4 



Association of American Geologists and Naturalists. 149 



merit of highly curious generalizations, in relation to the limits of these 

 extinct races, and the conditions which have controlled their distribution. 

 Guided by the ascertained boundaries of the principal groups of 

 fossils, and also influenced by the great natural lithological horizons, 

 the geologists in the different quarters of the wide Appalachian field 

 have sedulously aimed at making such an analysis and classification 

 of the strata as would best accord with the special type which they 

 present in their respective district. Seeking at first for a classification 

 founded on local and not general characteristics, the subdivisions hith- 

 erto instituted only admit of extension to districts beyond those for 

 which they were framed, in so far, as the strata retain with more than 

 usual constancy these local features. Hence a general scheme of 

 grouping, applicable, if possible, to the whole region occupied by the 

 strata, and expressed in terms significant of general and not local and 

 restricted relations, is yet to be supplied. 



I he most elaborate classification of our Appalachian palaeozoic 

 strata, hitherto published, is that of the New York geological survey. 



rom the very considerable amount of paUeontological research 

 aeeted with this survey, from the diversity of formations in the State, 

 ne clear typical characters which some of them possess, this clas- 

 sification merits much attention. It embraces under the title of the 



ew \ork system, the entire body of strata from the bottom of the 



°west fossiliferous rocks, to the base of the red sandstones of the 



ul Mountains, the whole having in their maximum expansion a 



, ess of abou t six thousand feet. This large mineral mass has 



en subdivided by the gentlemen of the New York survey in con- 



1 y? chiefly, to the horizons established by organic remains into 



y eight special formations, or subordinate masses, and these twenty 



8 are thrown into four series or divisions named from the districts 



ere they are best developed. Observing the ascending order, these 

 e "e Champlain division, the Ontario division, the Helderberg divi- 



n ' and tne Erie division. Referring you to the ample and well illus- 

 volumes on the geology of New York, for the views which have 



U the gentlemen of that survey to adopt the above classification 

 nomenclature of the rocks, and for many valuable details connected 



\Vltn tk 



e organic remains, I will embrace this opportunity to bring to 



con- 



your attention 



the Perusal of these works suggests. 



geology, 



s geological, as in all archaeological research, the earliest periods 

 m °st to enlist our attention. Ascending the stream of time, the 



