506 Mr. R. Mallet on the 



the diagonally shaded portion represents an ideal section of the island as 

 it now stands, taken through its highest point and the existing crater of 

 Stroniboli, while the lines beyond indicate the probable outlines of the 

 island when the great crater was active, of which the Stroniboli of to-day 

 may be viewed as little more than a f umarole. 



Diagram No. 2. 



I may add here, in reference to the Lipari group generally, that all the 

 islands present more or less distinctly these characteristics of craters 

 whose axes have shifted and formed new ones at immensely ancient 

 epochs,: and with vast intervals of time intervening. 



The entire -group presents, though in various degrees in the different 

 islands, the . general ,- character of great decadence of a once far jnore 

 powerful volcanic activity ; and, in every case, as the cone, or rather mound, 

 of each island increased in mass and height, the original vent thus in- 

 creasingly obstructed tended to move off and open new and easier vents 

 in directions approaching the coast-lines, just as in the case of very old 

 and massive volcanoes on land, such as Etna, migrations have occurred of 

 their most ancient great craters, and, in more recent times, new ones have 

 opened low down upon their flanks, such as Monte Rosso &c. The epoch 

 of primordial activity was far from contemporaneous in all the islands ; 

 and we find in them now the most varied stages of volcanic decadence. 

 In the island of Vulcano, we have an empty crater of enormous capacities 

 and depth (1100 to 1200 feet), the bottom of ', which reaches to within a 

 few feet of the sea-level, and is only separated from the shore-line at the 

 north-east of the island by an extremely steep bank of compact tufa. 

 The oldest craters having been situated much more centrally and far to 

 the south-west, while the little crater of Vulcanello was thrown up to 

 seaward of the ancient coast-line and between it and the deep crater just 

 spoken of, boiling springs and boiling streams of superheated vapours 

 issue below the sea-water, and a thermometer sunk amongst the pebbles 

 of the beach in many spots rises to above 300 Fahr. In the bottom of 

 the deep crater the principal " bocca," which is several feet in diameter, 

 and though only blowing out superheated steam, and gases with a mea- 



