1897.] NEW YORK ACADEMY OF SCIENCES. 371 



The granites are sheared into gneisses, and mention should also 

 be made of the eruptives, that have formed serpentines. Besides 

 these rocks, rhere are three classes which may be called stratified, 

 because folds can be measured within them. At the base may be 

 found a stratified granite, composing the Fordham gneiss ; above 

 this a thick limestone deposit, and above this the well-known mica- 

 schists, which compose the most of the island. The Fordham 

 gneiss is undoubtedl}' pre-Cambrian, and is covered locally as 

 at Lowerre, Hastings, Sparta, Peekskill, etc., with very thin 

 quartzite, probably the representative of the Georgian quartzite 

 of Dutchess count3\ The crj'-stalline limestones occupy the 

 navigable river-bottoms, and most of the valleys in the vicinity of 

 New York, and thus have had a very important effect on com- 

 merce. The mica-schist is probabl}' of Hudson River age, and 

 has a structure trending N. 40 E., with certain cross foldings. 

 Fissures are filled in certain places, by intrusions of granite and 

 pegmatites. The whole series is crossed by a fault, named by 

 Professor Dana the Manhattanville Fault, running from Manhat- 

 tanville on the North River to the East River, and thence between 

 Ward's and Blackwell's Islands, to Astoria. The throw of this 

 fault is probably a number of hundred feet. The paper was dis 

 cussed by Professor Kemp, Professor Martin and the secretary 



The second paper of the evening was by Captain J. J. Rile}', 

 entitled " The Guano Deposits of the Islands of the Southern 

 Pacific, and their Prehistoric Remains." Captain Riley paid 

 particular attention to the guano deposits of the Chincha Is- 

 lands, on which he had lived for a number of years. The first 

 guano was taken from the Island in 1804, by Humboldt ship- 

 ments began in 1840, and between 1850 and 1880, guano to the 

 value of 550 millions in gold was taken from the three islands 

 alone. The guano has been deposited by birds, and preserved 

 because the region lies in the rainless belt, where rain is uncom- 

 mon except about once in seven years. Captain Riley thinks 

 that the marked banding of the guano denotes variation from wet 

 to dry seasons. From the guano at the depth of 35 and 68 feet, 

 have been taken two burial structures, containing several bodies, 

 apparently entombed with great pomp, and showing a high state 



