severs the mountain, and rushes tumultuously through the rocky defile, wafting the trembling navigator at the rate of a mile in two or three minutes. This passage is called "The Suck." The summit of the Look-Out mountain overlooks the whole country. And to those who can be delighted with the view of an interminable forest, penetrated by the windings of a bold river, interspersed with hundreds of verdant prairies, and broken by many ridges and mountains, furnishes in the month of May, a landscape, which yields to few others in extent, variety or beauty. Even the aborigines have not been insensible to its charms; for in the name which they have given to the Look-Out mountain we have a laconic, but very striking description of the scenery. This name in the Cherokee language, without the aspirated sounds, is "O-tullēē-ton-tannâ-tâ-kunnâ-ēē;" literally, "mountains looking at each other."

I have already remarked that the limestone of this mountain lies in horizontal strata: one mile east from its base it is inclined. Like the Cumberland, it contains immense rocks of sandstone, but of a coarser grain, verging occasionally into pudding stone. I was told by a white man, a professed millwright, that among these sandstone rocks, he knew of many which were suitable for millstones. At the missionary establishment, called "Brainerd," eight miles east of the mountain, I saw one of them which was used for this purpose to much advantage. It is composed of fine and large grains of silicious stones, nearly white, and resembling pebbles of white quartz: the texture is firm.

Silicious Minerals, &c.

I will now notice an important fact, applicable to the whole extent of limestone country, which has come under my observation. It is its association with a description of minerals, all of which appear to be silicious. To describe them minutely, would require several pages. From the time I entered the limestone country till I left it this association was observed. The minerals included in it differ much in their external character. Their size varies from that of rocks to the smallest fragments. Usually they lie loose upon the earth, in angular forms, having the appearance of a stone that has been broken in pieces by the hammer. Sometimes they cover the sides of hills and mountains in such abundance as to prevent or impede vegetation. When the disintegration is minute, they are serviceable rather than otherwise; and the farmer talks of his "good black," or "white gravel land." It renders this service, I presume, not by decomposition, but by preventing the soil and its manure from being washed away. Indeed the different varieties of it are generally scattered over the surface, in pieces so small, that for convenience sake, the whole may be denominated a silicious gravel.

Sometimes the mineral is imbedded in limestone, in the form of nodules, thus indicating their original connexion with it.

The varieties, so far as I have observed, are quartz, hornstone, flint, jasper, and semi-opal; and several, which to me are non-descripts. Quartz is the most abundant. It is found of different colours; compact, and porous or cellular; of every size; simple and associated with other silicious stones; massive and crystallized. In Augusta and Rockbridge counties in Virginia, beautiful crystals of quartz, of a singular form, are found. They are six-sided prisms, with double acuminations, that is, with six-sided pyramids, mounted on the opposite ends of the prism. A specimen of two such crystals united, you have received. It was found near Lexington. A curious variety of the quartz gravel-stone occurs on both sides of Elk River, a few miles above its junction with the Tennessee, in the Alabama territory. As you travel to the west from Huntsville, it appears first in the neighbourhood of Fort Hampton, two miles east of Elk River, and may be seen for ten miles west of that river. The mineral is remarkable for containing a curious petrifaction. Its first appearance is that of a solid screw. On examination, however, you find it is not spiral; but consists of parallel concentric layers. Their diameter varies in different specimens, from that of a pin to half an inch. They stand in the centre of a hollow cylinder, extending its whole length, and occupying about one-third of its dimensions. The stone is sometimes perfectly filled with these forms. The petrifaction I could not have named, had you not pronounced it the "Entrochite."

Hornstone, next to quartz, is the most abundant of the silicious minerals associated with limestone. It is very often seen imbedded in rounded masses, both in the inclined and horizontal strata.

Flint is more rare. Several fine specimens were observed on the western declivity of the Look-Out Mountain, but in no instances in large masses or quantities.

Semi-Opal was found in one instance on the dividing ridge, which constitutes the southwestern boundary of the limestone strata.

Of the non-descripts you have several specimens. One variety strikes fire with steel, is a milk-white colour, adheres slightly to the tongue, and has no degree of translucency on its edges. As Mr. Kain has furnished you with an interesting detail of particular minerals found in East Tennessee and Western Virginia, I need not recapitulate what he has so well said.

(To be continued.)