410 J. D. Dana—Depression of Southern New England 
the tides, having the following heights above flood-level : near 
New Haven, 47 to 50 feet; at Birmingham, 95 feet; near Mid- 
dletown, 150 feet; at Norwich, 110 feet; and at Providence, 
80 feet. What are the necessary deductions to be made from 
these numbers in order to obtain for each place the amount of 
that change of level (the depression of the land when the 
deposits were made, and the subsequent elevation) which led 
to the present elevated position of these plains of stratified 
drift, making them into river-valley and estuary terraces? If 
any elevated shell-bearing sea-beaches existed on the shores of 
the Sound, the question as to the amount of elevation since 
the Champlain period would be easily answered. But such 
evidence as already explained, is wanting; and wanting also 
outside of the limits of the Sound, even to Cape Cod. 
In order to make correct observations on this subject and ar- 
rive at right conclusions, several points have to be noted, a 
brief review of which is here given by way of introduction. 
1. The height to be measured should be that of the highest 
terrace plain above the level of the highest modern flood-plain or 
lower flats. For the terrace-plain, where of full height, marks 
approximately the flood-level of the Champlain era, just as the 
flood-plain of a stream in these modern times marks the level 
nearly of modern floods. This point has been considered in 
obtaining the numbers for the heights above given, each beg 
d not of any 
sing in addition, 
the height of the 
ht, would have t 
