ABSTRACTS AND DISCUSSIONS OF PAPERS 61 



these quantities, both for natural oxides and for oxides made under known 

 conditions in the laboratory, it is possible to draw some conclusions concerning 

 the conditions under which the natural oxides were formed or to which they 

 have been subjected since their formation. 



Presented in abstract extemporaneously by the senior author. 



VARIABLE COMPOSITION OF MELANOCHALCITE 

 BY W. F. HUNT AND E. H. KRAUS 



{Abstract) 



Our previous knowledge of this rare mineral has been restricted to that of 

 a single paper by the late Prof. G. A. Koenig. An investigation of recently 

 acquired material shows, however, considerable variation in the chemical com- 

 position from that previously reported. Koenig's interpretation of the com- 

 position as a basic salt of an ortho-silico-carbonic acid is questioned, and evi- 

 dence is given . for considering melanochalcite as a mechanical mixture of 

 tenorite, malachite, and chrysocolla. 



Presented by title in the absence of the authors. 



DEFINITION AND DETERMINATION OF THE MINERAL HYDROXIDES OF IRON 

 BY H. E. MERWIN AND EUGEN POSNJAK 



(Abstract) 



Specimens from a large number of localities were grouped according to 

 optical characteristics. Those found to be sufficiently homogeneous were studied 

 chemically and thermally. Definitions are based on a correlation of char- 

 acters. Those characteristics most readily determined are emphasized. 



Presented in abstract extemporaneously by the senior author. 

 Brief remarks were made by Prof. J. E. Wolff. 



SALINE FUMAROLE DEPOSITS OF THE SOUTH ITALIAN VOLCANOES 

 BY HENKY S. WASHINGTON 



(Abstract) 



After a brief account of previous work on volcanic salts, the occurrences 

 observed in the summer of 1914 at Vesuvius, Etna, and Vulcano were described. 

 Analyses were given showing the characteristics of the salts found at each 

 volcano. They present certain rather remarkable features — among them the 

 practical absence of chlorides at Vulcano; the occurrences of thiosulphates (no 

 sulphites) within the crater, but not on the outer slope at the same volcano : 

 the prevalence of chlorides, with sulphates, at Etna; the relatively large 

 amount of iron at Vulcano and its paucity at Etna, though the lavas show 

 the converse relations. An interpretation of the results and their application 

 to our views on the constitution of the magma was attempted. The purely 



