"It won't be your fault if it doesn't work," said his son. "You certainly have done your best."
"And so have you and Mr. Sharp and the others, for that matter. Well, I have no doubt but that everything will be all right, Tom."
"There!" exclaimed Mr. Sharp the next morning, as he was adjusting a certain gage. "I knew I'd forget something. That special brand of lubricating oil. I meant to bring it from Shopton, and I didn't."
"Maybe I can get it in Atlantis," suggested Tom, naming the coast city nearest to them. "I'll take a walk over. It isn't far."
"Will you? I'll be glad to have you," resumed the balloonist. "A gallon will be all we'll need."
Tom was soon on his way. He had to walk, as the roads were too poor to permit him to use the motor-cycle, and the airship attracted too much attention to use on a short trip. He was strolling along, when from the other side of a row of sand dunes, that lined the uncertain road to Atlantis, he heard some one speaking. At first the tones were not distinct, but as the lad drew nearer to the voice he heard an exclamation.
"Bless my gold-headed cane! I believe I'm lost. He said it was out this way somewhere, but I don't see anything of it. If I had that Eradi-
