26 PHYSICAL AND GEOLOGICAL DESCRIPTION. 



few occur on the southeast side of the same swamp near 

 Dennisville. These boulders vary, from a few pounds up 

 to two or three tons. They are mostly of a stratified sili- 

 cious stone, some specimens compact enough to be called 

 quartz rock, and others more or less friable like a sand- 

 stone. Small boulders of granite rock are occasionally 

 met with. 



§ The gravel stones found with the boulders are very 

 coarse, and remarkable for the variety in their compo- 

 / sition. Quartz pebbles are most abundant, but those of 

 slate, limestone, and sandstone are common; and those 

 containing shells, corals, and other organic remains, are 

 frequently met with. These fossils appear to belong to 

 the Silurian rocks which are in place in the northwestern 

 part of the State, and in New York and Pennsylvania; 

 Towards the lower part of the Cape the gravel is not as 

 coarse, and is more quartzose in its character; not only 

 granular quartz, but impure agate, chalcedony, &c., being 

 common. The strands near the steamboat landing, and at 

 Town Bank^ are noted localities for transparent quartz 

 pebbles. These are much sought after by visitors, and are 

 known as Cape May diamonds. The same varieties of 

 pebble are also found in the banks and on the upland, but 

 being covered with loam, they are not as conspicuous as 

 they become after having been washed from the bank, and 

 exposed for some time to the roll of the surf. 



§ At Tuckaho^, casts and impressions of the common 

 clam ( Venii^ mercenaria) are found in cemented gravel. The 

 cementing material is oxide of iron, and no traces of the 

 lime of the original shell are left. Some of the casts are 



