192 
CATSKILL DIVISION. 
View in Cilboa. 
§ 3. Portage, itiiaca and chemung groups in the sciioharie and hudson-river 
DISTRICTS. 
The development of the Hamilton shales is excessive in the eastern part of New-York, 
but there are only slight differences in the lithological characters. At Summit in Scho¬ 
harie county, in a deep gorge near the village, the Chemung group occupies the upper 
part and the higher slopes adjacent to it, and also the hills above the village. As yet, 
however, the fossils of the Chemung narrows are not common or numerous ; and it seems 
to be established that the fossils of the Hamilton shales go up higher into the shales and 
llags, and occur nearer to the base of the Catskill division or Old Red sandstone, than at 
the west. The flags at the top of the Helderberg range, and the rocks occupying the 
highest position in the southern towns in Albany and Schoharie counties, belong to the 
Chemung group. 
The purposes of agriculture do not require an identification of the rocks under conside¬ 
ration : they belong chemically and mineralogically to the same class. The structure, the 
tendency to decomposition, and the soil which is formed by disintegration, does not differ 
essentially in Albany county from that of Allegany or Cattaraugus county. We do not 
find the exact equivalents when they are tested by fossils : it is possible, however, that 
this may be owing to exposure. Other fossiliferous strata than those, for example, which 
