450 /•'. . 1. Perret — Lava Eruption of Stromboli. 



high tension which are the cause of the explosions at the cra- 

 ter, and there results a quiet flow. Although the gas content 

 is still high, it is either still in solution or in the form of innu- 

 merable tiny vesicles in which the tension is too small to exert 

 further influence upon the form of the viscous mass, and the 

 lava possesses, in great part, the qualities of the "pahoehoe" 

 type. But the chemical constitution of this material, together 

 with the steepness of the slope upon which it flowed (36°), 

 caused the formation upon its surface of a layer of scoriae 

 which, rolling and sliding over the convex surface of the 

 stream, accumulated in lateral moraines and gave to the flow 

 the appearance of the " aa " type. We may say, therefore, 

 that although both types of lava appear, the pahoehoe quality 

 predominates, which is but natural considering that we have 

 here a lava overflowing from an open conduit. 



That the mass of the flow was compact, coherent and con- 

 tinuous was demonstrated by the two "re-fusions," one of 

 which was witnessed by the writer on the 29th. From the 

 well-known point of observation west of the crater it could be 

 seen that the stream of lava, which had ceased flowing several 

 days before, lay black and motionless on the Sciara slope. At 

 noon a movement was observed among the scoriae on the sur- 

 face of the stream nearest to the vent, and soon this movement 

 was propagated some distance forward. The first portion then 

 became incandescent and began to flow downward very slowly, 

 and this same succession of phenomena — movement of scoriae, 

 incandescence of the mass, and flowing movement— extended 

 progressively along the line of the stream until the whole 

 was in full flow for a hundred meters or more. There was 

 not the least attempt to break through or over in order to 

 seek a new channel, but a revivifying of the original mass 

 under the renewed supply of heat and material from the 

 source. There was no possibility of determining if the center 

 of the flow had retained its original incandescence up to the 

 time of the re-fusion. It is, of course, quite possible that a 

 tunnel had been left, but the writer has on several occasions 

 witnessed true re-fusion of perfectly consolidated lava under 

 the onset of fresh material and does not believe these other 

 conditions to have been essential to the renewing of the flow 

 in the present case. 



The temperature of the lava was, in all probability, at its 

 highest during the first period of the eruption when, according 

 to the inhabitants, it was possible to walk about at midnight 

 through the country lanes brightly illuminated by the reflected 

 glare. It would then have been easy to obtain temperature 

 measurements by means of an optical pyrometer if such an 

 instrument had been available. During the month of Novem- 



