112 History of tTte Geology of New York Island. 



ward, and some westward. The strike is also variable from northeast 

 to northwest, but north-northeast is the prevailing direction. Granite 

 in numerous beds and veins, some of which are very tortuous, were 

 observed. At Hurlgate ferry, at the east end of 86th st., the strata are 

 vertical, and are of gneiss more or less hornblendic, interlaminated with 

 beds and irregular masses of granite. The strata are frequently bent 

 "where these irregular masses of granite were observed." 



In the same year (1843), Mr. Issachar Cozzens,* resident 

 member and Librarian of the Society, published a small 

 volume on the Geology of New York and the adjacent Islands, 

 illustrated by colored maps and sections. 



It is one of the best contributions made upon the subject, 

 and abounds in many important and pleasing local reminis- 

 cences. The following is his description of our Island. 



"This island is about thirteen miles long. It consists of eight differ- 

 ent series or formations of rock, as follows : 



" 1st. Granite, — This begins to show itself at 28th st., a little east of 

 8th avenue, and runs in an interrupted line to the North River at 32d 

 st. ; from thence, it is seen between the 10th avenue and river, and paral- 

 lel with the river to 60th st. ; it then crops out at 86th st., between the 

 'Harlem Railroad Tunnel' and the 'Receiving Reservoir' of the Croton 

 Water Works ; in levelling east 22d st., near, and south of the ' Belle- 

 vue Almshouse,' it was exposed in a pyramidal form, the top of which 

 was cellular, and had a spongy appearance ; in the cells were found small 

 crystals of quartz, feldspar, and prismatic mica, the gneiss lying super- 

 incumbent, with its dip varying from 30° to 45°. 



" 2d. Syenite. — This crops out at the north edge of the serpentine ; it 

 may possibly be a boulder of greenstone, but if so, it is the largest on 

 the island. 



" 3c?. Serpentine. -^Between 54th and 62d streets, the shore and 10th 

 avenue, there are four or more small knolls of black serpentine, with 



* Mr. Cozzens, slightly bowed with the burden of eighty years, is a frequent 

 attendant of our meetings, one of the few representatives of the founders of our 

 Society. 



