438 PROF. G. A. J. COLE AND MR. G. W. BUTLER ON THE 



28. On the Lithophyses in the Obsidian of the Eocche Eosse, 

 LiPARi. By Prof. Grenville A. J. Cole, F.G.S., and Gerard 

 "W. Btjtler, Esq., B.A., P.G.S. (Eead May 11th, 1892.) 



[Plate XIL] 



The Eocche Eosse lava-stream, partly filling the pumice crater 

 of Monte Pelato, Lipari, and breaching it on the north-eastern side, 

 was described by Prof. Judd ^ in 1875. As recorded by him and 

 by Cortese ^ we find in this locality all varieties of obsidian lava, 

 from compact black glass to the pumice of coramerce, or even a 

 honeycombed material passing into ' thread-lace scoria.^ A person 

 who, arriving at the south-western or landward side of the crater, 

 begins walking over the hummocky surface of the Eocche Eosse 

 along the centre of that part which lies within the crater, cannot 

 fail to be struck by the fact, emphasized by Cortese, that much of 

 the lava here, as at the Porgia Yecchia, has a texture intermediate 

 between that of pumice and compact glass. In fact, he might walk 

 along the middle of perhaps the first third of the Eocche Eosse 

 without finding anything that he would call obsidian. However, 

 if he turn to the right and make his way towards the southern 

 margin of the lava, he will find portions of it in which black glass 

 predominates. 



Prom one of the numerous outstanding hummocks of this part 

 of the Eocche Eosse were obtained the specimens of black glass 

 with vesicles, lithophyses, and spherulites, which have led to the 

 writing of this paper, and from which the sections figured in 

 Plate XII. have been taken. It must not be supposed, however, 

 that the rock here difi'ered in any essential from the lithophyse- 

 bearing obsidian found elsewhere in this locality ; or from the 

 similar lava at the Porgia Yecchia described by Messrs. Iddings 

 and Penfield^ ; or from the obsidian on the northern flank of Yulcano. 

 But the specimens taken from this exposed hummock show in a 

 specially striking manner the passage, through various stages of 

 lithophysal structure, from indisputable steam-vesicles with glassy 

 walls to the typical solid spherulites of these Lipari obsidians. 



Messrs. Iddings and Penfield have described the characteristic 

 structures in the obsidian of the Porgia Yecchia as ' hollow 

 spherulites ' and * lithophysie.' The following examination of the 

 structures displayed by the Eocche Eosse mass will show that we 

 are dealing with a mode of devitrification which is certainly litho- 

 physal in character, in so far as it depends upon the liberation of 



^ ' Contributions to the Study of Yolcanos,' Geol. Mag. for 1875, p. 66. 

 See also Johnston-Lavis, Proc. Geol. Assoc, vol. xi. p, 394, and ' The South 

 Italian Volcanoes' (1891). 



2 Boll E. Comit. geol. d' Italia, toI. xii. (1881) p. 512. 



^ 'Payalite in the Obsidian of Lipari,' Amer. Journ. Sci. vol. xl. (1890) 

 p. 75. 



