Jounston-Lavis—The Eruption of Vesuvius in April, 1906. 185 
the cone, followed by a gradual rise of the lava in the chimney, the frothy surface 
which almost refilled a* with scoriaceous material. 
In dyke (s) that was in the north-west wall of the crater, and may have 
belonged to the Colle Umberto rift of 1895, we have four falls of level with 
intermissions; and, no doubt, if these hollow dykes could be approached in a 
suitable section, other interesting characters would become evident. 
I know of one hollow dyke in the Somma cliff that shows a new injection of 
fluid lava into and through the rubble-filling of an earlier hollow one. Other 
masses of compact rock are visible that have all the characters of small intrusive 
sills identical (fig. B, c) with similar ones in the Somma section. Most of the 
dykes cannot be traced in their complete extension; but others appear as fusiform 
Figure B.—Hottow anp orHpr Dykes SEEN IN SECTION IN CRATER-WALLS OF Vesuvius, Noy., 1906. 
masses in section. Most are vertical, but at (D) two are shown side by side, not 
far from the present edge of the crater with a marked hade. Their position with 
reference to the crater-edge is indicated by the irregular line above (p'). 
Passing now to other modifications in the shape of the cone, the point that 
strikes one is replacement of the relatively sharp angle at its foot, where it joined 
the Atrio or the Pedimentina by a gentle curve. This is quite apparent in the 
outline of the mountain in October, 19038, with the photograph taken by the same 
lens and camera, and from the same spot on the 4th May, 1906 (Pl. III.). We 
observe how the large amount of material that was ejected and slipped down the 
slopes as avalanches has collected around the foot of the great cone, filling up 
the angle. 
