Below the influx of Duck, the channel of Ten nessee rapidly approaches that of Cumberland on the right, whilst on the left the sources of Obion river flowing into the Mississippi, rise within 12 or 15 miles from the bank of Tennessee, confining upwards of 80 miles of the lower part of the valley to a width in no place 45 miles, and not averaging above ten or twelve miles mean breadth.
Taken as a whole, Lower Tennessee valley ap proaches the form of a trapezium : the western side, from the sources of Bear Creek in Alabama to the influx of Tennessee into Ohio, two hundred miles ; and an equal distance along the northeast ern side from the Ohio to Cumberland mountains at the source of Elk river. The southeastern and southern sides are also very nearly equal, or one hundred miles each ; the whole figure comprising very nearly 17,600 square miles ; of which the far largest proportion spreads above the mouth of Duck river.
If we except a small extent below the entrance of Tennessee river into the state of Kentucky, no part of Lower Tennessee valley is a tame level, though much less broken than the higher valley above Cumberland mountains. The soil of Lower Tennes see is also generally superior to that of the upper part. Limestone abounds more below the mountain chains.
Politically, Lower Tennessee valley comprises in Alabama, south of Tennessee river, a small section of Cherokee territory, on the east ; the counties of Morgan, Lawrence, and Franklin, with a section of Chickasaw territory on the west ; and north of Tennessee river all the counties of Lauderdale, Limestone, and Madison, with the western and larger portion of Jackson : in the state of T ennes see this section embraces all the counties of Frank lin, Lincoln, Bedford, Giles, Maurv, Hickman, Lawrence, Wayne, Hardin, Perry, and Humphries, with part of Stewart, Henry, Carroll, Henderson, 1I'Nair, Williamson, and Dickson : in Kentucky, part of Calloway and M'Cracken west, and of Li vingston, Caldwell and Trigg, east of Tennessee river.
The entire valley of Tennessee comprises an ex tent of 41,600 square miles. If the valley of Ten nessee is compared with the whole valley of Ohio, the former spreads over very nearly a fifth part of the latter, and gives to Tennessee the first rank amongst the confluent streams of the general re cipient.
Amongst the peculiar features of Tennessee, the most remarkable is, that rising as far north as Lat. 37' 10', and curving thence sou thwardly to Lat. se 23', the channel again recurves back to its original latitude. and falls into Ohio river almost exactly due W. from the primitive fountains in Tazewell county ; thus embosoming nearly the whole large valley of Cumberland, and part of that of Green river.
Geographically, Tennessee valley lies between N. lat. 34° 10' and 37° 10, and in long. between 4° 15' and 11° 40' W. from W. C. It is the first and largest, advancing from south to north, of those streams which gush from the elevated vales of the Appalachian system,and which flow westward into the great basin of the Mississippi.
In relative height above the ocean, if the moun tains are included, there is a difference of from 1700 to 2000 feet between the extremes of Tennes see valley. The arable surface of Tazewell and Wythe counties in Virginia we saw estimated at 12.00 feet ; that of high water at the confluence of Tennessee and Ohio but little, if any, exceeds 300 feet, giving a difference of 900 feet to the cultivated surft.ce. This comparison may be regarded as a nearly just mean, and is fully equal to two degrees of latitude, and in part accounts for the great dif ference of climate on the same curve of latitude near the Ohio and on the sources of Clinch and Holston rivers.
The current of every branch of Tennessee is very rapid, shoals are common, but direct falls rare. Of shoals, the most remarkable are those which have become so well known under the name Muscle Shoals, between the counties of Lauderdale and Lawrence in Alabama. These shoals are, at all seasons, difficult to navigate, though from the in frequency of accident, must be far less dangerous than usually represented. With all its impedi ments from shoals and rapid descent of the general plain, Tennessee valley is navigated downwards from very near the sources of most of its streams.