246 G. Poulett Scrope — On Vesuvius, 



into the yawning gulf, to be again immediately ejected by subsequent 

 explosions ; till, after repeated ascents and descents, in each of which 

 the hurtling shower undergoes intense trituration of its component 

 fragments against each other, their angles are worn off, and they 

 are reduced to small rounded gravel, then to sand, and finally to 

 almost impalpable dust, which the winds take up, sort and ti-ansport 

 to enormous distances. Blocks of pre-existing rock, volcanic or 

 other, which obstructed the vent before the eruption, share, of course, 

 in this process, which distributes the ejecta of the volcano more or 

 less plentifully around in the ratio of their size and weight. Though 

 drifted in some places by aqueous torrents, it is not, I believe, to 

 attrition in water, but in the air, that volcanic gravel (lapillo pozzo- 

 lana, etc.) owes its bouldered character. An eruption usually finishes 

 by the ejection, through some days or hours, of the finest dust alone ; 

 the steam bubbles that explode from the lava-surface, as it sinks 

 within the vent, having no longer power to throw out large fragments ; 

 in the end this stifling dust chokes the explosive force altogether, 

 and quiet succeeds ; the eruption has terminated for the time. 



In all these respects the late eruption of Vesuvius appears to have 

 followed the course of that of 1822, though clearly inferior to it in 

 violence and duration. Its effect on the form of the mountain has, 

 no doubt, been the same, that is to say, the truncation of the cone, 

 and the reproduction of a great crateral gulf in its centre. As yet 

 no details have reached us to throw light on this question. We must 

 wait the full report of Signor Palmieri on the subject from a scientific 

 point of view. The same must be said on another point which does 

 not come clear out of the accounts hitherto published, namely, whether 

 any lava-streams were really emitted on this occasionfrom new openings 

 in the southern flank of the mountain below the base* of the old cone, 

 as certainly haj^pened in the eruptions of 1760, 1777, and again in 

 that of 1861. Should such have been the fact, as some statements 

 aver, new small cones of ejected scoriaa (boccole) will have been 

 formed, as has always been the case, over each of the new mouths. 

 But it not unfrequently happens that a lava-current breaking out 

 from the summit, or some point on the side of the cone, penetrates 

 hollow gutters within or beneath some older consolidated flow, and 

 runs down out of sight until it forces an exit for itself at or near the 

 base, and thus puts on the false appearance of a new eruptive mouth. 

 The question has a rather important bearing on the security of Torre 

 del Greco, as all previous deviations from the old established channel 

 of eruption have been on the south side of the mountain on the line 

 of one or more fissures radiating from the centre of the cone in that 

 direction. So that if at any time Vesuvius should, following the 

 example of Etna, Volcano in the Lipari group, and many other 

 volcanos, shift its axis, it will in all probability be somewhere on the 

 southern base of the mountain that the new crater will be formed. 

 Naples may be considered quite safe, but Torre del Greco seems ex- 

 posed not only to invasion from torrents of lava flowing down from 

 the present eruptive vent behind, but also to the possible formation 

 of a new one beneath it. The alarm, therefore, exhibited by its in- 



