J. W. Judd — On Volcanos. 63 



Liparite, the ordinary hornblende and mica crystals do not appear ; 

 but instead of them, we find in the mass grains of magnetite with 

 groups of acicular, filiform, or capillary crystals, which we should at 

 first sight refer to Breislakite, but which, considering their association, 

 may probably be regarded as a variety of hornblende, bearing the same 

 relation to the Amphibole series which Breislakite does to the Pyroxene 

 series. 



In striking contrast to the basic lavas of Stromboli, the highly 

 acid lavas of the Lipari and Vulcano constantly tend to assume the 

 vitreous condition ; some of the lava-streams being, indeed, com- 

 posed of solid volcanic glass. These glasses in turn frequently 

 assume a more or less pumiceous structure, through the inflation of 

 their materials with blisters and bubbles, as a consequence of the dis- 

 engagement of those volatile constituents which the researches of many 

 chemists show that obsidians so abundantly contain. The cones 

 formed of the ejected fragments of these newer volcanos of Lipari 

 and Vulcano consist of fragments of typical pumice. So excellent 

 and abundant is the pumice of Campo Bianco in Lipari, that it is 

 sent to all parts of the world ; and its collection, preparation by 

 drying, and exportation, constitute one of the most important sources 

 of wealth to the islanders. 



Mingled with the white pumice, which constitutes fragments of 

 every conceivable size, there occur numerous volcanic bombs, in 

 which every stage of the transition from obsidian to pumice can be 

 admirably studied.- The exterior surface of these bombs is covered 

 with a crust of solid obsidian, which is usually cracked into a 

 number of polygonal fragments ; but, as we pass towards the centre 

 of the bomb, blisters gradually increase in number, till the centre is 

 found to be composed of a mass as light and porous as a sponge. 

 Bombs of this character, sometimes many feet in diameter, and 

 which have been usually broken by their fall, are found scattered 

 around the active cone of Yulcano, and are in all probability the 

 product of its last grand eruption in 1786. 



The wonderful variety of the acid rocks of the Liparis arises from 

 the fact that every possible gradation between the stony, vitreous, 

 and pumiceous characters, may be observed in them. The liquefied 

 material may, according to the conditions of its consolidation, assume 

 one of three forms, Liparite, Obsidian, or Pumice, or it may form a 

 material in which the diverse characters of these three products are 

 united in the most singular and unexpected combinations. 



Some of these remarkable and interesting varieties, which may be 

 well studied at Eocche Posse, Monte Perrara, Monte della Guardia, 

 Fossa del Monte, Punta Capparo and many other points in Lipari, 

 and in the great modern lava stream of Vulcano, it will be necessary 

 briefly to notice. 



First Series. — The most perfect glass is found passing by insen- 

 sible gradations into rocks of less strikingly vitreous lustre — pitch- 

 stones or retinites — and thence through materials of pearly or 

 porcellanous appearance into the most perfectly stony and crystal- 

 line, almost indeed granitic, masses. This series of changes is effected 



