94 J. D. Dana on the origin of sojne of the 



B. The Northern part. — Somewliere across the New Haven region 

 there was the limit of proper tidal action, or of the salt water flood- 

 grounds, an irregular line bending north along the river valleys. 

 [The northward bend for the rivers is much less than what the rise of 

 the tides in the streams would seem to indicate ; since this rise is 

 largely due to the fresh waters being dammed up by the incoming 

 tide ; and in case of river floods, the fresh waters, and also something 

 of the river slopes, may force their way to the bay, and even into it, 

 in spite of the tides.] Whatever the position of this line, the plain 

 to the north of it was made and leveled ofi" by the river floods, and 

 not by the tides. The slope of the surface in this upper part should 

 therefoi'e correspond with that of the waters in the flooded streams of 

 the Champlain era. 



It would be a great convenience if the sea had left its mark well 

 defined across the plain ; for then the present height of the former 

 sea-limit would be easily ascertained. But all traces of a line of beach, 

 if such there were, appear to be obliterated. We are left, therefore, 

 to approximations from uncertain data. 



We safely conclude that the land now at 30 feet elevation was with- 

 in the range of the sea, for this is the height directly on the hay, at 

 Halleck's ; and further, that of 35 feet, for this is the height on the 

 bay at the mouth of the Quinnipiac ; and, moreover, the whitish sands 

 overlying the terrace formation on what was the shore of the Quinni- 

 piac harbor (p. 84), have a height of 35 feet notwithstanding the de- 

 nudation they have undergone at top since their deposition. 



Again, the part of the plain between 38 and 44 feet in elevation 

 above mean tide is that which has the least slope, or is the most near- 

 ly level : and above it, or to the north, the plain rises at the rate of 11 

 to 12 feet a mile. There appears to be reason in this fact for placing 

 low-tide, or mean-tide, limit near the line of 44 or 45 feet. If 44 were 

 the low-tide limit, then high tide would have reached to the present 

 50 feet level ; and the terrace formation, in the Suydam grounds be- 

 low the Whitney ville dam west of the river, 53 feet high above mean- 

 tide level, might have been the work of the sea water alone. Fifty 

 feet as the high tide limit, would correspond to a difierence of level 

 in this region between the Champlain and Terrace eras of 50 to 51 

 feet, since the surface of the present river flats at Whitneyville is at 

 hio-h tide level. 



Along the Mill River valley, above Whitneyville, the rising grade 

 of 11 to 12 feet a mile for the plain continues not only to the mouth 

 of Pine-Marsh Creek, but also nearly to Ives' Station ; beyond, the 

 rate diminishes to 10 and 9 feet, the latter occurring just below Mt. 



