184 
GEOLOGY OF THE FOURTH DISTRICT. 
View of Sugarloaf Hill, at Hopeton, on tlie Crooked Lake Outlet. From a drawing by Mr. E. N. Horsford. 
24. HAMILTON GROUP. 
This group at present includes the Pyritiferous rock and Third greywacke of Eaton ; 
Ludlowville, Moscow and Skaneateles shales; Dark slaty fossiliferous shales, Compact 
calcareous blue shales, Olive shales, Shales near Apulia and Sherburne; Cazenovia 
g r oup, Encrinal limestone, tyc. of the Annual Reports. 
(Part of No. 8, Pennsylvania Survey.) 
[See Coast Section of Lake Erie, Plate 5, and Section along Cayuga lake, Plate 7; also O of woodcut, page 27. J 
This group consists of several members which may be considered distinct, but which, when 
viewed in connexion, present so many features in common, that they are all recognized as the 
products of one period, and thus constitute one great group. In the Fourth District, the only 
changes recognized in lithological products are from shaly to calcareous, with occasional thin 
beds of limestone, and more rarely of sandy shale. 
The group, as a whole, presents an immense development of dull olive, or bluish grey cal¬ 
careous shales, which, on weathering, assume a light grey or ashen tint; some portions be¬ 
come brownish on exposure, but these are of small thickness in this district. At a few points 
the shale becomes darker, or black, and exhibits a tendency to slaty structure ; but as a general 
