142 JoHnston-Lavis—The Eruption of Vesuvius in April, 1906. 
from Naples, was in part replaced by a third lower summit rising between 
the two. 
From February, 1894, to July 3rd, 1895, most of the volcanic energy was 
displayed in adding to the cone of eruption and repair of the mountain-summit. On 
the latter date and the following days a radial rift, or, more likely several parallel 
ones, split the great cone from summit to base in a W.N.W. direction. The 
azimuth seems to have been bent near the toe of the great cone, and then to have 
assumed a due east and west direction. The rift reached the surface at several 
spots, giving rise to fumaroles at higher levels and lava-flows at lower ones, about 
midway between the base of the great cone and the end of the remnant of a ridge 
of Monte Somma, known as the Crocelli. 
A permanent issue was established for the lava towards the surface-termination 
of the principal of these fissures; and from this for four years, almost without 
intermission, the same process went on as at Colle Margherita. At the end of this 
time an imposing lava cone had grown up nearly 150 m. in height, forming a 
marked feature on Vesuvius, and completely blocking out the view of the Atrio 
from the Observatory, and hiding a good portion of the cone. In September, 
1899, the last issue of lava took place, adding the final touches to a striking 
monument of mountain-building in the magnificent and imposing lava-cone now 
known as the Colle Umberto. 
For about the next four years volcanic activity was chiefly displayed at the 
top of Vesuvius, cone and small crater succeeding each other continuously, but all 
uniting to raise the summit to a higher level. In the middle of March, 1903, 
increased activity was visible, and the mountain was in a markedly agitated state. 
With some variations this continued till July, when some streams of lava flowed 
down on the south slope of the great cone, issuing from the side of the cone of 
eruption, and later a little on the north-east side. On August 26th a radial fissure 
made itself visible, splitting the eruptive and great cones ina W.N. W. direction, 
and giving issue to a lava-stream nearly a third of the way down the slope of the 
great cone, not far from that of the 1895 opening. This stream had a total 
length of about 700 m. only, and stretched very little beyond the toe of the great 
cone. On August 27th a fresh opening occurred on the EH. N. E. side of the cone, 
or rather at the foot, in the Val d’ Inferno. The lava continued to flow for some 
months, shut in by the slopes of the great cone, the precipices of Monte Somma, 
and the Colle Margherita. It had commenced to build up another lava-mound, 
which Prof. Mercalli estimates to have a maximum altitude of 70m., with its 
summit about midway between the base of the cone and the escarpment of Monte 
Somma,* and after flowing for over a year terminated on the 28th of September. 
This somewhat sudden arrest of the efflux of lava was followed by great activity 
* ¢ Notizie Vesuviana,” 1904, p. 16. Modena, 1906. 
