76 PROCEEDINGS OP THE ACADEMY OF [1883. 



color. The purple obtained from 250 cub. cent, of the solution 

 contained 



As.,0, . . = 0-0583 gram. 



Fe.Os . . = 0-0340 " 



Gold (Au) . . = 0-0188 " 



CaSO, . . = 0-0060 " 



The only jjold-purple heretofore known was the Purple of Cassias, 

 obtained by adding a mixture of stannic and stannous chlorides 

 to a dilute gold solution. Authors are divided in their opinions 

 as to whether the gold is contained therein in the metallic state 

 and only mechanically admixed as a red allotropic modification, 

 or chemically combined as gold dioxide. The speaker has 

 inclined hitherto to the first view, and finds in this ferric arseniate 

 gold-pu7'ple^ physically so very analagous to the stannic gold- 

 purple, a strong support to the mechanical hypothesis. Dilute 

 hydrochloric acid decomposes this purple at once into brown 

 gold, and arsenico-ferric solution. 



A Flint Nodule from the Greenland of New Jersey. — ^Prof. 

 Leidy directed attention to a flint nodule, presented this evening, 

 obtained from the greensand of Pemberton, N. J. It is discoid, 

 about the size of a dollar, pitted and smooth, homogeneous and 

 bluish black, and exhibits no trace of organic remains. He 

 remarked that as flint nodules, regarded to be of organic origin, 

 were so exceedingly abundant in the chalk formations of Europe, 

 he had wondered that similar nodules were not of more frequent 

 occurrence in the greensand deposits, of contemporary ago, in 

 our country. The nodule presented was the only one of the kind 

 he had ever seen from the New Jersey marl. 



March 27, 

 Mr. Geo. W. Tryon, Jr., in the chair. 

 Forty-five persons present. 



April 3. 



Rev. Dr. Henry C. McCook, Vice-President, in the chair. 



Thirty-eight persons present. 



A paper entitled " Aztec Music," by H, T, Cresson, was 

 presented for publication. 



The following was ordered to be printed : — 



