evident by its odour. Though commingled with sulphurous-acid gas, it
still had the characteristic smell of steam. For a half hour it was
possible to watch the successive explosions, and even to make rough
sketches of the scene. Occasionally the explosions would come in quick
succession, so that the lava was blown out of the tube; again, the
pool would merely sway up and down in a manner which could be
explained only by supposing that great bubbles of vapour were working
their way upward toward the point where they could burst. Each of
these bubbles probably filled a large part of the diameter of the
pipe. In general, the phenomena recalled the escape of the jet from a
geyser, or, to take a familiar instance, that of steam from the pipe
of a high-pressure engine. When the heat is great, steam may often be
seen at the mouth of the pipe with the same transparent appearance
which was observed in the throat of the crater. In the cold air of the
mountain the vapour was rapidly condensed, giving a rainbow hue in the
clouds when they were viewed at the right angle. The observations were
interrupted by the fact that the wind so far died away that large
balls of the ejected lava began to fall on the windward side of the
cone. These fragments, though cooled and blackened on their outside by
their considerable journey up and down through the air, were still so
soft that they splashed when they struck the surface of cinders.

Watching the cone from a distance, one could note that from time to
time the explosions, increasing in frequency, finally attained a point
where the action appeared to be continuous. The transition was
comparable to that which we may observe in a locomotive which, when it
first gets under way, gives forth occasional jets of steam, but,
slowly gaining speed, finally pours forth what to eye and ear alike
seem to be a continuous outrush. All the evidence that we have
concerning volcanic outbreaks corroborates that just cited, and is to