HYDROGRAPHY. 113 



westward from that range of elevations to the bed of the 

 Mississippi River, which is the great drain of the streams 

 which flow over the southern declivity of the vast central 

 basin, or the Mississippi and the Mackenzie plane of the in- 

 terior valley. 



The Alleghany Mountain, as the dividing ridge in the 

 midst of the eastern plateau, is the separating line or range 

 of centres of the streams flowing through the planes above 

 designated. In New York and Pennsylvania, we are pre- 

 sented with the third of the five Appalachian hydrographi- 

 cal centres on the eastern side of the continent, proceeding 

 from the north, described by physical geographers. The 

 water-systems of these axes, and their general connection 

 with the hydrography of the continent, is a subject of ex- 

 treme interest. Leaving the parallel Appalachian moun- 

 tains and their groups of streams, the waters of the Alleghany 

 demand a brief but special notice. 



The true fountains of the streams being the heavens, or in 

 other words, the waters which they convey being all meteoric 

 in their origin, as from the falling of rain and snow, with the 

 precipitation of vapors, it follows that the higher in the 

 mountain, and the nearer to their springs or points from 

 which they emerge after percolating the soil and rocks, the 

 freer and more perfect will be their waters from earthy 

 elements, and the least changed will they be from their ori- 

 ginal meteoric condition. After falling, the waters soon burst 

 forth in springs on the heights of the ranges, and seek by 

 the first declivity to flow east or west, as the lines of denuda- 

 tion may necessitate. 



The first springs which rise near the summits in the gaps 

 or gorges of the mountain, or in the valleys or washes from 

 its sides, form swift and rushing streams which fall over 

 rocky beds, broken by frequent rapids. 



It is often observed that these rivulets in the heights of the 

 mountain, rising from the same spring, separate and flow 

 in opposite directions, into the Gulf of Mexico and Atlantic 

 Ocean. 



10* 



