287 
THE MEDITERRANEAN NATURALIST 
pumice were being ejected in all directions to a 
height of-several meters. 
Many of these blocks on reaching the surface of 
the sea exploded throwing out jets of steam in all 
directions while others, exploded with a loud re- 
port and gave rise to a strong smell similar to 
that of pyric . powder. The temperature of these 
blocks was considerable, often being as much as 
415° C. The professor’s explanations for the for- 
mation of these bombs are of so much interest 
tha-t ve insert them here in full. “The melted 
lava says, the Professor whilst rolling down the 
sides of the submarine crater probably enclosed 
considerable quantities of the water in which it 
moved. Then as the melting point of the lava is 
higher than 1000° Pah,- the water thus imprisoned 
must remain in a spheroidal state i. e. liquid 
without passing into steam. But on the lava 
cooling, the temperature falls also in the inside and 
the enclosed water is then vaporized, and an enor- 
mous pressure of steam is exerted. As it is pro- 
bable that under these conditions that the lava 
may preserve much of its original plasticity, there- 
fore when the water is converted into steam, the 
lava probably expands. A vacuum is thus created 
and the bomb formed being rendered lighter than 
the volume of water which it displaces rises to the 
surface. During its jaseent however the hydros- 
tatic pressure of the sea-water diminishes, and at 
a certain point, especially at the surface, where 
the pressure suddenly diminishes the tension of 
the enclosed steam exceeds the outside pressure 
and an explosion results in the course of which 
steam and fragments of pumice are hurled to con- 
siderable distances in the air, and the peculiarly 
smelling gases are diffused through atmosphere. 
Alluding to the ■ -.uses which gave rise to the erupt- 
ion Professor liicco observes that on the day when 
the eruption broke forth (October 17th) the sun 
and the moon were nearly opposite to one another 
and in a line with the meridian of Pantelleria. 
Entomological Notes. 
Ceorocampo. : celerio L . — A specimen of this beau- 
tiful and uncommon hawkmoth, which hasnever 
as yet been noticed in Malta, was given me on the 
12th October last by Mr. J. Cooke F, G. S., who 
had taken it the proceeding day in his house at St. 
Julian’s. Another specimen was a few days after 
taken in Valletta by Mr. Briffa, and I was shown 
later on two more specimens also taken in Valletta. 
It is well known that its larvae feed on the vine. 
Sphinx convolvuli L. — This moth is never a 
rare species here, but I have been struck by the 
great numbers of it I have seen in September and 
October in all places where there were Pancratii 
in dower. 
Deilephila euphorhiae L. — The caterpillar of this 
moth, after the first rains, from September to De- 
cember, and often till spring time, may be seen in 
numbers on our common spurge — Euphorbia pitiea. 
I have constantly observed that the colour of our 
caterpillar is very much lighter than that which is 
given of it in all Entomological works. It changes 
into pupa generally before winter and it comes out 
late in the spring or in summer, but I have had 
pupae which came out only after fifteen or 
sixteen months. 
Co lias edusa and its var helice. Mr Cooke has 
remarked to me the abundance of this butterfly 
in Malta. I cannot help noticing this, but the 
edusa is always very common here in autumn; it is 
more so this year, because all butterflies are rather 
more frequent than usual. Bains fell early in 
September and we have had fair weather since, 
there is therefore a precocious growth of plants 
and the larvae had full time to develop. Vanessa 
cardui is not less abundant. A few weeks ago 
I was rumaging under stones outside Porta Beale 
when a street boy came to me and offered me a 
boxfull of chrysalides of this species, which I decli- 
ned to have; I can vouch there were thousands of 
pupae in that box together with the colias, I have 
in a much smaller proportion, with its var helice . 
A. C. G. 
SCIENCE GOSSIP, 
New Zealand has set apart two islands for the 
preservation of its remarkable w r ild birds and other 
animals, forbidding therein all hunting and trap- 
ping. 
Holland is considering the draining of the Zui- 
der Zee, a sheet of water covering 730 square miles. 
