GEOLOGICAL SOCIETY OF PENNSYLVANIA. 



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ginal level, when they would again be discharged atone 

 or both extremities of the trough. 



The conclusion, therefore, to which he would neces- 

 sarily arrive is, that these interior horizontal lines mark 

 the ancient beach of this lake. 



In its present state the valley of Kishacoquillas is a 

 deep elongated basin, having no other outlet for its wa- 

 ters but at this gap on its southern side; for it requires 

 to be stated that, notwithstanding the enclosing ridges 

 are prolonged many miles further to the east and west, 

 the trough is filled up to the height of several hundred 

 feet, at the positions marked A and B in the accompa- 

 nying map, pi. 9, fig. 1, by sandstone ridges and subor- 

 dinate hills. Beyond these points, A and B, it will be 

 seen that the waters now drain in opposite directions : 

 on the west into the Juniata ; on the east into the Sus- 

 quehanna. It is probable that this long continued 

 drainage action, for even during the existence of the 

 lake something like a similar action would be going on 

 longitudinally, has led to the degradation of these inter- 

 nal barriers, and they have evidently been lowered and 

 modified in a considerable degree. The west end of the 

 basin is somewhat confusedly crowded with subordinate 

 hills, swells and undulations, their present configuration 

 being influenced by the rapid descent of the surface wa- 

 ters, which have there a fall of upwards of three hundred 

 feet into the Juniata. Near A the valley terminates in 

 a mere wedge, being elFectually closed by a ridge of 

 white gritstone, and the limestone is hollowed out to the 

 depth of a hundred feet. It may be remarked here, in- 

 cidentally, that at this western extremity, beyond A, a 

 great change occurs in the inclination of the rock for- 

 mations. Instead of a southerly dip, they now incline to 

 the N. W. at as high an angle as 60 to 65°, gradually 

 diminishing, and again rising in a basin form at the dis- 

 tance of five or six miles to the north west, towards Hun- 



