﻿492 8. V. Wood,jun. — American and British Surface- Geology. 



extent, of which I consider the English formations to afford evidence. 

 Prof. Newberry, however, observes that most of the forest inter- 

 vening between the Erie clay and the beds 3a was Coniferous, and 

 that as it includes the Cedar and Cranberry, it may be regarded as 

 indicating a climate somewhat colder than the present ; for it is not 

 clear that the forest-beds which yield so many of the plants which 

 still grow in the same localities, and which could not have grown 

 if the climate had been much colder, are of the same age as are those 

 found intervening between the Erie clay and the beds 3a.^ 



It should, however, be borne in mind that if the forest-beds thus 

 intervening be in situ, a great amelioration must, it seems to me, 

 have ensued ; for unless the ice had completely thawed out of the 

 lower valley of the St. Lawrence, which lies in several degrees 

 higher latitude than Ohio, the lake-basin could not have been laid dry 

 so as to support a forest growth ; because an amelioration sufficient 

 only to release the Ohio portion of the basin from the glacier-ice 

 indicated by the Erie clay, and by the striated surface down to 

 latitude 39°, would have only brought about those conditions which 

 are described by Prof Newberry as giving rise to the beds 3a, and 

 which I have attributed to the return of a minor glaciation ; viz. the 

 filling of the Ohio lake-basin with freshwater instead of the for- 

 mation of a land-surface. Moreover, how could the lake-basin have 

 again become filled with freshwater after a land-surface, unless a 

 return of glacial conditions took place, minor in degree, but sufficient 

 to dam up the lower valley of the St. Lawrence with ice ? 



Whatever may prove to be the case, however, as to the nature of 

 the terrestrial climate which preceded the minor glaciation, I think 

 that we have in some parts of North-Western Europe evidences of a 

 warmer marine climate during a very late geological period, than 

 that which now exists in the same region as specified in the sequel. 



Besides the beds 3a, Prof. Newberry describes certain gravels form- 

 ing hills and mounds upon the water-parting which in Ohio divides 

 the drainage flowing to the St. Lawrence from that flowing to the 

 Mississippi. These gravels, which, in order not to dissever them from 

 Prof. Newberry's sequence of deposits, we will call Sb, he regards as 

 similar to Kames and Eskers as they are called in Scotland and Ire- 

 land ; and they are attributed by him to the action of shore-waves 

 among low islands and shallows, in which condition the highlands 

 of Ohio were at the time when, during the formation of the clays 

 with boulders (3a), North America underwent, he considers, a sub- 

 mergence so great that the sea overflowed the water-parting between 

 the St. Lawrence and Mississippi basins. 



I am unable, however, to understand why, if the sea overflowed 



^ It must not be, however, forgotten that the doubts which are being raised as to 

 whether the Forest-bed of the Norfolk coast is in situ apply with greater reason to 

 the forest-beds over the Erie clay which appear to have been only encountered in 

 sinkings, and therefore not open to so rigorous an examination as the Norfolk forest ; 

 so that if the latter should turn out to be a land-surface ploughed off and removed 

 by the agency of ice, it would be difficult to resist a similar explanation for the Ohio 

 forest-bed ; and in such case the beds 3a would probably prove to be only a con- 

 tinuation of the Erie clay formation itself. 



