"There we have recourse again to our analogy," Dr. Howard declared. "If
a mine attached to a great hollow globe of air were released at the
sea's bottom it would rush up toward the surface and float there. In
the same way, a mine attached to a great globe in which is a complete
vacuum would rush up through our air-ocean!
"We can construct those globes of the strongest and lightest material
known--_steelite_. As you all know, _steelite_ is the recently devised
metal that has immensely greater strength than steel but the merest
fraction of its weight. The tensile strength of a substance, its
hardness and other qualities, depend directly upon the arrangement of
its molecules. By the recent discoveries of Browning we know that when
steelite is synthetically made the arrangement of the molecules is such
that it forms an extremely strong and rigid substance. This gives the
material unheard-of strength with unheard-of lightness.
"A forty-foot globe of _steelite_ can be made, with a charge of
explosives of terrific power attached to it that will detonate when the
globe is touched. This done, all air is exhausted from the hollow globe
by great pumps, until the vacuum inside it is almost complete. The
enormous strength of the steelite shell prevents its being crushed by
the atmosphere's pressure as an ordinary steel shell would be.
"Released, the vacuum globe with its deadly charge will shoot up
through the atmosphere with terrific speed. Its lightness for its
size will be such that it will not halt until it floats on the very
surface of our atmosphere. We will make these globes in countless
thousands, each with its charge, and release them. Each globe will have
a device that will repel any other, so that they do not detonate each
other. We will sow the surface of our atmosphere with these deadly
air-mines! Sooner or later the ship or ships cruising to and fro on
our atmosphere's surface will strike one and will be destroyed by its
detonating charge. In this way, and only in this way, can we fight back
against the beings from space who are releasing this horror on us!"
"But to make these globes or mines in such numbers will engross all the
earth's industrial activities!" the British ambassador exclaimed.
"It will," Dr. Howard agreed quietly. "But what of it? Have you not yet
realized that a world crisis is upon us? Have you not yet realized that
in this case there is no question of countries or races, of profits
or dividends, or expediencies, but that we, as men, are fighting for
the existence of man? That we are fighting against beings who may be
immeasurably more advanced in knowledge and power than ourselves?"
"Dr. Howard is right," said the President. "Gentlemen, this emergency
must be clear to you all, and I think that it is equally clear that
Dr. Howard's plan is the only one that affords any possibility of
combatting this terror from above. I place all the resources of the
United States of America at your command, Dr. Howard, and I know that
when the representatives of the other nations here have reported to
their governments they will do the same. The whole world's efforts must
concentrate upon the prevention of these terrible disorders."
"There is but one thing earth's peoples can do," Dr. Howard said. "Make
air-mines! Thousands, tens of thousands--they must be turned out in
ceaseless floods and released. For it is only with them that we can
repel the menace above us."
Make air-mines! It was the watchword of all earth's races within a few
hours of that momentous meeting. For the President and the heads of
the earth's other governments sent statements in which Dr. Howard's
suggested method of combatting the danger was stressed as the world's
one chance. Thousands of air-mines must be made at once and continue to
be turned out until the menace was repelled--scientists agreed, as one
man, that it was the one possible way of fighting these grim visitors
from space who were hovering in their enigmatic vessels at the surface
of our atmosphere.
Within a half day after the meeting Dr. Howard and I, aided by several
masters of aeronautical, chemical, and physical sciences had drawn up
the plans of the air-mines. Each was to be a hollow steelite globe
forty-two feet in outside diameter. This would give the globes a
gross lifting power of about five thousand pounds and net of about
twenty-five hundred. Attached in a special chamber at the side of each
was the charge, a load of the most modern explosives, small in bulk but
terrific in power, while striking-pins on the globe's sides made it
inevitable that the charge be exploded whenever the globe was struck.
Through the night of the 6th, hundreds of men were busy in Washington
turning out copies of the simple plans of the air-mine, and scores of
planes were flying throughout the world with copies for all nations. On
the 7th the manufacture of the great engines had already been begun in
a hundred cities.
But on the night of the 7th the terror struck again. This time it
was with small loss of life, but the psychological effects were far
greater. It was upon upper Malaysia that the giant, glittering trawl
descended, flashing down to rip a great trench of destruction through
the jungle and along the edge of a native village, then flashing up
again, leaving untold panic behind it.