8 J. W. Jadd — On Volcanos. 



crater, in the Solfatara condition, remarkable alike for the abundance 

 and variety of its gaseous emanations, and for the beauty of the 

 minerals which result from them, but at the same time subject to 

 paroxysmic outbursts on the grandest scale. In all the islands we 

 find the most beautiful illustrations of the constant shifting of 

 centres of volcanic action along lines of subterranean fissure, and 

 the most instructive examples of the wide diversities in the charac- 

 ters of lavas, from those of the most highly silicic or acid composition 

 to those of the most ferruginous and basic, and from the highly 

 crystalline varieties on the one hand, to perfect glasses on the other. 

 The analogy between the relations and order of formation of the 

 great central volcano and the surrounding lines of volcanic vents in 

 the Lipari Islands on the one hand, and the ruined volcanos of Central 

 France, namely, the Mont Dore, the Cantal, and the Mezen, and the 

 long chains of " Puys " surrounding them, on the other, must strike 

 every student of volcanic geology, and is a sufficient justification for 

 our adopting the following order in our descriptions of the Lipari 

 volcanic formations : — 



I. The great central volcano now almost entirely submerged, and 

 of which we have only a few highly ruinous relics in Panaria and 

 the surrounding islets. 



II. The chains of extinct and more or less degraded cones which 

 constitute the larger part of the other islands. 



III. The very remarkable features and the interesting products of 

 the still active or but recently extinct vents in Stromboli, Lipari, 

 Vulcano and Vulcanello. 



IV. Our sketch of the district will appropriately conclude with 

 descriptions of the remarkable phenomena exhibited by Vulcano and 

 Stromboli respectively, and a history of the changes which have 

 taken place within them during the periods concerning which we 

 have authentic records. 



1. — First Period of Volcanic Activity in the Lipari Islands. 



The submerged tract (see Map, p. 7) which marks the probable 

 site of a great central volcano in the Lipari Islands is composed — 

 judging from the nature of the islands and rocks which still rise 

 above the sea-level — of various materials of the trachytic class. 

 These occur in the form of tuffs and agglomerates, of lava streams, 

 and of solid masses of enormous dimensions, which appear to have 

 been extruded in a viscid or pasty condition in the manner so com- 

 mon with rocks of their class. 



In the disposition of the materials in this central group of islets 

 the student of volcanic geology at once recognizes those forms so 

 characteristic of partially submerged and greatly denuded crater 

 rings, which are so well exemplified in the ruined volcanos of San- 

 torin in the iEgean Sea, and of Ventotiene, one of the Ponza Islands 

 (vide Scrope's 'Volcanos,' 2nd ed. p. 209). As shown in the sketch 

 (Fig. 2), the inclined streams of lava, with their alternating beds of 

 tuff, which doubtless once constituted the sides of a great cone, 

 gradually built up by their successive emission, now exist only as 



