Prof, Hall on the CattsJcill Group ofN. F. 377 



ARTICLE XXXrV.— 0^ the Cattskill Group of Nexo YcyrK 

 By Prof. James Ball. A Letter addressed to Principal 

 Dawson J dated Albany , October ^ 1862. 



Having furnished you with a cousiderable number of specimens 

 of DevoDiaa fossil plants, from the State collections, and from 

 my own cabinet, for study and desciiption, I have felt not only 

 great interest in the matter, but much solicitude in regard to the 

 geological position of some of them ; and this feeling has been 

 increased by studying your list of specimens with reference to the 

 geological formations, for it seemed to me that there were some 

 results not quite in accordance with palaeontological laws, and 

 that there was reason to question the geological order assigned 

 to the specimens. • 



A considerable number* of these had been collected by myself 

 or under my immediate direction many years since, and of these 

 I feel secure ; but there were others which, though obtained from 

 authenticated localities of the Cattskill group^ had not been col- 

 lected by myself ; and in regard to some of these and some of the 

 others not of my own collecting, I believe I expressed doubts, 

 though the greater proportion were reliable. 



Late investigations, combined with those heretofore made, have 

 forced upon me the conviction that the greater part of the area 

 colored on the geological map of New York as CattsJcill group^'is 

 in fact occupied by the Portage and Chemung groups. 



Several years since, in making sections across the country from 

 north to south, and through the counties of Albany and Schoharie, 

 I ascertained that the Hamilton group, as indicated by its well 

 marked and characteristic fossils, extends to the southern limit of 

 the coloring indicating Chemung group, on the geological map, 

 I am now prepared to show that the Hamilton group in the counties 

 of Albany, Greene, Schoharie, Otsego, and a part of Chenango, 

 with the exception of some outliers on the higher hills, occupies 

 nearly the entire belt colored as Chemung, the southern line cor- 

 responding very nearly with the limit assigned to that formation ; 

 thus leaving the Chemung group with its southern limits still un- 



The Investigation of the extent and limitation of this group 

 has been beset with difEcuUies, both towards the west and east of 

 the typical region in southern central New York. In tracing ta^l 

 the eastward the strata of the Chemung group, we find them gra- 



