This was accomplished in an ingenious manner. Of course, it would be impossible to merely open a door and step out.
Water would rush in and flood the cabin.
But Frank had provided a vestibule with two doors, one opening into the cabin and the other out on deck.
He had merely to enter the vestibule and close the cabin door. Then, by turning a valve, the vestibule would fill with water. It was easy then to open the outer door and walk out.
The return was accomplished much the same, though the pressure of a lever set the force-pump at work and cleared the water from the vestibule in quick time.
Frank and Wade entered the vestibule, and a few moments later were out on the vessel’s deck.
They clambered down the side and stood upon the pavement of the sunken city.
It was a strange sensation.
Probably no other men living could boast of the same experience. Down the street of the sunken city they walked.
It required Wade some little time to get used to the pressure, he being inexperienced.