The Appalachians are nowhere lofty, and only approach the characteristics of great mountains in their southern portion. The culminating summit is Mount Mitchell, in western North Carolina, which has an elevation of 6,711 feet. Roan Mountain, 27 miles to the northward of Mount Mitchell, rises 6,287 feet above the sea. In the neighbouring Unaka and Great Smoky Mountains, to the southwest and west of Mount Mitchell, there are many boldly rounded domes ranging in height from 5,000 to over 6,000 feet Northward of the highly picturesque southern Appalachians, the system decreases in height and is really a deeply dissected plateau, as will be shown later, in which the long, even-crested ridges have a general elevation of 4,000 feet in Virginia and about 2,000 feet in Pennsylvania and New Jersey. At its northern extension in New York it decreases still more in height, and is surpassed in elevation by the plateau on the west, there represented by the Catskill Mountains, the highest portion of which is 3,660 feet above the sea. The characteristic structural feature of the Appalachians is the presence of a great series of up and down folds, or anticlinals and synclinals as geologists term them, which run in a nearly parallel northeast and southwest direction, but in Pennsylvania especially exhibit many broad curves in their general course. These folds are similar to the waves that may be produced in a heavy rug or carpet by pressing against one of its margins. The rocks have been thrown into a series of great wrinkles which are not continuous throughout the length of the system, but as one dies out another takes its place. The folds overlap at the ends or are arranged _en echelon_. The longer axes of the folds are seldom horizontal, but have usually a gentle pitch; for this reason one end of a fold frequently passes beneath the surface, while the other end is exposed to erosion. Another characteristic is that the anticlinals, as a rule, are steep on their western margins, and slope more gently on their eastern flanks, or are unsymmetrical. The overturning of the folds where most pronounced has led to the breaking of the rocks on the west side of an upward wrinkle where the descending limb of an anticlinal is sharply bent in order to pass into the ascending limb of the adjacent synclinal. These breaks or faults in certain instances form thrust planes along which one portion of a series of beds has been carried westward, sometimes for several miles, over another portion of the same series. This highly characteristic system of unsymmetrical folds, passing at times, and especially in Tennessee and Alabama, into great thrust planes, is accounted for on the general theory that there has been lateral pressure or a tangential thrust, which has forced the strata into a series of elongated arches, in much the same manner as in the case of a rug, as above suggested, one margin of which has been forced by lateral pressure towards its central part.