ON THE VOLCANIC PHENOMENA OF VESUVIUS. 283 



Report of the Committee, consisting of Mr. H. Bauebman, Mr. F. 

 W. Rudleb, Mr. J. J. H. Teall, and Dr. H. J. Johnston-Lavis, 

 appointed for the investigation of the Volcanic Phenomena of 

 Vesuvius and its neighbourhood. {Drawn up by Dr. H. J. 

 Johnston-Lavis, F.G.S., Secretary.) 



Geological Map of Vesuvius and Monte Somma. — After many vicissi- 

 tudes, this map, which I completed last year, has been finally pat into 

 the hands of Messrs. Philip & Son ; the engraving in black is nearly 

 finished, and although not sufficiently advanced for exhibition at the 

 meeting, it will, no doubt, be completed in two or three months. At any 

 rate, I take this opportunity of heartily thanking the British Association 

 for the kind moral and financial support given to a solitary worker in a 

 foreign country, contending against many serious difficulties. In fact, 

 without such support this work would never have been brought to a 

 successful termination. 



State of Vesuvius. — During the month of June of 1888 the activity at 

 the crater was considerable, coincident with a marked diminution of the 

 oozing forth of lava from the side of the great cone, which lava eventually 

 stopped about the end of the month or beginning of July. Occasionally 

 the edges of the cone of eruption crumbled in, so that ash-ejections were 

 not infrequent. In July, however, the eruptive action was much less 

 and more uniform, nearly always varying from first to second degree, and 

 there was only a slight increment from August 6 to 10. In the month 

 of September, however, the commencement of a marked increase was 

 observable. About this time the eruptive mouth moved in a direction 

 S.W. of the original one, and commenced rapidly building up an eruptive 

 cone. Owing to the increased eruptive action due to the arrest of the 

 lateral outflow of lava from the groat cone, by the end of October this 

 eruptive cone was already 20 meters high from the base. The maximum 

 altitude, however, was on the S. side, as the N. wind had been persistent 

 and strong for many days before. This transfer of the vent along a S.W. 

 line was upon that fissure to which I had drawn attention as gradually 

 increasing for many months. The month of November was characterised 

 by considerable activity and marked increase in the height of the erup- 

 tive cone. 



During December eruptive action was much accentuated, in conse- 

 quence of which the cone of eruption had continued to rapidly increase, 

 filling about two-thirds of the 1886 crater, leaving a crescentic fossa 

 broadest at the N.E. On the 26th of the month a small opening appeared 

 on the E. side of the cone of eruption, but only allowed of a slight issue 

 of lava. Again on the 28th a little more oozed forth. 



On January 1, 1889, this opening enlarged downward, forming a deep 

 notch in the side of the eruptive cone, and allowed a considerable outflow of 

 lava, which filled the crescentic fossa just mentioned and extended to the 

 S.E. and N.W. along its horns, and there stopped. This outflow lowered 

 the central activity for a few days. (Figs. 1, 2, 3.) On January 6 I 

 happened to be in the crater preparing to photograph the cone of erup- 

 tion, when about one-third the way from its top a slight pufi" of dust 



