"Yes, if you want to hold a test tube for me," answered Jack.
"I'm going to try a new way of making oxygen."

"No, thanks! Not for mine!" exclaimed Dick as he turned away.
"I don't want to be around when you try your new experiments.
The old way of making oxygen is good enough for me."

"Well, I have a new scheme," went on Jack.

Soon he and Mark, whom he had again induced to help him, were
busy with test tubes, rubber hose, Bunsen flames, jars of water,
and all that is required to make oxygen.

Somewhat to his own surprise, the experiment Jack tried was a
success. He collected a jarful of oxygen, generated in a way he
had thought out for himself. It was much simpler than the usual
method.

Just as he concluded the test, some one opened the laboratory
door. It was Professor Lenton.

"I have a telegram for you," he said.

"A telegram?"

"Yes. It just arrived."

Jack tore open the yellow envelope.

"It's from Professor Henderson," he said.