Above all these the big plane sped. It swept on toward the open sea—or what had been the open sea until the Silver Menace had appeared. Soon the shore was left behind, and the huge aëroplane was flying between the two skies—the real sky above and the reflected sky below. Only a thin line from far inland showed dark. All the rest seemed but a universe of air without a horizon or any sign of tangibility. Davis kept his eyes on his instruments, and presently announced:
"I think we're far enough out. We'll drop our first bomb here."
He pressed the release switch as he spoke. The plane lifted a little as the heavy bomb dropped. For a few seconds there was no sound but the roaring of the motors, but then the reverberation of the explosion below reached them.
"Take a look below," said Davis, banking the machine sharply and beginning to swing in a narrow circle.
Gerrod looked down. He saw what seemed to be a ring of yellowish smoke, and a dark-blue spot in the middle of the silvery mass beneath them.
"It did something," he reported, "There's a dark spot on the surface. I can't judge how large it is, though."
Davis released a second bomb, and a third. Gerrod could watch them as they fell. They dwindled from winged, pear-shaped objects to dots. Then there was a flash far below and a spurting of water and spray. In a moment that had subsided, and he saw a second and larger dark-blue spot beside the first.
"I believe you've done it," said Gerrod excitedly. "You've certainly destroyed the silvery appearance. Dare you go lower?"
"Surely," said Davis cheerfully. The plane dived like an arrow, and flattened out barely five hundred feet above the surface.
Gerrod examined the dark spots through glasses. The disturbance had not completely abated, and he could see indubitable waves still radiating from the Spot where the bombs had fallen. Davis grinned like a boy when Gerrod told him.