22.47 16.15
Protoxide of Iron 10.80 16.32
Protoxide of Manganese .63 .54
Lime 9.05 9.31
Magnesia 2.68 4.58
Soda 3.07 3.45
Potash .98 .77
----- -----
99.31 99.95

The sublimations from the fumaroles are chiefly chloride of ammonium,
perchloride of iron, and sulphur. An analysis of the gases of the
fumaroles of 1865 gave the following results:--

Carbonic acid 50.5
Hydrosulphuric acid 11.9
Oxygen 7.1
Nitrogen 30.5
-----
100.0

An account of microscopic analysis of some of the lavas of Etna, for
which I am indebted to Mr. Frank Rutley, will be found appended to this
chapter. He considers that they are Plagioclase-basalts, and
occasionally Olivine-basalts; and that they consist of Plagioclase,
Augite, Olivine, Magnetite, Titaniferous iron, and a residuum of glass.

Near the summit of the great crater I found a mass of perfectly white,
vesicular, and very friable substance, somewhat pumiceous in appearance.
It proved to be a decomposed lava, and was found elsewhere on the sides
of the crater. Mr. Rutley examined a section of it, and reports: "Under
the microscope a tolerably thin section shows the outlines of felspar
crystals, lying in a hazy milk-white semi-opaque granular matrix. The
felspar crystals are lighter and more translucent than the matrix, but
are of much the same character, having a granulated or flocculent
appearance, somewhat like that of the decomposed felspars in diabase.
There are numerous roundish cavities in the section which may once have
contained olivine, or some other mineral, or they may be merely
vesicles."

A qualitative analysis of this substance, made by Mr. H. M. Elder, has
proved that it contains a large quantity of Silica (about 70 per cent.),
and smaller proportions of Alumina, Iron, Magnesium, Calcium, and
Potash; together with very small amounts of Sulphuric Acid and a trace
of Ammonia. Lithium is absent, and Sodium is only present in very minute
quantity. Water is present to the extent of nearly 20