PENNSYLVANIA AND DEPOSITS THEREIN. 75 



for some distance towards Stoneham. They are smaller than the 

 average of the pieces at Indian Hollow and at Clarendon, as would 

 be the case after such rough rearrangement, and they are mixed 

 with an equal proportion of local pieces eroded during the trench- 

 ing described above. (Figure 12.) 



Fig. 13 is the end of a bar composed of the Middle and the 

 Late Big Bend Gravels, of lower elevation than the Oakland Cem- 

 etery bar. The worked-over crystallines in its composition are very 

 much comminuted and among them are rocks foreign to the Claren- 

 don Gravels; but found north of Big Bend. This indicates such a 

 trenching of the col there that the scour reached to the Kinzua 

 Creek bottom. There are also large pieces of local rocks — both old 

 and fresh — which are absent from the older gravels. It is capped 

 by iceberg clay, which is from 10 to 12 feet thick in places, and 

 varies from a clayey matrix to nearly clean silt as it nears the end 

 of this bar. The figure shows the dropping of the bar-end to the 

 plain. This shaping and the decrease to one third of the thickness 

 one half mile east, shows the increase in the scour of the current, 

 'as does the absence of the clay from the sandy cap. This latter was 

 dropped after the shaping, and can be seen at the level of the plain 

 across the country road. None of these Warren formations are 

 remnants of a complete valley filling afterwards excavated. This 

 closes the various pondings of the old Allegheny River. 



TioNESTA Pondings. 

 Emlenton-Foster Pondings. 



Although the Emlenton Col is below that at Foster in the pres- 

 ent Allegheny Valley, it was the first to be trenched. Its original 

 elevation is inconsequential to this discussion, though it was below 

 1,500 feet, and probably between 1,430 and 1,480 feet, as shown by 

 beach lines about, and north of Warren. It is on account of these, 

 and of some sporadic gravels in the old West Sandy Valley that its 

 elevation is a matter of interest. 



Although the glacier crossed the mouth of the old Tionesta 

 River ages before it reached Franklin, and though there was prob- 

 ably ponding in its valley from an early date, the discharge was 



