208 



J. W. Judd — On Volcanos. 



crater of Stromboli, I was prevented from seeing the interesting 

 operations taking place at its bottom by the thick clouds of vapour, 

 which were poured forth by innumerable fumaroles both within and 

 around it. Seated near it, however, and occasionally getting glimpses 

 of its interior when the wind drifted aside the heavy cloud of vapour, 

 I was able to note the following phenomena. 



A succession of loud snorting puffs like those of a high-pressure 

 steam-engine, but quite destitute of their regularly rhythmical 



Fig. 12. — View of the active crater of Stromboli from the north side of the Sciarra, 

 during an explosion. 



character, were very distinctly audible. These were emitted con- 

 tinuously, but with most striking variations in their intensity, 

 duration, and rate of succession. A long succession of slight 

 short puffs would be followed by one or more longer and much 

 louder ones. I attempted in my note -book to record the succession 

 of these by means of lines, the length of which should represent the 

 duration of the puff, and its thickness the intensity. I give the 

 following as examples of these : — 



and 



Sometimes the snorting sound would die away almost entirely, but 

 at others it would burst out again suddenly with a loud series of 

 sudden puffs. 



From time to time violent outbursts of steam would take place at 

 the bottom of the crater, carrying aloft fragments of lava, scoriae, and 

 ashes. So far as I was able to judge, these outbursts were not pre- 

 ceded by warnings of any kind, but occurred with the greatest 

 suddenness. These outbursts certainly seemed to me to be quite 

 independent of the puffing sounds, and, I can scarcely doubt, took 

 place from a different mouth. The sound which accompanied the 

 explosions was always sudden, but by no means violent. It did not 



