"But what are we to do? Is there no method by which we can combat this menace? Must we lie supine and let whatever cataclysmic terror they choose descend on us?"
All eyes were upon Dr. Howard as he gravely answered. "Since I first comprehended what lay behind these catastrophes I have sought for some method of halting them, some method of striking back at whatever ship or ships from space are hovering over us. To find such a method I have had recourse to the same analogy that has been made so terribly clear to us, the analogy between ourselves at the bottom of our air-ocean and the creatures at the sea's bottom.
"Suppose those creatures far within the sea's depths had some intelligence and science, and suppose they wished to halt the trawling of our ships whose great scoops sweep down now and again upon them. How could they do so? They could not venture up to the ocean's surface. But one thing they could do, and that would be to send up something that would fight for them, that would make it impossible for the trawling ships to cruise longer on the surface!
"They could, granted science and intelligence enough, construct great mines in vast numbers. These, if attached to air-filled globes, would be swept instantly up to the ocean's surface when released. They would float there indefinitely, and any ships cruising to and fro would sooner or later strike one and be destroyed, unless they were warned by the previous destruction of one. In this way the creatures of the sea's depths could prevent our cruising above and trawling for them.
"And this is the way we must use to fight the beings who now cruise far above us! We must mine the air! We must send up thousands of great mines constructed so that they will float up to the surface of earth's atmospheric ocean and remain near that surface where, we know, the ships of these space-beings are coming and going. With thousands of mines floating about some of the invaders will inevitably be destroyed by a collision with one of them."
The others were silent for a moment. Then the Secretary of War broke out:
"Mine the air!" he repeated incredulously. "But how? How could any mine be constructed to float up in that way, so light as to float on the atmosphere's surface?"
By Means of Steelite
"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!