Their opportunity came sooner than they had hoped for—or wanted. It was about three o'clock in the morning when the telephone warning hummed loudly through the ship. Arcot answered.
Far to the east and south of them the line of scout planes that patrolled all the borders of Lanor had been broken. Instantaneously, it seemed, out of the dark, its lights obscured, the mighty Kaxorian craft had come, striking a tiny scout plane head on, destroying it utterly before the scout had a chance to turn from the path of the titanic ship. But even as the plane spun downward, the pilot had managed to release a magnesium flare, a blindingly brilliant light that floated down on a parachute, and in the blaze of the white light it gave off, the other scouts at a few miles distance had seen the mighty bulk of the Kaxorian plane. At once they had dropped to the ground and then, by telephone lines, had sent their report to far off Sonor.
In moments the interior of the Solarite became a scene of swift purposeful activity. All day the Terrestrians had been able to do so little in preparation for the conflict they knew must come, the battle for two worlds. They had wanted action, but they had no weapons except their invisibility and the atomic hydrogen. It would not sink a plane. It would only break open its armor, and they hoped, paralyze its crew. And on this alone they must pin their hopes.
VI
Arcot lifted the Solarite at once high into the air, and started toward the point on the border, where the plane had been seen crossing. In a short time Wade relieved him at the controls while he dressed.
They had been flying on in silence for about an hour, when suddenly Wade made out in the distance the great bulk of the plane, against the dull gray of the clouds, a mile or so above them. It seemed some monstrous black bat flying there against the sky, but down to the sensitive microphone on the side of the Solarite came the drone of the hundred mighty propellers as the great plane forged swiftly along.
Just how rapidly these giants moved, Arcot had not appreciated until he attempted to overtake this one. It was going over a mile a second now—a speed that demanded only that it move its own length in about five-eights of a second! It made this tremendous speed by streamlining and through sheer power.
The Solarite hovered high above the dark ship at length, the roar of the terrific air blast from its propellers below coming up to them as a mighty wave of sound that made their own craft tremble! The hundred gigantic propellers roaring below, however, would distribute their gas perfectly.
“We're going invisible,” Arcot exclaimed. “Look out!” There was a click as the switch shut, and the Solarite was as transparent as the air above it. Arcot drove his ship swiftly, above and ahead of the mighty colossus, then released the gas. There was a low hiss from the power room, barely detectable despite the vacuum that shut them off from the roar of the Kaxorian plane. The microphone had long since been disconnected. Out of the gas vent streamed a cloud of purplish gas, becoming faintly visible as it left the influence of the invisibility apparatus, but only to those who knew where to look for it. The men in that mighty plane could not see it as their machine bore down into the little cloud of gas.