The eruptions of lava are sometimes attended by peculiarities which
impart to them much additional grandeur. Instances have occurred in
which the fiery stream has plunged over a sheer precipice of
immense height, so as to produce a glowing cascade exceeding in
breadth and perpendicular descent the celebrated Falls of Niagara.
In other cases, the lava, instead of at once flowing down the sides
of the mountain, has been first thrown up into the air as a fiery
fountain several hundred feet in height. This happens when the
great crater at the summit of the cone is full of liquid lava but
does not overflow. Then, on the formation of an opening in the side
of the cone, a good way down, the lava issuing from it is projected
upwards to nearly the same height that it occupies in the interior
of the crater at the top of the cone. It is hardly possible for the
fancy to picture to itself anything so magnificent as such a
fountain of liquid fire must be. A simple jet of water of
considerable volume, thrown into the air to the height of a hundred
feet, is itself a beautiful spectacle. What then must be a huge jet
of glowing white lava projected to the height of several hundred
feet, and with what an awful thundering sound must it come tumbling
to the ground, thence to rush as a roaring torrent down the
mountain's side!

Lava, when congealed, differs in its consistency according as it is
near the top or near the bottom of the stream. When near the top it
is porous, owing to its rapid cooling; when near the bottom it is
dense, owing to its slow cooling and the great pressure to which it
is subjected. When the lighter superficial lava is brought suddenly
into contact with water, as when a lava-stream enters the sea, it
becomes still lighter and more porous--forming the well-known