﻿482 8. V. Woodyjun. — American and British Surface- Geology. 



J. S. Newberry, on the " Surface Deposits " of that State, and their 

 connexion with the general features of Glacial and post-Glacial 

 geology presented by the Central and Eastern parts of the North- 

 American Continent ; and from which the map of those regions that 

 accompanies this paper is taken. A discussion of the views of 

 American geologists occurs in the 35th chapter of the 2nd edition of 

 Mr. Geikie's " Great Ice Age," and it seems to me that, in the present 

 condition of our knowledge, the leading facts of this Memoir of 

 Prof. Newberry may be usefully epitomized, and examined, in the 

 way of analogy with those observed concerning our English Glacial 

 and post-Glacial formations ; and I propose here to make the at- 

 tempt to do so. 



Commencing with the oldest Glacial evidences in North America, 

 Prof. Newberry describes the grooved and furrowed rock-surface, 

 which is to be traced as far south as the 39 th parallel of north lati- 

 tude, and the extent and direction of which are indicated by the 

 arrows on the map. This evidence of the occupation of the Eastern 

 side of North America by glacier-ice is not confined to the basin of 

 the St. Lawrence, but extends in the State of Ohio over the water- 

 parting of the two great basins which receive the drainage of the 

 central part of North America east of the Rocky Mountains ; that is 

 to say, it extends on to the northern edge of the basin of the Missis- 

 sippi. These scratchings and groovings, though having a general 

 north and south direction, nevertheless conform, according to Prof. 

 Newberry, in a rude way to the present topography, and follow the 

 directions of the great line of drainage. To the action of this ice 

 when the continent stood several hundred feet higher than now. 

 Prof. Newberry attributes the excavation of the basins of the great 

 lakes, as will be further on described. 



1. The oldest of the surface deposits is the Erie clay (No. 1), the 

 origin of which Prof. Newberry attributes to the action of this sheet 

 of glacier-ice during the period of its retirement before returning 

 warmth, after the continent had become depressed 500 feet or more 

 below its present level, and when the basin of the great lakes 

 became, as this ice receded, occupied by an inland sea of freshwater. 



He does not explain how, if the continent were depressed 500 feet 

 below its present level, this basin could be occupied by freshwater, 

 seeing that such a depression would bring all but the upper edges of 

 the basin below the sea-level ; nearly all the area of the basin of the 

 St. Lawrence, as well as a large part of that of the Mississippi, in- 

 clusive of the water-parting of the two basins, being, according to 

 the map which accompanies the Professor's Memoir and is repro- 

 duced here, below the 800-feet line. I presume, however, that he 

 considers the sea to have been dammed out by a mass of the glacier- 

 ice left remaining and filling the lower and narrow part of the St. 

 Lawrence Valley, which lies several degrees of latitude further 

 north than Ohio ; but if so, there must have been an equal re-eleva- 

 tion of the continent before the growth of the forest surface (bed 

 No. 2) over the Erie clay, because the warmth necessary for that 

 growth must have thawed the dam and let in the sea, an event of 



