112 J. D. Dana on the ToiyograpJdcal Features of New Haven. 



well as those of the harbor are farther investigated, it may be found 

 that there is an impervious layer of this character beneath the water- 

 bearing one. 



We may add here one conclusion respecting East Creek. The facts 

 teach that this estuary has a deep under-bay channel ; and such a 

 channel as could have been excavated only by fresh waters when the 

 land was at a higher level than now. This era of higher level was 

 probably that of the old glacier. The 36 feet that were occupied 

 with mud in the artesian boring at the railroad depot (p. 109, § /i") are 

 only a part of the whole depth of the excavation ; for the sands and 

 gravel of the drift must lie beneath. The depth to which the mud ex- 

 tends here and over the harbor is probably an indication of the depth 

 of water in the channel and bay, in the later Champlain or earlier 

 part of the Terrace or Recent era ; and when the mud deposit has 

 been sounded throughout we shall have some idea of the topography 

 characterizing the bottom of the New Haven bay at that time. 



