l894-] NEW-YORK MICROSCOPICAL SOCIETY. 85 



7. Hypersthene ; silicate of magnesia containing iron. 



8. Oolite from India. 



9. Oolitic sand from Great Salt Lake. 



Mr. Ashby said of his exhibit of Labradorite : " The play of 

 colors, especially remarkable in much Labradorite, indicates, 

 according to Reusch, the existence of a cleavage structure of 

 extreme delicacy, transverse to the median or brachydiagonal 

 section. The play of color appears to be that of thin plates ; 

 yet the linings of what he regards as a cleavage system appear to 

 be of indistinguishable minuteness ; and although the existence 

 of thin plates can hardly be established by means of the micro- 

 scope, it is proved by their effects in the play of colors, nebulous 

 images within, and the phenomena of inflection or diffraction 

 which result from their regular grouping. This play of colors is 

 independent of the disseminated microscopic crystals of foreign 

 substances which occasion the aventurine effect." 



Meeting of May i8th, 1894. 



The President, Mr. Charles S. Shultz, in the chair. 



Eighteen persons present. 



The Recording Secretary read a communication from the 

 American Geographical Society relative to the Sella collection of 

 mountain photographs now on exhibition at the American Mu- 

 seum of Natural History. The Recording Secretary stated that 

 he had replied to this, and had received tickets of admission 

 which he would distribute to the members. On motion the 

 Recording Secretary was directed to express the thanks of the 

 Society to the American Geographical Society. 



The President called the attention of the Society to the pro- 

 posed meeting of the American Microscopical Society, to be held 

 in Brooklyn three days before the meeting of the American 

 Association for the Advancement of Science. After an address 

 on the subject by Mr. George S. Woolman, and the reading by 

 the Recording Secretary of a communication from the Secretary 

 of the American Microscopical Society to Mr. Woolman asking 

 for information regarding accommodations, on motion the Chair 

 appointed the following committee to consider and report any 



