The tremble of enthusiasm was in his voice as he went on, pointing with his long arm:  “Think of it!  We’re spending a hundred thousand dollars going through that rock that people who travel on the Grand Trunk Pacific in the future will be saved seven minutes in their journey from coast to coast!  We’re spending a hundred thousand there, and millions along the line, that we may have the smoothest roadbed in the world when we’re done, and the quickest route from sea to sea.  It looks like waste, but it isn’t.  It’s science!  It’s the fight of competition!  It’s the determination behind the forces—­the determination to make this road the greatest road in the world!  Listen!”

The gloom was thickening swiftly.  The black mountain was fading slowly away, and up out of that gloom came now ghostly and far-reaching voices of men booming faintly through giant megaphones.

“Clear away!  Clear away!  Clear away!” they said, and the valley and the mountain-sides caught up the echoes, until it seemed that a hundred voices were crying out the warning.  Then fell a strange and weird silence, and the echoes faded away like the voices of dying men, and all was still save the 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