far-away barking of a coyote that answered the mysterious challenges of the
night. Joanne was close to the rock. Quietly the men who had been working
on the battery drew back.

"It is ready!" said one.

"Wait!" said Blackton, as his wife went to speak, "Listen!"

For five minutes there was silence. Then out of the night a single
megaphone cried the word:

"_Fire!_"

"All is clear," said the engineer, with a deep breath. "All you have to do,
Miss Gray, is to move that little lever from the side on which it now rests
to the opposite side. Are you ready?"

In the darkness Joanne's left hand had sought John's. It clung to his
tightly. He could feel a little shiver run through her.

"Yes," she whispered.

"Then--if you please--press the button!"

Slowly Joanne's right hand crept out, while the fingers of her left clung
tighter to Aldous. She touched the button--thrust it over. A little cry
that fell from between her tense lips told them she had done the work, and
a silence like that of death fell on those who waited.

A half a minute--perhaps three quarters--and a shiver ran under their feet,
but there was no sound; and then a black pall, darker than the night,
seemed to rise up out of the mountain, and with that, a second later, came
the explosion. There was a rumbling and a jarring, as if the earth were
convulsed under foot; volumes of dense black smoke shot upward, and in
another instant these rolling, twisting volumes of black became lurid, and
an explosion like that of a thousand great guns rent the air. As fast as
the eye could follow sheets of flame shot up out of the sea of smoke,
climbing higher and higher, in lightning flashes, until the lurid tongues
licked the air a quarter of a mile above the startled wilderness. Explosion
followed explosion, some of them coming in hollow, reverberating booms,
others sounding as if in midair. Unseen by the watchers, the heavens were
filled with hurtling rocks; solid masses of granite ten feet square were
thrown a hundred feet away; rocks weighing a ton were hurled still farther,
as if they were no more than stones flung by the hands of a giant; chunks
that would have crashed from the roof to the basement of a skyscraper
dropped a third of a mile away. For three minutes the frightful convulsions
continued, and the tongues of flame leaped into the night. Then the lurid
lights died out, shorter and shorter grew the sullen flashes, and then
again fell--silence!

During