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 those appalling moments, unconscious of the act, Joanne had shrank close to Aldous, so that he felt the soft crush of her hair and the swift movement of her bosom.  Blackton’s voice brought them back to life.

He laughed, and it was the laugh of a man who had looked upon work well done.

“It has done the trick,” he said.  “To-morrow we will come and see.  And I have changed my plans about Coyote Number Twenty-eight.  Hutchins, the superintendent, is passing through in the afternoon, and I want him to see it.”  He spoke now to a man who had come up out of the darkness.  “Gregg, have Twenty-eight ready at four o’clock to-morrow afternoon—­four o’clock—­sharp!”

Then he said: 

“Dust and a bad smell will soon be settling about us.  Come, let’s go home!”

And as they went back to the buckboard wagon through the gloom John Aldous still held Joanne’s hand in his own, and she made no effort to take it from him.

CHAPTER XVIII

The next morning, when Aldous joined the engineer in the dining-room below, he was disappointed to find the breakfast table prepared for two instead of four.  It was evident that Peggy Blackton and Joanne were not going to interrupt their beauty nap on their account.

Blackton saw his friend’s inquiring look, and chuckled.

“Guess we’ll have to get along without ’em this morning, old man.  Lord bless me, did you hear them last night—­after you went to bed?”

“No.”

“You were too far away,” chuckled Blackton again, “I was in the room across the hall from them.  You see, old man, Peggy sometimes gets fairly starved for the right sort of company up here, and last night they didn’t go to bed until after twelve o’clock.  I looked at my watch.  Mebby they were in bed, but I could hear ’em buzzing like two bees, and every little while they’d giggle, and then go on buzzing again.  By George, there wasn’t a break in it!  When one let up the other’d begin, and sometimes I guess they were both going at once.  Consequently, they’re sleeping now.”

When breakfast was finished Blackton looked at his watch.