But they had reckoned without the two-mile-a-minute birdmen that circle the heavens like giant eagles and swoop down on their prey from high altitudes to send forth their flaming bombs and death-dealing hand grenades. A lookout on one of the destroyers detected at this moment an aerial fleet looming out of the north like spectral dots in the dim light of the skies. From the masthead of the vessel glowed instantly the light that had been agreed upon as a danger signal. "Airplanes!" shouted the _Dewey's_ commander, as he strained his eyes through the portholes of the conning tower in a vain effort to search the skies. In another moment, after giving the "wheel" over to his flag officer, the lieutenant had thrown open the conning tower and was gazing into the heavens with his binoculars. "Yes, there they come," he announced, after a short pause. "Two---three---four; there's a half dozen or more of them," he continued after a careful survey of the sky. The singing down in the hold abated when the reported approach of the air fleet became known throughout the ship. "What's up?" queried Ted, as he joined his chum outside the wireless room. "The Kaiser's imperial flying corps is out for a little evening exercise," answered Jack, as he hurried along to keep within call of his commander. For the men in the _Dewey_ there was nothing to do but take the reports from the conning tower as to what was going on outside the submarine. Their impatience, however, was short-lived, for there came very quickly an order to man the anti-aircraft guns on deck. The hatches fore and aft were thrown open and the gun crews scrambled on deck. "Not afraid of 'em, are we?" chuckled Ted, as he followed Bill Witt up the ladder. "Chances are they can't see us in the twilight," answered Bill. "And this is a real chance for us to give the 'twins' a little tuning up." From the conning tower came the order to unlimber the guns, load and stand by. "Wait until they come within range, and then fire away!" directed the _Dewey's_ commander. From a height of five thousand feet the leader of the "air cavalry" suddenly turned the nose of his craft downward, and came volplaning toward the sea at a dizzy pace. Following suit, the remaining units of the attacking squadron dived to get within better range. "Now, boys!" shouted Lieutenant McClure. Time-fuse shells had been inserted in the "Twins," the breeches closed and the muzzles elevated to point at the fast-flying airships. At the aft gun Ted gripped the trigger ready to fire, while Mike Mowrey jammed his good right eye into the telescopic sight to make sure of his aim. "Fire!" he yelled, and Ted, let her go. The shot sped away into the sky while the crew gazed eagerly upward to watch for the explosion. Soon the shell burst with a white puff of smoke. "Little too far to the right," said the observer.