(Fig. 21), and Fusiyama, and hence it is that the crater
is so often at, or very near, the summit. [Illustration: Fig.
21.--Cotopaxi.] Perhaps no spectacle in Nature is more magnificent than
a Volcano in activity. It has been my
good fortune to have stood more than once at the edge of the crater of
Vesuvius during an eruption, to have watched the lava seething below,
while enormous stones were shot up high
into the air. Such a spectacle can never be forgotten. The most imposing
crater in the world is probably that of Kilauea, at a height
of about 4000 feet on the side of Mouna Loa, in the Island of Hawaii. It
has a diameter of 2 miles, and is elliptic in outline, with a longer
axis of about 3, and a circumference of about 7 miles. The interior is a
great lake of lava, the level
of which is constantly changing. Generally, it stands about 800 feet
below the edge, and the depth
is about 1400 feet. The heat is intense, and, especially at night, when
the clouds are coloured scarlet by the reflection from the molten lava,
the
effect is said to be magnificent. Gradually the lava mounts in the
crater until it either
bursts through the side or runs over the edge, after which the crater
remains empty, sometimes for years. A lava stream flows down the slope
of the mountain like a burning river,
at first rapidly, but as it cools, scoriae gradually form, and at length
the molten matter covers itself completely (Fig. 22), both above
and at the sides, with a solid crust, within which, as in a tunnel, it
continues to flow slowly as long as it is suppli