hundred miles in length, about one hundred broad, and BOOK having an elevation varying from 1000 to 2000 feet above LXXIX. the sea. This range of low mountains, which is penetrated by two branches of the Mississippi, the Arkansas, and Red River, was nearly altogether unknown till within these few years, and has not been delineated, so far as we know, in any maps hitherto published in this country. Mr. Maclure, an American geologist, informs us that Geology. a zone of primitive rocks extends from the mouth of the St. Lawrence to the confines of Florida, varying in breadth from twenty to a hundred and fifty leagues, following the shores of the Atlantic, but with an alluvial zone interposed between it and the coast, from Cape Cod to the Bay of Mexico. The primitive formations slope upward, with declivities more or less steep towards the crest of the eastern chain of the Alleghanies. They consist of granite, gneiss, mica, and clay slate, primitive limestone, and trap, serpentine, porphyry, sienite, quartz, flinty slate, primitive gypsum, &c. The strata dip generally to the south east, at an angle of more than 45 degrees, forming mountains sometimes with round tops, as the White Hills, [Mountains] and sometimes with pyramidal summits, as the Peaks of Otter. Metals and minerals abound in this zone. There are found in it the garnet, epidote, various magnesian stones, the emerald, graphic granite, the tourmaline, amphibole, arragonite, martial pyrites in the gneiss, magnetic iron oxide in the amphibolic rocks, hematite, plumbago, molybdena, white cobalt, grey copper, sulphuretted zinc, and three varieties of titanium. This primitive zone, continues Mr. Maclure, is not unmixed with other rocks. It is crossed by a small belt of secondary rocks, fifteen or twenty miles broad, which is first seen in the lower part of the valley of Connecticut River, re-appears on the west side of the Hudson, crosses the Delaware, Schuylkill, Susquehannah, Potomac, and terminates at the Rappahannock in Virginia. This secondary formation, enclosed as it were among the primitive rocks, is composed of old sandstone, limestone, silicious BOOK conglomerate, mixed with quartzy rolled masses of amLXXIX. phibolic rocks and wacké, covering usually the sand stone on the heights. A narrow belt of transition rocks, about fifteen miles broad at its north, and two miles at its south end, skirts the eastern side of this secondary formation, as far as the Potomac, where it crosses it, and then skirts its western side. This belt of transition rocks is composed of a fine grained limestone, alternating with beds of grey wacké, and mixed with dolomite, flint, white granular marble, and calc-spar. Between the secondary and transition rocks, there is, about twelve miles from Richmond, a bed of coal twenty miles long, and six broad, reposing in an oblong basin on the granite, mixed with whitish sandstone and clay slate, and containing impres sions of plants.* Independently of this partial transition formation, Mr. Maclure has traced a zone of transition rocks immediately on the west side of the primitive, with a breadth varying from twenty miles to forty, and dipping to the west at an angle of forty-five degrees. This zone, generally speaking, occupies the middle of the chain of the Alleghanies, but traverses it near the south end, and disappears in the plains of Florida. The transition limestone, the greywacké and the silicious slate, are generally found in the valleys, while the quartzy aggregates, among which are found millstone rock, fossil remains of quadrupeds and marine animals, form the mass of the mountains. This zone presents scarcely any other minerals than beds of pyrites, galena, anthracite, accompanied by aluminous schistús, and veins of sulphate of barytes. A secondary formation, commencing beyond this last, extends westward, over a vast space, to the lakes and the Rocky Mountains. The beds are almost horizontal, except where they undulate with the surface. They consist of old sandstone, limestone, and stratified gypsum of two *Maclure's Memoir on the Geology of the United States, in the Transactions of the Philosophical Society of Philadelphia, Vol. VI. page 41. different ages, tertiary sandstone, rock salt, chalk, coal, BOOK and stratified trap, or basalt of a recent origin. The basis LXXIX. of all these strata appears to be an immense bed of secondary limestone of all shades. The western front of the Alleghanies presents also a large bed of coal, accompanied by sandstone and slate clay, which extends from the sources of the Ohio to those of the Tombigbee. This formation contains few minerals. Clay, ironstone, and pyrites, are found in it. The alluvial zone, which skirts the coast from Cape Cod to the mouth of the Mississippi, and along the banks of that river, beyond the confluence of the Missouri, consists generally of beds of sand, clay, and travelled soil, mixed with deposits of shells, whose succession and thickness indicate the periods the surface had been covered by the ocean. But the zone altogether is properly divided into two bands -the one a little raised above the level of the sea, and traversed by the tidewater in the rivers-the other commencing at a distance inland, reaching from sixty to a hundred and twenty miles, forming sandy eminences, a hundred and fifty or two hundred feet high, and behind which we find an undulating surface, and some travelled masses of rock. It appears that this more elevated band, increasing in size as it proceeds southward, forms the spine of the peninsula of Florida. The lowest parts of both bands are composed of a fertile soil deposited by the rivers. The Ozark mountains are similar in structure to the Alleghanies. Primitive rocks, granite and clay slate, are found on their east side. These are covered by transition rocks, which are followed by coal and other secondary formations. At the few points where the Rocky Mountains have been examined, they are found to consist of primitive rocks, granite, gneiss, quartz rock, &c., with an extensive formation of old red sandstone at their foot on the east side.* In our account of Canada, we have described the great James's account of an Expedition from Pittsburg to the Rocky Mountains in 1819, 1820, vol. iii. p. 238, and engraved sections. Lakes and BOOK lakes of fresh water which extend along the northern fronLXXIX. tier of the United States, and were the scene of some bloody contests between the English and the Americans in the last war. Of the smaller lakes, lake Champlain, 128 miles long, and 12 broad, is the only one considerable enough to require notice in this work. There are several extensive swamps or marshes, of which that called the Dismal Swamp, is the largest on the eastern side of the mountains. The name is applied to two marshy tracts, one on the north and the other on the south side of Albermarle Sound, in North Carolina. The former, which covers 150,000 acres, bears a growth of juniper and cypress in the wet parts, and of white and red oak and pine in the dry parts. The other, which is still larger, and also covered with wood, has a lake in the middle of it. Both afford some excellent rice grounds. The Great Swamp, lying on the west side of the Mississippi, 200 miles long, and 20 broad, becomes a lake in the beginning of summer, when it receives a part of the overflowing waters of that river; but the waters gradually dry up, and it then exhibits a parched surface, thickly covered with cypress. Rivers. We have already described the St. Lawrence in our account of Canada. The Mississippi is a still more celebrated stream; but it is now known that the Missouri is the principal branch, and has the best claim to the magnificent title of "Father of waters," conferred on the smaller branch by the Indians. Of the former river we shall speak afterwards. The Mississippi Proper has its source in Turtle Lake,(a) near the 48th degree of north latitude. At the picturesque Falls of St. Anthony it descends from the plateau, where it has its origin, to a vast plain, which accompanies it to the sea. After a course of 280 leagues its limpid waters are blended with the turbid stream of the Missouri. At the point of confluence each of these rivers is nearly half a league broad. Above the mouth of the Missouri the most considerable rivers are, the St. Peter's, (a) [According to Mr. Schoolcraft, in Beesh Lake, in Lat. 49. N.]-AM. Ep. LXXIX. and Des Moines on the west side, the Wisconsin, Rock Ri- BOOK ver, and the Illinois on the east. At the distance of 160 miles below the mouth of the Missouri, it is joined by the Ohio, after the latter has received the tributary waters of the Wabash, the Cumberland, and the Tennessee rivers. Lower down, the Mississippi has its volume augmented by the Arkansas and Red River, and falls into the Gulf of Mexico, after a course of 2500 miles. The river, in the last part of its course, presents some peculiar phenomena. Besides its principal and permanent mouth, it has several lateral outlets, called Bayous, which carry off part of its waters. In Louisiana, the surface of the stream is more elevated than the adjoining lands. Its immense volume of waters is confined and supported by dykes or levees, composed of soft earth, and rising a few feet above the usual height of the inundations. These banks of the river, which decline gradually into the swampy plains behind, are from a quarter to half a mile in breadth, and form the richest and best soil in the country. The three principal outlets or bayous, called the Atchafalaya, the Lafourche, and the Ibberville, embrace an extensive delta, composed of soft, swampy earth, rising very little above tidewater. The actual embouchure of the river parts into three branches, each of which has a bar at its entrance, the deepest affording only seventeen feet water. Within the bar the depth of the river, for two or three hundred miles, is from 50 to 150 feet. The average breadth of the Mississippi, below its junction with the Missouri, is about 1000 yards, or two thirds of a mile.* The Mississippi and its branches traverse countries thick- Mississippi ly wooded, and hence vast numbers of trees, either uprooted by the winds, or falling from the effects of age, are borne down by its waters. United by lianas, and cemented by soft adhesive mud, these spoils of the forest become floating islands, upon which young trees take root. There the Pistia and the Nenuphar display their yellow flowers, and Melish, p. 32. Warden's Statistical Account of the United States, 1819, Vol. I. |