Triassic Formation of the Connecticut Valley. 433 



fault planes that bound the several blocks. The original 

 surface of the uppermost bed of sandstone would have been 

 essentially parallel to this surface of the trap sheet, but a few 

 thousand feet higher. 



Percival long ago called attention to the great curve of the 

 main trap sheet from the Hanging Hills to Mount Holyoke in 

 Massachusetts. The restored surface of the sheet, although 

 somewhat interrupted by faults, forms a great half-boat, with 

 the keel along the line joining the ends of the curve and the 

 western side of the boat following the main trap ridge. The 

 boat may be enlarged by extending the sheet southeast from 

 the Hanging Hills through Lamentation, Higby (Besick), Paug 

 and Toket Mountains to the eastern margin of the Triassic 

 formation north of JBranford. In this portion of the curve, 

 the faults are much stronger than farther north ; but viewed 

 in a large way, the whole sheet from Toket to Holyoke may 

 be regarded as a somewhat broken half-boat, in the attitude 

 already described, with the bow at Belchertown, Massachusetts, 

 and the stern above Branford, Connecticut. Before the Creta- 

 ceous base-leveling was completed, the western side of the 

 half-boat reached much higher into the air than the crests of 

 the main ridges reach now. 



The upper surface of the Triassic formation would have had 

 a form similar to this, if not eroded. A drainage-system 

 established upon it must have found outlet not to the west or 

 south, where the side and the stern of the boat prevented 

 discharge, but to the east, where the boat was open, and the 

 location of the discharge would be somewhere about the lowest 

 point of the keel. In other words, the chief stream of the 

 region, during the early development of the dislocated country, 

 would have run out to the east, some distance north of the 

 point where the main sheet now reaches the crystalline rocks 

 on the eastern margin of the formation. This corresponds 

 with the general course of the Connecticut closely enough to 

 give some degree of acceptance to the explanation ; and the 

 lower Connecticut may therefore be tentatively classified as an 

 originally consequent stream, which has lived far through one 

 cycle of life, and has now in obedience to the general eleva- 

 tion of its drainage area, entered a second cycle in which it 

 is well advanced, still persisting more or less closely in the 

 course chosen in its first cycle. 



Thus explained, it may be called in this portion of its valley 

 a revived river of originally consequent course. It is not 

 intended to imply that the dislocated Triassic region ever had 

 a purely " structural surface ;" but only to indicate that the 

 summation of all the movements of deformation, which would 

 produce such a surface, sufficed to throw the drainage of the 

 region into the area of least elevation. 



