110 History of the Geology of JVew York Island. 



" The quartz is of the foetid kind, giving out an unpleasant odor on 

 being fractured." 



In 1839, L. D. Gale, M.D., resident member of our Society, 

 in the preliminary report on the geology of the first district ot 

 the State, gives the first minute and detailed description of the 

 geology and topography of the island. 



He considers the elevation of the Island to be due to a force 

 acting in a KN.E. and S.S.E. direction. By it, Staten 

 Island, Governor's Island, the smaller islands of New York 

 Bay, with Manhattan, were elevated. From the Island it 

 passed by Hurlgate, through Westchester into Dutchess, Ches- 

 nut Ridge, and Winchell Mountain, belonging to it. 



He was the first to give the geological topography of the 

 Island, as being a group of gneissoid islands, and separated 

 from each other by low levels, slightly elevated above tide and 

 filled with drift or alluvial. 



Dr. Gale's observations on the character of the rock, its dip 

 and strike, and its surface markings, were very accurate, and 

 need at the present time no emendations. . The following is 

 his description of the Island of New York : 



" The basis rock of the island is gneiss, if we except about one mile 

 in length of the northern part of the island, which is limestone. The 

 gneiss varies considerably in character in different portions of the island. 

 For example, the northern part abounds largely in limestone, and the 

 western in veins of granite and quartz ; while the southern and eastern, 

 as well as the middle portions, are more purely gneiss. 



"The general direction of the strata is N. 25° E., to 35° E., and cor- 

 responds with the direction of the avenues ; and the clip, though gene- 

 rally to the west, averages within ten degrees of the vertical. 



" In a few cases, it has been found that carbonate of lime enters into 

 the composition of the rock of the island. This is the case on the east 

 side of Fourth Avenue, from 118th st. to 120th st. Here the rock 

 retains its identity, as gneiss, to all appearance ; although half its mine- 

 ral matter is carbonate of lime. Again, at 157th st., and about one 



