"They look just like places where you intend to mount guns," said Ned to Tom. "And that's exactly what they are," the young inventor replied. "I have the guns nearly ready for mounting, but I can't seem to think of a way of providing for the recoil. And if I don't take care of that, I'm likely to find my ship coming apart under me, after we bombard the enemy with a broadside or two." "Then you intend to fight with this ship?" asked Ned. "Well, no; not exactly personally. I was thinking of offering it to the United States Government. Foreign nations are getting ready large fleets of aerial warships, so why shouldn't we? Matters in Europe are mighty uncertain. There may be a great war there in which aerial craft will play a big part. I am conceited enough to think I can build one that will measure up to the foreign ones, and I'll soon be in a position to know." "What do you mean?" "I mean I have already communicated with our government experts, and they are soon to come and inspect this craft. I have sent them word that it is about finished. There is only the matter of the guns, and some of the ordnance officers may be able to help me out with a suggestion, for I admit I am stuck!" exclaimed Tom. "Then you're going to do the same with this aerial warship as you did with your big lantern and that immense gun you perfected?" asked Ned. "That's right," confirmed Tom. My former readers will know to what Ned Newton referred, and those of you who do not may learn the details of how Tom helped Uncle Sam, by reading the previous volumes, "Tom Swift and His Great Searchlight," and "Tom Swift and His Giant Cannon." "When do you expect the government experts?" Ned asked. "Within a few days, now. But I'll have to hustle to get ready for them, as this fire has put me back. There are quite a number of details I need to change. Well, now, let me explain about that gun recoil business. Maybe you can help me." "Fire away," laughed Ned. "I'll do the best I can." Tom led the way from the main shed, where the aerial warship was housed, to a small private office. As Ned entered, the door, pulled by a strong spring, swung after him. He held back his hand to prevent it from slamming, but there was no need, for a patent arrangement took up all the force, and the door closed gently. Ned looked around, not much surprised, for the same sort of door-check was in use at his bank. But a sudden idea came to him. "There you are, Tom!" he cried. "Why not take up the recoil of the guns on your aerial warship by some such device as that?" and Ned pointed to the door-check. CHAPTER VII WARNINGS For a moment or two Tom Swift did not seem to comprehend what Ned had said. He remained staring, first at his chum, who stood pointing, and from him Tom's gaze wandered to the top of the door. It may have been, and probably was, that Tom was thinking of other matters at that instant. But Ned said again: