e at any conclusion a long and patient
investigation, requiring means and assistance which the Observatory does
not possess, would be necessary.

Professor Fuchs, of Heidelberg, has devoted himself to this work for
years past, and if he continue it with well-selected and sufficiently
large specimens we may hope some day to obtain satisfactory results.

5. Every specimen of lava which I examined with a very
sensitive magnetoscope improved by myself, was invariably
magneto-polar, not excepting the pieces of the bombs, whether
rejected from the crater or carried along with the lava.

III.

FUMAROLES OF THE LAVAS.

Smoke generally issues from all lava when it cools down to a certain
degree, hence it is more abundant at the edges of the fiery torrent, or
is liberated from the scoriae that form on its surface. But when the lava
stops, the smoke issues only from certain vent-holes, through which we
can still see the fire, and at the edge of which different amorphous or
crystallized matters collect by sublimation. These centres of heat, of
more or less duration, are the fumaroles of the lavas. I believe I have
on other occasions shown that a fumarole is nothing but a communication
between the more or less cooled and hardened surface of the lava and the
interior, which is still incandescent. Some fumaroles last but a day,
others preserve their activity for weeks, months or years, according to
the depth of lava through which they penetrate; and when they cease to
be active, that is, when the sublimations are formed, or smoke or other
aeriform matters issue from them, they still retain a rather elevated
temperature. In the lavas of 1858, in a place where they had a
transverse width of 150 metres, a vent-hole may still be found where the
thermometer registers 60 deg. and the scoriae are warm. Sometimes, while
the lava is in process of cooling, new fumaroles appear, in which the fire
is visible. This phenomenon, which appeared marvellous and inexplicable
when I first observed it in 1855, is now very easily understood; the
cooled and hardened crust of the lava fractures with noise and suddenly,
and so a new communication is opened with the incandescent lava below,
thus creating a new fumarole.

As the smoke of the fluid lava is perfectly neutral, that is, neither
acid nor alkaline, so the fumaroles at the first period of their
existence with sublimations of sea-salt, mixed frequently with oxide of
c