"So am I," said Mark, "but let's not think of it." All that day they wandered on, crossing the rugged mountains, climbing towering peaks, and descending into deep valleys. At times they skirted the lips of craters, to look shudderingly into the depths of which made them dizzy, for the bottoms were lost to sight in the black gloom that enshrouded the yawning holes. Their food was getting less and less, and what there was of it was most unpalatable, for the bread was stale and dry, though the meat kept perfectly in that freezing temperature. How they longed for a hot cup of coffee, such as Washington used to make! and how they would have even exchanged their chance of filling their pockets with the moon diamonds for a good meal, such as was so often served in the projectile! On and on they went. Once, as they were crossing the lip of a great crater, Mark became dizzy, and would have fallen had not Jack caught him. Mark had forgotten, for the moment, and had lowered his life-torch, so that his mouth and nose were not enclosed in the film of vapor that emanated from the perforated box. "You must be careful," Andy warned them. "What's the use?" asked Mark despondently. "I don't believe we'll ever find the projectile." "Of course we will!" exclaimed Jack. "I know we can't be far from it, only we can't see it because of the mountains. If we only had some way of letting them know where we are, they could signal to us." "By gum!" suddenly exclaimed Andy. "What's the matter?" asked Jack, for the old hunter was capering about like a boy. "Matter? Why, the matter is that I'm a double-barrelled dunce," was the answer. "Look here; do you see that?" and he held up his rifle. "Sure," replied Jack, wondering if their sufferings and worry had made the old hunter simple-minded. "What is it?" asked Andy, shaking it in the air. "Your rifle," answered Mark, looking at Jack in surprise. "Of course," answered the hunter, "and a rifle is made to be fired off, and here I've been carrying mine for nearly three days now, and I haven't shot it once. You wanted a signal to make the folks in the projectile hear us. Well, here it is I I guess they can hear this, and when they do they can come and get us, for we don't seem able to reach them. I'll just fire some signal shots." "That's the stuff!" cried Jack, and Andy proceeded to discharge his rifle. The report the gun made in that quiet place was tremendous, and the effect was curious, for, there being no air in the ordinary acceptance of the word, there was no echo. It was as if one had hit two shingles together. Merely a loud, sharp sound, and then an utter silence, the vibrations being swallowed up instantly. "Do you think they can hear that?" asked Andy.