134 On the geological Theory supported by Mr. Smithson, 
With respect to the nature of Javas,—a most important point 
concerning all the volcanie phenomena, with which the author 
is totally unacquainted,—my brother has found in it all the cha~ 
racters of a combustible substance, which is burning before it 
comes out, and continuing to durn outside as long as it retains a 
sufficient heat. This combustion is shown by the sw/phurcous 
smoke that lavas emit all along their course, But that smoke is 
not the immediate product of the combustion ; it proceeds from 
the decomposition of some elastic fluids, which, as long as they 
find no vent, are the cause of the ascent of /7vas in the cones. 
This circumstance is known to the inhabitants around Yesu- 
vius; for, when they observe almost a cessation of the smoke 
issuing from its crater, they are in fearful expectation of the 
consequences, as it indicates that some dava, ascending in the 
channel, has cooled and hardened in it. The first consequence 
is earthquakes; and the next probable event, which is very dan- 
gerous, is the bursting of a dava from some other part of the 
cone. If that new lava fiows over cultivated grounds, it sets on 
fire trees, vines, and even houses. But the new /ava melting 
that which had stopped the channel, the smoke again issues 
from the crater, and these fatal effects cease. 
The showers of cinders sometimes emitted from the craters of 
volcanoes, being an astonishing character of their operations, in- 
terested my brother very much, and he resolved to try whether it 
would be possible to observe it in the very crater of Vesuvius. 
At a time, therefore, when it was observed from Naples that 
such showers were frequently emitted, consisting of large red-hot 
masses mixed with smaller, always preceded by a thundering 
noise, and thrown up very high, which in the night appeared 
a most tremendous fire-work ; my brother, taking notice of a 
favourable circumstance, that of a strong wind which repelled 
these ejections on one side of the crater, thought to avail him- 
self of that opportunity. He therefore set out immediately from 
Naples, and ascended the cone on the side against which blew 
the wind. 
Arrived at the top of the mount, he descended imto the crater, 
and eame as near the edge of the channel as he thought it pru- 
dent. At first he saw only some redness deep in the channel ; 
but after a little time he heard the thundering noise ; it began very 
deep ; then it was heard to ascend at the same time that the red 
matter rose ; and when its column ayrived at a certain height, in 
a part of the channel which was wider, the elastic fluid that had 
pressed it so far upwards, burst through it, and a shower was 
produced. This being a remarkable phenomenon, not to be ex- 
pected frequently with the favourable circumstance of a strong 
wind, my brother remained there a suificient time to see it re- 
peated with its various degrees, Desirous 
