in working on the submarine.

"We'll launch her day after to-morrow," declared Mr. Swift
enthusiastically. "Then to see whether my calculations are
right or wrong."

"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