ing of extreme importance,
and as he visualized to Eva the helplessness of a deep-sea diver, his
air-line cut, struggling in vain to release himself and rise to the
surface, he began to win her over.

At the moment when Quentin and Eva were in the library, Zita was taking
advantage and was ransacking Locke's laboratory, not with any definite
purpose in mind, but searching in every nook for some clue which might
tell her what he was about.

The speed with which she worked was extraordinary. Yet, before she moved
an instrument, a retort, a book, its position was minutely studied, so
that she could restore it to its former place without any one suspecting
that it had ever been moved.

It was while she was thus occupied that her eye fell upon an instrument
which aroused in her an excited interest. It was very like the headpiece
used by operators of telephones, and she hastened to adjust it. In a
moment it was as though she were in the library. She could hear Locke's
earnest laugh and in it Zita could detect an undercurrent of tenderness.
Her lips compressed and her eyes hardened as she listened. Locke was
speaking about a letter and it seemed to be something important. Zita
was all ears.

But Locke's next words which she heard were his decision to test the
diving-suit, and as she listened she became tense, for this information
she knew was important. The continued note of tenderness in Locke's
voice more infuriated Zita. She removed the headpiece of the dictagraph,
slammed it back into the desk drawer from which she had taken it, and
hurried out.

In the library, Locke, having persuaded Eva, left her and went down into
the Graveyard of Genius, where he touched the secret spring and the
massive door flew open. He entered the gloomy place and went at once to
the shelf upon which lay the self-liberating diving-suit. He took the
suit down and examined its every detail minutely. As he did so he became
more and more enthusiastic and he could find no fault with any of its
features.

"It's entirely practical," he exclaimed to himself. "I'm going to try it
to-day."

He closed the great door and remounted the stairs, carrying the suit
with him. But had he noticed the fiery eyes that had watched him through
the secret rock door of the cavern he would not have been so eager to
try the test he had in mind.

By this time Eva had called her car, and together Locke and Eva drove to
the near-by cove, where there was a little laun