Ne REN i perenne 
EY ers 
J. Hail on the Potsdam Sandstone in Vermont. 107 
It is only necessary for me to mention in this place, that in the 
years 1844 and 1845 I made several sections from the Hudson 
tiver and Champlain valleys eastward, with a view to determine 
whether the slates of the Hudson river valley were identical 
with those farther to the east; and I recognized the Potsdam 
sandstone in its position, and by the presence of Scolithus, at sev- 
eral localities in Vermont and within the limits of Massachusetts, 
These sections were brought, by me, before the American 
lation of Geologists at their meeting in 1845 and 1846, and 
were then fully discussed, more particularly in reference to the 
aconic system, since my sections showed the contorted shaly 
rocks of the Taconic system to lie above the sandstone. 
_In vol. I, Paleontology of New York, I have cited Scolithus 
linearis from the Potsdam sandstone of Western Massachusetts ; 
and I considered the Conocephalus shown me by Prof. Adams to 
m the same rock. But the views of Prof. Adams in regard 
to the position of the sandstone did not coincide with my own, 
and the meagre information then possessed of the genus Cono- 
crate and Medina Sandstone by some of the best authorities in 
the country. 
I do not recollect the occasion when Mr. Hitchcock showed 
me the Conocephalus in 1858, but it is very true that I had no 
Rew information to give hi new my original views re- 
Ing the age of this sandstone, and he had my sections in his 
ton er and imperative duties have revented me 
advanced by geologists who had examined that country had 
been generally adopted. But I believe the opinion I then held 
independent of other influences, both in regard to the sandstone _ 
LG ats fossils, is sufficiently recorded; and the determination of 
the Potsdam sandstone in Vermont was known and recogniz 
more than fifteen years since.+ 
in Would - Adams that I compared this fossil 
in cco. g in the Clinton Group of noe York; but as there is een Mansy 
ton Group having a similar character, I can on pose that 
. some error may have arise 
ha ees 
Oo hin. oi 
i aes retained the impression that Profs. W. B. and H. D. Rogers coincided 
toni a 
rth i tions were placed 
to the f this sandstone. Cupies of my sec’ p 
and stands © f Ad -? f Hit k and other geologis as 1846 
wenn and my view the ition of the stone then entertained ai 
we se gentlemen. In later correspond wit y “3 " 
ized the Potsdam sandstone at other localities, and in e 
