30 Hobbs.—Notes on a Trip to the Lipari Islands. 
ical and chemical relations of these projectiles will be treated in another 
paper. 
The explanation of Dr. Johnston-Lavis for the formation of the 
projectiles is so satisfactory that I quote from him: 
Their structure is “ due to the obsidian reaching that intermediate 
stage between a liquid and a solid or in other words a state of intense 
viscosity, like slightly warmed sealing wax or hardened Canada balsam, 
which break when exposed to strong and violent mechanical stress but 
bend under a slight and gradually applied one. The magma in the upper 
part of this volcanic chimney seems to be in this critical state, and, as 
the vapor collects and escapes from the more heated and fluid portion 
beneath the upper part, is broken in fragments and ejected, when it is 
relieved from the surrounding pressure and allowed to expand. The 
crust has cooled along the cracks before this, and continues to do so, as 
it is whirled through the air, and after its fall, whilst the interior ex¬ 
pands at the same time, innumerable vesicles being formed from the 
water dissolved in the magma separating as steam. This expansion 
causes the cracking of the hardened crust and in some cases protrusion 
through the crust.” (Proc. Geol. Assoc. London, XI, p. 390, August, 
1890.) 
View of Volcano from Mte Saraceno, showing the “Barrancos 11 and the beginning of an 
eruption. The island in the distance is Lipari. 
We climbed Monte Saraceno and Mr. Hobson again photographed Vol¬ 
cano during the explosion. From this point the cone shows well the gul¬ 
lies (Barrancos) which in other regions figured so prominently in the “ ele¬ 
vation crater theory.” From this point we could see that the wind, which 
was fresh from the west, carried the projectiles of the eruptions to the 
east of the crater. Owing to this favorable circumstance we hoped to be 
able to safely ascend to the crater from the west side. Mr. Hobson and my¬ 
self therefore attempted the ascent and had toiled half way to the summit 
through lapillo and ash lying at the angle of repose, when a severe squall 
that had been threatening for some time, broke upon us. The sea 
about the island was lashed into foam. The strong wind picked up the 
