"As long as we don't fall into the sun and get burned up we'll be all right," went on Jack. "And when we get to Mars I know what I'm going to do." "What?" "Go for a sail on one of the big canals. Mars is covered with them, astronomers say." "Maybe the Martians won't let you." "Maybe not. I wish we could start to-morrow." "Well, we can't. The Annihilator isn't near done. We will be at her for two weeks yet." The boys were busy for some time fitting up the living-room. They were in the midst of this occupation, and were conversing about the strange experiences in store for them, when Jack was startled by hearing a strange voice say: "Say, don't you want some help building this airship?" He looked up, to see a man standing near one of the entrances to the projectile--an entrance that would be closed when the Annihilator was finished. The man was a stranger, and from his appearance Jack judged that he was a mechanic. "How'd you get in here?" asked Mark, for he knew it was against the rules for any stranger to enter the machine shop, much less approach the projectile. "I walked," replied the man. "I saw the door open, and I heard hammering going on in here. I knew it was a machine shop, and as I'm a first class machinist, out of work, I thought I'd apply for the job." "How'd you get past the doorkeeper?" inquired Jack, for he knew that Andy Sudds was supposed to be on guard with his gun. "He wasn't at the door," went on the man. "There was nobody there, so I walked in. Can't you give me a job on the airship?" "How do you know it's an airship?" asked Jack. "Oh, I know. I know lots of things," and the man winked one eye at the lad. "I built a balloon once." "Did you?" asked Mark. He began to think perhaps the man might be able to aid them. "Sure I did. I know about airships. I'll work for low wages, and I'll keep my mouth closed. Oh, I know what patents mean. Say," he went on in a whisper, "you'd be surprised to know where I went in my balloon. I'll tell you," and he looked around as if to make sure no one was listening. "Where did you go?" asked Jack. "Up to the moon," was the surprising reply. "And, say, it's all a mistake about it being made of green cheese. It's green apples--that's what it's made of. I know, for I was there, and I ate some. They gave me an awful pain in my head, too," and the man passed his hand across his brow. "A fearful pain," he went on. Jack and Mark looked at each other. They did not understand the man's strange talk and actions. "You don't believe me, do you?" the stranger asked. "Well, if you want a good machinist, hire me. I know all about airships and traveling through space. Why, I once did a dance on the tail of a comet, only the comet got mad and shook me off. I'll show you how I danced."