156 N. S. SHALER — EVIDENCES AS TO CHANGE OF SEALEVEL. 



not complicated with the scouring action of ice. Although this flooded 

 estuary has doubtless had its bottom considerably elevated by sediments 

 imported into it during and after the Glacial period, we may by pro- 

 longing the slopes of the land on either side interpret its original depth 

 in an approximate way. From such evidence it seems likely that the 

 floor of the original stream-bed which occupied the valley was 200 feet 

 or more below the present bottom. 



Delaivare River to Cape Cod. — To the north and eastward of the Dela- 

 ware, as before indicated, the process of glacial excavation has somewdiat 

 confused the record of submergence made by the flooding of valleys ; 

 yet the evidence seems to me to indicate an increase in the recent average 

 downsinking of the continent as we advance along its eastern margin 

 toward the pole. 



The valley of Hudson river is flooded as far as Albany, and although 

 it is considerably clogged it has, owing to the peculiar condition of its 

 headwaters, but little filling due to delta-action. 



The channel of Connecticut river, owing apparently to the fact that it 

 was the pathway of a great subglacial stream which was heavily laden 

 with sediment, is overfilled with the detritus of its terrace deposits. 



Farther to the eastward the valley of the Thames, in Connecticut, 

 though somewhat affected by glacial erosion, appears to be in form sub- 

 stantially what it was just before the advent of the ice. In it the flood- 

 ing is conspicuous and extensive. So, too, in Narragansett bay we have 

 a river basin which appears to have been mainly shaped by the action of 

 land water, which has been very extensively flooded. 



Cape Cod Peninsula. — The peninsula of cape Cod and the remnants of 

 an ancient land preserved in Block island, the Elizabeth islands, Marthas 

 Vineyard and Nantucket show us that down to relatively late stages of 

 the Tertiary the part of the shore on which they lie w^as very much higher 

 than at present. Although the old surface of these areas is to a consider- 

 able extent hidden, it is possible to trace a system of valleys partly 

 clogged by drift, but frequently with their mouths considerably flooded 

 in a way that indicates recent submergence. 



It now seems to me tolerably clear that Vineyard sound was the seat 

 of a considerable stream, the divides of which are partly preserved in the 

 ridges of cape Cod, the Elizabeth islands and Marthas Vineyard. Another 

 similar valley occupied by a considerable stream is now flooded by the 

 waters of Buzzards bay. The obliteration of these ancient river-systems 

 seems to be much more complete than is the case with those between the 

 southern margin of the ice-front and Florida. 



Cape Cod to Bay of Fandy. — North of cape Cod it has not as 3^et ap- 

 peared to me possible to discriminate the measure of flooding of the valleys 



