110 WATER IN VOLCANIC ERUPTIONS [iv

around Vesuvius — the total drying up of some and
the increased descent of the bucket in all," during
times of Volcanic disturbances, as an important fact.
M. Ch. St. Claire Deville ^ remarks : " It is well
known that there is only one tolerably certain indica-
tion of an approaching eruption of Vesuvius, and that
is the disappearance of the water in the wells of
Eesina and Torre del Greco."

According to Poulett-Scrope,^ the threatening in-
dications of an approaching crisis "are accom-
panied by the disturbance or total disappearance of
springs, and such accidents as the cracking, splitting,
and heaving of the substructure of the mountain
must naturally occasion."

Professor Guiscardi, of Naples, in answer to my
inquiry, wrote : ^ " As a rule the water of wells in the
neighbourhood of Vesuvius undergoes changes in quan-
tity, and even quite disappear before the commence-
ment of eruptions. Only as well as I know in the
eruption of 1861, the phenomena followed the
eruption. I add a list of such diminishing and
■drying wells."

" 1843. Decrease of water in the wells of Eesina ; it was

preceded by emission of lava.
" 1846. Some wells of Eesina dried, and emission of lava

followed.
" 1846. Six adventive cones in the crater; water decreases at

Eesina in wells.
" 1847. Decrease of water in the wells of Eesina ; great lava

flowings.
1 BuU. Soc. G'eol. de France, 2nd ser., vol. xiv. p. 254 (1856).
2 Yolocmos, 2nd edit., 1862, p. 21.
3 Letter to the author dated 1st September, 1881.
iv] WATEE IN VOLCANIC ERUPTIONS 111

" 1848. Water decreases in the wells of Resina and Torre del
Greco. Earthquakes in the neighbourhood of Vesuvius.
Lava flowing.
