446 Ht 8. Washington — Rhyolites of Lipari. 



Art. XXX. — The Rhyolites of Lipari; by Henry S. 



Washington. 



contents. 



Introduction. 



Bhyolite Obsidian. (Hephaestal Liparose.) 



Lithoidal Bhyolite. (Aeolal Liparose.) 



Hyalo-Dacite. 



Bhyolite Obsidian, Island of Milos. 



The Eelation of Iron Oxides and Glass Content. 



Refractive Indices of Bhyolite Glasses. 



Introduction. 



The rhyolites of Lipari would seem to have been the 

 earliest of these lavas to be studied chemically, analyses 

 by Abich having* been published by him in 1841. 1 Since 

 his time no analyses of the Lipari rocks appear in the 

 literature, until Lagorio 2 published a couple of poor ones 

 in 1887, followed by those of Glaser 3 in 1899. None of 

 the analyses of these Lipari rocks are of first rate qual- 

 ity. In view of their wide-spread occurrence in collec- 

 tions, the typical character of these obsidians, and the 

 well-nigh world-wide use of the pumice of Lipari, this 

 neglect would be somewhat surprising, were it not the 

 common fate of well-known rocks, many of which are 

 so "well-known' that they are not studied or described. 



To make up for this deficiency, I have recently 

 analysed some specimens of the rhyolitic lavas of Lipari, 

 which were collected by Dr. A. L. Day and myself in July, 

 1914. Brief descriptions of them will be given here, 

 along with the analyses, so that they may be on record. 



The characters, occurrence, and sequence of the lavas 

 of the volcanoes of Lipari have been described in some 

 detail by Cortese and Sabatini, 4 and by Bergeat, 5 to 

 whose descriptions the reader may be referred. The 

 sequence of volcanic events would seem to have been 

 about as follows. 



Volcanic activity appears to have begun with the for- 

 mation of the basaltic cones of the "Timponi'' on the 

 west coast, followed by the basaltic and andesitic cones 



1 Abich, Vulk. Ersch., Braunschweig, 1841, p. 62. 



2 Lagorio, Tsch. Min. Petr. Mitth., 8, 440 and 491, 1887. 



3 Bergeat, Abh. Bayer. Akad. Wiss., 20, 108-118, 1899. 



4 Cortese and Sabatini, Descrizione delle Isole Eolie, Mem. Carta GeoL 

 Ital., VII, 25-45, 98-112, 1892. 



5 Bergeat, Abh. Bayer. Akad. Wiss., 20, 92-141, 1899. 



