THE NEW YORK GEOLOGICAL SURVEY. 821 



During these years the New York geologists had accumulated a 

 vast amount of material and of facts regarding the geological forma- 

 tions within the State, proving conclusively that they could not be 

 parallelized with any of the described and well-determined formations 

 of Europe. The Silurian system of Murchison, as described and illus- 

 trated in the " Edinburgh Review," in 1838, and as finally published 

 in 1839, although covering a portion of similar ground, was not broad 

 enough to meet the requirements of the geology of New York. Thus 

 failing to find the means of comparison and identification, the term 

 " New York System " was proposed, to embrace the sedimentary for- 

 mations from the Potsdam sandstone to the base of the carboniferous 

 system ; or, as the formations were developed in New York and south- 

 erly into Pennsylvania, the upward extension of this term reached to 

 the base of the coal-measures.* This term, " New York System," in- 

 cludes the formations ordinarily embraced in the names Cambrian, 

 Silurian, and Devonian of England and the Continent of Europe. The 

 geological series in New York is so complete that the succession leaves 

 no lines or breaks for the establishment of " systems," the whole being 

 but a single system ; and had the older rocks of the globe been first 

 studied in this State, no such terms or subdivisions would ever have 

 found their way into geological nomenclature. The strongest line of 

 demarkation, however, or the most marked interruption of continuity 

 in the succession, occurs at the termination of the Hudson River group, 

 where a great conglomerate or a heavy-bedded and well-marked sand- 

 stone terminates the physical and biological conditions of the preced- 

 ing period. This break in the continuity, which is the proposed limit 

 of the Cambrian system, is, however, only of local importance. 



Since there was no possibility of identifying the individual rocks 

 and groups of strata with those of Europe, as described, the New 

 York geologists were compelled to give names to the different mem- 

 bers of the series ; and since the sandstones, limestones, slates, and 

 shales are so similar in different and successive groups, it was impos- 

 sible to give descriptive names which would discriminate the one from 

 the other. Therefore, local names were proposed and adopted, as, for 

 example : Potsdam sandstone, Trenton limestone, Niagara limestone, 

 and Niagara shale (the two latter, with subordinate beds, making the 

 Niagara group), the Medina sandstone, the Onondaga salt group,f the 

 Hamilton, Portage, and Chemung groups, thus giving typical localities 

 of the rock instead of descriptive names. This method or system 



* In Southern New York and adjacent Pennsylvania the highest member of the New 

 York system is the Upper Catskill gray sandstone and conglomerate. The rocks pertain* 

 ing to the coal-measures supervene, without the presence of the great carboniferous lime- 

 stone and associated strata of this age in the States of the West and bordering the Missis- 

 sippi Valley. 



f The term " Onondaga salt group " was regarded as objectionable on account of its 

 length, and the term Salina was not adopted simply because the rocks of the formation 

 or group are not visible nor accessible in the town of Salina. 



