SOME RIVERS OF CONNECTICUT. 385 



part of the Tertiary cycle, the Farmington did not have its pres- 

 ent course, but followed the open sandstone valley, along the 

 course of the Quinnipiac and Mill rivers of to-day. The earlier 

 history of this river is purely conjectural; one fact may shed a 

 little light upon it, a fact which may indicate that this course 

 was an adjusted one taken during Tertiary times. 



In pre -Tertiary times. Origin of Cook's Gap. A few miles 

 southeast of where the river emerges from the crystallines, the 

 trap ridge is cut by a deep wind notch — Cook's Gap — through 

 which the New York and New England Railroad passes west 

 from New Britain. As was pointed out some time ago by Prof. 

 Davis, ^ this is not a fault gap, because the alignment of the ridge 

 is not broken, but it is probably an abandoned water gap, the 

 head -waters of the stream which formerly occupied it having 

 been abstracted by a rival, which did not have to cross 

 a hard trap ridge. Perhaps this river was the ancestor of the 

 present Farmington, and in that case its history would seem to 

 have been as follows. A stream consequent upon the construc- 

 tional topography after the faulting and tilting at the close of 

 the Triassic, it had its upper course on the crystallines, its lower 

 on the sandstones and buried trap sheets. In its old age it crossed 

 by a shallow gap the trap sheet, which had been uncovered by 

 erosion. In the second or Tertiary cycle it was simply a revived 

 stream quickened to a new life by the post-Cretaceous uplift of the 

 peneplain. This uplift gave opportunity to a rival stream, which 

 did not have to cross the hard trap beds to intercept the waters 

 of the old Farmington, and lead them out by a shorter, easier 

 path, probably down the sandstone valley west of the trap 

 ridge. The path across the trap was abandoned, and the notch 

 became a wind gap; the river following its new course, until the 

 incursion of the ice-sheet interrupted its normal development. 

 This is of course almost entirely speculative. Cook's Gap is 

 best explained as an adandoned river gap; the Farmington is the 

 nearest river of a size proportional to the size of the gap, and the 



' P'aults in the Triassic Formation near Meriden, Conn. Bulletin of the Miis. Comp. 

 Zool. Harvard Univ. vol. xvi. No. 4, p. 82. 



