There was a gentle shock, and then the window shutters slid back. A fine view of the bed of the tank was had.
Stanhope gazed upon the spectacle with interest and wonderment.
He breathed as freely and regularly as ever, and the chemical air of the boat seemed fully as good as that of the upper part of the world.
For fully half an hour the boat remained at the bottom of the tank. The generators were a complete success.
Then Stanhope said:
“I am satisfied, Frank, that one could live indefinitely under water with your generator.”
“I am glad of that,” said Frank. “Now I will prove to you that the Dolphin can travel under water.”
This time Frank stepped into the pilot-house, and took the wheel. He pressed a key, which set the propellers in motion. Then the Dolphin glided forward.
Round and round the tank went the submarine boat.
Stanhope’s last doubt was removed. He caught Frank’s hands and wrung them.