198 
Prof Milne — Visit to an aclive Volcano. 
became gradually less and less, until they seemed to pause and float 
in mid-air, before turning to descend, which they did with an 
augmenting speed. The large masses only rose to a comparatively 
small height. Many of the pieces feil upon the sides of the exterior 
of the cone from which they had been shot, where they at once 
created a small cloud of steam, and rolled a short distance down its 
side to form a natural slope. As the material, which approximately 
feil vertically, increased in quantity, the angle of this slope would 
naturally increase up to a certain point, because, where the slope is 
short, any material that might fall upon its side has sufficient 
momentum to roll to the base ; but as the length of the slope 
inoreases, an element of friction is brought to play, which prevents 
such action taking place. The direction in which the material was 
shot up was generally vertical, but sometimes it had a little inclina- 
tion in a direction opposite to that in which we were Standing. 
Should the ejections from a volcano not be in an approximately 
vertical line, or during the time of its action winds should blow 
in one direction more than another, we might reasonably expect the 
resulting cone, which would be formed by the falling material, to 
have a less steep inclination upon the side where the greatest 
quantity of material had accumulated. Such actions may perhaps 
give some explanation to the slight differences in slope which are so 
often to be observed in recent oonicalty-shaped volcanic mountains. 
This is of course presuming that the form of the mountain has not 
been materially altered by subsequent denudation. Many of the 
larger pieces often appeared to separate when in mid-air. This I do 
not think was due to any explosion which took place within them, 
but rather perhaps to some such cause as a sudden cooling. 
Looking at some of these bombs, which had fallen on the level 
where I was standing, they appeared to have done so whilst still in 
a pasty condition, because some of them showed a decided flat- 
tening, as if produced by impact. Both the bombs and lapilli were of 
a black colour, and pumiceous texture. Although I believe each of 
these explosions to have been the res ult of a sudden bursting of 
steam through the molten lava, I did not see any aqueous vapour 
which I could reoognize as having been evolved whilst I was standing 
near the crater. This may have been perhaps due to the intense 
heat keeping the vapour in an invisible state until it became hidden 
in the fog and murky atmosphere which enveloped us. 
Notwithstanding a strong ice-cokl breeze blowing in the direction 
of the eruption, which was about 150 yards distant from us, the 
effect of radiation was distinctly feit, especially when the ejected 
column of ashes was large. 
Independently of variations, produced by unusually large ejec- 
tions, two thermometers in boxes were each raised 3° C. so long as 
we remained in this position. This warmth was all that made 
our position bearable, as otherwise it was bitterly cold, with a 
sleety rain pouring down, and we were all wet through. Once 
or twice a little fine ash feil upon us, and a slightly sulphureous 
smell could be detected. The journey down the mountain was 
