e heavy hush of the desert night settled down once more after he
left.

* * * * *

As his figure merged with the shadows in the distance, the elderly
scientist murmured aloud to his daughter:

"You know, it's good to realize that my dream is about to become a
reality. If it hadn't been for Phil.... Or no--I really ought to thank
you, Sue. You're the one responsible for his participation!" And he
smiled fondly at the slender girl by his side.

"Phil joined us just for the scientific interest, and for the thrill
of going four miles down into the earth," she retorted at once, in
spite of the blush her father saw on her face. But he did not insist.
Once more he turned, as to a magnet, to the machine that was his
handiwork.

The fifteen-foot sphere was an earth-borer--Guinness's own invention.
In it he had utilized for the first time for boring purposes the newly
developed atomic disintegrators. Many holes equally spaced over the
sphere were the outlets for the dissolving ray--most of them on the
bottom and alternating with them on the bottom and sides were the
outlets of powerful rocket propulsion tubes, which would enable it to
rise easily from the hole it would presently blast into the earth. A
small, tight-fitting door gave entrance to the double-walled interior,
where, in spite of the space taken up by batteries and mechanisms and
an enclosed gyroscope for keeping the borer on an even keel, there was
room for several people.

The earth-borer had been designed not so much for scientific
investigation as the specific purpose of reaching a rich store of
radium ore buried four miles below the Guinness desert camp. Many
geologists and mining engineers knew that the radium was there, for
their instruments had proven it often; but no one up to then knew how
to get to it. David Guinness did--first. The borer had been
constructed in his laboratory in San Francisco, then dismantled and
freighted to the little desert town of Palmdale, from whence Holmes
had brought the parts to their isolated camp by truck. Strict secrecy
had been kept. Rather than risk assistants they had done all the work
themselves.

* * * * *

Fifteen minutes passed by, while the slight figure of the inventor
puttered about the interior of the sphere, brightly lit by a
detachable searchlight, inspecting all mechanisms in preparation for
their descent. Sue stood by the door watching him, n