THE MEDITLHIEYNEAA N ATI KALIST 
DO 
lent photographers so that with two of my own 
machines we were able to make an extensive pic- 
torial record of some very unique formations. 
We ascended to the point of issue of the lava at 
the junction of the foot of great Vesuvian cone 
and the Altrio del Cavallo. Here the first lava 
had cooled sufficiently to allow us to walk over it, 
but beneath our feet could still be seen, in a few 
holes, the flowing lava. At the foot of the great 
cone and extending for half was across the Altrio 
along the radius of the eruptive rent as if this 
The lava had first flowed towards the escarpment 
of Mount Somma in a fan like manner so that the 
j eastern extremity reached that great natural 
sect ion just beneath the Punta del Nasone. Still 
following the natural inclination of the ground it 
turned to the TV. and on June the 15th. was op 
posite dyke 16 advancing at a very slow rate. 
The lava is a vitreous and coarse grained rock 
especially in the included leucite crystals, whilst 
the surface is of the coarded or “pahochol” type. 
This is due to the magma being one that has been 
had continued so far were a series of driblet cone 
fumaroles. We counted 7 complete and well formed 
examples, besides numerous abortive ones, (see 
Fig.) Most. were giving out jets of intensely heated 
vapour which was liberated from the lava flow- 
ing beneath and which soon carbonized a piece 
of wood placed in it. Around the lips of the 
upper opening, haematite with fused chlorides 
of potash, soda, iron, copper, etc., were being 
condensed and trickling down the outersurface 
of the fumarole consolidated into curious vari- 
egated stalactites of very deliquescent nature. 
simmering since January in the chimney of the vol- 
cano, so that most of its dissolved H 2 0 had been 
boiled off and so allowing it to cool wflthout the 
formation of scoria from the vapour that otherwise 
would escape after its exit. Leucite I have also 
demonstrated to be formed while the magma is 
simmering under low pressure with free escape 
for vapour in upper part of the volcanic chimney. 
See:— H. J. J. L.— The Geology of Monte Somma and 
Vesuvius, being a study in Vulcanology.— Q. J. G. S. Lond. 
Vol. XL. and Relationship of the structure of Igneous 
Rocks to the Conditions of their formation,- Sci, Proceed, 
It. Dublin Soc., Vol, Y, 
