"That's a new kind of diving bell," Tom answered. "You know it isn't easy to get treasure out of a sunken ship. It isn't like picking it off the bottom of the ocean. We've got to get it out from inside—perhaps from inside a strong box or a safe. This bell may come in useful."
"Can't you use the special diving suits that you always used to carry?" the financial manager wanted to know.
"We might, if the water isn't too deep," replied Tom. "But you know there is a limit to how far down a man in even my kind of diving dress can go. With this diving bell a much greater depth can be reached. And this diving bell is not like any you have ever seen or read about. My father gave me the idea for it. I'll demonstrate it to you some day."
A diving bell is shaped like its name. A common glass tumbler thrust down into a pail of water, with the open side down, will show exactly the principle on which a diving bell works. It illustrates the fact that two things cannot occupy the same place at the same time.
Pushing the tumbler, open end down, into the pail of water, leaves a space in the upper end of the tumbler which the water cannot fill, because it is already occupied with air. Imagine a big tumbler, made of thick steel, lowered into the water. Air pumped into the upper part not only keeps the water from entering, but also enables a man inside to breathe and to move about inside the bell which may be lowered to the floor of the ocean. But, as Tom told Ned, his diving bell was a big improvement over those commonly used.
The two young men inspected the progress made in refitting the submarine, and Tom expressed himself as satisfied.
"How soon do you think you can start?" asked Ned.
"In about two weeks," was the answer. "I'll want to get to the West Indies before the fall storms start. Not only will it be impossible to make a search then, but the very location of the sunken wreck may be changed."
"How so?" asked Ned.
"Because of undersea currents. They are strong enough, not only to sweep a wreck away from the place where it may have settled, but they may cover it with sand, and then it is hopeless to try to dig it out. So we've got to go soon, if we go at all."