352 



NATURE 



[Feb. 12, 1S80 



blowing from the north-west, and we should be more 01 

 less inlhe teeth of it. Accordingly we bore to the south- 

 west so as to get the mountain between us and the 

 ■wind'. Even thus the ascent was very trying ; violent 

 gusts of wind sometimes caught us, and volcanic san 1 

 and small stones were blown across our path. On 

 arriving at the summit I saw that the small cone, which, 

 when I had seen it a year before, was no larger than an 

 iron furnace, had in the course of the year increased 

 both in bulk and height. It now reaches to a height of 

 more than fifty feet above the rim of the great crater, and 

 very large masses of cinders have accumulated around 

 it. Moreover, it has almost filled up the great crater of 

 1872 by masses of lava and scoriae. When the crater 

 gets quite filled up, and the throat of the small cone 

 choked with lava, we may look for a grand paroxysmal 

 outburst like that of 1631 or 1872. 



The cone of November, 1878, was giving off dense 

 volumes of white steam and reddish smoke. Its dynamic 



activity was considerably greater than it had been the 

 year before, and large ma-ses of scoriae were ejected t<> 

 a considerable height at frequent intervals. The lava, 

 surged up within the throat of the cone very frequently, 

 from the sudden disengagement of vapours within the 

 seething mass. Near the base of this cone a small hole, 

 apparently about five feet in diameter, had opened to 

 give vent to lava, the great pressure of which had pre- 

 vented it from rising high in the cone, and had caused 

 the latter to give way at the point of least resistance. 

 Two streams had recently flowed from this ; a small one 

 towards the south-west had not reached the rim of the 

 crater ; it was red-hot, not more than two inches beneath 

 the surface, but we ran over it with no worse result 

 than scorching our boots. The other stream — the main 

 stream of December 17, 1879 — {vide the accompanying 

 woodcut) had flowed towards the north-west, and had 

 found its way into the Atrio del Cavallo. 



As wc watched the lateral bocca, the lava within it 



became furiously agitated ; it was thrown up three or 

 four feet above the opening, exactly in every respect re- 

 sembling small geysers which I have seen at Reykir, and at 

 Haukadalr in Iceland j and presently the liquid mass 

 filled completely the bocca, and flowed over as a very 

 fluid stream along the course of the lava of December 17. 

 By the time we reached the Observatory again, the 

 stream, which was about twenty-five feet wide, was seen 

 to have flowed over the rim of the crater ; by ten o'clock 

 the same evening it had flowed half way down the great 

 cone, and by 1 a.m. the next morning it had reached the 

 Atrio del Cavallo, presenting an appearance almost pre- 

 cisely similar to that of the stream of December 17. 

 Dense clouds of vapours marked the course of the stream ; 

 a good deal of hydrochloric acid was disengaged ; and 

 the icy tramontana in blowing over the liquid mass was 

 converted into an unbearably hot furnace-breath. The 

 next day (January 14) the energy of the mountain ap- 

 peared to have slackened; and on the morning of the 



15 th a good deal of snow fell, and the course of the lava 

 stream was well shown by a jet black line through the 

 snow. 



The lava is very leucitic, and is somewhat similar to 

 that of 1871. The fumeroles have afforded copious 

 sublimations of chlorides and sulphates, in which the 

 spectroscope has revealed the presence of lithium and 

 thallium. The gases evoked nearest to the centre of 

 activity are sulphurous acid and hydrochloric acid. Car- 

 bonic acid still appears in some of the remoter sources 

 of emanations. 



Prof. Palmieri, in the MS. to which I have alluded 

 above, writes as follows :— " This long and mild eruptive 

 period, in which Vesuvius has become a mere imitator of 

 Stromboli, will not in our opinion come to an end without 

 displaying more decided activity. The whole history ot 

 Vesuvius, though its greater eruptions only have been 

 chronicled by ancient writers, may be divided into periods 

 of activity, with occasional phases of violence, and short 



