"No use going any farther," suggested Jack, pulling up at the far side of the bridge. "There are two roads around the bend, and we couldn't tell which one he'd take. Besides, it might not be altogether safe to risk it." Mark and Jack, on their return, told Professor Henderson and the German scientist something of their little excursion. "But who could he have been?" asked Mr. Roumann. "Perhaps if you ask the boy who brought the note he can tell you." "We'll do it in the morning," decided Mark. "It's peculiar that he wanted Mark to meet him," spoke Amos Henderson. "Have you any enemies that you know of, Mark?" "Not a one. But what makes you think this man was an enemy, Professor?" "From the fact that he ran when he saw you and Jack together. Evidently he expected to get Mark out alone." They discussed the matter for some time, and then the boys and the scientists retired to bed, ready to begin active preparations on the morrow, for their trip to the moon. There was much to be done, but their experience in making other wonderful trips, particularly the one to Mars, stood the travellers in good stead. They knew just how to go to work. To Washington was entrusted the task of preparing the food supply, since he was to act as cook. Andy Sudds was instructed to look after the clothing and other supplies, except those of a scientific nature, while the two young men were to act as general helpers to the two professors. As the _Annihilator_ has been fully described in the volume entitled, "Through Space to Mars," there is no need to dwell at any length on the construction of the projectile in which our friends hoped to travel to the moon. Sufficient to say that it was a sort of enclosed airship, capable of travelling through space--that is, air or ether--at enormous speed, that there were contained within it many complicated machines, some for operating the projectile, some for offence or defence against enemies, such as electric guns, apparatus for making air or water, and scores of scientific instruments. The _Annihilator_ was controlled either from the engine room, or from a pilot house forward. As for the motive power it was, for the trip to the moon, to be of that wonderful Martian substance, Cardite, which would operate the motors. The projectile moved through space by the throwing off of waves of energy, similar to wireless vibrations, from large plates of metal, and these plates were the invention of Professor Roumann. Perhaps to some of my readers it may seem strange to speak so casually of a trip to the moon, but it must be remembered that our friends had already accomplished a much more difficult journey, namely, that to Mars. So the moon voyage was not to daunt them.