The reporter has much gratification in presenting to the Association the great geological map of Monte Somma and Vesuvius, which has been now published some months, and in the construction of which much substantial help, and above all moral encouragement, has been given by the British Association. The reporter hopes that his colleagues in the science of geology will be satisfied that he has done his utmost to win their confidence. During the latter part of 1890 and the early part of 1891, the central activity of Vesuvius has very slightly varied, except about the new year, when it was considerably increased, rising to the third or fourth degree, simultaneously with the stoppage of the lateral outflow of lava that had been going on since August 7, 1890. Since then, up to the present outburst, the central activity has been generally at the first degree, and the cone of eruption has slowly grown in height (see Plate). On June 1 there was a crater within the central cone of eruption, of about 50 m. in diameter, near the centre of which was the eruptive vent, surrounded by another embryonic eruptive cone. On that day, four small eruptive mouths opened around the embryonic cone in the bottom of the central crater, the smallest being to the east. Thus the volcano remained till June 7, at 10 a.m., when activity stopped, only a small quantity of vapour escaping from central vents. At midday a radial cleft opened at the north toe of the cone of eruption (May 1889, June 1891), traversing towards its east end the little sickleshaped ridge, the remnant of the 1885-86 crater, but, as yet, gave out little vapour. At 4 to 4.30 p.m., shocks of earthquake commenced, limited only to the upper slopes of Vesuvius, and simultaneous with the extension of the radial fissure down the side of the great Vesuvian cone for nearly half its way opposite the Punta del Nasone of Monte Somma, from which, at about 5.30 p.m., issued a little lava, whilst from the upper extremity of the fissure at the toe of the cone of eruption much vapour escaped, so that as seen from Naples the smoke-plume arose from this point. From 5.30 to 7 p.m. the fissure still extended lower, accompanied from time to time by local earthquakes, noises, and the elevation of columns of black dusty smoke. At a few minutes to 7 the floor of the Atrio del Cavallo was reached, and a remarkably black column of smoke had arisen. My friend Dr. L. Sambon saw this column arise, and came to inform me immediately, as I had left off watching the mountain at 5.30. After photographing the mountain, we left Naples at 9 p.m., and spent some time in inquiries at Resina and near the Observatory. Everything was now dark, as the volcano had calmed down at 8 p.m. At 2 a.m., June 8, we were at the eastern extremity of the Observatory ridge, and commenced to wend our way across the lava surface towards Monte Somma. We were at the lowest part of the depression at the west end of the Atrio del Cavallo, where it joins the Fossa della Vetrana, and along which some of the largest lava-streams have flowed (1855, 1872, &c.), when suddenly on our right above us (2.23 a.m.) a vast quantity of bright red vapour arose from the new outpour of lava. We hastened our steps as much as the road and our lantern would allow us, so as to reach the escarpment of Monte Somma, the foot of which was followed till near the Punta del Nasone, and close to the theatre of eruption. Here we clambered up some distance above the level of the Atrio to watch events whilst we ate our late supper or early breakfast. Along the slope of the great cone in the line of fissure were a few luminous points from some pieces of still uncooled lava of the little that had oozed forth from the lower half of the fissure. At about 60 or 80 yards from the foot of the great cone two or three fountains of lava were throwing up jets of molten rock for 2 or 3 m., and the lava was slowly spreading out on the almost horizontal plain of the Atrio in several tongues. The lava must have still been high in the main chimney, as the issued at the top of the fissure showed a slightly red illumination. So vapour that FIG. 1.-Great cone of Vesuvius, as seen from a little W. of the Punta del Nasone of Monte Somma, showing the eruptive rift of June 7, 1891. (Photographed by the author.) C, crater plain and cone of eruption; B, rift, marked balf-way down by an irregular we remained till daylight, when we could see the fissure on the side of the cone. The mouth that formed at 5.30 the previous day was still smoking a little, whilst the fissure below it sent off several ramifications at an acute angle like the branches of an inverted tree, from several of which little streams of lava had been given out, where they had soon consolidated (see fig. 1). We now followed the base of the great cone to the lower railway station, where we found all the people up and dressed, frightened by strong shocks and noises at 2.23 a.m., coincident with the fresh outflow of lava that we had witnessed, but which shocks we had not felt, although they were described as the most severe that had been felt. Having ascended to the summit of Vesuvius, we found the central crater rapidly enlarging by the falling in of its edges. From the new fissure at its summit was issuing much vapour under pressure, and rich in sulphurous acid, which is, even in traces, intolerable; and the hot air coming from innumerable new fissures rendered approach very difficult. We did, in fact, once jump across part of the fissure, but returned much quicker on account of the hot irritant vapours. An approach from the opposite side was equally unsuccessful. At some old fumaroles on the 1872 crater plain I collected some crusts of boric acid and alum, both rare products at this volcano. I then wrote that one of three terminations we may expect to these phenomena, which are very characteristic of a lateral disruption, so common at Vesuvius: 1. Should the lava cool sufficiently to plug the radial dyke, no further phenomena will occur, and activity will be restored to the central vent. 2. If this plugging only partially takes place, lava may dribble forth for months, but probably the escape of vapour will soon be restored to the central vent. 3. If the rent should widen, considering how low it extends, we may expect a grand eruption which might rival that of 1872, which commenced near the same spot and much in the same way; the mechanism by which this occurs I have explained elsewhere. 2 The suggestion that I published in several newspapers has been fully confirmed namely, that the second alternative type of eruptive character would be pursued by the volcano. Now, for a period of nearly two months lava has continued to dribble forth, activity has returned to the central vent, and no great changes have occurred. The throat of the volcano commenced to be cleared on June 9, the vapour forcing its way up from the crater bottom through the choke of loose materials, and rose above as a column carrying with it much dust; at the same time the powerful vapour blast issuing from the upper extremity of the lateral rift soon stopped. Each day I was kept informed of the state of the volcano by the kindness of Messrs. Ferber and Treiber, the director and engineer respectively of the Vesuvian Railway. On June 15 I considered it right to again visit the mountain, and had the good fortune to be accompanied by Messrs. H. Elliot, A. Green, Linden, Newstead, and Treiber, several of whom are excellent photographers, so that with two of my own cameras we were able to make an extensive pictorial record of some very unique formations. At the point of issue of the lava, at the junction of the foot of the great Vesuvian cone and the Atrio del Cavallo, the first lava had cooled sufficiently to walk over it, but beneath our feet could still be seen in a few holes the flowing lava. At the foot of the great cone, and extending for half-way across the Atrio, along the radius of the eruptive rent, as if this had continued so far, were a series of driblet cone fumaroles. We counted seven complete and well-formed examples, besides numerous 1 Nature, vol. xliv. June 18, 1891, pp. 160-161; Corriere di Napoli, June 10: L'Italie, June 11: The Mediterranean Naturalist for July. 2 H. J J. L., The Relationship of the Structure of Igneous Rocks to the Conditions of their Formation,' Scientific Proceedings Roy. Dublin Soc., vol. v., N.S., pp. 112-56. FIG. 2.-Fumaroles formed on the new lava at some distance from the base of the great cone in the Atrio, as seen on June 15, 1891. (Photographed by the author.) abortive ones. Most were giving out intensely heated vapour, which was liberated from the lava flowing beneath, and which soon carbonised a piece of wood placed in it. Around the lips of the upper opening, hæmatite with fused chlorides of potash, soda, iron, copper, &c., were being condensed from the vapour, and trickling down the outer surface of the fumarole, consolidated as curious vari-coloured stalactites of very deliquescent nature. |