106 J. Hall on the Potsdam Sandstone in Vermont. 
paleontologist than a wish to put forward any claim of this de 
scription, as the credit is wholly due to Mr. Billings the Paleon- 
tologist of the Canadian Survey. 
In 1848 and 1849, founding myself upon the apparent superp 
sition in Hastern Canada of what we now call the Quebec group, 
I enunciated the opinion that the whole series belonged to the 
— of the structure would make them all older than the 
eee 
Art. XV.—Letter from James Hawt, Esq., on the Potsdam Sand- 
stone and Hudson River Rocks in Vermont. To the Kditors # 
the American Journal of Scienee and Arts. 
In the November number of this Journal,t there is a lett? 
from C. H, Hitchcock in reference to the occurrence of | “ 
dus, in the Potsdam Sandstone in Vermont. In a pam hlet 
lately published by the “ Geological Survey of Canada,” Sir Se 
yogan, Director, Mr. Billings has copied this notice, p. 12, 42 
remarks upon what he terms “the astonishing part of the com 
munication.” 
* See this Jour. [2], xxxii, 429. + This Jour. [2], xxxi, 216. $ Vol. xxxii, 454 
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