152 IJii Alii'l'K'Hii (fininijtxt. Sf^ptembJT, IWn. 
tlian ailmire iheir splL'iulicl c(niiajrt' and dovutioii to science; but 
:it the same time we cannot fail to remember tlie proverb. 
••There's many a slip twixt the cup and the lip. ' for no other 
conditions could more sugijest it than the slippery, erevassed ice- 
sheet, and pinching, crushing ice-floes of great thickness and 
piled together, driven capriciously by winds and sea currents. 
AN EPISODE IN THE PAL/EOZOIC HISTORY OF 
PENNSYLVANIA. 
E. W. Claypdlk, .\kioii, O. 
In an article printed in The Geologist for the month of April, 
. 1890, the writer sketched the palaeozoic history of Pennsylvania. 
The sketch was the merest outline. Superficial it could not but 
be, for our knowledge of the subject at present warrants no more 
ambitious attempt. All details were omitted, indeed few are 
known. Whole chapters of geological history will one day be 
written on these as they gradually come to light, but at present a 
dense darkness hangs over the field allowing but a dim view of the 
most prominent features of the landscape. 
One of these details, forming a single episode in the paleozoic 
history of the Keystone State, will be the burden of this paper — 
an episode that may help us to realize the immense length of 
palaeozoic time and the complexity of paL-eozoic history. 
Among the Devonian strata that are conspicuous for their ex- 
tent, thickness and fossil treasures, is the Hamilton group, so 
named by Prof. Hall. This group, as known in western New 
York, is for the most part a mass of shales enclosing a thin bed of 
limestone — the Encrinal limestone — and capped by another thin 
])ed — the Tully limestone. It is thus arranged : 
4. Tull^- limestone. 
8. Moscow shales. 
2. Encrinal limestone. 
1. Blue shale. 
This is the original and typical section of the ILimilton group. 
But from this it varies even within the limits of the state of New 
York. Eastwardly it contains a thin bed of sandstone from which 
the excellent flagging (juarried on the Hudson near Kingston, etc., 
is taken, and still farther east in Maine and New Brunswick the- 
shale gives place almost entirely to sandstone. 
