136 Washington — Submarine Eruptions of 1831 and 1891. 



which broke both her masts, the air was filled with a sulphur- 

 ous odor, and three immense globes of fire were seen. The 

 other eruption took place in the night of October 4-5, 1846, 

 a little west of Girgenti, and nine miles from the coast. There 

 does not appear to have been any shock, but the captain of a 

 passing vessel, seeing a bright light, approached, and saw an 

 immense mass of flames and smoke rising from the sea, from 

 which were hurled incandescent globes. It is reported that 

 the area covered by the flames was more than a mile in cir- 

 cumference and that the sea appeared to be boiling. 



Petrography . 



Although it is commonly thought that the lavas of Graham 

 Island were wholly basaltic, yet the descriptions of Gemmellaro 

 and an analysis by Abich, as well as a brief description of one 

 specimen by Foerstner, indicate that there was considerable 

 diversity among them, those belonging to the earlier phases of 

 the eruption having been distinctly trachytic in character. 



The specimen examined by me is in the collection of the 

 Peabody Museum at Yale University, having formed part of 

 an old collection of rocks, though all record of its acquisition 

 has been lost, according to Professor E. S. Dana, to whom I 

 am deeply indebted for his kindness in supplying the material 

 for analysis and microscopical study. The small specimen is 

 accompanied by a label, on which is written in now faded ink 

 and in an old-fashioned script: "Lava from the volcano that 

 rose from under the sea off Sciacca, 40 miles from Sicily, Aug. 

 1831. Water 600 feet deep. Brought home by the Kev'd 

 Eli Smith " (no date). There is no reason for doubting that it 

 is what it purports to be, especially as its characters agree with 

 Foerstner's descriptions of well-authenticated specimens. 



The specimens examined by Foerstner came respectively 

 from the museums at Palermo, Naples, and Strasburg; the 

 first having been collected by C. Gemmellaro and the last 

 (which differed much from the others) being labeled as 

 "lapilH floating on the sea," and thus probably belonging to 

 the early period when masses of such lapilli were washed 

 ashore near Sciacca, as pointed out by Foerstner. Of these 

 specimens Foerstner gives an analysis only of the first. 



Megascopic. — My specimen is jet-black in color, and but 

 slightly vesicular, the vesicles being very minute, and much of 

 the small piece being quite compact. Foerstner's specimens 

 would seem to have been much more scoriaceous and vesicular. 

 Delicate, very small, glistening gray tables of feldspar are 

 abundant, but no other phenocrysts are visible. 



Microscopic. — The largest and most abundant phenoci^ysts 

 are of labradorite, in tables from 0*5 to 2'0 mm long, by 0*02 -0-10 

 thick, which are twinned according to the Carlsbad and albite 

 laws. The extinction angles show that the composition is 



