W. E. Logan on the Rocks of Canada. 227 
they are composed, yet present important differences in their 
structural condition. Each area belongs to a great trough of fos- 
siliferous strata resting in Canada, with the exception of the sup- 
porting Cambrian formation of Lakes Huron and Superior, on 
gneissoid rocks, and containing coal measures in the centre, and 
the conditions in which the two areas differ, are the general 
quiescence and conformable sequence of the formations from the 
of the Lower Silurian upwards in the western, and the vio- 
lent contortions and unconformable relations of those in the east- 
ern. The coal measures of the eastern area are those of Rhode 
Island, and in a metamorphic state of Massachusetts, and those of 
Nova Scotia and New Brunswick. None of the productive part 
of the New Brunswick coal-measures reaches Canada, but there 
Gulf of St. Lawrence, first to Memphramagog Lake in Canada, 
area, and are distinctly traceable by the Appalachian chain through 
Vermont into Canada, and through Canada to the Gulf of St. 
_ “@Wrence ; in this part constituting the northwestern rim of the 
a 
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