1823.] M. Humboldt on Volcanoes, III 



Berlin, an excellent chemist, no traces of either metal, could bq 

 discovered. 



However great may be the discrepancy between the results that 

 I have here given, but which agree with Monticelli's more exact 

 observations, and those which have been circulated during 

 several months past, yet the eruption of ashes from Vesuvius^ 

 from the 24th to the 28th of October, still remains the most re- 

 markable of which we have any certain account since the death 

 of the elder Phny. Its quantity, perhaps, was three times as 

 great as that of all the ashes, collectively, which have beeii 

 observed to fall, during the time in which volcanic phsenomena 

 have been attentively considered. A stratum of from 15 to 18 

 inches in thickness, seems at first view unimportant, if compared 

 to the mass with which we find Pompeii to be covered ; but 

 without speaking of the torrents and inundations which certainly 

 may have increased this mass for centuries, without renewing 

 the violent dispute concerning the cause of the destruction of 

 the Campanian towns, which has been carried on with so much 

 scepticism on the other side of the Alps, it may be affirmed that 

 the eruptions of one and the same volcano at distant periods can 

 by no means be compared with respect to their intensity. All 

 conclusions founded on analogy are insufficient, when the ques- 

 tion is about quantitative proportions, — the quantity of ashes 

 and lava, the height of the column of smoke, or the violence pf 

 the detonation. 



From the geographical description of Strabo, and from aa 

 opinion of Vitruvius concerning the volcanic origin of pumice, 

 we see that until the year in which Vespasian died, that is to 

 say, until the eruption which overwhelmed Pompeii, Vesuvius 

 was more like an extinguished volcano than a solfatara. 



When after long rest the subterranean powers suddenly 

 open new passages, and again break through beds of pri- 

 mitive rocks and of trachyte, effects must necessarily take 

 place, for which all the phaenoraena subsequently observed do 

 not afford any standard of comparison. It may be clearly seen 

 from the well-known letter in which the younger Pliny announce 

 the death of his uncle to Tacitus, that the recommencement of 

 the eruptions, 1 might say, the awakening of the dormant vol- 

 cano, began with an eruption of ashes. The same circumstance 

 was observed at Xorullo, in Sept. 1759, when the new volcano, 

 breaking through beds of syenite and trachyte, suddenly arose 

 in the plain. The peasants fled, because they found m their 

 huts, ashes that had been ejected from the fissures of the earth, 

 which was burst in every place. Every partial eruption, in the 

 periodical general eruptions of volcanoes terminates with a shower 

 of ashes. 



There is a passage in Pliny's letter, which shows, that the dry 

 ashes which had fallen from the air had already attained a height 

 of from four to five feet* in the commencement of the eruption, 



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