"How long will you keep at it before you give up?" asked Ned one evening, as they went aloft to replenish the air tanks and charge the batteries.
"Oh, another week, anyhow. I have a new theory, Ned."
"What's that?"
"Ocean currents. I believe there are powerful currents in these waters, and that they may have shifted the position of the Pandora considerably. I'm going to study the currents."
"Good idea!" cried his chum.
And the next day they began observations which were destined to have surprising results.
CHAPTER XXIII
AN UNDERSEA COLLISION
Under the warm, tropical sun the submarine floated idly on the surface of the calm sea. She had risen from the depths, her hatches had been opened, and now the crew, the owner, and his guests were breathing free air. The men were taking advantage of the period above water to wash out some of their garments, hanging them on improvised lines stretched along the deck. For Tom Swift had said he would remain above the surface all day.