under and lightning
are frequent accompaniments of an eruption. The hydrochloric acid
probably points to the agency of sea-water. Besides the gases just
mentioned, sulphuretted hydrogen, ammonia and common salt occur; but
mainly as secondary products, formed by the union of the vapors issuing
from the volcano, and commonly found also in the vapors rising from
cooling lava streams or dormant volcanic districts. It is important to
notice that the vapors issue from the volcano spasmodically, explosions
succeeding each other with great rapidity and noise.

All substances thrown out by the volcano, whether gaseous, liquid or
solid, are conveniently united under the term ejectamenta (Latin, things
thrown out), and all of them are in an intensely heated, if not an
incandescent state. Most of the gases are incombustible, but the
hydrogen and those containing sulphur burn with a true flame, perhaps
rendered more visible by the presence of solid particles. Much of the
so-called flame, however, in popular descriptions of eruptions is
an error of observation due to the red-hot solid particles and the
reflection of the glowing orifice on the over-hanging clouds.

ENORMOUS FORCE DISPLAYED

Solid bodies are thrown into the air with enormous force and to
proportionally great heights, those not projected vertically falling in
consequence at considerable distances from the volcano. A block weighing
200 tons is said to have been thrown nine miles by Cotopaxi; masses
of rock weighing as much as twenty tons to have been ejected by
Mount Ararat in 1840; and stones to have been hurled to a distance
of thirty-six miles in other cases. The solid matter thrown out by
volcanoes consists of lapilli, scoriae, dust and bombs.

Though on the first formation of the volcano, masses of non-volcanic
rock may be torn from the chimney or pipe of the mountain, only slightly
fused externally owing to the bad conducting power of most rocks,
and hurled to a distance; and though at the beginning of a subsequent
eruption the solid plug of rock which has cooled at the bottom of the
crater, or, in fact, any part of the volcano, may be similarly blown up,
the bulk of the solid particles of which the volcano itself is composed
is derived from the lake of lava or molten rock which seethes at the
orifice. Solid pieces rent from this fused mass and cast up by the
explosive force of the steam with which the lava is saturated are known
as lapilli. Cooling rapidly