Seriously alarmed, the boys shouted to him to keep up his courage, and that they would get him out.
"How did you get in?" asked Zeb, cupping his hands.
"I fell in," rejoined the poor professor. "The ground gave way under my feet. Hurry and get me out, it's terribly hot."
They looked about them desperately for some means of extricating him from his predicament. But just at the moment none was offered, and with every struggle the professor was sinking deeper in the black, evil-smelling pool of mud.
"Gracious, what are we to do?" cried Jack in despair.
"He's too far out to reach him," said Zeb, equally at a loss.
"But we must do something," chimed in Tom.
Suddenly Zeb had an inspiration. A tree grew on the banks of the mud volcano, the sudden caving in of which, under the professor's weight, had precipitated him into it.
"If I could get out on that branch," said Zeb, "I might be able to bend it enough to bring my feet over him and then work back toward the edge of the mudhole."
"It's worth trying—anything is worthy trying," agreed Jack.