"There was—er—a slight explosion," replied Jack, a faint smile spreading over his face.
"Are you hurt?" the professor asked quickly, stepping over to Mark. "Shall I get a doctor?"
"A book hit him," explained Jack.
"A book! Did a book explode?"
"No, sir. You see, I was making a new kind of gas, and Mark was helping me. He was afraid the test tube would explode, so I piled books around it, and—"
"And it did blow up!" cried Mark, still rubbing his head. "The test tube, and the other tube, and the rubber hose, and the bell–jar. I told you it would, Jack."
"Then you weren't disappointed," retorted Jack, this time with a broad smile. "I don't like to disappoint people," he added.
"What kind of gas was it, Darrow?" asked Professor Lenton.
"Well, I hadn't exactly named it yet," answered the young inventor. "I was going to show it to you, and see what you thought of it. It's the kind you said I couldn't make."
"And did you make it?" asked the instructor grimly.