Speeding along with a swiftness unrivalled even by some stars, the projectile was lurching toward a great, black heavenly body. "It's a meteor! An immense meteor!" cried Professor Henderson, "and it's coming right toward us." "Will it hit us?" gasped Mark and Jack together. "I don't know. We must try to avoid it. Boys, notify Professor Roumann at once. We are in grave danger!" CHAPTER XVII TURNING TURTLE Together Mark and Jack leaped for the engine room. Their faces showed the fear they felt. Even before they reached it, they realized that, at the awful speed at which they were travelling, and the fearful velocity of the meteor, there might be a crash in mid-air which would destroy the projectile and end their lives. "I wonder if we can steer clear of it?" gasped Jack. "If it's possible the professor will do it," responded his chum. The next instant they were in the engine room, where Mr. Roumann was bending over the Cardite motor. "Shut off the power!" yelled Jack. "We are going to hit a meteor!" gasped Mark. The German looked up with a startled glance. "Slow down?" he repeated. "It is impossible to slow down at once! We are going ninety miles a second!" He pointed to the speed gauge. "Then there's going to be a fearful collision!" cried Jack, and he blurted out the fact of the nearness of the heavenly wanderer. "So!" exclaimed Professor Roumann. "Dot is bat! ferry bat!" and he lapsed into the broken language that seldom marked his almost perfect English. Then, murmuring something in his own tongue, he leaped away from the motor, calling to the boys: "Slow it down gradually! Keep pulling the speed lever toward you! I will set in motion the repelling apparatus and go to help Professor Henderson steer out of the way. It is our only chance!" Mark and Jack took their places beside the Cardite motor, which was still keeping up a fearful speed, though not so fast as at first. To stop it suddenly would mean that the cessation of strain could not all be diffused at once, and serious damage might result. The only way was to come gradually down to the former speed, and, while Mark kept his eyes on the indicator, Jack pulled the lever toward him, notch by notch. "She's down to seventy-five miles a second," whispered Mark. They were as anxious now to reduce speed as they had been before to increase it. Meanwhile Professor Roumann had set in motion a curious bit of apparatus, designed to repel stray meteors or detached bits of comets. As is well known, bodies floating in space, away from the attraction of gravitation, attract or repel each other as does a magnet or an electrically charged object.