FROM PHILADELPHIA 143 



excellent citizens for any land and in America, in a 

 shorter time than any other people, they have changed 

 numerous wildernesses to flourishing spots. 



The hills about Bethlehem consist of the common, 

 coarse, grey limestone in which, as elsewhere, occur 

 hardly any traces of petrifactions. Beyond the Le- 

 heigh in a shaly rock, (presumably limestone also) 

 large cavities are often found, when the stone is split, 

 full of a fine yellowish meal which they use here for 

 blotting strew-sand : in the meal there always occurs a 

 spherical pyrites. On another declivity beyond the 

 river there are to be seen, I am told, remarkable stone- 

 falls, i. e. large flaws are found hollowed out of the 

 rock-wall and stuffed with little pieces of stone of the 

 same description as the solid rock as if designedly 

 broken up and poured in. By reason of later changes it 

 could not be accurately determined what was the cause 

 of this local disturbance of a former time. Similar 

 stone-falls are not rare in other parts of America. 

 Also, landslips (as they are here called), tunnel-like 

 hollows 20-30 ft. and more in depth and section are 

 not infrequently found in these limestone hills and are 

 caused by the shifting and sinking of the rock-beds at 

 a depth. For the same reason caverns are almost al- 

 ways found under landslips, but they are not every- 

 where of easy access. 



Some six miles from Bethlehem and two from Dur- 

 ham on the Delaware there is a rather large cave of 

 which people at Philadelphia already talk with respect 

 under the name of the grotto of Durham. Mr. Otto, 

 the younger, has several times visited the cave. It is 

 near the ferry, opens towards the north, is probably 

 150-160 ft. deep, has a sloping course, but is wide 



