here spurted a broad beam of
dead black. There was a searing flash of blue-white flame as the black
beam struck the cliff face. There followed a brief second during which
the rock melted into nothingness in the heart of that area of blue
radiance. Then the stabbing beam bored steadily on back into the cliff
like the flame of a blow torch melting a way through a block of butter.

Layroh adjusted the nozzles until the black beam was a solid shaft of
opacity seven feet in height and nearly five in width. The hole in the
cliff became a tunnel from which blue radiance surged outward in a
shimmering mist as the black beam steadily bit deeper into the rock.

* * * * *

"Follow me," Layroh ordered the men, "but do not approach too close."

He stepped forward and entered the mouth of the tunnel. Shaken by the
spectacular thing occurring before their eyes, yet, driven by curiosity
as to what might lie at the end of that swift-forming tunnel, the men
came crowding obediently after him. A moment later they were within the
passage, stumbling dazedly forward through the billowing fog of bluish
radiance. There was an odd, almost electric, tingle of exhilaration in
that radiant mist as it surged about their bodies.

Fragments of almost-forgotten scientific lore flitted through Foster's
brain as he groped for a clue to the action of the strange ray. Not
quite complete disintegration of matter, but something very close to
it--probably the transformation of matter into radiant energy, an
ingenious harnessing of the same forces that are forever at work in the
cosmic crucibles of the universe's myriad suns.

The action of the black ray was amazingly rapid. They were forced to
hurry forward at a fast walk to keep their distance behind Layroh. The
vertical stratum of lighter-colored rock continued straight back into
the heart of the mountain. It apparently served as a guide. The color of
the blue flame-mist changed perceptibly whenever Layroh allowed the
black ray to stray into the rock at either side of it.

* * * * *

For nearly two hundred yards they bored their way steadily into the
mountain, their path gradually sloping downward. The walls and floor of
the swift-forming tunnel were as smooth and hard as though glazed with a
film of diamond.

Then abruptly Layroh shut the black ray projector off as the rock ahead
of them ended and they broke through into another larger