1885.] :new YORK academy of sciences. 5Y 



all the other saline constituents were held in solution. With 

 further evaporation a l>elt or margin of gypsum would be left 

 around tlie shallower portion of the lake, and chemically pure 

 salt would be deposited when the concentration passed the point 

 of saturation for salt. The diminished waters now retiring to 

 the deeper parts of the basin would leave behind them in places 

 sheets of pure salt, while the precipitates subsequently made 

 would contain an abnormal quantity of bitterns. 



Just such a record we seem to have in the sediments of the 

 old Salina lake as well as those of later date in other parts of 

 the world ; the salt of certain localities or certain layers be- 

 ing nearly pure, while that of other localities or layers contains 

 an imdue proportion of impurities. The salt basins of the Up- 

 per Ohio and of Michigan, l)oth distinct from and of later age 

 than that we have been considering, show the same peculiarities. 



By some writers the gypsum of the Salina Group, as well as 

 that of other formations, is attributed to the action of acid wa- 

 ters on carbonate of lime, but the continuous sheets of gypsum 

 contained in the Salina Group, separated by thin bands of pure 

 limestone, disprove this theory. They are evidently chemical 

 precipitates from saline waters, alternating ^vith the limestones, 

 which were formed from the hard parts of organisms inhabiting 

 the water during the intervals when it was pure enough to sus- 

 tain animal life. 



Dr. Arthur H. Elliot read a paper on 



SANDSTONES USED FOR BDILDING PURPOSES IN NEW YORK CITY. 



(Illustrated by specimens and tallies of analyses). 



The subject was discussed by Dr. Julien, Mr. Collingwoop 

 and the President. 



March 30th, 1885. 



Stated Meeting. 



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



Thirty-one persons present. 



Mr. B. B. Chamberlin exhibited a line specimen of black 

 tourmaline from Russell, St. Lawrence Co., N. Y, 



