252 The Physical History of the Trias. 



have seen, is not the case either in ISTew Jersey or the Con- 

 necticut Valley. These views, also, fail to explain many of the 

 peculiar relations that exist between the two separate portions 

 of this formation. The little outlying mass of these rocks in 

 the valley of the Rousatonic, instead of being a remnant left 

 by denudation, must be looked upon, in the light of this theory, 

 as a distinct deposit formed in a isolated basin. 



This view, moreover, requires as great an amount of subsi- 

 dence and sedimentation as the one advanced in this paper, and 

 as great an amount of vertical upheaval, which instead of oc- 

 curring with a transverse axis a hundred miles in extent, 

 must have been confined to the narrow limits of each separate 

 valley. [See note C, page 254.] 



As a synopsis of the views advanced in this paper, we may 

 state briefly ; 



1st. That the facts which we have gathered as to the physical 

 history of the Triassic beds of New Jersey and the Connecti- 

 cut Valley, tend strongly to show that these two areas are the 

 borders of one great estuary deposit, the central portion of 

 which was slowly upheaved, and then removed by denudation. 



2d. That the trap-sheets were derived from a reservoir be- 

 neath the estuary deposits, and represent in part the force that 

 caused the upheaval. The outburst of trap, as we have seen, 

 must have been the closing event of the Triassic changes, and 

 have occurred after the sedimentary beds had been up- 

 heaved and eroded. 



3rd. The detached areas of Triassic rocks occurring alono- 

 the Atlantic border from New England to North Carolina, 

 seem fragments of one great estuary formation, now broken up 

 and separated through the agency of upheaval and denudation. 



These broad generalizations have been reached by simply 

 following the path marked out by well-authenticated facts. 

 Having two portions of an arch given, we have endeavored to 

 reconstruct the curve. 



Since reading this paper before the Academy, my attention 

 has been called to the fact that Professor Keiv, in his report on 



