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DONATIONS TO THE CABINET. 



Ammonite from the lias of England, fine specimen. From 

 Nathaniel Breioer, Esq. 



January 7, 1846. 



Dr. A. A. Gould in the Chair. 



Mr. Francis Alger exhibited certain minerals, and read a 

 paper concerning them, which was referred to the Publishing 

 Committee. The following is an abstract of it. 



Mr. Alger announced that he had discovered Phacolite among 

 specimens of minerals from New York Island. The crystals are 

 beautifully perfect, double six-sided pyramids, implanted on car- 

 bonate of lime. They are of a wax-yellow color, have also a 

 waxy lustre, and are translucent. This mineral, he observed, 

 had been regarded by some as a species distinct from Chabasite, 

 but it is now, principally on the authority of Tamnau, of Berlin, 

 admitted to be only a variety of that mineral, derived from the 

 same primary rhombohedron. Mr. A. remarked that the New 

 York crystals were very interesting, from the fact that they 

 showed the incipient modifications by which the ultimate double 

 six-sided pyramids were produced from the rhombohedron, 

 thereby clearly proving the Phacolite to be a secondary to the 

 primary form of Chabasite. This he had not observed in any of 

 the specimens from Bohemia or Ireland. It should nevertheless 

 be remembered that the analyses of Phacolite, by Anderson and 

 Rammelsberg, make it differ somewhat from common Chabasite, 

 one being a bisilicate of alumina, -f- bisilicate of lime, potash 

 and soda, + six atoms water ; the other, a tersilicate of the first 

 term, and a simple silicate of the second, along with three atoms 

 water. 



Yttro-cerite. Mr. A. had found this very rare mineral in the 

 limestone from Orange county. New York. It presents all the 

 characters of the mineral from Finbo, in Sweden, and cannot be 



