ON THE VOLCANIC PHENOMENA OF VESUVItJS, 313 



The reporter has much gratification in presentinor to the Association 

 the great geological map of Monte Somma and Vesuvius, which has 

 been now pubHshed 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 

 v/in 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 sickle- 

 shaped 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 sinanltaneous 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, 

 fiom which, at about 5.30 p.m., issued a little lava, whilst from the npper 

 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, accom- 

 panied 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 nolumn 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 Obsei'vatory. 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 com- 

 menced to wend our way across the lava sui'face 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 quantitj^ 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 



