12 GEOLOGY OF THE NAERAGANSETT BASIN. 



trough of the Connecticut Valley may be regarded as in its nature essen- 

 tially equivalent to the more southern basins, the only substantial difference 

 being that on both sides it is bordered by a wide field of high-lying ancient 

 rocks, which extends eastward nearly to Worcester and has a height that 

 is not found in the case of the walls on the Atlantic side of the more southern 

 basins. 



At Worcester we come upon the most southern of the troughs on the 

 eastern side of the central Appalachian axis in which well-determined Car- 

 boniferous rocks appear. The form of this basin is not well known, but, 

 from what has been learned concerning it, it appears to be relatively narrow 

 and long, having in general a closer resemblance to the synclines of the 

 Alleghenies than any other of the troughs in the group which we will here- 

 after term the East Appalachians. The Narragansett trough is next in order, 

 but, as it is to receive special treatment, it may here be dismissed with 

 the brief statement that in its type of form and in the nature of its dis- 

 locations it differs from the West Appalachian or Alleghenian series of 

 dislocations. 



North of the Narragansett district we have in the Boston Basin a con- 

 siderable downfold, the axis of which extends in a prevailing east-west 

 direction, the depression having a characteristically great proportionate 

 width and an irregular form which belongs to the other East Appalachian 

 depressions. 



From the Boston Basin northward the complicated and imperfectly 

 known geology of the country indicates a succession of these basins dis- 

 tributed along the coast of Massachusetts, New Hampshire, and Maine to the 

 New Brunswick district. One of these occurs at Newburyport; another is 

 traversed by the Penobscot River; others lie between Mount Desert and the 

 outer Cranberry Islands and to the north of the Mount Desert Mountains ; 

 yet another, or perhaps two partly separated basins, are to a great extent 

 occupied by Cobscook and Passamaquoddy bays ; still others exist along 

 the coast of Maine, though their outlines have not been traced. The Car- 

 boniferous areas of New Brunswick and Nova Scotia appear to have been 

 preserved in basins having the general character of the East Appalachian 

 troughs 



Reference has already been made to the decided differences in the 

 forms of the folds which occur on the two sides of the old Appalachian axis. 



