It is in the central section of the uprushing mass, if anywhere, that
the dust might attain the height necessary to put it beyond the
earth's attraction, bringing it fairly into the realm of the solar
system, or to the position where its own motion and the attraction of
the other spheres would give it an independent orbital movement about
the sun, or perhaps about the earth. We can only say that observations
on the height of volcanic ejections are extremely desirable; they can
probably only be made from a balloon. An ascension thus made beyond
the cloud disk which the eruption produces might bring the observer
where he could discern enough to determine the matter. Although the
movements of the rocky particles could not be observed, the colour
which they would give to the heavens might tell the story which we
wish to know. There is evidence that large masses of stone hurled up
by volcanic eruption have fallen seven miles from the base of the
cone. Assuming that the masses went straight upward at the beginning
of their ascent, and that they were afterward borne outwardly by the
expansion of the column, computations which have a general but no
absolute value appear to indicate that the masses attained a height of
from thirty to fifty miles, and had an initial velocity which, if
doubled, might have carried them into space.

Last of all, we shall note the conditions which attend the eruptions
of submarine volcanoes. Such explosions have been observed in but a
few instances, and only in those cases where there is reason to
believe that the crater at the time of its explosion had attained to
within a few hundred feet of the sea level. In these cases the
ejections, never as yet observed in the state of lava, but in the
condition of dust and pumice, have occasionally formed a low island,
which has shortly been washed away by the waves. Knowing as we do that
volcanoes abound on the sea floor, the question why we do not oftener