22 Campbell — Changes in the Drainage of Virginia. 



arrangement of the drainage lines. Guest river, from the 

 Norton divide to Coeburn, exhibits unmistakable evidence of 

 a reversal of its course. All the tributaries, in this interval, 

 turn westward to join the river which flows due east. They 

 thus form a very acute angle where they unite. The present 

 position of these tributaries is found to bear no particular 

 relation to the geologic structure, but to be due to some con- 

 dition affecting 1 the stream alone. 



The tributaries which enter the river above the mouth of 

 Tom creek from the south flow, throughout their upper 

 courses, in gorges cut in the heavy conglomerate of Powell 

 mountain and much of their irregularity is due to the way in 

 which they cross its various hard beds. Before reaching the 

 river they emerge from the mountain and flow, for perhaps a 

 quarter of a mile, across the level surface of a shale valley. 

 Their normal course in this plain would be northeast, but in 

 every case they turn northwest. Below Coeburn there are 

 several small branches which in general appear to follow the 

 same law, but their courses were determined by the geologic 

 structure and hence cannot be used as evidence of reversal. 



On the north side of the river there are three main branches 

 which show this westward deflection even more strikingly than 

 the southern tributaries. Big Tom creek, joining the river 

 near Coeburn, has a decidedly westward course not in harmony 

 with the present conditions. Geologic structure did not deter- 

 mine this bend in the creek, since the rocks are approximately 

 horizontal except in the immediate vicinity of the mountain 

 where there is a gentle northerly dip away from the anticlinal 

 axis. Yellow creek also affords a good example of this west- 

 ward deflection, for in persevering in its course the stream has 

 been obliged to cut diagonally across a small anticline (x y, 



