WILLIAM B. DWIGHT. od 
one would constitute the most southern one of the series 
yet described. 
With regard to the eastern boundary line of this strip 
of Potsdam nothing definite can be determined from 
present data. There are no fossils to indicate the points 
of transition to the Calciferous and Trenton, which 
doubtless lie in abundant development to the east. The 
uncertainty is increased by the fact that a great part of 
the rock is deeply buried under drift. Thus, at the 
northern extremity, east of the fossiliferous Potsdam, 
after about six hundred feet of strata (which are prob- 
ably to some extent at least of the same group), the lime- 
stone entirely disappears under a large hill of more than 
fifty feet depth of drift in A. Vanderberg’s farm. (This 
hill is so covered with debris of Hudson river shale that 
one might readily suppose it to be the rock in place.) 
The limestone does not reappear until the southeastern 
base of Richmond hill on Casper creek is reached. 
That this eastern margin of the belt is Trenton is proved 
by a distinct outcrop of fossiliferous Trenton filled with 
Solenopora compacta (‘* Chetetes compacta’) appearing 
in a small patch on a hillside five hundred twenty feet 
from the house of R. J. Kimlin ona course of N. 101° E. 
The Calciferous is doubtless extensively represented be- 
tween the Trenton and the Potsdam, but this has not 
been paleontologically determined. 
In view of the above facts, I can make only the general 
statement that the minimum width of the belt of Pots- 
dam strata, measured on the surface of the ground, is 
somewhat over six hundred feet. If, as seems probable, 
there is at least one compressed fold, the actual thick- 
ness of the deposit must be over three hundred feet. 
It is my present impression that the Potsdam folds oc- 
cupy, as indicated on the accompanying map, a strip of 
about one thousand four hundred feet in width, and 
that the high and continuous limestone hill (K) on the 
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