J. D. Dana— Flood of the Connecticut Biver Valley. 103 



as this at least, that if, as is probable, antedating in first origin 

 the Glacial era, the final deepest erosion took place at that time. 

 Being proof of water erosion, they are proof of the emerged 

 state of lands where now are seas 1,000 to 3,000 feet deep. 

 But they do not prove that there may not have been several 

 successive emergences and Glacial eras concerned in their 



(b.) Again, there are deserted water-courses which appear to 

 owe their desertion to a change of level which took the flow 

 from the waters. In many cases the desertion was due simply 

 to a decline of the flood, and a filling of channels by the depo- 

 sitions. But in other cases, like that of the discharge of the 

 St. Lawrence from the Great Lakes, an appeal to dii 

 southward pitch in the land is necessary to account for the 

 depositions oi the Chnmplain period, and" also for the present 

 condition of the lakes as to outlet. 



(d.) An argument for the probability of a greater elevation 

 in the Glacial than Champhiin period 1 have i>ased, in earlier 

 papers, on the progressive elevation of the continent which was 

 going on during the preceding Tertiary era; and this has lost 

 none of its force by recent discovery. The elevation of the 

 Koeky Mountain region from Mexieo'on the south to the Arctic 

 seas, and which amounted to 10,000 and 11,000 feet in the 

 higher portions of the United States, was not completed until 

 the close of the Pliocene— the vast Pliocene fresh-water lakes 

 proving this; and the close of the Pliocene was the beginning 

 of the Glacial era. Besides this upward movement in the 

 western two-thirds of the continent, a smaller took place in its 

 eastern portion, as geologists have inferred from the absence of 

 marine Tertiary either above or at the sea-level north of Cape 

 Cod, and of Pliocene Tertiary to a large extent south of it. 

 Thus the Tertiary changes of level were, in the main, upward 

 to the end of this age. 



It is evident, too, that these changes of level in the Tertiary 

 were changes of land-level. For changes due to a transfer of 

 the ocean's water meridionally would have been alike on the 



It is deserving of consideration also that an elevation of 

 large portions of the Arctic regions would be favorable to the 



production of Glacial conditions, tor it would diminish the 

 depth of the arctic seas, and consequently would diminish the 

 volume of arctic currents ihnving southward, and of tropical 

 waters reach in if the arctic: and 'it would hence increase the 

 cold of arctic seas and lands and of the lands south, and the 

 warmth and rate of evaporation of the North Atlantic in tem- 



The evidence reviewed thus shows that there were real 



