"Yes, there is vapor in the jar," he said.
"Good! That's the stuff!" cried Jack. "Now I guess Professor Lenton will admit that I'm right."
He turned the Bunsen flame up higher. A moment later he uttered a cry, for he saw the cork being forced from the test tube. The pressure of the new gas was too much for it.
"Lookout!" cried Jack. "She's going up!"
Then followed a sharp explosion, and the laboratory seemed filled with fragments of broken glass and torn books.
CHAPTER II
JACK MAKES OXYGEN
"There it goes! There it goes!" cried Mark, making a dive for the laboratory door, but slipping and sprawling on the floor. "There it goes, Jack!"
"No; it's gone already!" cried Jack, who, even in the midst of danger and excitement, seemed to remain calm and still to have his appreciation of it joke.
"Come on!" cried Mark as he scrambled to his feet. "We must get out of here, Jack!"