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. The fog drove in fast. Through straining eyes he tried in vain to glimpse the drama spread above. The world grew dark and gray. He buried his face in his hands. And again came the thunder. The men on the ground forced their gaze to the clouds, though they knew some fresh horror awaited. The fog-clouds reflected the blue terror above. They were riven and torn. And through them black objects were falling. Some blazed as they fell. They slipped into unthought maneuvers--they darted to earth trailing yellow and black of gasoline fires. The air was filled with the dread rain of death that was spewed from the gray clouds. Gone was the roaring of motors. The air-force of the San Diego area swept in silence to the earth, whose impact alone could give kindly concealment to their flame-stricken burden. Thurston's last control snapped. He flung himself flat to bury his face in the sheltering earth. * * * * * Only the driving necessity of work to be done saved the sanity of the survivors. The commercial broadcasting stations were demolished, a part of the fuel for the terrible furnace across the bay. But the Naval radio station was beyond on an outlying hill. The Secretary of War was in charge. An hour's work and this was again in commission to flash to the world the story of disaster. It told the world also of what lay ahead. The writing was plain. No prophet was needed to forecast the doom and destruction that awaited the earth. Civilization was helpless. What of armies and cannon, of navies, of aircraft, when from some unreachable height these monsters within their bulbous machines could drop coldly--methodically--their diminutive bombs. And when each bomb meant shattering destruction; each explosion blasting all within a radius of miles; each followed by the blue blast of fire that melted the twisted framework of buildings and powdered the stones to make of a proud city a desolation of wreckage, black and silent beneath the cold stars. There was no crumb of comfort for the world in the terror the radio told. Slim Riley was lying on an improvised cot when Thurston and the representative of the Bureau of Standards joined him. Four walls of a room still gave shelter in a half-wrecked building. There were candles burning: the dark was unbearable. "Sit down," said MacGregor quietly; "we must think...."