“Then crawl in, and go to sleep,” advised the new guard, as he watched Ethan trying to smother a huge yawn.

“Guess I will, because it’s quite some time to daylight, and there’s little use for a pair of us to stand sentry duty.”

So Ethan vanished inside the shack, and Phil was left to insure their safety, as the brilliant heavenly bodies kept up their steady western march, and the night breeze sang mysterious chants through the snow-covered branches of the firs.

[CHAPTER XII—LAYING PLANS]

“Is that the way you keep a promise, Phil?” asked X-Ray, reproachfully, as he came crawling out of the shack, to find it beginning to get daylight, and with the sentry busying himself before a cheery fire, where he meant evidently to forestall Lub in starting breakfast.

“Oh! the joke is on you, that’s all,” laughed Phil.

“I don’t see how,” complained X-Ray, who really felt hurt in that he had not been allowed to stand his share of the night watch after being told he might.

“You’ll have to learn to figure better, that’s all, my boy,” the other told him.

“Figure; how’s that, Phil?”

“Well, learn to judge distances that are millions of miles away, to be more definite. Look over there to the west; see that star just going down? Well, that’s the one you told me would set in two hours after Jupiter disappeared. I’ve been watching it right along, and somehow it just refused to vanish. There, I believe it’s just dropped out of sight. If you were asleep, X-Ray, I’d think it my duty to go and get you on deck, because I promised I would.”