Geology. 135 
which, in a former review of Marcou’s map in the Journal, was made a 
prominent objection to his representation of American geology, can be 
of any importance in such a general survey of the subject. Rogers in 
his Marcou, 
have struck the authors of these differe When in his paper 
he Geological Society of France, Marcou s' imself as a travel- 
ling geologist who “ brings his little stone to the great edifice” (page 
3) it does not appear to me as vain-glorious ing, and we ought to 
take gratefully the contributions of a Frenchman, using nguage 
the fashion of his nation, even though it be not the way in which we 
x d ourse onfess t 
oO 
the general features of the orography and geology of the Western half 
of our continent, than in the other representations I have read up 
tures of that remarkable country, 
and to connect in an intelligible way the geology of the West with that 
of the East. e middle tract of our continent is pa snare occu- 
Pied by deposits younger than the coal; I do not allude to the Lake 
Which Marcon’s assertions call forth, may be founded. We know that 
Tetac formations extend from the Atlantic slope of the Alle- 
ghany range round their southern spur into the great geological gulf 
t 
