i 92 



CATSK1I.1. DIVISION. 



§ 3. Portage, ithaca and chemung groups in the schoharie and hudson-river 



districts. 



The development of the Hamilton shales is excessive in the eastern part of New-York, 

 but there are only slight difference^ 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 (he hills above the village. As yet, 

 however, the fossils of the Chemung narrows arc not common or numerous; and it seems 

 to be established that the fossiK of the Hamilton shales go up higher into the shales and 

 ill - cur nearer to the base of the Catskill division or Old Red sandstone, than at 



the west. The flags at the top of the Heidelberg range, and the rocks occupying the 

 best position in the southern towns in Albany .and Schoharie counties. In-long 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 

 lency to decomposition, and the soil which is formed by disintegration, does not differ 

 ntially in Albany county from that of Allegany or Cattaraugus county. We do not 

 find the exact equivalents when they arc tested by fossils : it is possible, however, thai 

 this may 1 e owing to exposure. Other Cossiliferous strata than those, for example, which 



