"Because I was sure I closed and locked it from the inside early this morning," was the answer. "Washington, did you open it when you put your rooster in there?" "No, sah. I went in de inside way. I didn't tetch it." "That's very strange," murmured Mr. Roumann, as he locked the port, and each one, in turn, had denied meddling with it. "I was sure I locked it." The matter appeared to give him a little uneasiness, but, as he had much to do to get the projectile ready for the flight, he had to leave the solution of the matter until another time. The great doors of the machine shed were thrown open. They were designed to allow such large bodies as airships to pass out, as Professor Henderson had, in years previous, constructed a number of aeroplanes and dirigible balloons. So there would be no trouble in speeding the projectile directly out of the shop. The great question, now that all was finished, was whether or not the projectile would move, and in the manner and with the speed necessary to get to Mars. There had been no chance for a trial flight, and it all depended on whether or not Mr. Roumann had correctly estimated the powers of his motors. He was sure he was right, and, from calculations made, Professor Henderson was also positive. But it yet remained to prove this. "Well, we may as well get in," said Mr. Roumann at length. "Everything is done that can be done. The next thing is to start the motors, and--then we'll see what happens." It was a nervous moment. Once they were in, side the great projectile, sealed up, would they ever be able to emerge again? It was a momentous question. "Well, here goes!" exclaimed Jack with a jerky laugh as he stepped into the Annihilator. "I'm with You," added Mark as he followed his chum. "Come on, Washington!" cried Jack from within. "Wait till I take one mo' look at terra cotta!" said the colored man. "You mean terra firma, I guess," spoke the professor. "Yes, sah. Dat's hit. Terra flirma--de earth. I wants t' bid it good-by." Andy Sudds, still carrying his gun, went in next. Then followed Amos Henderson, and finally the German scientist. The latter clamped fast the cover of the opening by which they had entered. The interior of the Annihilator was brilliant with electric lights. Mr. Roumann made his way to the pilot house, to see that all the levers and wheels that controlled the engines were in working order. Then he went to the engine-room, where he adjusted the two motors. "Well," he said a bit nervously, "we are all ready to start." "Let her go!" cried Jack gaily. There was no crowd on hand to see them off. Professor Henderson's relative was the only spectator. Mr. Roumann and Mr. Henderson went to pilot house again. They held a brief consultation. "Come here, boys, if you want to see us start the motors going," called the professor.