426 Dana — Long Island Sound in the Quaternary Era. 



1. The Condition of Long Island Sound in the 

 Glacial Period. 



1. The southern of the Sound rivers in the Glacial period. 

 — In a memoir of 1809, on the " Origin of some of the 

 topographic features of the New Haven Region," (read in 

 September of that year before the Connecticut Academy of 

 Sciences,)* I mention the fact that along the middle third of 

 the Sound, over the larger part of which the depth is 10 to 

 15-| fathoms, there is near the southern shore a channel of 20 

 to 25 fathoms ; and I further point out that this channel ends 

 with strange abruptness about a mile and a half from the 

 shore-line with a depth of 18f fathoms, the next soundings 

 beyond being 11J, 10, 9 fathoms. This abrnpt termination 

 occurs thirty miles short of the outlet of the Sound, and at a 

 point where the coast-line takes a N. 35° E. course, right in 

 the face of this east-west channel. 



It was manifest that this channel could not be due to the 

 scour of the ebb current ; for the deepest excavations of the 

 tide occur, as the map shows, at the narrowings of the Sound i 

 as for example, south of ISTorwalk, Conn., where a bank from 

 Eaton's Point, L. I., stretches out nearly half way across the 

 Sound, and occasions an increase of depth from 10-12 fathoms 

 to 32, to return again just beyond to 12 and 13 fathoms ; and 

 south of Stratford, where there is a like effect in consequence 

 of shoals ; and still more strikingly at the eastern discharge of 

 the Sound, where the depth gradually increases (through the. 

 20 miles of narrowing) from 12-15 fathoms to 50-55 fathoms 

 at the two sluice-ways between Eisher Island and Plum Island,f 

 returning again to 12-18 fathoms in the 20 miles. The trough 

 along the south side of the Sound is deepened at the narrows 

 south of Stratford to 27 fathoms ; but it continues on eastward, 

 with a depth exceeding 20 fathoms through the widest part of 

 the Sound and terminates before a narrowing begins. Since 

 the depth to the eastward of the termination is only 9 to 13 

 fathoms, there is here an abrupt rise in the bottom of 25 feet, 

 and this would have the effect of a dam, and reduce the ebb 

 movement within the trough to a minimum. 



In view of these facts, I suggested in 1869 that the south-side 

 channel or trough was the bed of a Sound river in the Glacial 



* Trans. Conn. Acad. Sci., ii, pp. 42-112, 1870. An Appendix containing 

 extracts from this paper is annexed to the author's separate copies of his paper 

 on the Phenomena of the Glacial and Champlain periods in the New Haven 

 region. This paper is published in vols, xxvi, xxvii (1883-4) of this Journal, but 

 without the Appendix. 



f The deepest areas at these sluice-ways are left blank on the map without 

 the soundings; the depths of the two at the northern sluice-way are 50 and 51 

 fathoms, of the two at the southern, for the western area 53, 55 fathoms, and 

 for the eastern 52, 54 fathoms. 



