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POPULAR SCIENCE REVIEW. 
from 80° 0. to 90° C., at the depth of little more than six 
inches "below the surface. 
In several caverns on the hill-side enclosing the crater 
to the north, there are similar issues of gas and hot steam, 
rendering the temperature inside the caverns almost unbear- 
able; but these are not in a line with the bocca principale , 
or chief vent, which is marked by fissures and heated ground. 
The caverns have been used sometimes by the country people 
with great success for curative purposes ; and they are, in 
fact, admirable natural vapour baths. They are called 
stufe. The quantity of steam issuing is very considerable, 
and the chief effect must arise from the violent perspira- 
tion into which the patient is thrown, and the absorption 
of the sulphurous and other gases into the system whilst 
the pores are open. 
Caverns of this kind, some natural and others artificial, 
are accessible in various places. Thus, on the Lake of 
Agnano, where the celebrated Grotto del Cane is situated, 
there is a kind of establishment for this purpose, on the 
very rudest scale about a mile and a half due east of 
the Solfatara. The ruins of old Roman baths are still to 
be traced on the hill-side adjacent. The Grotto del Cane is 
a few hundred yards beyond the stufe , to the east ; and 
between the two is another small cavern, now closed, 
where, it is said, ammoniacal vapours issue. This, how- 
ever, is doubtful. About three and a half miles to the 
west of the Solfatara, or in the opposite direction, are 
the Baths of Hero, which are stufe of the same kind. 
Considerable eruptions of gas take place, both in the 
waters of the Lake of Agnano and in the sea on the 
shores of the bay, between Pozzuoli and Baia. 
Besides the stufe in the caverns on the north side of 
the Solfatara, which, as I have said, are quite distinct from 
the fissure of the bocca grande , or great eruption of steam, 
I found, on crossing the hill and coming into the valley between 
the hills of the crater of the Solfatara and the remains of those 
that once inclosed the crater of the Lake of Agnano, satisfac- 
tory proof that the phenomena extended in this direction un- 
interruptedly. There is even a small hut used as a vapour- 
bath, or stufa, and though I could not obtain access to the 
interior, I found the vapour issuing at a high temperature from 
a kind of chimney constructed for that purpose. The place is 
not occupied except during the season. I found other indica- 
tions of the same phenomena in the broken outline and colour 
of the ground, although there was no perceptible increase oi 
heat on the surface of the rock. After some search, however, 
I noticed a very small opening surrounded with ants, not more 
