As the coast came close ahead of the monster subs the little aero-subs, to the surprise of the Secret Agents, all vanished into their respective mother ships.
"But they have to use them," groaned Munson. "For their submarines are useless in frontal attack against our shores!"
"I am not so sure of that," said Prester Kleig. "For I have a suspicion that those submarines have tractors under their keels, and that they can come out on land! If this is so the monsters can, guarded by armour-plate, penetrate to the very heart of our most populated areas before their aero-subs are released."
None of the Secret Agents as yet had stopped to ponder how the monsters had reached their positions, and why Moyen was attacking from the east, when the Pacific side of the continents would have appeared to be the obvious point of attack, and would have obviated the necessity of long, secret under-sea journeys wherein discovery prematurely must have been one of the many worries of the submarine commanders.
The mere fact of the presence of the monsters was enough. What had preceded their presence was unimportant, save that their presence, and their near approach to the shore undetected, further proved the executive and planning genius of Moyen.
Two miles, on an average, off the eastern coast the submarines laid their eggs—the aero-subs, which darted from the sides of the mother ships in flights and squadrons, made the surface, and leaped into the sky.
Five minutes later and the signal went forth to the phalanx of the volunteers.
"Take off! Fly east and engage the enemy, and hold him in check, and the God of our fathers go with you!"
One hour had passed since Moyen's ultimatum when the first vanguard of the American flyers, obeying the peremptory signal, took the air and darted eastward to meet the winged death-harbingers of Moyen.