DRAINAGE DEVELOPMENT. The region now oc cupied by the Appalachian \lountains has been the scene of many physiographical changes too complex to explain here. At a comparatively re cent time, however, the whole of the Appalachian system consisted of a great rounded plateau with an elevation of perhaps 4000 feet, the surface of which is called by geologists the Kittatinny Plain. Above this plain arose to a moderate height the now high mountains of western North Carolina. Along a central zone the land in creased in altitude to a region in Virginia which thus became the watershed. The rain now did its work, and the great rivers—the New, the Roanoke, James, Potomac. and Susquehanna— cut out their paths through the then nearly level region, and a well-developed system of highlands and drainage was established. However, the sub sequent elevation of land in this region by amounts ranging from 200 feet in the north to 1700 feet in Virginia, once more disturbed the adjustment of the water systems, and gave a new impetus to the work of the flowing waters.
While the Appalachian Mountains form the watershed between the Atlantic Slope and the \lissi- ippi Valley. yet throughout there is no definite watershed line on one side of which the rivers flow to the west, and on the other toward the east. In the northern part the streams ehietly break through the mountains from the western side to the east, In the middle part, some escape toward the east and some toward the west; while at the south the eastern moun tain range of the Blue Ridge forms the water shed. The watercourses appear to be independ ent of the direction of the mountain ranges, and instead of pursuing what appear to be the natu ral directions along the present great valleys, they flow across the ridges through deep gaps in them. This peculiar circumstance is due to the
fact that these gaps were cut by the streams be tore the intervening ridges were upheaved.
The chief streams draining the eastern slope of the Appalachian into the Atlantic are the HI:d son and its branches on the west, the Delaware, Schuylkill, Susquehanna, Potomac, and the James, which cut their way eastward through the mountain ranges; and the Rappahannock, Dan, Vadkin (Pedee), Catawba, Broad, Saluda (branches of the Santee), and the Savannah, which rise from the eastern slope of the Blue Midge, whose western slopes drain into the Sus quehanna, Shenandoah (Potomac), ,James or Tennessee. On the south are the Chattahoochee I head stream of the Apalaehieola) and the ('oosa (head stream of the Alabama), flowing into the Gulf of \lexico. The streams draining the Appalachian region on the west are tributary to the Ohio River. They are they Hiwassee, the Little Tennessee, and the French Broad, which flow from the Blue Ridge through a network of high mountains, and break through the great Unaka range to the Tennessee; the Ilolston and Clinch rivers, al-o tributaries of the Ten nessee; the C'umherland, the New (head of the Kanawha), the Little Kanawha, Allegheny, and Monongahela. The last two join to form the Ohio.