Arrangement of the Italian Volcanoes. 
23 
be noticed that the main fissure there indicated runs parallel to the 
backbone of the Italian Peninsula, which finds its extension in the 
mountain range skirting the north coast of Sicily. This principal line 
of vents begins with the extinct Mte. Amiata on the north, is extended 
in the crater lakes of the Roman Campagna — Lago di Bolsena, Lago di 
Vico, and Lago di Bracciano — in the Alban Hills to the south of Rome, 
Frosinone, the Rocca Monfina, and Vesuvius. Here the fissure line to 
continue its course parallel to the peninsular backbone would enter the 
sea. Following its approximate course we see that the Lipari islands 
form a continuation of it. The enlarged view giving the arrangement of 
individual vents on the islands indicates that this fissure forks in the 
island of Panaria, one branch passing westward through the extinct 
craters of Salina, Filicudi and Alicudi and probably continued in 
the shoal of Graham’s Island and in Pantellaria. The other branch 
passes southward through Mti. Campo Bianco, Sant’ Angelo and Guardia 
in Lipari, the vents of Vulcanello and Vulcano, and a submarine fumar- 
ole off Cape Calava on the north shore of Sicily, to Etna. Crossing the 
main fissure near Naples is a shorter one passing roughly east and west 
through the Ponza Islands, Ischia, Procida, the Campi Phlegraeii or 
Burning Fields near Naples, Vesuvius and Mte. Vultura on the eastern 
slope of the Apennines. This secondary fissure runs parallel to an out¬ 
lying arm of the Apennines indicated in the Sorrento Peninsula and 
Capri. Vesuvius, the present focus of volcanic activity on the Italian 
Peninsula, is situated at the intersection of these two fissure-lines. Ob¬ 
servations in other regions have shown that the largest cones have gen¬ 
erally been built up where the fissure is widened from this or some 
other cause. In the Lipari islands, strangely enough it would seem, the 
active foci are not on Panaria where the fissure forks but on Stromboli 
and Volcano some distances to the northward and southward. It has 
been argued that Panaria was once the seat of an outburst so violent as to 
destroy itself, the remnants of a great crater being made out in the islets 
of the vicinity. To recapitulate, the positions of the Italian volcanoes 
illustrate well two almost universal features of volcanic regions; first, a 
linear arrangement of the vents, indicating that they are formed on fis¬ 
sures in the crust of the earth, and second a substantial agreement be¬ 
tween the direction of this fissure and the trend of important folds in 
the strata (as shown in the prominent mountain ranges) which are 
structurally directions of weakness. 
In the spring of 1889 I visited Italy in company with an English 
friend, Mr. Bernard Hobson, now lecturer in geology in the Victoria 
University, Manchester. It was our intention to observe as much as 
possible of the volcanic areas, especially Vesuvius and Vulcano, both of 
which were then active. In Naples we were privileged to meet Dr. H. J. 
Johnston-Lavis, the energetic and careful student of volcanic phen¬ 
omena, the authority on Vesuvius as well as the best authority on 
