GEOLOGICAL RELATIONS. 21 



(2) The Carboniferous limestone. 



(3) The millstone grit series, 5000 to 6000 feet thick. 



(4) The middle coal formation, 4000 feet thick. 



(5) The upper coal formation, 3000 feet thick. 



Logan's section at the Joggins gives 14,700 feet thickness to the whole 

 Carboniferous series. At Pictou it has also a thickness of 16,000 feet. 

 J. P. Lesley thinks these thicknesses must be exaggerated. 



Triassic. Three well-marked areas of the Triassic formation appear 

 on the map. The one best known occupies the Connecticut valley in 

 Massachusetts and Connecticut, the area being about 2200 square miles. 

 The formation is at least 5000 feet thick, divided into three sections. 

 The lower part consists of coarse red sandstone ; the middle, of fine sand- 

 stones, shales, flags, etc. ; the upper, of reddish sandstones and conglom- 

 erates. Over most of this area a mass of dolerite divides the middle 

 from the lower section. The two upper divisions contain the footmarks 

 of birds, which have given the Connecticut River sandstones their well- 

 known celebrity. 



The second Triassic area occupies the shores of the Bay of Fundy. A 

 very large amount of trap containing native copper occurs in connection 

 with it. The third area occupies nearly the whole of Prince Edwards 

 island. 



Cretaceous. This formation appears at the southern extremity of the 

 map, on the northern shore of Long island. It is a continuation of the 

 plastic clay of New Jersey. It is a fresh-water deposit, containing lignite 

 and a few shells. Its character suggests the existence in the early Cre- 

 taceous period of a long, narrow, fresh-water lake, necessitating the pres- 

 ence of very different physical conditions from those now existing in that 

 vicinity. 



Cenozoic. The tertiary and alluvial deposits represented on the map 

 occupy a place outside the Cretaceous, between New York and Cape Cod. 

 Their absence north-east of Massachusetts has suggested the theory of 

 the submergence of the middle and northern sections of the Atlantic 

 district in very recent times. Possibly Sable island, off Nova Scotia, and 

 the great banks of Newfoundland, may indicate the position of the place 

 of these Cenozoic deposits, and consequently the outer limit of this por- 

 tion of the continent at the close of the Tertiary period. 



