66 J. D. Dana on the origin of some of the 



5. Events and Results of the Champlain era. 



The Glacial era closed in a subsidence of the land over a large part 

 of the continent, the initiatory event of the next or Champlain era. 



1. Amount of Subsidence. — The amount of the subsidence about 

 New Haven is uncertain, because the actual height of the land in the 

 Glacial era is not yet satisfactorily determined. It was so great as to 

 carry the land considerably below its present level, as evinced by the 

 height of the New Haven plain, this plain having been made and lev- 

 eled off in the waters of the era. Taking the level of this plain as 

 marking the water level, we learn that about the College square and 

 for some distance to the north, and either side of this region on the 

 same east-and-west line, the depression was near 40 feet. Farther to 

 the north it increased gradually to 70 feet and more in Hamden ; w^hile 



the Housatonic and other rivers to the west, may have discharged through an open- 

 ing into Peconic bay. and that this opening was filled up by sands during the following 

 era of submergence (the Champlain era), and cotemporaneously the adjoining southern 

 portion of the Sound was made shallow by the same means. The form of the bottom 

 in this part of the Sound favors the idea that the sands for fiUing it came from the di- 

 rection of the Peconic bay. 



But the existence of the oblong deep hole in the course of a direct line to the south- 

 ern arm of the great eastern deep water region of the Sound hardly nine miles distant, 

 brings up the enquiry whether the river channel may not after all have been over this 

 route within the Sound. The submergence of the Champlain era would have afforded 

 the same means as stated above for filling up with sands this part of the Sound and 

 for stopping off abruptly not only the channel of the Sound river, but the great depres- 

 sion in which the channel lay ; for the waves of that era must have swept across the 

 land in one or more places from the Peconic bay into the Sound. 



If this latter view is the right one, the great Sound river, commencing in the rivers 

 of the vicinity of Greenwich and taking into itself the waters of other rivers eastward 

 to the Housatonic, and still others from Long Island, would, after receiving the Housa- 

 tonic, have derived little else du'ectly from the north until reaching what is now the 

 eastern deep-water region ; and this it would enter by the southern arm of that region. 

 The rivers of the New Haven coast and other small streams between it and Sachem's 

 Head, would have taken an intermediate course over the Sound to the same meridian, 

 and then entered the middle arm. The rivers from Guilford to Killingworth harbor 

 would have flowed eastward to the commencement of the northern of the three arras. 

 And then a few miles beyond this, the northern arm would have received the Connec- 

 ticut river, the great tributary, and from this point all the fresh waters of the various 

 rivers would have been combined in one grand flow on their way to the ocean. From 

 the depth of water and the character of the deep holes over the deep-water region 

 south of the Connecticut, it may be inferred that here was actually the great bay of 

 the Sound river into which the ocean waves set as they do now into the mouth of the 

 present Connecticut. The latter has its deep holes inside of its bar; for the depth 

 within the channel of the present river at low tide is 6 to 7 fathoms, while there are 

 but 10 feet of water over the bar. 



