390 Merrill — Metamorphic Strata of S. E. New York. 



hundred to seven hundred and fifty feet. The measurements 

 of the writer would indicate that the thickness varies from six 

 hundred to eight hundred feet, it being apparently greater on 

 New York Island than in Morrisania. The eastern bed at 

 Tuckahoe is but one hundred and fifty feet thick. For this 

 rock I propose the name of Inwood limestone, from the locality 

 •on New York Island in the vicinity of which it is well exposed. 



The rocks which overlie the limestone are highly schistose 

 and consist largely of mica with a small proportion of quartz 

 and usually little or no feldspar. Garnet, staurolite, fibrolite 

 and cyanite are the chief accessories. There are some beds of 

 gneiss among them, but these are very small and the studies of 

 the writer enable him to state positively that mica preponder- 

 ates in the rocks above the limestone beds. No sections have 

 yet been found which would warrant an expression of opinion 

 as to the exact thickness of these schists, but it probably ex- 

 ceeds one thousand feet. 



The mica schist formation which belongs above the lime- 

 stone is of very limited extent in Westchester County. A 

 synclinal ridge of this rock extends from Park Hill, in Yon- 

 kers, northward along the east bank of the Saw Mill Eiver 

 and has been traced to Elmsford. 



North of Croton landing the mica schist containing garnet 

 and staurolite extends along the bank of the Hudson for about 

 a mile and east to the norite area of the Cortlandt Series. 

 Near Crugers the schists have been described by Professor 

 Dana 



Between the Bronx Biver and Long Island Sound, in South- 

 ern Westchester County, there is a considerable extent of 

 mica schist but its limits are not determined. In Eastchester 

 village, on the west shore of Eastchester Creek the rock is 

 a gneissoid quartzite. At New Bochelle the rock along the 

 shore of the Sound probably belongs below the limestone. 

 The same rock, essentially a gneissoid quartzite, occurs on the 

 shore of Mamaroneck Harbor, while Milton Point in Bye 

 township seems to be composed of. the mica schists. On the 

 Hudson Biver shore, in general, the limestone areas are suc- 

 ceeded to the north by mica schists and to the south by the 

 arkose gneisses. 



As these uppermost beds are well exposed on Manhattan 

 Island of which they constitute the principal rock formation 

 they may well be called the Manhattan schists. 



The name Manhattan Group was proposed in 1868 by B. P. 

 Stevens, Esq., to include the rocks of New York Island and it 

 seems proper that it should, for the present, be retained, in- 

 cluding in it, with the Manhattan schists, the Inwood limestone 

 .and the Fordham gneiss, the Yonkers gneiss which though not 



