Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/610

Rh 560 high angle. Across the middle of the State lies an exten sive zone, 20 to 40 miles wide, of the Archaean slates, with a predominance of chlorite and felsite slates, schists, clay slates, and shales, with steep westerly dips. This is Geological Map of North Carolina. succeeded in the region of Raleigh by another terrane of gneisses and schists about 20 miles wide, inclined eastward at high angles and disappearing southward and eastward under the Tertiary formation, and giving place in turn, farther eastward, to an equal breadth of slates and felsites, (with occasional bosses of granite), which are only seen where they have been uncovered in the beds and bluffs of the larger rivers. The whole eastern region is mantled over with a thin covering of Tertiary rocks. These consist of sands, gravels, and clays, and of shingle beds and earths rudely stratified, towards the western border. The thick ness of this formation ranges from a few feet to 25 and 50 feet, occasionally reaching 100 and 200 feet. Through out the eastern and larger part of the division, in the ravines and in the beds and banks of the streams, are numerous outcrops of Middle Tertiary marls, Lower Ter tiary shell-limestones, and coarse chalk beds. And in the southern half of this section, in the river beds and near the water-line of their banks, the Cretaceous formation appears in beds of half-compacted greensand, occasionally filled with shells. Overlying the Tertiary are sporadic patches of Quaternary clays, gravels, and shingle beds, the latter chiefly near the great channel ways of the rivers, where they sometimes reach a thickness of 30 and 50 feet. The Mesozoic formation is represented by two long narrow trough-like terranes of Triassic sandstones, conglomerates, clay slates, and shales, with bituminous coal. One of these, 5 to 6 miles wide with a south-easterly dip of 10 to 20, enters the State from South Carolina a few miles west of the Pedee river and, passing within 10 miles (west) of Raleigh, disappears within 15 miles of the Virginia line ; the other, about 40 miles long and 2 to 4 miles wide, lies along the valley of the Dan river, nearly east and west in direction and near the Virginia line. These beds have a north-westerly dip of 30 to 70. The rocks of these two belts have a thickness of several thousand feet and are evidently the remnant fringes of a broad, flat anticlinal which has suffered extensive erosion. These two outcrops converge in the direction of the Richmond coal-beds, and were no doubt once continuous with them and with the Mesozoic of New Jersey and Connecticut. The former of these belts carries a 6-foot seam of bituminous, the other a 3-foot seam of semi-bituminous coal. Both are of good quality, but have been little worked. The Palaeozoic rocks are entirely wanting, and the Primordial cross the State line from Ten nessee only in a few places along the Smoky Mountains. Minerals. In consequence of the wide distribution of the older rocks there is a notable abundance and variety of minerals. More than 180 species have been discovered, some of great rarity ; and one of them has recently yielded to science two new metallic chemical elements. Nearly a score different species of gems have been found, including the diamond, ruby, sapphire, emerald, beryl, lazulite, amethyst, garnet, agate, and zircon. There occur also many minerals having special applications in the use ful arts, viz., mica, corundum, asbestos, baryte, chromic iron, garnet, zircon, kaolin, black oxide of manganese, talc, pyrophyllite, &c. Mica is found in large veins or dykes in all the terranes of Montalban gneisses, but the most extensive and valuable mines are found in the mountain region, where workable veins are numerous and extensive and the sheets of mica of unusual size and excellence. Corundum is about as widely distributed as mica, and occurs in the same series of rocks, as well as in some of the slate belts. The chief sources of supply of both corun dum and mica for the arts, in the United States and in Europe, are the deposits of the mountains of this State. In this region are also numerous beds of white and variously- coloured marbles. Building stones of every variety are found in nearly all the sections, and whetstone, millstone, and grindstone grits, as well as potter s clay and fire clay ; and in the seaboard section are immense beds of peat. Iron, copper, and gold ores are coextensive with the outcrops of the metamorphic rocks. Several parallel ranges of magnetic and haematite iron-ore beds cross the State in a north-east direction, in both the middle and the mountain regions. These ores are of a high grade and are in great demand at the Bessemer furnaces in Pennsyl vania and elsewhere. Beds of limonite are numerous and extensive in all parts of the State. Blackband ore is associated with the coal, and spathic ore occurs as the gangue of several copper and gold mines in the middle region. Iron for domestic consumption has been manu factured for a hundred years in the middle region and half as long in the other sections. Gold occurs in both placers and veins from Halifax county on the upper margin of the eastern champaign, within 110 miles of the sea-coast, through all the intermediate sections to Cherokee county in the extreme south-west. The more extensive and pro ductive deposits are found in the midland region in the southern half of the great slate belt, and in the central part of the Piedmont region among the foot hills and spurs of the mountains. These placers consist of coarse shingle in the beds of the streams and the bordering level bottoms ; climbing the slopes and benches of the hills adjacent, they pass insensibly from half -stratified shingle, gravel, and sand beds into unstratified earths with mingled fragments of stone. These deposits cover several hundred square miles of territory, and are of Quaternary or more recent age. Compared with those of California, they are of very slight thickness, generally not above 5 or 10 to 20 feet, and only occasionally reaching 40 and 50 feet. The most important and valuable vein mines are also found in the midland region. One cf these, the Gold Hill mine near Salisbury, has been wrought to a depth of 750 feet, and its total produce exceeds two million dollars of bullion. In the same section are several noted silver mines, Silver Hill, Silver Valley, and others. Many of the gold veins of the midland region carry also copper ores, and there are numerous copper veins in various parts of the middle and western regions. The more common ore is chal- copyrite, but there are also important lodes of grey copper. Soils, The soils of the eastern region are transported sands, gravels, and clays, of Tertiary and Quaternary origin, the assorted detritus of the abraded hills of the metamorphic rocks in the midland country to the westward. The upland soils of the region (the com mon characteristic cotton soils) are generally sands and loams of moderate fertility, with here and there considerable areas in long narrow ridges or oval patches called pine barrens, that are very sandy and sterile. Between these, on the benches and lower levels, stretch wide and fertile alluvial tracts, especially along the borders of the streams and the shores of the sounds and bays. On the flattish swells between the lower reaches of the great bay-like rivers and around the margins of the lakes, as well as along the borders of many of the creeks, are extensive tracts of swampy lands with a black peaty soil of great depth and inexhaustible fertility. These soils resemble those of the prairies of the north-western States, but contain a larger percentage of organic matter, and are more produc-