398 REPORT—1890. 
cone, and in this outflow the lava dribbles only a few yards; great 
bosses and buttresses are built up so as to constitute very important 
additions, both in bulk and strength, to the cone. During this month of 
October a little progress was made in raising and enlarging the eruptive 
crater ring into a low cone; but during the following month of Novem- 
ber the activity arose frequently to the 2nd degree, and consequently 
Fig. 1.—Sketch Plan of the Summit of the Great Cone of Vesuvius on April 11, 1890 
HI HAAN WY ee 2 
TET ee 
ro 
Limit of the 1872 crater where overflowed by lava, a, and where still visible, a’; 
6, remnant of cone of 1885-6 ; ¢, part of crater edge of May 1886; d, crater 
of May 1889 ; e, part of cone of eruption up to end of April 1889; f, cone of 
eruption from May 1889 to April 1890; 9, fissure of May 1889; h, yellow 
patches of decomposing lava, scoriw, and dust, marking situation of old hot- 
air passages and fumaroles ; %, fissure emitting HCl vapours; j, guides’ 
shelter; #, numerous fissures on S.E. edge of great cone; J, other fissures on 
N.E. edge of great cone. 
the growth went on more rapidly. This increased activity was rather an 
indication of the increasing obstruction to the lateral outflow, so that 
lava had risen in the chimney. The obstruction, and probably other 
circumstances, culminated on December 2, when the activity rose from 
the 3rd to the 4th deg. and lava stopped flowing ; but after a few hours 
the fluid rock again forced its way out, and activity dropped to the Ist 
degree. Towards the middle of the month the activity again rose to the 
2nd degree, and remained so, when visible, until the 23rd. On that 
day the smoke issued in a puffy and intermittent manner; in the evening 
there was cloud-cap, but the next day the activity rose to the 3rd degree, 
coincident with a marked diminution in the outflow, which during the 
next days entirely stopped. 
