“You don’t say?” repeated the fat boy. “How often?”

“About once every hour, I believe, Come! The others are getting ahead of us,” urged Grace, moving on up the mountain-side.

Stacy glanced up the terraces, then down at the ponies, and concluding that his party would have to pass the “Infant” on their return, decided to remain where he was and “wait for the explosion” of the little geyser. The Overlanders, however, apprehensive that the boy might get into fresh difficulties, cast frequent glances in his direction. Finally, Jim Badger became suddenly interested too.

“What’s he doin’?” demanded the guide.

Stacy appeared to be hammering at something, and was so busy at his task that he probably had forgotten the very existence of his companions. After a few moments of activity on his part, they saw him get up and begin to jump up and down.

“I reckon we’d better find out what that boy is up to,” suggested Tom Gray. “After this we mustn’t let him get away from us. We had better make haste.” Tom started sprinting down the terraces, followed by the others of the party, running, sliding, stumbling and laughing at their frequent mishaps.

“Oh, look!” cried Emma Dean.

There was no need for her warning shout, for every member of the Overland party had seen Stacy Brown suddenly fade out of sight, as a dull report assailed their ears, and a volume of steam and water showered over the immediate vicinity of the “Infant.” The fat boy was now nowhere to be seen.

“He’s done it! He’s done it!” wailed Nora.

“What’s happened?” shouted Lieutenant Wingate, the first to reach the “Infant.”