mass, which we found near the summit, proved to be the
result of the decomposition of lava by hot acid vapours. In the
different lavas, the crystals of labradorite, and of olivine, vary in
size considerably. Magnetic oxide of iron is very visible in thin
slices of the lavas when placed under the microscope; and iron appears
to be a constant constituent in nearly all the products of the mountain.

Within the last few months Prof. Silvestri has detected a mineral oil in
the cavities of a prehistoric doleritic lava found near Paterno.[21] The
lava is in close contiguity to the clay deposits of a mud volcano, and
when examined under the microscope is seen to consist mainly of augite,
together with olivine and transparent crystals of labradorite. It
contains numerous cavities coated with arragonite, and filled with a
mineral oil which constitutes about one per cent of the whole weight of
the lava. It was taken from the lava at a temperature of 24 deg. C., (75.2 deg.
F.), and solidified at 17 deg. C. (62.6 deg. F.) to a yellowish green mass,
which on analysis gave the following percentage composition:--

Liquid hydrocarbons boiling at 79 deg. C. = 17.97
Hydrocarbons solidifying below 0 deg. C., boiling }
between 280 deg. and 400 deg. C. } = 31.95
Paraffine melting between 52 deg. and 57 deg. C. = 42.79
Asphalt containing 12 per cent of ash = 2.90
Sulphur = 4.32
------
99.93

[21] "Atti Accademia Gioenia," serie iii., vol. xii.

Prof. Silvestri has recently made some interesting determinations of the
specific gravity and chemical composition of the different products of
Etna. They are given in full in his work entitled, "_I Fenomeni
Vulcanici presentati dall'Etna, nel 1863, 1864, 1865, 1866_," which was
published in Catania in 1867. The following table gives the specific
gravity of various ancient and modern forms of lava, ashes, etc. of
Etna:--

_Sp. Gr._

Ashes ejected in 1865 2.644
Sand " " " 2.715
Scoriae " " " 2.633
Compact lava " " 2.771
Scoriae ejected in 1669 2.622
Compact lava "