﻿198 Prof. Milne — Visit to an active Volcano. 



became gradually less and less, tintil 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 fell 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 appi'oximately 

 fell 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 

 increases, 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 conically-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 result of a sudden bursting of 

 steam through the molten lava, I did not see any aqueous vapour 

 which I could recognize 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 atmosiDhere which enveloped us. 



Notwithstanding a strong ice-cold breeze blowing in the direction 

 of the eruption, which was about 150 yards distant from us, the 

 effect of radiation was distinctly felt, 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 fell upon us, and a slightly sulphureous 

 smell could be detected. The journey down the mountain was 



