INTRODUCTION I99 



And under Sandstones : 



Potsdam 



Hudson River 



Oneida 



Medina 



Clinton 



Hamilton 



Portage 



Chemung 



Catskill 



Triassic 



The order of succession in the series of geological forma- 

 tions in New York is shown in the columnar section on 

 pages 200 and 201. In the first column the longer eras of 

 the geological time are given, Paleozoic, Mesozoic and 

 Cenozoic. The second column has the subdivisions into the 

 several ages, Cambrian, Silurian, etc. In the third, the further 

 division into periods and epochs is given. "^ The fourth 

 column exhibits by conventional signs the nature of the 

 predominant types of rock belonging to the several subdi- 

 visions. And the names of these leading kinds are given 

 in the last column. 



* The term " formation " is used in this report as comprising the deposits laid down 

 during the epoch, e. g., the Potsdam sandstone formation. 

 2 



