Chapter XVIII. A Separation

"Mr. Hardley," began Tom calmly, as he took a seat in the main cabin, "when we started this search I told you that hunting for something on the bottom of the sea was not like locating a building at the intersection of two streets."

"Well, what if you did?" snapped the gold-seeker. "You're supposed to do the navigating, not I! You said if I gave you the latitude and longitude, down to seconds, as well as degrees and minutes, which I have done, that you could bring your submarine to that exact point."

"I said that, and I have done it," declared Tom. "When we computed our position the other day we were at the exact location you gave me as being the spot where the Pandora foundered."

"Then why isn't she here?" demanded the unpleasant adventurer. "We went down to the bottom at the exact spot, and we've been cruising around it ever since, but there isn't a sign of the wreck. Why is it?"

"I'm trying to explain," replied Tom, endeavoring to keep his temper. "As I said, finding a place on the open sea is not like going to the intersection of two streets. There everything is in plain sight. But here our vision is limited, even with my big searchlight. And being a few feet out of the way, as one is bound to be in making nautical calculations, makes a lot of difference. We may have been close to the wreck, but may have missed it by a few yards."

"Then what's to be done?" asked Mr. Hardley.

"Keep on searching," Tom answered. "We have plenty of food and supplies. I came out equipped for a long voyage, and I'm not discouraged yet. Another thing. The ship may have moved on several fathoms, or even a mile or two, after her last position was taken before she went down. In that case she'd be all the harder to find. And even granting that she sank where you think she did, the ocean currents since then may have shifted her. Or she may be covered by sand."

"Covered by sand!" exclaimed the gold-seeker.

"Yes," replied Tom. "The bottom of the ocean is always changing and shifting. Storms produce changes in currents, and currents wash the sand on the bottom in different directions. So that a wreck which may have been exposed at one time may be covered a day or so later. We'll have to keep on searching. I'm not ready to give up."

"Maybe not. But I am!" snapped out Mr. Hardley.

"What do you mean?" asked the young inventor.

"Just what I said," was the quick answer. "I'm not going to stay down here, cruising about without knowing where I'm going. It looks to me as if you were hunting for a needle in a haystack."

"That's just about what we are doing," and Tom tried to speak good-naturedly.

"Then do you know what I