198 ANNALS NEW YORK ACADEMY OF SCIENCES 



W. W. Mather, who was working on the geology of the lirst district 

 comprising the southeastern portion of the State, also began the study of 

 these formations. He published his first article in 1838/ and in his final 

 report in 1843" on the geology of the first geological district for the New 

 York survey gave the first comprehensive discussion of the geology and 

 relationship of the Poughquag-Wappinger-Hudson Eiver series and the 

 Inwood limestone and Manhattan schist to the south. He traced the 

 gra,y semi-crystalline limestone and overlapping slate north of the High- 

 lands through their various stages of metamorphism into the white and 

 gray crystalline limestones and mica schist to the east. The more crystal- 

 line Inw^ood limestone and overlying Manhattan mica schist with asso- 

 ciated hornblende schist and granite intrusions to the south of the High- 

 lands, he considered the equivalent of the above series, but in a more 

 highly metamorphosed phase. 



Another paper published about this time, dealing with the geology of a 

 portion of this region, is one by Issachar Cozzens^ on the geological his- 

 tory of Manhattan Island. He divides the formations of the island into 

 the following series: Granite, syenite, serpentine, gneiss, hornblende 

 slate, quartz rock occurring as veins, primitive limestone and diluvium. 

 A map accompanying the report shows the distribution of these different 

 formations. The relationship of the formations to one another is indi- 

 cated by a number of cross-sections. Cozzens conceived the island to be 

 underlain by a huge batholith of granite from which the granite dikes 

 radiated out. 



In 1867, R. P. Stevens,^ in his paper on the geology of New York 

 Island, proposed the name "Manhattan Group" for the formations under- 

 lying the island which he believed to be the equivalent of Emmons's old 

 Taconic system, now known to represent Cambrian and Ordovician strata 

 that have been highly metamorphosed. Stevens considered the granite 

 dikes which are so numerous on the island to be of metamorphic origin, 

 the same as the gneiss itself. The same applies to the hornblende, antho- 

 phyllite and other masses of rock frequently found. He thought that 

 they represented simply different conditions of the same elementary ma- 

 terial as the gneiss, which had merely undergone different forms of 

 metamorphism. 



•'"Report of the geolojrist of the first geoIo}?ical district of the State of New York." 

 Second ann. rept. Geol, Surv. New York, pp. 121-183, 1838. 



'' Geology of New York. Part T. comprising the geologj' of the lirst geological district. 

 Albany, 1843. 



®A geological history of Manhattan or New York Island, together with a map of the 

 Island and a suite of sections, tables, and columns for the study of geology. New York, 

 184.3. 



""Report upon the I'ast and Present History of the Geology of New York Island."' 

 Annals N. Y. Lye. Nat. Hist.. Vol. VII. pp. 108-120. 1867. 



