482 S. V. Wood,jun. — American and British Surf ace- Geolog y. 
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 ltnowledge, the leading facts of this Memoir of 
Prof. Newberry may be usefully epitomized, and examined, in tbe 
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 39th 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 pärt 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 rüde 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 tbe 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 
oonsiders 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 tbe Erie clay, because the warmth necessary for that 
growth must have thawed the dam and let in the sea, an event of 
