Stromeyer detected the presence of selenium in a mixture of sal ammoniac
and sulphur. Another product, supposed to be peculiar to this volcano, is
boracic acid, which lines the sides of the cavities in beautiful white silky
crystals. Daubeney, op. cit., p. 257.] -- Tr.
The vapors that rise from the 'fumarolles' cause the sublimation of the
chlorids of iron, copper, lead, and ammonium; iron glanceI and chlorid of
sodium (the latter often in large quantities) fill the cavities of recent
lava streams and the fissures of the margin of the crater.
[footnote] *Regarding the chemical origin of iron glance in volcanic
masses, see Mitscherlich, in Poggend., 'Annalen', bd. xv., s. 630; and on
the liberation of hydrochloric acid in the crater, see Gay-Lussac, in the
'Annals de Chimique et de Physique', t. xxii., p. 423.
The mineral composition of lava differs according to the nature of the
crystalline rock of which the volcano is formed, the height of the point
where the eruption occurs, whether at the foot of the mountain or in the
neighborhood of the crater, and the condition of temperature of the
interior. Vitreous volcanic formations, obsidian, pearl-stone, and pumice,
are entirely wanting in some volcanoes, while in the case of others they
only proceed from the crater, or, at any rate, from very considerable
heights.
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