Merrill — Metamorphic Strata of 8* /.' New York. 



sped the most ooticeable are those of Anthony's Nose and 

 Sugar L<»;it', the latter of which exhibits this peculiarity by Its 

 profile to the most careless observer. 



On the southeastern tlank of Dunderberg and Manitou 

 Mountains the stratified granulites again appear and these are 

 succeeded alter a drift-covered interval near Peekskill and 

 Jones Pt, by slightly metamorphosed sandstones. Limestones 

 and slate, presumably of Paleozoic age, the relation of which 

 to the Bub-crystalline rocks of Westchester and New Fork 

 is still an interesting problem. 



Younger Rocks. — The metamorphic strata of Xew York 

 and Westchester Counties have long attracted the attention of 

 and several attempts have been made to solve the 

 problems of their age and history. The extended researches 

 of Prof. das. I). Dana on the relations of the limestone belts 

 in the vicinity of Manhattan Island have furnished a clue to 

 the stratigraphy, and, after a careful study of a portion of the 

 terrane to which those limestones belong, the writer is enabled 

 t«« announce the following general results. As Prof. Dana has 

 noted (Am. Jour. Sci., Ill, vol. xxi, p. -139), the beds underlying 

 the limestones of Xew York County are highly quartzose, 

 while those overlvin^ them, are chiefly micaceous. Throuo-liout 

 Westchester County south of the latitude of Sing Sing, an 

 area of about one hundred square miles, the writer has found 

 this lithological difference to prevail. The exact relation of 

 the lower beds to the granitoid gneisses and granulites of the 

 Highlands of Rockland, Orange and Putnam Counties has not 

 yet been determined by the writer, but his investigations have 

 satisfied him that the former, w T ith the exception of the lime- 

 Bt< »nes, are distinctly detrital rocks in which are preserved the 

 fragmental character of the quartz and feldspar which they 

 contain. The mica, chiefly biotite, is of metamorphic origin, 

 having been developed from aluminous mud rich in potash, 

 iron and magnesia. 



A- the limestones of the region under consideration contain 

 no organic traces, so far as we know, there is no direct clue to 

 their origin, but in the absence of evidence to the contrary we 

 may believe that the carbonate of lime was separated by organic 

 agencies from the sea water which held it in solution. The 



1 known chemical theory of Dr. Hunt accounts very satis- 

 factorily for the presence of bicarbonate of lime in sea water, 

 but it does not account so well for the separation of the car- 

 bonate from solution, and as this separation is effected very 

 extensively at the present time by various marine organisms 

 ami as the cases of chemical separation of carbonate of lime 

 from solution in sea water are very few, we are justified in be- 

 lieving that the former process was in operation as far back in 



