1894.] NATURAL SCIENCES OF PHILADELPHIA. 103 



the Delaware, got into its place with nowhere save the gritty hill 

 crest just above to come from, is the question. Could it have been 

 the residuum of the rock decomposition which originally formed 

 the cave cavity or in other words the rubbish of cave ero- 

 sion choking up three- fourths of the eroded hole?^ We would 

 know how and why successive pools of yellow mud-bearing water 

 could cover the floor once upon a time and not now, where 

 the water came from, since any down running rivulet would 

 have rolled in the hillside grit with it, and why the flooding pro- 

 cess was not interrupted by intervals, when animals came in and de- 

 bris was formed ? 



A possible answer to these questions seems to be suggested in the 

 important and interesting fact that Hartman's Cave lies eight miles 

 north of the glacial moraine, diflering therein by position from all 

 other caves in the United States lying to the southward of the now 

 well-known silhouette of pebbles that profiles the southern limit of ice 

 advance. It is therefore one of those glaciated caves distinct and 

 individual by position, full, perhaps, of new secrets for us, which, it 

 the glacial theory be true, must have been sealed up with superin- 

 cumbent ice like a tightly corked bottle throughout most of the frozen 

 period. 



If this clay is due to the banking up of ice and the draining of 

 muddy glacial waters into the caves' mouth then we can account for 

 it, but if ice damming and ice water had nothing to do with it, and 

 on the other hand it is due to a subsequent submergence of the hill 

 top below water level in the Champlain period, then similar clay beds 

 ought to be found in caves, like Durham, south of the moraine and 

 their absence remains to be accounted for. 



Moreover if this clay is glacial then other caves north of the 

 moraine should show the same ice-sealed barrier, beyond which no 

 preserved relic of post glacial age penetrates. 



The Indian and his relics, the fossil castoroides and peccary, 

 were left behind as we got down into the clay with nothing before us 

 it seemed but the beginning of the cavern itself. Was the cave then 

 no older than the melting ice ? If so, why and how had the 



3 If this were the case the composition of the clay should, I am told, show its 

 limestone parentage. But no carbonates have been found in it to suggest that 

 it was a near relative of limestone, while on tlie other hand it showed the same 

 reactions as clay dredged up from the bottom of the Delaware Eiver, near 

 Chester. 



