Jounston-Lavis—The Hruption of Vesuvius in April, 1906. 199 
Sulphur I saw in minute quantities, just sufficient for recognition. On the 
N.N.E. side of the cone, the apron of lava, whether it be formed during this 
eruption or anterior to it, exhibits a large number of fissures, extending from the 
crater-edge radially down to the level of the top of the Colle Margherita. 
These fissures gave forth considerable quantities of vapour, constituting quite 
a large fumarole-field. These fumaroles have remained active for many months 
after the eruption. In fact, a very large portion of the vapour of the volcano 
found its escape by these fissures when the main vent had become choked by the 
falling-in of materials of the eruption. These fissures point to a very weakened 
condition of the cone in this direction; in fact, in the line of lowest truncation 
during the great blast, and in the line in which the materials were directed. These 
fissures are bunged or choked by the large collection of debris at the base of the 
cone; but in the Atrio, in the same azimuth, a series of fumaroles have shown 
through the ejecta-mantle, right away to the Somma escarpment. For months 
after the eruption, these fumaroles afforded abundant deposits of sulphur, 
sulphides, chlorides, sulphates, and other rare sublimates, 
Sulphur occurred in most of the fumaroles, from the crater-edge to the cliff of 
Somma, and chlorides of iron, with potash and soda, were likewise to be met with 
in nearly all. Realgar, mostly in globular, fused crusts, mixed with seleno-sulphur, 
was chiefly deposited on the edges of those fissures on the side of the cone. Hematite, 
as usual, could be found in many of the more important fumaroles. Galena, a 
new sublimate at Vesuvius, was discovered associated with pyrite and chalcopyrite. 
The last-named minerals, also new as sublimates, were found soon after the 
eruption in these fissures at the crater-edge. Sig. Zambinelli mentions them as 
being found in the crater; but that is not so, as no human being could enter it in 
May, when this material was collected. Amongst the fumaroles on the cone-flank, 
near the crater-edge, were rare specimens of anglesite, pseudocotunnite, and 
later beautiful small crystals of cotunnite, the finest I ever saw from Vesuvius. 
Very fine tenorite has been produced at the hotter fumaroles on the slope of the 
cone. Apthitalite has also been recorded, but in very poor and limited quantities. 
An extremely interesting discovery is a new mineral analysed by Prof. A. 
Casoria.* It is a hydrated silicate of nickel and magnesia, and is, no doubt, a 
variety of garnierite, quite new to Vesuvius. 
It will thus be evident that Vesuvius has not only afforded a series of eruptive 
phenomena of great interest from a general point of view in the study of volcanoes, 
but has produced much material for the study of volcanic mineralogy. In fact, 
* ‘Sopra un nuovo minerale di Nichelio nei prodotti dell’ eruzione Vesuviana dell’ Aprile, 1906.” 
-—Ann, d. R. Scuola Sup. @ Agric. di Portici, vol. vii. 
TRANS. ROY. DUB. SOO., VOL. IX., PART VIII. 21 
