1886.] NEW YORK ACADEMY OF SCIENCES. 41 



November 22, 1886. 

 Stated Meeting. 



The President, Dr. J. S. Newbekry, in the chair. 



Forty-one persons present. 



Mr. a. p. Bjerregaard exhibited galena from shaft 23 of 

 the new aqneduct, Fordham Heights; and the President re- 

 marked upon the occurrence and origin of the mineral. 



The Secretary spoke of the discovery by Prof. Branner, of 

 Indiana, as announced in the November number of the A7ne7'ican 

 Jonrnal of Science, of undoubted glacial stride upon the summit 

 of Elk Mountain, the highest point in Northern Pennsylvania, 

 it being 2,700 feet above tide. 



The thickness of the ice-sheet of the Glacial Epoch was dis- 

 cussed by the President ; also its work and the evidences of 

 more than one ice period. He referred to the recent discovery 

 in India of supposed glaciated boulders in clay slates, which lie 

 at the base of tertiary strata, and the added force which this dis- 

 covery gives to the theory of cosmic causes of the climatic 

 changes. 



Prof. D. S. Martin thought that in deposits of ice periods 

 due to astronomical causes could be found a key to the length of 

 geologic time. 



The subject of the peculiarities and amount of glacial erosion 

 was discussed at length by Mr. L. E. Chittenden, Mr. F. J. 

 H. Merrill, and the President. 



Prof. D. S. Martin in behalf of a special committee read a 

 memorial sketch of 



November 29, 1886. 

 Stated Meeting. 

 The President, Dr. J. S. Newberry, in the chair. 

 Thirty-seven persons present. 



Mr. J. J. Friedrich exhibited malachite, with its associated 

 minerals, from 117th street, between Fourth and Madison 



