Chapter Five. Mr. Berg is Suspicious - Page 2

idea the tank was airtight when he closed it. He had seen Tom enter and a sudden whim came to him to revenge himself.

But that did not help the young inventor any. There was no doubt about it now--the air was becoming close. Tom had been imprisoned nearly two hours, and as he was a healthy, strong lad, he required plenty of oxygen. There was certainly less than there had been in the tank. His head began to buzz, and there was a ringing in his ears.

Once more he fell upon his knees, and his fingers sought the small projections of the gear on the inside of the door He could no more budge the mechanism than a child could open a burglar-proof vault.

"It's no use," he moaned, and he sprawled at full length on the floor of the tank, for there the air was purer. As he did so his fingers touched something. He started as they closed around the handle of a big monkey wrench. It was one he had brought into the place with him. Imbued with new hope be struck a match and lighted his lantern, which he had allowed to go out as it burned up too much of the oxygen. By the gleam of it he looked to see if there were any bolts or nuts he could loosen with the wrench, in order to slide the door back. It needed but a glance to show him the futility of this.

"It's no go," he murmured, and he let the wrench fall to the floor. There was a ringing, clanging sound, and as it smote his ears Tom sprang up with an exclamation.

"That's the thing!" he cried. "I wonder I didn't think of it before. I can signal for help by pounding on the sides of the tank with the wrench. The blows will carry a good deal farther than my voice would." Every one knows how far the noise of a boiler shop, with hammers falling on steel plates, can be heard; much farther than can a human voice.

Tom began a lusty tattoo on the metal sides of the tank. At first he merely rattled out blow after blow, and then, as another thought came to him, he adopted a certain plan. Some time previous, when he and Mr. Sharp had planned their trip in the air, the two had adopted a code of signals. As it was difficult in a high wind to shout from one end of the airship to the other, the young inventor would sometimes pound on the pipe which ran from the pilot house of the Red Cloud to the engine-room. By a combination of numbers, simple messages could be conveyed. The code included a call for help. Forty-seven was the number, but there had never been any occasion to use it.

Tom remembered this now. At once he ceased his indiscriminate hammering, and began to beat out regularly-- one, two, three, four--then a pause, and seven blows would be given. Over and over again he rang out this number--forty seven--the call for help.

"If Mr. Sharp only comes back he will hear that, even in the house," thought poor Tom "Maybe Garret or Mrs. Baggert will hear it, too, but they won't know what