274 [Oct. 1847. 



from the present relations of the carboniferous rocks to older systems, in this 

 province, it is probable that the sea basins in which gypsum was deposited, 

 were not very extensive. In these sea basins the deposition of gypsum alter- 

 nated with mechanical deposits of sand and marl, and with the growth of shells 

 and corals; but the conditions which produced beds of gypsum, were unfavora- 

 ble both to the transport of sediment and the existence of animals or plants. 



From a consideration of these facts, I am disposed to refer the formation of 

 gypsum to springs and rivers, containing free sulphuric acid, and poured into 

 seas in which carbonate of lime had been deposited. The sulphuric acid may 

 have been derived from the volcanic regions of the neighboring ranges of older 

 rocks, and may have been a product of the oxidation of iron pyrites, which still 

 abound in some parts of these older strata, either directly by the action of air 

 and water, or, perhaps, indirectly by the formation of sulphuretted hydrogen, 

 and its oxidation in passing through fissures in contact with water and air. To 

 realize the operation of these causes, you need only imagine streams like the 

 South American Rio Vinaigre flowing into a sheltered bay containing beds of 

 shells and corals, or into the space between a coast and its coral reef. I do not, 

 however, pretend to explain the mode of former action of anhydrite in this 

 way, though it, like the common gypsum, has evidently been deposited in beds 

 by water." 



A letter was read from Dr. S. P. Hildreth, of Marietta, 

 Ohio, dated Aug. 19, 1847, relative to his donation of this 

 evening. 



On motion of Mr. Haldeman, a committee was appointed to 

 confer with Mr. A. Vattemare, on the subject of international 

 exchanges. Committee, Prof. Johnson, Dr. Leidy and Mr. 

 Cassin. 



Stated Meeting, October 12, 1847. 

 Vice President Morton in the Chair. 



DONATIONS TO MUSEUM. 



Forty specimens, in skin, of European birds. From Prof. 



Bronn, of Heidelberg, in exchange. 

 Meandrina cerebriformis, attached to Area Noae, M. crispa 



with Serpula and Pyrgonia ; Agaricia ampliata with Pyrgonia, 



Pocilipora damicornis ; Megaphyllum with Nobia. From Dr. 



Wilson. 

 A mineral, supposed to be new. From Mr. L. J. Germain. 



