428 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



to be the natural mode of proceeding. We shall then endeavour to 

 show the grounds on which these groups have been combined into 

 stages and systems. 



I am aware that, by not including the Carboniferous system within 

 the scope of these inquiries, except incidentally, some useful lights 

 are lost ; but the subject is so extensive that my hands are already 

 full — not to mention that there is no coal in New York State. 



I was induced to draw up a Synoptical View of the treasures 

 buried, as it were, in the official Reports of the State Geologists of 

 New York by a desire to see them in a more methodical and ac- 

 cessible form ; and now a similar feeling prompts me to explain the 

 stratigraphical treatment they have received. 



I venture to suggest the subjoined Table as exhibiting the natural 

 arrangement of the palaeozoic sedimentary strata of New York. 



This Table, which is mainly that used by the State Geologists of 

 New York, and which, like every other part of this paper, has 

 reference to that tract of country only, I adopt and hope to justify, 

 having, however, presumed to introduce the two following modi- 

 fications : — 



1. I have united into natural groups, A, B, C, and others, such 

 allied strata as seemed to me needlessly separated. These strata are 

 named " sections" in the Table. 



2. I have established a distinct middle stage in the Silurian and 

 Devonian systems, respectively, of New York, — a division suggested 

 by others, but never effected, and this partly on account of the diffi- 

 culty of finding a satisfactory summit. 



It must not be forgotten that all such arrangements are imperfect, 

 and that they are made to facilitate reference and for other uses — to 

 give brief expression to ascertained facts, and to aid in the construc- 

 tion and use of extensive tables of fossils for particular purposes. 



Of the separation, by American observers, of the groups into the 

 four divisions, Champlain, Ontario, Helderberg, and Erie, very 

 little will be said, as it is merely geographical, and was proposed 

 before the almost universal prevalence of these strata was known. 

 It also involves some false classification, in uniting the upper and 

 lower Helderberg groups, for they include rocks which do not even 

 belong to the same system. 



The arrangement of the palaeozoic sedimentary rocks of this State, 

 after some few mistakes committed and corrected, was early agreed 

 upon, and the twenty-nine groups (sections) of our Table erected by 

 common consent. Granting that the official Geologists have in some 

 instances been too minute in their distinctions (a pardonable error 

 in new territory, where a broad base was required), they are fully 

 justified in the groups they have set up. Their distinctions might 

 have been advantageously carried still further, but for the limited 

 faculties of man ; for a single New York group of moderate thick- 

 ness may contain several "formations" in Deshayes' sense of the 

 word. According to Deshayes, a formation "is a space of time re- 

 presented by a certain number of beds, laid down under the influence 

 of the same phenomena;" or, in other words, a formation is cha- 



