144 TERRENE DEPOSITS. Now when the general appearance and geological features of the South-West, including the south part of Mississippi and nearly the whole of Louisiana, are observed with reference to the preceding statements, the irresistible conviction of the observer is, that the immense plain now rich with sugar and cotton fields, a great emporium, numerous villages and a thousand villas, was formed by the mechanical deposits of the Mississippi upon the bed of the lat. 32 30 N. to the ocean or Gulf of Mexico. The elevation of the bluff at Natchez is about 200 feet; at St. Francisville, seventy miles lower, it is a little more than 100 feet; at Baton Rouge, about thirty miles lower, it is less than 40 feet, at New Orleans, according to the above statement eight feet, and at the Balize less than two feet. This vast glacis, at a similar angle of inclination, extends for some leagues into the Gulf of Mexico, till lost in the natural bed of the ocean. The river, whose current is said to be the most rapid at the period when it is about to overflow its banks, runs in its swiftest vein or portion about five miles an hour. I allude to the line of upper current, and not to the mass, which moves much slower than the surface. The average velocity of the river when not in flood is not above two miles an hour. This is easily ascertained, by the progression and regular motion of its swells, and not by its apparent motion. In November, 1800, as before observed, the motion of the stream was so sluggish as to be scarcely perceptible. A vessel that then lay opposite the Government House, advanced against it with a light breeze. I was told by a respectable lady, Mdme. Robin, who lives about six leagues below the city, that the water of the river was so brackish that she was obliged to drink other water, and that there were an abundance of porpoises, sharks, mullet, and other sea-fish, even above her plantation, nearly one hundred miles from the Gulf. The citizens thought the water brackish opposite the town. It looked quite green like sea-water, and when held to the light was quite clear. Although I did not think it brackish, I found it vapid and disagreeable. This is a phenomenon of rare occurrence, and not satisfactorily accounted for." ORIGINAL MOUTH OF THE RIVER. 145 ocean, precisely as they are now building up fields into the Mexican Gulf. Do not understand me that the present fertile surface of this region was the original bed of the ocean, but that it rose out of it, as the coral islands come up out of the sea, by the gradual accumulation of deposits. The appearance of these inland promontories or cliffs, which suggested these remarks, and the fact that the highlands of the south-west, all terminate along the southern border of this region, from fifty to one hundred miles from the sea, leaving a broad alluvial tract between, and presenting a well defined inland sea-board, go far to strengthen the opinion I have adopted. The chain of cliffs along the eastern shore of the Mississippi, have a parallel chain opposite to them on the other side of the great savana, skirted by the Mississippi, about forty miles distant. This savana or valley gradually widens to the south until near the mouth of the river, where it is increased to one hundred and forty or fifty miles in breadth. It is this great valley which is of mechanical formation, and its present site was in all probability covered by the waters of a bay similar to the Chesapeake, extending many leagues above Natchez to the nearest approximation of the cliffs on either side, where alone must have been an original mouth of this great river. Where the spectator, in looking westward from these bluffs; now beholds an extensive and level forest, in ages past rolled the waters of the Mexican sea-and where he now gazes upon a broad and placid river flow 146 GEOGRAPHY AND GEOLOGY. ing onward to mingle with the distant ocean, the very waves of that ocean rolled in loud surges, dashed against the lofty cliffs, and kissed the pebbles at his feet. XXXVI. Geography of Mississippi-Ridges and bottoms-The Mississip pi at its efflux-Pine and table lands-General features of the state-Bayous-Back water of rivers-Springs-St. Catharine's harp-Bankston springs-Mineral waters of this state-Petrifactions-Quartz crystals-" Thunderbolts"-Rivers-The Yazoo and Pearl. THOUGH not much given to theorising, I have been drawn into some undigested remarks in my last letter, upon a theory, which is beginning to command the attention of scientific men, to which the result of geological researches daily adds weight, and to which time, with correct observations and farther discoveries, must add the truth of demonstration. This letter I will devote to a subject, naturally arising from the preceding, perhaps not entirely without interest-I mean the physical geography and geology of this state. In the limits of a letter it is impossible to treat this subject as the nature of it demands, yet I will endeavour to go so far into its detail, as to give you a tolerable idea of the general features of the region. Besides the cliffs, or great head-lands, alluded to in my last letter, frowning, at long intervals, over the Mississippi, serrated ridges, formed of continuous hills projecting from these points, extend in various directions over the state. These again branch into lower ridges, which often terminate near the river, between the great bluffs, leaving a flat space from their base to the water, from a third of a mile to a league in breadth. These flats, or "bottoms," as they are termed in western phraseology, are inundated at the periodical floods, increasing, at those places, the breadth of the river to the dimensions of a lake. The forest-covered savana, nearly forty miles across, through which the Mississippi flows, and which is bordered by the mural high lands or cliffs alluded to in my last letter, is also overflowed at such seasons; so that the river then becomes, in reality, the breadth of its valley. The grandeur of such a spectacle as a river, forty miles in breadth, .descending to the ocean between banks of lofty cliffs, too far distant to be within each other's horizon, challenges a parallel. But, as this vast plain is covered with a forest, the lower half of which only is inundated, the width of the river remains as usual to the eye of the spectator on the cliffs, who will have to call in the aid of his imagination to realize, that in the bosom of the vast forest outspread beneath him rolls a river, to which, in breadth, the noble stream before him is but a rivulet. The interior hills, or ridges, mentioned above, are usually covered with pine; which is found only on such eminences, and in no other section of the south or west, except an isolated wood in Missouri, for more than fifteen hundred miles. The surface of the whole state is thus diversified with hills, with the exception of an occasional interval on the borders of a stream, or a few leagues of prairie in the north part of the state, covered with thin forests of stunted oaks. These hills rise and fall in regular undulations, clothed with forests of inconceivable majesty, springing from a rich, black loam, peculiarly fitted to the production of cotton; though, according to a late writer on this plant, “it flourishes with equal luxuriance in the black alluvial soil of Alatamaha and in the glowing sands of St. Simon's.* The general features of this state have suggested the idea of an immense ploughed field, whose gigantic furrows intersect each other at various angles. -Imagine the hills, formed by these intersections, clothed with verdure, whitened with cotton fields, or covered with noble woods, with streams winding along in the deep ravines, repeatedly turning back upon their course, in their serpentine windings, before they disembogue into the Mississippi on the west, or the Pearl on the east, and you will have a rude though generally correct idea of the bolder features of this state. A "plain," or extensive level expanse, which is not a marsh, forms, consequently, no part of its scenery, hill and hollow being its stronger characteristics. For a hilly country it presents one striking peculiarity. The surface of the forests, viewed * It has been said that cotton will thrive as well in a sandy soil, with a sea exposure, as in a rich loam in the interior. |