414 F. A. Per ret — Vesuvius. 



boli in 1907 and that of Etna in 1908, together with the Mes- 

 sina earthquake, have claimed attention, and I have, in addition, 

 made several visits to the United States ; it is therefore with 

 far less than the desired thoroughness and only as time and 

 circumstance would permit that I have been able to make 

 those observations and studies which form the subject matter 

 of the present paper. 



For the sake of clearness I propose to treat of the character- 

 istics and phenomena of the volcano during this time under 

 the following heads : — 



1. Morphology. 4. The mud flows. 



2. The lavas. 5. The internal avalanches. 



3. The fumaroles. 



1. It would be interesting to be able to compare at a glance 

 the external form of Vesuvius as it was at the time of the 

 last repose-period — 1872-1875 — with its appearance at pres- 

 ent; the difference would represent the constructional capacity of 

 a single eruptive period and would be instructive in showing 

 how rapidly the old crater basin of Monte Somma is being 

 filled by the accumulations of lava and fragmentary ejecta. 

 The slow flows of 1881-3, of 1885-6, 1891-4, 1895-9 and 

 1903-4 ail formed lava-cupolas of considerable size which, 

 with the sub-terminal streams on the westerly flank in 1905-6, 

 form quite a regular distribution around the central cone. 

 The great cupola of 1895-9 is especially important from a 

 practical point of view, as showing the encroachment of the 

 new Vesuvius on that spur of the ancient mountain — the Colle 

 Canteroni — where stand the Royal Observatory and the Eremo 

 Hotel. A glance at fig. 4 will show how little remains of that 

 oasis in the desert of lava, and it would seem not improbable 

 that one or two more eruptive periods — say sixty years of 

 time— may sufiice to cover the site; unless, indeed, the very 

 presence of this great lava-mound wdth its roots shall prove 

 to have so sealed the approaches in this direction that future 

 flows here may be of rarer occurrence. 



The rapid lateral outflows on the southeast flank during the 

 last great eruption were not accumulative and did not mate- 

 rially alter the contour of the mountain although they were 

 probably responsible for the great external collapse of the 

 cone on that side ; but the enormous quantity of fragmentary 

 ejecta has altered the outline of the cone and greatly aided in 

 the filling up of the Atrio del Cavallo, half obliterating the 

 lava cupolas of 1891 and 1903 and rounding over the many 

 little bosses — the so-called " Montagnelle " — resulting from 

 these flows. 



