CLASSIFICATION OF ROCKS. 



13 



the " Coal formation" having always been debateable ground ; one class of geologists placing 

 it in the Transition, the other in the Secondary class. 



In adopting the new tenn, an old one is gotten rid of with great advantage. It was odious 

 to many, in consequence of its inappropriate meaning as originally applied ; that import being 

 disregarded by those who still retain it, considering it in no other point of view than as desig- 

 nating the class, system or division of rocks which exist between the Primary and the Secon- 

 dary classes, without any reference whatever to its original meaning. 



In adopting the terms Cliamplain^ Ontario and Erie,, there is no intention to make any 

 other arrangement than one which, in great part, is purely geographic, the advantage being 

 that these names are well known, and that the rocks included under their heads, respectively, 

 are, with some exceptions, in force and well characterized along their border. In adopting 

 the terms Ontario and Erie, for example, it must be borne in mind that reference alone is 

 made to the geology of their southern or New- York border. 



Tabular View of the New-York System in the ascer^ing order. 



New-York 

 System. 



Champlain division. 



(Ontario division. 



. Helderberg division. 



Erie dlTision. 



Catskill group. 



c Potsdam sandstone, Calciferous group. Black River 

 < limestone, Trenton limestone, Utica slate, Hudson 

 ' River group. 



( Gray sandstone, Medina sandstone, Oneida conglome- 

 \ rate, Clinton group, Niagara group. 



( Onondaga salt group, Water lime group, Pentamerus 

 1 limestone, Catskill shaly limestone, Oriskany sand- 

 \ stone, Cauda-galli grit, Schoharie grit, Onondaga 

 ' limestone, Corniferous limestone. 



r Marccllus shales, Hamilton group, Tully limestone, 

 ^ Genesee slate. Portage group, Ithaca group, Che- 

 ' mung group. 



With the above important and convenient arrangement, the whole of the rocks and other 

 geological products of the third district will be reduced to a few simple heads, namely, four 

 systems and seven divisions, as in the following table : 



1 . Primary System, Requires no further illustration. 



2. Taconic System, . . . 



3. New-York System, 



4. Quaternary System, 



( Embraces the products between the primary 



< and the Potsdam sandstone, which are very 



' partial in the district. 



Champlain division. 

 Ontario division. 

 Helderberg division. 

 Erie division. 

 Catskill division. 



< 1. Transported materials. 

 ( 2. Local materials. 



