TOPOGRAPHY. Three of the four topographical belts which form the Eastern United States may be recognized in this State, running across its territory from southwest to northeast. The At lantic coastal plain does not come within the State limits, so that the first of the three belts is the Piedmont Plain (q.v.), which occupies the southeastern portion between the lower course of the Delaware and the Blue or Kittatinny Moun tain range. It has a width of about 60 miles. and ascends by gentle undulations from sea-level at the Delaware estuary to an elevation of 500 feet at the base of the mountains. It is broken, however, by several low ridges in the southeast. and farther inland by the interrupted chain of semi-isolated groups of hills known as the South Mountain, which farther north becomes the High lands of New Jersey and New York. The second belt is the Appalachian Mountain region. It crosses the State toward the northeastern corner as a system of more or less parallel ridges, to gether from 50 to 80 miles wide. The eastern ridge is the Blue Mountain. known farther north and in New Jersey as the Kittatinny Range. It rises abruptly from the plain to a uniform height of a little over 1000 feet, or about 1500 feet above the level of the sea. It is broken by but few river gaps, notably that of the Susquehanna (which pierces the entire mountain belt). and the Delaware Water-Gap, on the eastern bound ary of the State. West of the Blue Mountain there follows a succession of low ridges bearing various names, and intersected here and there by transverse river valleys. They appear almost like waves on the ocean, turning their steep faces southeastward and sloping gently toward the northwest, and they inclose a number of fertile and populous valleys. North of the Susquehanna they pass in the west into irregular masses which merge with the western plateau. but in the south ern half the undulating belt is sharply limited on the west by the high and steep face of the Allegheny Range. The western slope of the lat
ter falls gradually toward the plateau. though it is flanked by a few minor ridges, the extreme western outliers of the system, chief among which is Laurel Hill in the southwestern part of the State. The highest point in the State is North Knob, 2684 feet above the sea. The third topographical region is the broad Allegheny Pla teau, covering the entire western half of the State. Its horizon has an elevation of 1000 to 2000 feet, sloping gently to the south and west. But it has been reduced by erosion to a compli cated hill-country, or rather valley-country, being intersected in all directions by river-valleys, some broad and open, others narrow, with abrupt slopes 500 to 800 feet deep. The line of 1000 feet elevation is only two to five miles from the shore of Lake Erie, so that there is here no lake shore plain.
IlvtatoGnAeur. The three chief river systems are, in the order of their drainage areas, the Sus quehanna, the Ohio, and the Delaware. These to gether drain over 90 per cent. of the State. An insignificant area in the south belongs to the Potomac system, and in the north to the Gene see, while the extreme northwestern corner is drained by short streams flowing into Lake Erie. The Delaware, which is navigable for the largest ships to Philadelphia, and for small steamers some distance above, drains, the eastern slope through its right tributaries, chief of which are the Lehigh and the Schuylkill. The Susquehanna traverses the State in a large zigzag from north to south. receiving its two main the West Branch and the Juniata, from the west. It is broad, but shallow and unnavigable. The western part of the State is drained by the Ohio and its two great headstreanis. the Allegheny and Monongahela, both of which are navigable for some distance above their junction at Pittsburg.