112 Association of American Geologists and Naturalists. 



They then gave a sketch of the classification and nomenclature they 

 had framed, illustrating their views by vertical sections of the strata, as 

 exhibited in New York, Pennsylvania and Virginia. Referring to their 

 organic remains, mineral character, and relative expansion throughout 

 nearly the whole extent of the Apalachian chain, they exhibited lists of 

 the fossils and tables of the comparative thicknesses of each formation 

 in the different districts, as explored and measured by them during the 

 last eight years in the region from New York to Alabama, pointing out 

 the limits or area of each formation in the basin, and the range of the 

 principal fossil species both as respects their geographical limits and 

 their extension through successive strata. 



Mr. James Hall, in reference to the paper of the Profs. Rogers, 

 congratulated them and ourselves that they had borne such able 

 evidence of the value of organic remains in determining the age of 

 rocks. * * * Prof. W. B. Rogers, taking up the subject, said that 

 they had not been understood on this point ; they had followed 

 out the intricate structural geology of Pennsylvania and Virginia, 

 relying chiefly on lithological characters, and had found to their 

 great gratification that they had been working in parallel planes 

 to the New York geologists, whose labors among the regular and 

 horizontal strata of that state, relying on the evidence of fossil re- 

 mains, had brought out results in the main, quite consistent with 

 the determinations of the Virginia and Pennsylvania strata. 



Mr. Hall replied that the term " New York system" of rocks 

 was considered by the gentlemen who agreed on it, as a conven- 

 ient conventional term, but never as a permanent one, and that 

 they were ready to abandon it whenever another, more general 

 and better adapted to cover all the facts, should be presented. 



In expounding their views, Messrs. Rogers objected strongly to 

 any nomenclature, based upon an examination of local districts, 

 and, referring to the vast fields of American geology now suffi- 

 ciently explored to justify and require a general classification, and 

 to the opportunity which the yet untrammeled state of the sci- 

 ence amongst us affords for the adoption of a comprehensive no- 

 menclature of the rocks, urged the importance of seizing the 

 occasion for framing such a system upon an independent and 

 enlarged basis. 



Mr. James Hall and others advocated the more cautious meth- 

 od, in the present state of our knowledge, of adopting a provisional 

 nomenclature, founded mainly on the labors of foreign geologists. 



