Both Larry and Dick grumbled a little at this sort of war-like messing-up of their vacation when, as a matter of fact, it was, or ought to be, utterly needless. But they agreed to Purdick’s plan in the end as being the really sensible thing to do, and shortly afterward they turned in and left the small one sitting with his back to a tree and his rifle across his knees, determined to stay awake if the thing were humanly possible.
For an hour or more he found it entirely possible. Apart from the deep breathing of his two sleeping companions and the nibbling noises made by the grazing burros, there were no sounds to disturb the solemn silence of the immensities. Having to study pretty hard for what he was getting in college, Purdick had a pretty safe recipe for keeping awake. It took the form of memory exercises; the recalling, word for word, of certain formulas like this: “If the point of suspension of a pendulum have an imposed simple vibration of y equals a cosine st in a horizontal line, the equation of small motion of the bob is mx equals minus mg times x minus y; over l”—things like that.
Just now, being intensely interested in the science of mineralogy, he was repeating the names of all the “ites” he could remember by their different groups, with the chemical composition of each; and he had just got as far as, “Pyrargyrite: silver three atoms, antimony one atom, sulphur six atoms,” when he sat up and rubbed his eyes and began to wonder if, after all, he had gone to sleep and was dreaming.
For while he stared and stared again, the camp-fire, with its back-log and bed of glowing coals, began to sink slowly into the ground, the unburnt ends of the back-log uprearing as the fire sank away. Before he had time to gasp twice, there was a gurgle and a hiss, and the fire disappeared as if by magic, leaving the tree-shadowed ravine in total darkness.
CHAPTER VIII
THE ICE CAVERN
For a second or so after he had seen the camp-fire disappear as if a conjuror had waved his wand over it, Purdick was too greatly astounded even to yell. Twice he opened his mouth to shout at his two sleeping companions, but no sound came. With his teeth rattling in something that was a good bit like panic, he felt his way over to where Dick and Larry were lying rolled in their blankets and shook them awake.
“Wake up! S-s-something’s happened!” he stuttered.
“What is it?” said Dick sleepily, getting up on an elbow. Then: “Hello! What made you let the fire go out?”