i6o 



SURFACE GEOLOGY. 



for a distance of 150 feet Near its east end, iron-stained gravel and sev- 

 eral stones a foot in diameter were found between the clay and the west 

 edge of the underlying sand. 



Eastward, these deposits lie in a kame-like ridge, a section of which 

 (Fig. 45) shows one side of it to be wholly gray clay, while the other side 



Gray clay, its lower portion 

 distinctly stratified. 



Silver street, 

 bridge over R. R. 



Sand overlain by gray clay. 



Fig. 45.— Excavation for the Portsmouth & Dover Railroad, iooo 



FEET EAST FROM FiG. 44. 



Length, about 500 feet; depth, 20 feet; top of .section is about 100 feet 

 above the sea. 



is mainly sand ; but their junction is concealed by the abutments of a 

 bridge. The outer edge of the sand, however, is overlain by similar clay. 

 Pine Hill cemetery, a half mile farther south-east, is a level plain of 

 horizontally stratified sand, 150 feet above the sea. It is bounded on the 

 north and west by escarpments, which descend steeply 30 feet. The dep- 

 osition of this sand appears to have been confined here by walls of ice. 

 On the south-east are ledgy hills which are somewhat higher, in whose 

 hollows are low mounds or ridges of gravel and sand, one of which was 

 observed to contain masses of till, one to three feet thick, full of angular 

 boulders up to two feet in diameter (Fig. 46). These materials probably 



^ fell from the glacier upon the margin of 



ice at its foot, and when this was broken 

 up, they were floated away on rafts, which 

 at length melted, dropping their freight 

 to be thus embedded in modified drift. 

 The pebbles which we have mentioned as 

 occurring here and there in the gray clay, 

 were distributed in the same manner. This clay and its pebbles were 

 deiDOsited at a later date, following the withdrawal of the ice-sheet by 

 which the earlier gravel and sand were confined in these kame-like plains. 

 The sea in this period stood at a higher level than now ; and the 

 clay was probably a marine deposit brought down from the melting ice- 

 sheet at the north-west. It is well shown in Dover, Madbury, Durham, 

 and Newington, forming the surface of much of these towns, but not 



Fig. 46. — Section in a Kame 



SOUTH-EAST OF PiNE HiLL 



Cemetery, Dover. 

 Scale, I inchz^io feet. 



