﻿538 S. V. Wood,jun. — American and British Surface- Geology. 



As a preliminary, however, it may be well, for clearness sake, to 

 recapitulate in their descending order, from the newest to the oldest, 

 the deposits of the St. Lawrence basin, with such alterations in 

 their relative ages as I have suggested, viz. : 



The later part of the Lake Terraces (beds No. 4), and the Eskers and Karnes of 



the Canadian Highlands. 

 The earlier part of the Lake Terraces (beds No. 4), and the Marine Clays. 

 The Yellow Clays with Gravel and Boulders (beds No. 3a), and possibly a part 



of the Marine Clays. 

 The Forest surface resting on the Erie Clay (bed No. 2) . 

 The Erie Clay (bed No. 1) which commenced with the formation of Eskers and 



Karnes on the Ohio water-parting (beds No. 2,b), 



Approaching then the examination in detail of the conditions 

 under which we may seek to find grounds of synchronism between 

 the American and English series, we have first the oldest members 

 in the series of each country to examine ; and therefore, but without 

 suggesting any synchronism between them by so doing, I place 

 them side b}'- side, viz. : 



English. 



St. Lawrence Basin. 



The Lower Glacial Series. 



This series begins with a littoral and estuarine deposit 

 of pebbly sands (the Bure Valley beds of myself, and 

 Westleton Shingle of Prestwich), containing a molluscan 

 fauna differing but little (chiefly in the introduction of 

 Tellina Baltliica) from the later (Chillesford) beds of the 

 Crag. These sands are fossiliferous in places, and con- 

 tain Mija truncata with valves united and siphonal ex- 

 tremities vertical just as they lived; and they pass up by 

 interbedding into the Cromer Till, which is a deposit 

 of deeper water, though also estuarine, and whose for- 

 mation took place wMle the sands continued still in 

 progress of accumulation in South Norfolk and North- 

 East Suffolk. Up to this time, though the ice ripped off 

 long sheets of Chalk, which are interstratitied in the 

 Cromer Till, it appears to me that the glacier-ice had 

 not, in England at least, become confluent, i.e. formed 

 into a continuous sheet. The series ends with the Con- 

 torted Drift, a marjne deposit of reddish-brown mud and 

 silt, into which the Cromer Till passes up. This Drift 

 was accumulated under a depth of water sutficient to float 

 large bergs ; for these in grounding have buried huge 

 masses of remanie Chalk in the mud and silt, contorting 

 it in the process, though what that depth may have been 

 is very difBcult to estimate. The glaciers had evidently 

 much increased at this time, so as to form these bergs, 

 but whether even then they were confluent over England 

 is not apparent, as the glacier from which the bergs 

 bearing the imbedded masses broke off must have been 

 for great part of its course confined to the Chalk country, 

 because these masses are formed almost entirely of recon- 

 structed Chalk. 



The Eskers and Kames 

 of the Ohio water-part- 

 ing, being the washed- 

 out moraine of the first 

 ice-sheet, due to its 

 dissolution subaerially, 

 when at its southern- 

 most extension it termi- 

 nated on that water- 

 parting ; and the water 

 dissolving fi'om it flowed 

 into the Valley of the 

 Mississippi. The Erie 

 clay (No. 1), being the 

 unwashed moraine of 

 this ice-sheet extruded 

 at its margin, and left 

 behind as it receded 

 beneath the waters of 

 the lake, which began 

 to form so soon as the 

 sheet shrunk back with- 

 in the St. Lawrence 

 basin. 



Of these accumulations of the period of first glacier development 

 in either country, those of England clearly accompanied its incep- 

 tion and increase, but those of America seem to have accompanied 



