"Well, I shall try the Cardite motor to-morrow," announced Professor Roumann one night, after a hard day's work on the projectile. "Do you think it will work?" asked Mr. Henderson. "I think so, yes. My experiments have made me hopeful." "And if it does work, when can we start?" asked Jack. "Two days later; that is, if everything else is in readiness, the food and other, supplies on board." "They are all ready to be stowed away," said Andy Sudds, who had been hunting all day. It was an anxious assemblage that gathered inside the big shed the next day, to watch Professor Roumann try the Cardite motor. Would it work as well as had the Etherium one? Would it send them along through space at enormous speed? True, they would not have to travel so far, nor so fast, but more power would be needed, since, as it was feared no food, water, nor air could be had on the moon, many more supplies were to be taken along than on the trip to Mars, and this made the projectile heavier. "We will test the Cardite in this small motor first," said Mr. Roumann, as he pointed to a machine in the projectile used for winding a cable around a windlass when there was necessity for hauling the _Annihilator_ about, without sending it into the air. Into the receptacle of the motor, the German professor placed some of the wonderful red substance he had secured from Mars. Then he closed the heavy metal box that held it, and, looking about to see if all was in readiness, he motioned to those watching him that he was about to shift the lever that would start the motor. "If it works as well as I hope it will," he said, "it ought to pull the projectile slowly across the shop--a task that would be impossible in a motor of this size, if operated by electricity, gasoline, or any other force at present in use. And, if this small motor will do that, I know the large ones will send us through space to the moon. All ready, now." Slowly the professor shoved over the lever, while Jack, Mark and the others watched him carefully. They were standing back of him, in the engine room of the projectile. There was a clicking sound as the lever snapped into place. This was succeeded by a buzzing hum, as the motor began to absorb the great power from the red substance, which was not unlike radium in its action. There was a trembling to the great projectile. "She's moving!" cried Jack. Hardly had he spoken when there was a flash of red fire, a sound as of a bursting bomb, and everyone was knocked from his feet, over backward, while Professor Roumann was hurled the entire length of the engine room. "The Cardite motor has exploded!" cried Mark. "Professor Roumann is killed!" CHAPTER V THE WORK OF AN ENEMY