ART. TENNESSEE RIVER, Vol. XVIII. pp. 666-7.
Between the valley of Sandy river and its reach ing Tennessee river, in a distance of 325 miles, the Cumberland chain is a dividing line eyriver source, and in many parts presents an impassable wall of rock. if we, however, compare the mountain sys tem with the great inflections of the Ohio, Ken tucky, Cumberland, and Tenness&., rivers, we dis cover the influence of the former over the channels of the latter far westward of any regularly de lineated chain. Similar observations have been made on the structure of the Atlantic slope, east ward of the Appalachian system. Restricting the system, nevertheless, to the space over which dis tinct chains extend in the United States, it stretches along something above one thousand miles. The breadth is generally not far from one hundred and seventy; of course, the physical section of the United States embraced by the Appalachian sys tem, comprises one hundred and seventy thousand square miles. This physical region, though moun tainous, is very far indeed from uniform in appear ance, or in soil. The intermediate valleys between the chains are real table lands, varying in elevation above the Atlantic tides, from 500 to 2500 feet. It has been shown in this article, that the chains tra verse obliquely over the river valleys on both sides of the summit of the river source. We have also briefly traced the main chains, but so numerous are the intervening ridges, and so defective all de lineations of their position, or even individual ex istence, that it is utterly impracticable to deter mine to any decided exactness the space actually occupied by mountains. The number of chains may be assumed at 12. and the mean breadth of their bases at three miles, without much danger of great error either way. This would yield an ag gregate length of mountain of 12,000 miles, and the area occupied by the chains at 36,000 square miles; leaving for the intermediate table lands 134,000 square miles.
We now proceed to a specific description of the rivers flowing from this great mountain physical section, commencing with the Alatamaha, and advancing north-eastwardly along the Atlantic slope to the St. Johns of Maine and New Bruns
wick, and returning to the Alatamaha, and pro ceeding by the opposite direction to complete the circuit of the system.
Alatamaha is formed by two main branches, Oco nee and Ocmulgee. Both confluents have their sources in the lateral spurs of the Appalachian chains, and, what is very remarkable, in a distance of seventy miles the remote fountains of both streams rise from five to ten miles from the main channel of Chatahoochee river. The Oconee, or eastern branch, rises between the sources of Broad river branch of Savannah and Soquie branch of Chatahoochee river, at North Lat. 34° 18', Lon. W. from \V.C. 6° 40', and in Hall county, Georgia. Flowing thence S.S.E., by comparative courses, 175 miles, receives the Ocmulgee, almost exactly on North Lat. 32°. The valley of the Oconee is narrow, when compared with its length, being under fifty miles where Ns idest, and not much, if any, exceed ing a mean breadth of 25 miles.
The Ocmulgee is, in fact, the main stream. both as to length of course and surface drained, and ris ing at North Lat. Lon. 70 NV. from W.C. in Gwinnett county, Georgia, flows thence 170 miles, by comparative courses, and, in a remarkable man ner, parallel to, and distant about 35 miles from the Oconee. Sweeping round to east and north east, the Ocmulgee joins the Oconee between Mont gomery and Appling counties.
The entire upper valley of the basin of Alatamaha is in length 170 miles, and having a mean breadth of 60, comprises an area of 10,200 square miles.
Below the union of its two main constituent streams, the Alatamaha pursues a comparative course of about ninety miles, in a south eastern di rection, to its entrance into the Atlantic Ocean, at the northern extremity of St. Simon Island, North Lat. 31° 19', and Lon. 1V. from W.C. 6° 22'.