A door led out into a vestibule as from the pilot-house and thence to the railed platforms.
Bull’s-eye windows were seven in number on each side of the vessel.
“But how do you make the vessel sink?” asked Harmon.
Frank led the way down in the vessel’s hold.
“Here are the dynamo rooms,” he said. “All the electrical machinery is here. Just aft there are large chambers which we fill with water when we wish to sink, and when we wish to rise the water is expelled in a few seconds by the action of compressed air.”
A few minor points were explained by Frank, and then the inspection ended.
“Wonderful, indeed,” agreed Harmon, as they finally emerged into the yard once more. “I have never seen or heard of its like. It is all ready to launch, I suppose?”
“Perfectly.”
Just back of the building was a deep basin of water, connected with the river by a canal.
Large doors could be thrown open and the Explorer quickly launched upon the waters of the basin.