1882.] 117 [Davis. 



erally admitted that the fossils they contain show them to be of 

 rather early Mesozoic age, though whether strictly Triassic, Lias- 

 sic or Oolitic remains an obscure problem. 



The several patches are found on Prince Edward Island, in 

 Nova Scotia around the Bay of Fundy ; in the Connecticut val- 

 ley from Northern Massachusetts to the Sound at New Haven; in 

 a small, oval basin about Waterbury, Conn. ; in a long, nearly con- 

 tinuous strip from the lower Hudson across New Jersey, Penn- 

 sylvania, Maryland and Virginia into North Carolina ; and in sev- 

 eral disconnected patches in Virginia and North Carolina east of 

 the long strip. The best known of these are probably the Con- 

 necticut Valley and the New Jersey areas : to certain points in 

 the history of the former this paper is devoted. 



The ordinary view of the formation of these Triassic deposits is 

 that their sands and muds were washed into long, narrow lakes 

 or estuaries from either side, and strewn about in flat layers ; 

 that later they were tilted into a peculiar monoclinal position (of 

 which more beyond), and at about the time of tilting or after it, 

 the trap was injected in sheets between the inclined layers, sel- 

 dom reaching the surface then, but exposed now by a long acting 

 erosion which has worn away a considerable share of the old 

 deposits. The trap, as now laid bare, stands up in long ridges, 

 because it is harder than the adjoining sand-stones and has more 

 stubbornly resisted the down-wearing of erosion; and as the 

 sheets are inclined with the sandstone layers, the ridges formed 

 by their outcropping edges show steep bluffs on the side of out- 

 crop, and present long, gently sloping backs toward the dip. 

 West Rock by New Haven, Mt. Tom by Northampton, the Pali- 

 sades on the Hudson, and the Newark (or Watchung) Mountains 

 of New Jersey, are familiar examples of these peculiar forms of 

 relief, and all these are much alike in surface features ; but in 

 relative position they are remarkably contrasted. All the ridges 

 of the Massachusetts-Connecticut area face boldly to the west, 

 and slope gently to the east ; while in New Jersey, these direc 

 tions are reversed ; further, the ridges are not straight, but are 

 curved, and in such away that all those in the former area are 

 convex to the west ; in the latter, to the east. The dip of the 

 sandstone shows the same contrasts in the two regions. The gen- 



