Why do you hope to lift the wreck when the salvage men could not ?" Cartwright smiled.

"I have been asked this before, but saw no grounds for satisfying the inquirer's curiosity.

All the same, I'll enlighten you." He did so, and Lister looked up sharply.

He had known Cartwright was clever, but the old fellow was cleverer than he thought.

It was possible he had solved a puzzle that had baffled the salvage engineers.