“Well, I hope he and Andy keep away from us.  They make trouble everywhere they go.  Now come on, get busy.”

And, though Tom tried to drive from his mind the thoughts of the Fogers, yet it was with an uneasy sense of some portending disaster that he went on with the work of preparing for the trip into the unknown.  He said nothing to Ned about it, but perhaps his chum guessed.

“That’ll do,” said Tom after an hour’s labor.  “We’ll call it a night’s work and quit.  Can’t you stay here—­we’ve got several spare beds.”

“No, I’m expected home.”

“I’ll walk a ways with you,” said Tom, and when he had left his chum at his house our hero returned by a street that would take him past the Foger residence.  It was shrouded in darkness.

“Everybody’s cleared out,” said Tom in a low voice as he glance at the gloomy house.  “Well, all I hope is that they don’t camp on our trail.”

CHAPTER VIII

ERADICATE WILL GO

“I guess everything is all ready,” remarked Tom.

“I can’t think of anything more to do,” said Ned.

“Bless my grip-sack!” exclaimed Mr. Damon, “if there is, someone else has got to do it.  I’m tired to death!  I never thought getting ready to go off on a simple little trip was so much work.  We ought to have made the whole journey from start to finish in an airship, Tom, as we’ve done before.”

“It was hardly practical,” answered the young inventor.  “I’m afraid we’ll be searching for this underground city for some time, and we’ll only need an airship or a dirigible balloon for short trips here and there.  We’ve got to go a good deal by information the natives can furnish us, and we can’t get at them very well when sailing in the air.”

“That’s right,” agreed the eccentric man.  “Well, I’m glad we’re ready to start,”

It was the evening of the day before they were to leave for New York, there to take steamer to a small port on the Mexican coast, and every one was busy putting the finishing details to the packing of his personal baggage.

The balloon, taken apart for easy transportation, had been sent on ahead, as had most of their supplies, weapons and other needed articles.  All they would carry with them were handbags, containing some clothing.

“Then you’ve fully made up your mind not to go; eh Rad?” asked Tom of the colored man, who was busy helping them pack.  “You won’t take a chance in the underground city?”

“No, Massa Tom, I’s gwine t’ stay home an’ look after yo’ daddy.  ‘Sides, Boomerang is gettin’ old, an’ when a mule gits along in yeahs him temper ain’t none ob de best.”

“Boomerang’s temper never was very good, anyhow,” said Tom.  “Many’s the time he’s balked on you, Rad.”

“I know it, Massa Tom, but dat jest shows what strong character he done hab.  Nobody kin manage dat air mule but me, an’ if I were to leave him, dere suah would be trouble.  No, I cain’t go to no underground city, nohow.”