318 REroRT— 1891. 



volcanic chimney of the impeding materials, which were constantly beinof 

 added to by the slips from the crater's edge ; but ou that eveninfr a dull 

 I'ed glow was visible in the crater bottom, showing that a fairly clear 

 passage had been temporarily made for the continuous escape of vapour, 

 and also that the lava was at no very great depth from the summit of the 

 volcano. This of course indicates that the lateral opening was insufBcient 

 to drain off much of the lava which occupies the chimney above the level 

 of the lateral outlet. Had such evacuation really taken place the eruption 

 would have assumed enormous proportions, from the actual amount of 

 lava above the tap, but more from frothing up of lava below that level, in 

 consequence of the relief of pressure which in that case would occur. Of 

 course, during all these days the ejection of dust with the smoke occurred, 

 giving the latter its peculiar dark grey colour. Further destruction of 

 the crater edge took place, so as to partly block the outlet, and it was not 

 till our next visit that it again cleared. 



On June 30 I again visited the crater, accompanied by my friend 

 Mr. A. Green. All the summit of the great cone was covered by a thick 

 coating of dust and sand, upon the surface of which were the usual white 

 and yellowish-green chloride crusts seen on such occasions, so rich in 

 copper as to plate with that metal the iron nails of our boots. The crater 

 had considerably enlarged, the edges were in an extremely unstable state, 

 with often considerable strips marked off by cracks parallel to the free 

 edge, so that with a slight push by a stick it was possible to detach large 

 masses of the materials which form the sides of the crater in the recent 

 cone of eruption. So dangerous were the edges that it was but two 

 places that my experience indicated as being safe to approach and look 

 over, and that even with several precautions; so that the fatal accident 

 to Senor Silva Jardim, who lost his life here but a few hours after our 

 departure, is not to be wondered at. 



On looking down some 45 to 50 m. beneath us, we could see the glow 

 from a month some 2 or 3 m. in diameter. The walls of the crater were 

 concave, so that, although overhanging at the top, yet a plumb-line let 

 fall from the edge would strike the bottom of the cliff. The crater 

 bottom was roughly plain, due to the combination of a talus all round, 

 and an attempt at a cone encircling the main vent. It will be thus seen 

 that the crater cavity was of the form of a convex-sided cylinder, or more 

 simply barrel-shaped, with its upper diameter some 50 to 55 m. 



With much difhculty we made our way around to the north side of 

 the cone of eruption, which did not show its usual loose scoriaa surface, 

 as it was buried beneath a thick coat of sand and dust, covered with a 

 thin saline crust on its surface. The upper limit of the radial rift, which 

 we were prevented from examining three weeks previously, on account 

 of its giving out so much vapour as to constitute the temporary escape 

 aperture of the volcano, had now become quiescent, so that we could 

 fully examine it. Only a current of hot air was now issuing from it, but 

 1 was able to collect some fine masses of crystallised molysite and 

 kremersite from its edges. Its average breadth was about 0'50 m. where 

 it traversed old compact lava, but of course it disappeared as soon as it 

 reached the looser materials. The real azimuth of its orientation, which 

 we could now determine with greater accuracy than when we were 

 walking over hot rock and enveloped in hot irritating vapours, proves to 

 be, as it radiates away from the axis of Vesuvius, about 15° west of 

 north. It curves then a little to the north, and near the foot of the 



