A deeper detonation was merging into the uproar. It came from the ships, Thurston knew, where anti-aircraft guns poured a rain of shells into the sky. About the invaders they bloomed into clusters of smoke balls. The globes shot a thousand feet into the air. Again the shells found them, and again they retreated.
He groaned as a long curving arc of speed showed that the big bulb was under control. Over the ships it paused, to balance and swing, then shot to the zenith as one of the great boats exploded in a cloud of vapor.
The following blast swept the airdrome. Planes yet on the ground went like dry autumn leaves. The hangars were flattened.
Thurston cowered in awe. They were sheltered, he saw, by a slope of the ground. No ridicule now for the bombs!
A second blast marked when the gas-cloud ignited. The billowing flames were blue. They writhed in tortured convulsions through the air. Endless explosions merged into one rumbling roar.
MacGregor had roused from his stupor; he raised to a sitting position.
"Hydrogen," he stated positively, and pointed where great volumes of flame were sent whirling aloft. "It burns as it mixes with air." The scientist was studying intently the mammoth reaction. "But the volume," he marveled, "the volume! From that small container! Impossible!"
"Impossible," the Secretary agreed, "but...." He pointed with his one good arm toward the Pacific. Two great ships of steel, blackened and battered in that fiery breath, tossed helplessly upon the pitching, heaving sea. They furnished to the scientist's exclamation the only adequate reply.
Each man stared aghast into the pallid faces of his companions. "I think we have underestimated the opposition," said the Secretary of War quietly. "Look--the fog is coming in, but it's too late to save them."
The big ships were vanishing in the oncoming fog. Whirls of vapor were eddying toward them in the flame-blaster air. Above them the watchers saw dimly the five gleaming bulbs. There were airplanes attacking: the tapping of machine-gun fire came to them faintly.
Fast planes circled and swooped toward the enemy. An armada of big planes drove in from beyond. Formations were blocking space above.... Every branch of the service was there, Thurston exulted, the army, Marine Corps, the Navy. He gripped hard at the dry ground in a paralysis of taut nerves. The battle was on, and in the balance hung the fate of the world.