G. Poulett Scrope — The Mechanism of Btromboli. 533 



In reality, there is positively nothing in the recurrent explosions 

 of Stromboli essentially different (as I shall presently show by ample 

 testimony) from the similarly recurrent outbursts of any ordinary 

 volcano during prolonged eruptions of moderate violence. There is, 

 therefore, no call for any extraordinary explanation of these "rhyth- 

 mical" outbursts in this particular case. And if Mr. Mallet, instead 

 of setting his imagination to work upon the possible cause of their 

 more or less regular occurrence, had adopted the humbler but more 

 legitimate course of inquiring whether Stromboli stands alone in this 

 respect, or whether other volcanos do not exhibit at times pheno- 

 mena exactly similar — though rarely continuing for so long a time — 

 he might have seen it to be quite unnecessary to invent a peculiar 

 " mechanism " for Stromboli, unless, indeed, he means to apply it to 

 all other volcanos likewise, which he has not gone the length of 

 doing yet, 



Mr. Mallet's theory is, that this celebrated island, which has 

 hitherto been considered by all geologists as a typical volcano, is no 

 volcano at all — at least, not of the usual igneous type — but a geyser, or 

 intermittent fountain of boiling water, which, by some extraordinary 

 chance, is situated at the bottom of a crater immediately beneath the 

 mass of white-hot and liquid lava, which here, as in other volcanic 

 craters when in activity, occupies that position, and is consequently 

 tossed up into the air, in the shape of scorise, etc., at each outburst of 

 the water. The tube of the supposed geyser is represented as occupy- 

 ing the place of the axial chimney of the volcano, and as alternately 

 filled and emptied by the rise and escape from its mouth of a jet of 

 boiling water and steam derived from some ducts or channels beneath 

 the sea-level. The lava, which even Mr. Mallet cannot dispense with, 

 since its projection into the air is the most obvious of all the phenomena, 

 is supposed by him to flow to the mouth of the tube through lateral 

 ducts from some undefined quarter, and the steam to be derived from 

 a third kind of duct at a still greater depth below the sea than that 

 which produces the water (page 512, Diag. 4). I submit that such 

 a fortuitous concurrence of water, steam, and lava, proceeding from 

 different sources or ducts, is a complicated and wholly imaginary 

 supposition, without example, and unsupported by any facts or reason- 

 ing of the slightest value. Such an hypothesis could hardly have 

 been expected of Mr. Mallet, who, in page 500 of his paper, justly 

 says, "It may be taken as certain that in explaining all natural 

 phenomena, the simplest explanation is the true one." 



The simplest explanation of the phenomena of Stromboli would 

 be to refer them to the ordinary mode of action of other volcanos. 

 And certainly Mr. Mallet does not give any adequate, or even plaus- 

 ible, grounds for ascribing them to any different and extraordinary 

 " mechanism." Mr. Mallet, I may remark, does not venture to say 

 that he saw any column of water, like that of a geyser, thrown up 

 from the crater's bottom, nor that any one else had ever witnessed 

 such a sight. He admits that he could not see the bottom of the 

 crater, owing to the clouds of vapour that obscured it, nor could he 

 form a guess as to its depth, nor as to what was going on there, except 

 from the detonations he heard, and the jets of red-hot stones, accom- 



