514 On the Mechanism of Stromboli. 



into the air. The augite crystals are probably formed within the tube, 

 from small portions of lava dropping in a liquid state into the water it 

 contains. 



Reverting now to the remarks made at the beginning upon the relations 

 traditionally said to exist between the phenomena of this volcano and 

 the state of the weather. It is obvious that the notions of nicely balanced 

 equilibrium in a tube always filled to the lip with liquid lava can no 

 more account for any such relation with the weather than it can explain 

 the rhythmical recurrence of the outbursts themselves ; and if supposed 

 relations with changes of weather, as alleged to be indicated by Stromboli, 

 could be thus explained, every constantly active volcano in the world 

 would be equally a " weather-glass." Kilauia, for example, must present 

 upon an exaggerated scale all the weather-prognostics attributed to 

 Stromboli. In examining the vague statements made upon this subject, 

 we should bear in mind the extreme incapacity of ignorant peoples to 

 observe phenomena with accuracy, their proneness to exaggeration, and 

 the readiness with which they accept traditional statements, however 

 improbable. The statements made to me by several of the more intelli- 

 gent people of Stromboli as to the height to which stones were alleged to 

 be thrown, viz. far above the highest point of the island, as to the filling 

 of the crater brim-full with liquid lava (which, however, no one had actually 

 himself seen), and the forcing through the slope of debris of vertical dykes 

 thereof, as well as the projection of the huge blocks we saw at the bottom 

 of the slope, and such like, should be borne in mind before we attempt to 

 square theoretic views with statements of facts that probably have no 

 real existence. The only intelligible statements that I could gather from 

 the inhabitants of Stromboli as to relations between the weather and 

 their volcano resolved themselves really into two propositions : first, that 

 in fine weather the light reflected upwards from the crater was more 

 brilliant, and apparent at a greater distance, than in windy or uncertain 

 weather ; secondly, that in cold and broken weather the light was dimi- 

 nished, and a heavy cloud of vapour hung more or less over the crater. 



These are intelligible facts, and admit easily of being accounted for on 

 well-known meteorological principles. A tendency, though not a marked 

 one, to the production of sea- and land-breezes in the morning and even- 

 ing is observable in these islands, the sun-heat during the day being 

 often very great, as also the nocturnal radiation. These, taken in con- 

 nexion with the prevailing direction of the wind at a given time, viz. 

 whether it sweeps over the island and over the highest points from the 

 southward and eastward, or blows against its steep north-western face 

 and into the crater, will, by altering the state of the atmosphere above 

 the latter, tend to produce changes both in the light and in the vapour- 

 cloud of the volcano. But that there is any real connexion, in the way 

 of direct cause and effect, between the energy or frequency of the out- 

 bursts and the state of the weather, or fluctuations of barometric pressure, 

 or vice versa, seems devoid of any foundation whatever. 



