_ Jounston-Lavis—The Hruption of Vesuvius in April, 1906. 151 
April 16th.—Relatively quiet; seismographs quiet. 
April 17th.—With slight seismic tremors, quiet continues; some dust being 
ejected, falling to the north-east and east. 
April 18th to 30th.—Gradually the output of the grey dust diminished. The 
crumbling in of the crater-edges and sides still went on apace, and more and more. 
blocked up the volcanic chimney, so that the puffs of vapour and dust became 
feebler, and the intervals increased between each one. This condition prevailed 
when I reached the crater-edge at the end of the month. 
For many days after the eruption any attempt at approaching the base of the 
cone was attended with great danger, as one sank in the hot dust and lapilli. A 
few unwary and unpractised persons who made the attempt were severely burned. 
It was not till a good rainpour had cooled and set the surface that walking was 
practicable during this memorable month of April. There are considerable 
discrepancies as to the sequence and interpretation of events between the different 
observers ; but the difficulties of observation are clearly so great that all excuses may 
be made for those who have attempted to record this great convulsion of Nature. 
One observer cannot be awake both night and day; he cannot be at many spots 
at once; dust and vapour often cut out his view; and, above all, those who know 
the people of this region are fully aware of the slovenly state of their observational 
powers and memory of events, and their uncontrollable tendency to exaggerate. 
GENERAL CONSIDERATIONS. 
Vesuvius had for a considerable time been in what I would call the ordinary or 
chronic Vesuvian state. I would define the Vesuvian state of a volcano as that 
slightly varying activity at the top of the main chimney, the ejection of incan- 
descent, pasty lava-cakes, building up a cone of eruption with a small, steady, 
almost continuous lateral outflow of fluid magma as small lava-streams. When, 
after a period of no lava issue, a lateral outburst occurs, a rapid outpour takes 
place, with the sudden fall of the lava-level im the volcano chimney, the activity 
passes from the essential lava-cake and cone-forming stage to that of the projection 
of fragmentary, accessory ejecta, and the crater-forming stage. As already stated, 
Professor Mercalli has referred to certain conditions of Vesuvius as Strombolian and 
Vulcanian. It is more especially concerning this last adjective that I would strongly 
protest. I know both volcanoes well, and I saw a good deal of the eruption of 
Vulcano in 1889. I have no hesitation in saying that there could hardly be a worse 
comparison of the phenomena of Vesuvius than with that of an acid volcano usually 
in a chronic-solfataric state, bursting forth with explosions from a highly viscous 
magma, and extending its eruptive period over months, and without any outflow 
