and is sustained by the
largest number of scientific men is that which traces volcanic effects
back to the old accepted cause of internal fires in the center of the
earth. Only in this way can the molten streams of lava emitted by
volcanoes be accounted for.

The youngest student of familiar science knows that heat generates an
upward and outward force, and like all other forces that it follows
the path of least resistance. This force is always present in the
internal regions of the earth, which for ages upon ages has been
gradually cooling from its poles toward its center. When conditions
occur by which it can outwardly manifest itself, it follows the
natural law and escapes where the crust of the earth is thinnest.

But something more than the mere presence of internal fire is
necessary to account for volcanic action, although it may in a large
degree account for minor seismic convulsions in the form of an
earthquake. The elements which enter into the source of volcanic
eruption are fire and water. The characteristic phenomenon of a
volcanic eruption is the steam which issues from the crater before the
appearance of the molten lava, dust, ashes and scoria. This accepted
theory is plainly illustrated in the eruption of a geyser, which is
merely a small water volcano. The water basin of a geyser is connected
by a natural bore with a region of great internal heat, and as fast as
the heat turns the water into steam, columns of steam and hot water
are thrown up from the crater.

One form of volcanic eruption, and its simplest form, is likewise
illustrated in a boiler explosion. Observations of the most violent
volcanic eruptions show them to be only tremendous boiler explosions
at a great depth beneath the earth's surface, where a great quantity
of water has been temporarily imprisoned and suddenly converted into
steam. In minor eruptions the presence of steam is not noticeable in
such quantities, which is simply because the amount of imprisoned
water was small and the amount of steam generated was only sufficient
to expel the volcanic dust and ashes which formed between the earth's
surface and the internal fires of the volcano. The flow of lava which
follows violent eruptions is expelled by the outward and upward force
of the great internal heat, through the opening made by the steam
which precedes it.

The two lines of volcanoes, one north and south, the other east and
west, which intersect in the neighborhood of t