The titaniferous iron of Etna is found disseminated through the mass of the lavas, and is plainly distinguished when a thin section is examined under the microscope. It is sometimes met with in masses. A specimen from Etna, analysed by Von Waltershausen, was found to contain:-- Titanic Acid 11·14 Sesquioxide of Iron 58·86 Protoxide of Iron 30·00 ------ 100·00 The basalts of the Isole de'Ciclopi enclose beautiful transparent crystals of Analcime, the _zeolite dure_ of Dolomieu. The word is derived from ~analkis~ weak, in allusion to the weak electric power which the mineral acquires when heated or rubbed. Dana prefers the term _analcite_. Specimens from the Cyclops Islands have been analysed by Von Waltershausen and Rammelsberg, with the following results:-- I. II. III. Silica 53·72 55·22 54·34 Alumina 24·03 23·14 23·61 Lime 1·23 ·25 ·21 Soda (Na{2}O) 7·92 12·19 12·95 Potash (K{2}O) 4·46 1·52 ·66 Water 8·50 7·68 8·11 Magnesia ·05 -- -- Sesquioxide of Iron -- -- ·12 ----- ------ ------ 99·91 100·00 100·00 The minerals of Etna are not nearly as numerous as those of Vesuvius. It has been remarked that no area of equal size on the face of the globe furnishes so many different species of minerals as Vesuvius and its immediate neighbourhood. Out of the 380 species of simple minerals enumerated by Hauy, no less than 82 had been found on and around Vesuvius, as long ago as 1828, and many have been since found. Of other common products of Etna, there are sulphur in various forms, sulphurous acid gas, ammonia salts, hydrochloric acid gas, and steam. A curious white 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.