1885.] NATURAL SCIENCES OF PHILADELPHIA. 105 



obtained show an anticlinal structure within. As already stated, 

 their materials are finer in the interior, and most coarse in the 

 exterior, and sometimes, though rarely, large boulders lie on the 

 surface. The comparative shortness of their courses distin- 

 guish them from the long river-like osars. Their origin and 

 significance can best be appreciated after a description of a few 

 of them in detail. The accompanjnng map gives their general 

 position with regard to the terminal moraine. 



There are three kames in Northampton County, Pa., which are 

 especially instructive. The most prominent of these is that 

 which traverses the centre of Mt. Bethel Township in a north- 

 east direction, follows approximately the valley of Jacobus 

 Creek, and ends upon the banks of the Delaware at Portland. 1 



This kame, which has been mistaken for the terminal moraine, 2 

 is composed of a series of interlacing ridges and hummocks, 

 often enclosing kettle-holes, and formed of stratified sand and 

 water-worn gravel, carrying occasional rounded boulders upon 

 the surface. 



The town of Portland is built upon the kame, which here rises 

 100 or more feet above the river, forming a prominent hill. Some 

 fine railroad cuts, through several ridges of the kame, 2^ miles 

 from Portland, show it to consist of a stratified sand overlaid b} T 

 a boulder-bearing clay, or till, as though it had been formed by 

 running water beneath the ice, which on melting dropped the till. 

 At this place, one mile southeast of Roxborough ( Johnsonville 

 P. 0.), the kame is composed of a series of reticulated ridges, 

 enclosing typical kettle-holes. One of these, known locally as 

 the devil's kettle, and supposed by some to be an old Indian fort, 

 is a symmetrical oval depression, surrounded by a raised rim, 300 

 feet long by 200 wide, and 30 deep. Like most kettle-holes, it 

 has its longer axis parallel to the direction of the kame in which 

 it lies. In the same neighborhood, similar rounded shallow depres- 

 sions, with neither inlet nor outlet, lie upon the very summit of 

 sandy ridges 100 feet above the level of the surrounding country. 



These kettle-holes do not appear to be the result of natural 

 erosion, and they are in no way allied to ordinary valleys or 

 ravines, produced by the action of running water. The instruc- 



1 See Page Plates 8 and 9, in Report Z, pp. 53, 68. 



2 F. Prime, Proc. Amer. Phil, Soc, xviii, 85. 



