114 MERRILL. 



channel on either side of the island being underlain by decom- 

 posed material resembling a kaolin. 



This material I recognized to be similar to that collected by 

 Dr. Martin in Morrisania. Subsequently in making a detailed 

 study of the geology of Manhattan Island, I had occasion to 

 investigate the material of the bottom of the East and North 

 Rivers. 



My first visit was to the office of the engineer of the Dock 

 Department where I ascertained that a whitish material like 

 kaolin had been found at many points on the bottom of the 

 East and North Rivers. Then going to the office of Colonel 

 Gillespie, in charge of the harbor improvements, I found sam- 

 ples of similar material from the East River near the foot of loth 

 street and from the "middle ground" near Astoria. Further 

 effort put me in possession of some material from the latter 

 place where dredging was going on. 



It then seemed desirable to make a chemical examination of 

 this residual material and this work was placed in the hands of 

 Dr. H. C. Bowen of New York. The results of the analyses 

 arc given in the following table. 



These analyses show a very close relation in chemical com- 

 position between the white and variegated clays of the North 

 Shore of Long Island, of which those from Elm Point and Ea- 

 ton's Neck may be regarded as types, and the residual products 

 of the decay of the metamorphosed Palaeozoic limestone of 

 New York and Westchester counties. 



A geologic study of the shores of Long Island Sound and 

 the adjacent territory shows that the prevailing rock on the 

 north shore of that territory is the Manhattan schist, a meta- 

 morphosed representative of the Hudson River group and that 

 on Long Island wherever solid rock is found beneath the loose 

 deposits of mesozoic and cenozoic age, it is a banded gneiss, 

 identical in lithologic character with that which has been deter- 

 mined to be Precambrian on New York Island and in West- 

 chester County.^ 



This may be regarded as conclusive evidence that the former 



J See Fiftieth Annual Report, N. Y. State Museum, 1896, pp. 21-31. 



