14 PHYSICAL GEOGRAPHY OF 



The summit between the Muskingum and Cuyahoga, in Ohio, is but 990 feet 

 above tide ; that between the Sandusky and Scioto, also in Ohio, and further 

 west, is 923 feet ; the dividing ground between the Wabash and Maumee, in 

 Indiana, is reduced to 745 feet; and, finally, that between the Ilhnois river and 

 Lake Michigan is but about 610 feet above the level of the sea. 



Proceeding from the Ohio to the west, the plane of the country descends 

 towards the Mississippi; where, as before described, it intersects the great 

 plane which forms the bed of the western tributaries of the Father of Rivers. 

 In fact, the great slope from north to south has here, also, a dip from east to 

 west, partaking of the general inclination of the country which prevails from the 

 summit of the Alleghany to the bed of the Mississippi. 



This profile must be regarded as a beautiful practical illustration of the accu- 

 racy of the spirit level. Many of the elevations which it exhibits have been 

 obtained by lines of survey carried from the Hudson to Lake Erie, and from 

 Lake Erie, through Ohio, Indiana, and Illinois, to different points along the 

 Ohio river ; others, by surveys across the mountains of Pennsylvania and Vir- 

 ginia, made by different agents, and requiring the transfer of some fifteen or 

 twenty thousand different observations. Yet these results, continued as the 

 levels have been along lines of five hundred, and in some instances more than a 

 thousand miles in length, are so accurate and consistent, that when the writer 

 had projected in profile the elevation of a point on the Ohio only sixteen feet in 

 error, he was enabled to detect the discrepancy, and obtain an authentic result 

 in conformity with other estabhshed facts. 



It is not practicable to exhibit even all the principal tributaries of the Ohio 

 on the same profile, without producing confusion. They must be compared, 

 therefore, by their respective inclinations and developments. 



The Tennessee river is, without question, the first in magnitude and import- 

 ance, and destined when improved, as it will probably hereafter be, and con- 

 nected by railroads with the great valley of Virginia, and the seaports of South 

 Carolina, Georgia, and Alabama, to perform a part in the commerce of this 

 Union more important than that of any other stream, save the Ohio, from the 

 Atlantic to the Mississippi. 



The mouth of the Tennessee is computed to be 45 miles from that of the 

 Ohio ; and its low water level is there about 286 feet above the Atlantic. Its 

 elevation at Chattanooga is 643 feet above tide ;t and the average descent of the 

 stream below that place is about seven inches per mile. 



The elevation of the Holston, the principal tributary of the Tennessee, is 

 1914 feet above tide at Seven Miles ford, in Virginia;* and the fall of that por- 

 tion of the river, between Seven Miles ford and Chattanooga, is about two and 

 a half feet per mile. 



The summit which separates the head waters of the Tennessee from those of 

 New river, at Mount Airy, is 2563 feet above the Atlantic* 



• Surveys of C. Crozet, civil engineer. t Surveys of J. Edgar Thomson, civil engineer. 



