150 Washington — Submarine Eruptions of 1831 and 1891. 



whole progress of the Graham Island eruption, a gas which is 

 so commonly observed at other volcanoes, as Vesuvius. 



The very high FeO : Fe 2 3 ratio shown by the basalt of the 

 Zeneti dike does not seem to be explicable by the hypothesis 

 advanced above, as it is decidedly vesicular and jet apparently 

 not due to a submarine eruption. Discussion of this rock 

 must, however, be reserved for a later publication, in connec- 

 tion with the geology and petrography of Pantelleria. 



In both his papers cited above Foerstner suggests that the 

 basalts of the eruptions of 1831 and 1891, as well as those of 

 Pantelleria, are connected with those of Etna. Of the lavas 

 of Etna, however, we have no modern or satisfactory chemical 

 analyses, strange as it may appear. With the exception of one 

 of an ash by Picciardi in 1884,* none of them are later than 

 1881. The lavas and ashes of Etna have been analyzed^ by 

 O. Silvestri, Fuchs, Giimbel, Von Lasaulx, and Picciardi. 

 Most of the analyses show a general resemblance to each other, 

 as well as to those by Foerstner of the basalts of Graham Island 

 and Pantelleria, in which Ti0 2 and other minor constituents 

 have not been determined. The studies of Von Waltershausen 

 and Von Lasaulx also show that, while the lavas of Etna are 

 predominantly basaltic, there are numerous flows and dikes of 

 more salic rocks, especially belonging to the earlier phases of 

 this volcano, a fact already noted by Abich. There is, there- 

 fore, reason for the belief that the magmas of Etna and of 

 Pantelleria and the submarine eruptions are chemically similar 

 and probably genetically connected. But, as a marked charac- 

 teristic of the basalts of the latter volcanoes is the high content 

 in titanium, it is clear that modern, complete analyses of the 

 Etna lavas are needed before the matter can be discussed intel- 

 ligently. 



Locust, N. J., August, 1908. 



*L. Ricciardi, Att. Ace, Gioen., vol. xviii, p. 4, 1884. 



f J. Roth, Beitrage zur Petrographie, p. exxviii, 1869, and pp. lxxvi-lxxx^ 



1884. 



