668 MARIUS R. CAMPBELL 



(^) Character of the river valley. — From South Pittsburgh, 

 Tennessee to the head of the shoals, the valley of the Tennessee 

 River is broad and worn down about to the baselevel of the 

 stream at the head of the shoals. Reliable data concerning the 

 character of the valley below the shoals are difficult to obtain, 

 but the preponderance of evidence seems to show that this also 

 is a rather old valley, with all of the side branches cut down to 

 the level of the river. From this it appears that the valley 

 below the shoals is fairly comparable in age and amount of 

 excavation to the valley above the shoals, and that both have 

 the appearance of considerable age. Between these two old 

 portions of the valley lie the Muscle Shoals in which active cor- 

 rasion is going on today. This result could not have been pro- 

 duced if the region had suffered general elevation alone ; hence 

 the question is narrowed down to the theory of a local uplift. 



(<:) Character of the stream. — Since the rocks composing the 

 shoals are the hard, cherty beds of the lower Carboniferous, we 

 should expect to find some evidence of ponding above the shoals, 

 if they were caused by a local uplift. According to the Hunts- 

 ville sheet of the United States Geological Survey and the 

 description given by the Army Engineers^ who made the survey 

 of the river there are distinct traces of ponding from Brown's 

 Ferry to a point south of Huntsville. All of the phenomena 

 associated with the Muscle Shoals point to a recent and local 

 uplift as the cause of the barrier. 



There are many other streams in the Appalachian region 

 which show barriers and gorges of quite recent construction, but 

 in most cases they are due to a general elevation which has 

 simply produced a revival of the stream. A critical study of 

 these obstructions fails to reveal the characteristic features found 

 in the Tennessee River at the Muscle Shoals. 



(2) REMOTE CHANGES SHOWN IN THE STREAMS OF THE MIS- 

 SISSIPPI VALLEY. 



The adjustments of this order are confined to the rearrange- 

 ' Report of the Secretary of War, Vol. II, 1868-69, P- 584- 



