| Sp. Gr. before fusion. | Sp. Gr. after fusion. | |
| Pyroxene of Etna | 3·453 | 2·148 |
| Felspar ,, ,, | 2·925 | 1·361 |
| Olivine ,, ,, | 3·410 | 2·290 |
| Lava of 1865 | 2·771 | 1·972 |
| Ancient basaltic lava from the Scogli de'Ciclopi | 2·854 | 2·000 |
| Ancient basaltic lava from Aci Reale | 2·795 | 1·947 |
It will be seen from the following analyses that the sand, ashes, scoriæ, and compact lava have virtually the same composition—indeed they consist of the same substance in different states of aggregation.
| Ashes. | Sand. | Scoriæ. | Compact lava. | |
| Silica Alumina Protoxide of iron Protoxide of Manganese Lime Magnesia Potash Soda Water | 50·00 19·08 12·16 ·40 9·98 4·12 ·60 3·72 ·36 | 49·80 18·20 12·42 ·45 11·00 4·00 ·49 3·60 ·29 | 50·00 19·00 11·70 ·50 10·28 4·20 ·69 3·40 ·33 | 49·95 18·75 11·21 ·49 11·10 4·05 ·70 3·71 ·23 |
| Phosphoric acid Titanic acid Vanadic acid Sesquioxide of iron | traces | traces | traces | traces |
| 100·42 | 100·25 | 100·10 | 100·19 |
With these we may compare the composition of the lava which issued from Monti Rossi in 1669, and was analysed by Lowe, and of an ancient lava of Etna ejected during an unknown eruption, and analysed by Hesser.
| Ancient lava. | Lava of 1669. | |
| Silica Alumina Protoxide of Iron Protoxide of Manganese Lime Magnesia Soda Potash | 49·63 22·47 10·80 ·63 9·05 2·68 3·07 ·98 99·31 | 48·83 16·15 16·32 ·54 9·31 4·58 3·45 ·77 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 Hydrosulphuric acid Oxygen Nitrogen | 50·5 11·9 7·1 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."