"I—ugh—ugh!" grunted the professor, putting all his strength into it, but the ring never budged an inch.
"Here, give me a hand, boys!" he cried.
"How are we to find you?" asked Ralph.
"Here, extend your hands. Ah, that's it," went on the scientist, seizing hold of the boys' wrists and guiding them down to the ring.
"Now, all together," he said; "pull!"
With all their strength the three adventurers tugged with a mighty heave at the iron. At first it seemed that it was going to prove obdurate even to their combined efforts, but continued tugging resulted in a slight quiver of whatever the iron ring was fastened to.
"Now, once more—he-a-ve!"
There was a sudden give on the part of the iron ring, and its foundation gave way with a rush.
A strange, pungent odor filled the air!
"I—I—I'm choking," gasped Walt, gripping his collar with both hands and tearing it open, to relieve the terrible congestion that had suddenly seized upon his throat.