"Hush! Not a word about that!" cried Mr. Roumann warningly. "That must be kept a profound secret!" The next day the boys, Professor Henderson, Washington White, and some trusty machinists began the building of the Annihilator, as the projectile was to be called, because it was to annihilate space. CHAPTER VII AT TERRIFIC SPEED "Now, boys," remarked Mr. Roumann one morning about a week after work had been in progress on the projectile, "I did not mention it, of course, but I hope you will not let it become known in the village that we are constructing a machine in which to proceed to Mars. It would not do to have a lot of curious people out here." "Oh, you needn't worry about that," replied Jack. "We have built several things in the shop here, and no one ever knew about them until we were ready to have them start off." "We'll tell Andy Sudds to keep on guard with his rifle," suggested Mark. "That will prevent curious persons coming too close." "That will be a good idea," declared Mr. Roumann. "You need have no fear of anything being discovered," put in Mr. Henderson, who was busy planning the engine-room of the strange craft. "When we first came here we used to be bothered by curious persons, but I soon found a method of keeping them away." "How was that?" inquired the German. "Why, I ran a wire all around the shop, and charged the conductor with a mild current of electricity. Some people got shocked by coming too close, and after that they gave my place a wide berth. I'll do the same thing now." "A fine idea," commented Mr. Roumann. "But what about Washington White? He is so fond of talking, and using big words, that he may disclose our plans." "No, I can trust Washington," declared the professor. "But, as a further precaution, I have not told him what our object is. All he knows is that we are building a new machine, but he does not know what it is for, nor where we are going." "That's good." "Maybe when he does find out he'll not want to go," added Mark. "Do you intend to take him with us?" asked Mr. Roumann. "I think so--if he'll go," replied Mr. Henderson. "He has always been with me, and he is very helpful on these trips. But I shall not tell him where we are going until we are almost ready to start. But now, Mr. Roumann, I'd like to consult with you about the installation of the motor, or whatever we are to call it, by means of which your secret force is to be used." "A motor will be as good a name as any other. We'll call it the Etherium motor." "What will we call the other one?" asked Jack. "What other one?" "The motive power by which we are to go through the atmosphere of the earth." "Well, we can call that the atmospheric motor," replied Mr. Roumann. "However, there is no hurry about that. I want to get the work in the engine-room under way first."