GEOLOGICAL SOCIETY OF PENNSYLVANIA. 



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whirling in them by streams of water, similar to those 

 which I have seen at the summit of the lofty hills of Lake 

 George, in the state of New^ York. This Snake Run 

 mountain stood, as I found by compass, N. N. E. by E. 

 from the Sweet Springs ; and Peter's mountain, of which 

 I could get a peep through the trees, bore east of the 

 place where I stood. 



Here was an extraordinary phenomenon 1 an immense 

 deposit of travertin lying 350 feet above the level of 

 the spring from which it probably was derived. It seems 

 to be susceptible of no other explanation, than that the 

 level of the valley was, at some remote period, much 

 higher than it is now, and that the springs were at least 

 at this level. The Snake Run mountain is a large lime- 

 stone outlier from Peter's mountain, such as are con- 

 stantly found in the valleys. Before these were scooped 

 out by the retiring currents, it is probable the w^hole sur- 

 face of the now deeply sulcated region was continuous, 

 and that the springs issued from the bottom of the ocean. 

 When the valleys were swept out, these knobs, hills and 

 spurs, being hard compact transition limestone, resisted, 

 and were left; whilst the conglomerates, shales and sand- 

 stones, were carried away : since that period, the softer 

 parts of the formations occupying that part of the valley 

 where the springs now are, have been gradually worn 

 down, and a new direction given to the stream, whilst 

 the old travertin remains a monument of the ancient level, 

 and one of the strong geological proofs of the process of 

 denudation. 



These mountainous countries have undergone great 

 changes. 1 frequently found fragments of conglomerate 

 sandstone (old red) abounding on the slopes and in the 

 valleys, together v^^ith slabs and pieces of encrinital lime- 

 stone, which are not to be found in situ, except this last, 

 which I found near the summit of White Rock mountain, 

 a conspicuous eminence, a few miles west by south from 



