for us to visit Mars as representatives of the Space Navy, I see no reason why we cannot tackle this job—well, let us say—unofficially."
"Just what do you have in mind, Captain Brink?"
"What's to prevent us from organizing a free-lance expedition to attempt the rescue of Miss Andersen?" Without waiting for an answer to this question, Brink hurried on: "I would like very much to command such an expedition. From what Ensign Mayer has just said, I take it for granted that he will be willing to accompany me. How about you, Jim?"
Sullivan's bronzed countenance lighted up with joyous anticipation and he said: "You know me, Chief. Whenever there's a chance for solving a mystery and getting into a good scrap, you can always count me in."
"But what will you do for transportation?" Colonel Steiner demanded. "You must realize of course that you would not be permitted to use the Hyperion or any of the other E. R. S. N. flyers. If one of our spaceships—all of which are known to the Martians—were to land on Mars it would give them the excuse they are looking for and they would immediately declare war on the Earth."
"I realize that completely," Brink assured him. "I wasn't planning to use one of the Space Navy ships. Doubtless you already know that for over a year Lieutenant Sullivan and I have been devoting our spare time to the construction of an improved type of spaceship."
Steiner smiled and said: "I have heard something about your off-duty activities of course. As you know, I gave orders that all your requisitions for materials and labor should be honored."
"For which we have been very grateful," Brink thanked him. "Perhaps you do not know that our new ship is now ready. It embodies several unique improvements and added features which are not found in the spaceships of standard design. We have decided to call it the 'Cosmicraft.' Jim and I are itching to try it out. Perhaps this will be a good opportunity to put it through its paces."
"Perhaps," the Colonel half agreed.
"Then you will give your consent?" Brink asked. "You will allow us to go on this free-lance expedition?"
"You realize, do you not, that this expedition as you call it will be the most dangerous mission you have ever undertaken?" Steiner hedged.
"I realize that fully," Brink told him. "And that makes me even more anxious to tackle it. Unless I am deluding myself, I have every reason to believe that Jim and Dan feel the same way about this great adventure. What is your verdict, Sir? May we go?"
"With my blessing," the Colonel acceded.
CHAPTER IV
The Invisible Spaceship
FOR a tense period of sleepless watchfulness—which according to their recording chronometers, corresponded to about five earth-days, the three spacefarers blasted their way through that perilous merry-go-round of cosmic junk known as "the zone of asteroids," which made the region between Jupiter and Mars a nightmare for spaceflyers.
As they neared the end of their three hundred and fifty million mile journey, the course of the Cosmicraft was regulated in such a way that the planet Mars was directly between them and the center of the sun. At
