G. Poulett Scrope — The Mechanism of Stromboli. 535 



objections, to remark, that no siliceous sinter is found on the walls 

 of the crater of Stromboli, such as geysers all over the world plenti- 

 fully deposit, wherever their waters splash. On the other hand, the 

 gases evolved from the crater, and the products of their action on its 

 rocks, have been shown by the chemical anal^'ses of Abich, Deville, 

 and Fouque, and the spectroscopic observations of Jansenn, to agree 

 with those of ordinary volcanos. 



As already mentioned, Mr. Mallet was not able to see to the 

 bottom of the crater, owing to the vapour, which, he says, " nearly 

 filled the cavity and obscured the bottom, even between the out- 

 bursts." Nevertheless, he guesses it to be 300 feet in dej)th below 

 the rim (D in his Diagram). On what grounds he makes this guess 

 he does not state. There is good reason to believe that the floor of 

 the crater is but little below the lip D. Signer Salino estimated 

 it (of course it is unapproachable) at 2,215 feet above the sea. 

 The deep funnel-shaped cavity represented in Mr. Mallet's diagram 

 may then be considered as wholly imaginary. My own estimate 

 of 2,000 feet is declared by Mr. Mallet (p. 504), to involve "a 

 physical impossibility;" his argument being founded on his own 

 measurements of relative heights, which I have shown to be wholly 

 erroneous. But then Mr. Mallet is in the habit of denouncing as 

 "physical impossibilities," all alleged facts that do not square with 

 his theories. 



Mr. Mallet is evidently under the impression that the intermittent 

 explosions of Stromboli, which he calls rhythmical, but which, as 

 he himself admits, occur at very irregular intervals, are of an ex- 

 traordinary and elsewhere unexampled character. But so far is 

 this from the case that it forms the usual feature in every vol- 

 canic eruption of moderate violence. And of this Mr. Mallet 

 would be aware if he had ever seen any other volcano than Strom- 

 boli in this phase. For example, M. Charles Ste. -Claire Deville 

 thus summarizes his observations of Vesuvius in 1856, " Voila le Vesuve 

 actuellement dans la phase strGmbolienne." Monticelli thus describes the 

 phenomena of Vesuvius in 1815 : " The crater was often quiet for 

 minutes together, and then burst out into explosions of considerable 

 violence, sending fluid lava and ignited stones and ashes to a height 

 of several hundred feet into the air." So, too, Sir H. Davy, de- 

 scribing the phenomena of December, 1819, says, " It threw up 

 showers of red-hot stones every two or three minutes." (Phil. Trans. 

 1828.) I may add that, through several successive months in the 

 years 1817-21, I myself watched nightly from Naples streams of 

 lava which constantly overflowed the summit crater-lip of Vesuvius, 

 and dribbled down the side of the cone, proving that the lava 

 throughout that long time entirely filled the vent of the volcano; 

 while from it successive explosions of steam, throwing up scoriae, 

 precisely like those of Stromboli, only somewhat more frequent, 

 were continually taking place. Both phenomena — the overflow 

 of lava and the outbursts of steam from it — went on without any 

 apparent interference with each other ; though it seemed evident that 

 the continuous rise and expansion of successive steam bubbles from 



