PENNSYLVANIA AND DEPOSITS THEREIN. 



63 



deep water by a current moving to the Barnes col, and in quiet water, 

 as shown by the uniform thickness of the beds. Fig. 6 shows a 



Fig. 6. Lower Jiidian Hollow Sands, west side. 



westward extension of the same beds on the edge of the scour of the 

 stream in the reversed Conewango, as each bed thins out, and some- 

 times completely disappears, as it is influenced by it. In fine, the 

 strata were shaped at that time as we see them to-day, for this is no 

 subsequent cutting down. Each bed becomes thinner, and the dip 

 of the upper layers is steeper than of those at the base. Besides this, 

 there can have been no sculpturing of these beds or of their surface 

 since the deposition of the iceberg clay which is found — with vary- 

 ing degrees of sandiness or of silt — capping everything about War- 

 ren, and so down the Allegheny to Pittsburgh. At times the boulders 

 in this cap are of large size, and speak of ice masses floating in deep 

 ponding, as the deposit in which they occur is so uniformly com- 

 posed of small sorts : at times it is clean silt with little or no larger 

 sorts. Along the Conewango the Lozuer Indian Hollow Sands vary 

 in thickness from 30 to 125 feet, depending upon the conditions of 

 deposition in the different areas where it is found. It rests in the 

 blued, sticky Conezvango Clay, which carries wood fragments and 

 logs, and is sometimes over 200 feet thick. 



