508 Mr. R. Mallet on the 



the products of the great craters. Lava from these, generally imper- 

 fectly melted, but occasionally in a complete state of fusion, still finds its 

 way from these into the upper parts of the existing tube of Stromboli, 

 but in comparatively very small quantity. 



On leaving St. Vincenzo we circumnavigated the island of Stromboli 

 and examined the slope of debris in Schiarrazza cove ; the actual average 

 angle of slope is much overrated by Mr. Scrope at 50 ('Yolcanos,' 

 page 32). By the clinometer it proved to be from 34 to 36 with the 

 horizontal. The slope consists almost wholly of angular fragments, 

 averaging but a few hundredweight each, and of shreds and tails of lava 

 that have fallen in a semifused condition. Mixed with these, in a wholly 

 irregular manner, are here and there sinuous and twisted flakes of lara. 

 These have been often taken for dykes of lava forced out by hydrostatic 

 pressure through the bank of debris, when the crater has been assumed 

 brim-full of liquid lava ; but I am not aware of any evidence whatever 

 in support of the notion that this crater ever has been so filled. Its 

 steep walls present no traces of the contact of liquid lava at any time 

 since their formation ; and it can scarcely be doubted that had the crater 

 ever been filled with liquid lava to the brim, the loose and incoherent 

 slope of debris would have been utterly unable to sustain the pressure, 

 and must have been forced bodily into the sea, into which the mass of 

 liquid lava must have followed it. The base of the slope appears to con- 

 sist of solid and, no doubt, comparatively water-tight beds of lava, like 

 those described, as seen from above, at both sides of the Schiarrazza ; and 

 but for these the existing crater could have never been formed, or its 

 activity preserved, for it must have been drowned out by the inroad of the 

 sea, as so many other and recent craters in the other islands prove to 

 have been. The sinuous masses of lava seen at various parts of the slope 

 of debris appeared to me no more than huge splashes of very liquid lava, 

 which, in outbursts of greatly more than usual intensity (such as was one 

 of those witnessed by Hoffman) and with a larger supply of lava than 

 usual, were blown out over the crest of the slope and fell amongst the 

 blocks of debris. Fresh deposits of debris obscure the features of most 

 of these plashes ; but I observed, in some cases, that the lava had distinctly 

 moulded itself, like a mantle, to the sinuosities between and the forms of 

 the blocks upon which it fell. Within a yard or two of the base, or 

 water-line, of the slope were two blocks of lava of exceptional magnitude, 

 the larger having a volume of 8 or 10 cubic yards. These blocks were 

 confidently affirmed to us to have been projected during some violent 

 burst forth and thrown clean over the crest of the slope, and to be in fact 

 blocs rejetes thrown from the bottom of the crater ; examination proved 

 that they could be nothing of the sort. They were sharply angular, and 

 all the surfaces had the crystalline texture of dark pyroxenic lava not 

 very long fractured, except in some places, where distinct signs of wea- 

 thering were evident in the larger block. Had they been blocs rejetes 



