rposes, it having an edge of
razor-like sharpness. They also used it as the cutting part of their
weapons of war.

CHAPTER XX.

The Active Volcanoes of the Earth.

It is not by any means an easy task to frame an estimate of the number
of volcanoes in the world. Volcanoes vary greatly in their dimensions,
from vast mountain masses, rising to a height of nearly 25,000 feet
above sea-level, to mere molehills. They likewise exhibit every possible
stage of development and decay: while some are in a state of chronic
active eruption, others are reduced to the condition of solfataras, or
vents emitting acid vapors, and others again have fallen into a more or
less complete state of ruin through the action of denuding forces.

NUMBER OF ACTIVE VOLCANOES

Even if we confine our attention to the larger volcanoes, which merit
the name of mountains, and such of these as we have reason to believe to
be in a still active condition, our difficulties will be diminished, but
not by any means removed. Volcanoes may sink into a dormant condition
that at times endures for hundreds or even thousands of years, and
then burst forth into a state of renewed activity; and it is quite
impossible, in many cases, to distinguish between the conditions of
dormancy and extinction.

We shall, however, probably be within the limits of truth in stating
that the number of great habitual volcanic vents upon the globe which
we have reason to believe are still in active condition, is somewhere
between 300 and 350. Most of these are marked by more or less
considerable mountains, composed of the materials ejected from them.
But if we include mountains which exhibit the external conical form,
crater-like hollows, and other features of volcanoes, yet concerning the
activity of which we have no record or tradition, the number will fall
little, if anything, short of 1,000.

The mountains composed of volcanic materials, but which have lost
through denudation the external form of volcanoes, are still more
numerous, and the smaller temporary openings which are usually
subordinate to the habitual vents that have been active during the
periods covered by history and tradition, must be numbered by thousands.
There are still feebler manifestations of the volcanic forces--such as
steam-jets, geysers, thermal and mineral waters, spouting saline and
muddy springs, and mud volcanoes--that may be reckoned by millions.
It is not improbable that these less powe