“What makes you think there will be an earthquake?” asked Tom.

“Because I can hear the rumbling beneath the ground at this very minute.  It is increasing in volume, showing that the tremors are working this way.  There will soon be a great subterranean upheaval!  Listen for yourself.”

Tom cast himself down on the grass.  Placing his ear close to the ground he did hear a series of dull thuds.  He arose, not a little alarmed.  There had never been any earthquakes in Shopton, yet he had great respect for Mr. Parker’s scientific attainments.

Just then Eradicate Sampson came along.  He saw Tom and Mr. Parker lying flat on the ground, and surprise showed on his honest, black face.

“Fo’ de land sakes!” cried Eradicate.  “What am de mattah now, Massa Tom?”

“Earthquake coming,” answered Tom, briefly.  “Better get away from the buildings, Rad.  They might fall!” Tom’s face showed the alarm he felt.  What would happen to all of his valuable machines—­to the Red Cloud?

“Earthquake?” murmured Eradicate, and he, too, cast himself down to listen.  A moment later he arose with a laugh.

“What’s the matter?” cried Tom.

“Why, dat ain’t no earthquake!” declared the colored man.

“No.  Then perhaps you know what it is,” said Mr. Parker, somewhat sharply.

“Course I knows what it am,” answered Eradicate, with dignity.  “Dat noise am my mule Boomerang, kickin’ in his stable, on account oh me not feedin’ him yet.  Dat’s what it am.  I’se gwine right now t’ gib him his oats, and den yo’ see dat de noise stop.  Boomerang allers kick dat way when he’s hungry.  I show yo’!”

And, sure enough, when Eradicate had gone to the mule’s stable, which was near where Mr. Parker had heard the mysterious sounds, they immediately ceased.

“Dat mule was all de earthquake dere was around here,” said the colored man as he came out.

Mr. Parker walked away, saying nothing, and Tom did not make any comments—­just then.

CHAPTER VIII—­OFF FOR THE WEST

It was a great relief to Tom, to find that there was no danger from an earth tremor.  Now that he had made up his mind to go in search of the diamond makers, he wanted nothing to interfere with it.  Lest the feelings of Mr. Parker might be hurt by the mistake he had made, the young inventor cautioned Eradicate not to say anything more about the matter.

“‘Deed an’ I won’t,” the colored man promised.  “I’se only too glad dere wa’n’t no earthquake, dat’s what I is.”

As for Mr. Parker, he did not appear much put out by his error in predicting.

“I am sure that what I heard was a tremor, due to some distant earthquake shock,” he said.  “The mule’s kicking was only a coincidence.”

And Tom let him have his way about it.  The week was drawing to a close, and the Red Cloud was nearly in shape for the voyage.  At almost the last minute Tom found that he needed some electrical apparatus for the airship, and as he had to go to Chester for it, he decided he would make the trip in his monoplane, and, while in the city, would also get the diamond pin he was having made for Mary Nestor.