ON THE SOLFATAKA, ETC., OF NAPLES. 199 
communications may extend beyond that island towards the 
middle of the Mediterranean. 
With scarcely an exception, the whole country alluded to 
consists of trachytic lava and tufa. By far the greatest part 
has been erupted into the air before falling on the earth, — in 
other words, is tufa rather than lava. The lava currents 
are numerous and extensive ; but the heaps of tufaceous 
matter are immeasurably larger. The whole line of coast 
has certainly been subject to upheaval and depression. 
One of the most singular and interesting spots in the dis- 
trict, and one in which the phenomena of chemical action 
are most strikingly displayed, is that known as the “ Solfa- 
tara,” an extinct crater about six hundred yards across, 
surrounded by low hills, pierced in various places, and on 
both sides, by small crevices, through which still issue con- 
siderable quantities of hot vapour, containing a very small 
admixture of sulphurous gases. Similar emanations of gas 
take place from the ground in the interior of the crater, 
which exhibits cracks and fissures, not very wide, but all 
yielding fumaroles or smoke-holes, emitting hot air and 
vapour. The name solfatara is clearly derived from the 
sulphur emitted; but the proportion of this mineral is very 
small, though perceptible. Arsenic is emitted with the 
sulphur vapours. 
On ordinary occasions there is nothing to mark the site 
of the smaller fumaroles, which, indeed, are constantly chang- 
ing their position. Everywhere, in certain directions, holes 
may be seen in the earth, into which a stick may be thrust 
to some depth. If a thermometer be introduced into these 
holes, the temperature will be found to be very high, varying 
according to circumstances, from 40° 0. to 90° 0. I have 
even seen the instrument mark 96° 0. ; reaching, therefore, 
nearly to the boiling-point of water. Besides these nume- 
rous small orifices, there are a few larger and more per- 
manent, and it is to these that chief attention has been paid. 
Out of the principal one, in the basin of the Solfatara, there 
rises constantly, with a great rushing noise, a very large jet 
of steam. It proceeds from under a kind of roof a few feet 
below the ground. I endeavoured several times to approach 
closely to the point of emission, and even ventured down 
into the hollow, with the intention of taking the temperature 
of the steam jet, but was always driven back by the scalding 
heat and the acid fumes, which at once burnt and stifled 
me. Immediately adjacent, and to a distance of a couple of 
hundred yards towards the west, the ground was much 
cracked, and from every part of the cracks there proceeded 
similar emanations of scalding vapour, showing a heat of 
