"What happened? Is any one hurt? Was there an explosion here?"
he asked.

Then he saw the devastation on all sides--the broken glass, the
scattered and torn books--and he noticed Mark rubbing his head.

"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