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Rh higher elevations, like the steeper slopes, lie towards the west. Cross Fell Edge terminates southward at a high pass (about 1400 ft.) between the head of the Belah, a tributary of the Eden, and the Greta, a tributary of the Tees. This pass is followed by the Tebay and Barnard Castle line of the North Eastern railway. The hills between the Lune valley on the west and the headstream of the Eden and the Ribble on the east are broken into masses by the dales of tributaries to the first-named river—here the chief elevations are Wild Boar Fell (2323 ft.), Whernside (2414 ft.), and Ingleborough (2373 ft.). The Ribble and Eden valleys afford a route for the main line of the Midland railway. Well-marked eastward ranges occur here between Swaledale and the river Ure, which traverses the celebrated (q.v.), and between the Ure and Wharfe. In the first the highest points are High Seat (2328 ft.) and Great Shunner Fell (2340 ft.); and in the second Buckden Pike (2302 ft.) and Great Whernside (2310 ft.). There is then a general southerly slope to the Aire gap.

The southern section of the system calls for less detailed notice. Heights exceeding 2000 ft. are rare. The centre of the section is the well-known (q.v.) of Derbyshire. Both here and throughout the system the summits of the hills are high uplands, rounded or nearly flat, consisting of heathery, peaty moorland or hill pasture. The profile of the Pennines is thus not striking as a rule, but much fine scenery is found in the narrow dales throughout; Wensleydale, Wharfedale and other Yorkshire dales being no less famous than the dales of Derbyshire. In the parts about Settle below Ingleborough, in Derbyshire, and elsewhere, remarkable caverns and subterranean watercourses in the limestone have been explored to great depths. In Ingleborough itself are the Ingleborough cave, near Clapham; the chasm of Gaping Ghyll, over 350 ft. deep; Helln or Hellan Pot, a vast swallow-hole 359 ft. deep, only exceeded by Rowten Pot (365 ft.) near Whernside; and many others. Malham Tarn, near the head of the Aire, is drained by a stream which quickly disappears below ground, and the Aire itself is fed by a brook gushing forth in full stream at the foot of the cliffs of Malham Cove. A notable example in Derbyshire is the disappearance of the Wye into Plunge Hole, after which it traverses Poole's Cave, close to Buxton. There may also be noted the remarkable series of caverns near (q.v.). Lakes are few and small in the Pennine district, but in some of the upland valleys, such as those of the Nidd and the Etherow, reservoirs have been formed for the supply of the populous manufacturing districts of Lancashire and the West Riding of Yorkshire, which he on either flank of the system between the Aire gap and the Peak. (For geology see and articles on the several counties.)

PENNSYLVANIA, a North Atlantic state of the United States of America and one of the original thirteen, lying for the most part between latitudes 39° 43′ 26.3″ and 42° N. and between longitudes 74° 40′ and 80° 31′ 36″ W. The state is in the form of a rectangle, except in the north-west where a triangular projection, extending to 42° 15′ N. lat., gives it a shoreline of almost 40 m. on Lake Erie, on the east where the Delaware river with two large bends separates it from New York and New Jersey, and in the south-east where the arc of a circle which was described with a 12-m. radius from New Castle, Delaware, forms the boundary between it and Delaware. The forty-second parallel of N. latitude forms the boundary between it and New York on the N.; Mason and Dixon's line is the border between it and Maryland and West Virginia on the south and a north and south line marks the boundary between it and West Virginia and Ohio on the west. The total area is 45,126 sq. m. and of this 294 sq. m. are water surface.

Physical Features.—Pennsylvania skirts the coastal plain in the south-east below Philadelphia, is traversed from north-east to south-west by the three divisions of the Appalachian province—Piedmont or older Appalachian belt, younger Appalachian ridges and valleys and Alleghany plateau—and in the north-west corner is a small part of the Erie plain. The entire surface has a mean elevation of about 1100 ft. above the sea. It rises from 20 ft. or less on the bank of the Delaware between Philadelphia and Chester to 2000–3000 ft. on the higher ridges in the middle section (3136 ft. on Blue Knob in Bedford county), and falls again to 900–1000 ft. on the Ohio border and to 750 ft. or less on the Erie plain; in the south-east is an area of about 6100 sq. m. that is less than 500 ft. above the sea, while on the ridges in the middle of the state is an aggregate area of about 2000 sq. m. that everywhere exceeds 2000 ft. in elevation. The area below 500 ft. is mostly in the Triassic lowland of the Piedmont region, or, as the Pennsylvania portion of it is called, the south-east province. This is an undulating plain which has been produced by the wearing away of weak sandstones, &c. On the north and west borders of this plain are two parts of a chain of semi-detached and usually rounded hills, known as the South Mountains. The north-east part is a south-westward arm of the New England uplands, is known as the Reading Prong, and extends from New Jersey through Easton to Reading. The south-west part is a north-eastern prolongation of the Virginia Piedmont, is known as the Cumberland Prong, and extends N.N.E. through the south part of Cumberland county. In the Reading Prong most of the hills rise 900–1000 ft. above the sea and about one-half that height above the surrounding country; in the Cumberland Prong their height increases to the southward until, on the Maryland border, they rise 2100 ft. above the sea and 1400 ft. above the adjoining plain. Another range of hills, known as the Trenton Prong, extends from the northern suburbs of Philadelphia both westward and southward through Chester, Delaware, Lancaster and York counties, but these rise only 400–600 ft. above the sea and have few steep slopes. Both of these ranges of hills are composed of hard crystalline rocks, and between them lies the lowland eroded on the weaker sandstones and sediments. In Bucks and Montgomery counties is a large sandstone area; traversing Chester county is the narrow Chester Valley with a limestone bottom, and in Lancaster county is the most extensive limestone plain. The Pennsylvania portion of the younger Appalachian ridges and valleys, known as the central province of the state, embraces the region between the South Mountains, on the south-east, and the crest of the Alleghany plateau or Alleghany Front, on the north-west. It extends from south-west to north-east about 230 m. and has a nearly uniform width of 50 m. except that it narrows rapidly as it approaches the north-east corner of the state. The ridges and intervening valleys, long parts of which have an approximately parallel trend from south-west to north-east, were formed by the erosion of folded sediments of varying hardness, the weak belts of rock being etched out to form valleys and the hard belts remaining as mountain ridges. After the folding the whole region was worn down nearly to sea-level, forming a low plain which bevelled across the geological structure of the entire state, including the Piedmont area to the south-east and the plateau area to the north-west. Then came a broad uplift followed by the erosion which carved out the valleys, leaving hard rocks as mountain ridges which rise about to the level of the old erosion plain. In Bedford county and elsewhere the ridges rise to 2400 ft. or more above the sea, but their more usual height is 1400 to 2000 ft. above the sea and 500 to 1000 ft. above the intervening valleys. Their crest lines are often of nearly uniform height for miles and generally are little broken except by an occasional V-shaped wind gap, a narrow water gap or a rounded knob. The valleys rarely exceed more than a few miles in width, are usually steep-sided, and frequently are traversed by longitudinal ranges of hills and cross ridges; but the Pennsylvania portion of the Appalachian or Great Valley, which forms a distinct division of the central province and lies between the South Mountains and the long rampart of Blue Mountain, is about 10 m. in width on the Maryland border and to the north-east its width increases to 20 m. The north-west part of it is a slate belt that has been much dissected by eroding streams, but the south-east part is a gently rolling belt of limestone to which occasionally a steep hill descends from the slate belt. The Pocono plateau, into which the central province merges at its north-east extremity, is a continuation of the Catskill plateau southward from New York and covers Wayne, Pike and Monroe counties and the east portion of Carbon county. Its surface is underlaid by a hard sandstone and conglomerate which erode slowly, and the general upland level, which is 1400–1800 ft. above the sea, is little broken except by shallow valleys and occasional knobs. The Alleghany plateau, which extends from the crest of the Alleghany Front to and beyond the west and north borders of Pennsylvania and covers more than one-half of the state, is much more dissected. In Tioga and Potter counties on the north middle border, it rises 2400–2500 ft. above the sea, but from this height the general upland level falls gradually to 1200–1300 ft. in the south-west and 900–1000 ft. along the Ohio border, and in Erie county there is a sudden fall of about 200 ft. to the Erie plain. In the northern, middle and south-west portions of this plateau province the upland is cut by an intricate network of narrow valleys and ravines that are commonly 300–600 ft. deep and occasionally 800–1000 ft. deep, but west of the Allegheny river, where harder rocks have resisted such deep dissection and glacial drift has filled depressions or smoothed rough surfaces, the uplands are broader and the valleys wider and shallower. Most of the Pennsylvania shore of Lake Erie is lined with a wall of sand and clay 50–100 ft. in height and along the foot of this is only a narrow beach, but in front of the city of Erie the shore currents have formed a spit, known as Presque Isle, which affords a good harbour.

The Pocono plateau, nearly all of the central and south-east provinces and the north-east portion of the Alleghany plateau are drained by the Susquehanna and Delaware river-systems into the Chesapeake and Delaware Bays; the greater part of the Alleghany plateau is drained by the Allegheny and Monongahela rivers into the Ohio river; the extreme southern portion of the central province and the extreme western portion of the south-east province are drained by tributaries of the Potomac; the Erie plain is drained by short streams into Lake Erie; and a very small section of the Alleghany plateau, in the northern part of Potter county, is drained by the Genesee river into Lake Ontario. The Susquehanna drains about 21,000 sq. m. of the state; the Ohio, Allegheny and Monongahela