The little vessel had reached the limit of height to which it was designed to ascend and, upon realizing this, I became aware that, for safety, all aerenoids are limited to a certain height by the amount of repelling metal used in their construction.  The high-speed aerenoids, owing to their build, being better adapted to withstand the atmospheric conditions at a great altitude, can ascend several thousand feet, but all are limited to what is considered a safe height for the class to which they belong.  The action of the repelling metal being independent of the atmosphere, the danger of an aerenoid getting beyond control, and rising above the envelope of air which surrounds the planet is thus eliminated.

As these thoughts came into my mind, I glanced up into the heavens with its countless stars—­one being the world from which I came—­when lo! a remarkable phenomenon met my gaze.  In the west hung a crescent moon, somewhat smaller than Earth’s moon, but extremely brilliant, while out of the east rose another moon at its full.  So rapidly did this latter moon rise, that its journey through the heavens was perceptible, and it was evident that within an hour it would sink into the western horizon, having gradually changed its phase to a crescent.  In seven hours it would encircle Mars, and again appear above the eastern horizon.

My interest in this moon was intensified when I realized that it was but a few thousand miles distant, and so small, that it would require but a couple of days’ comfortable walking to encircle it.  Compared with my journey from Earth, this few thousand miles seemed but an insignificant distance, and I immediately thought of the possibility of reaching it in a high-speed aerenoid to which a sufficient amount of the repelling metal was attached to overcome the gravity of Mars.  But I instantly was aware of the fact that an attempt to reach this moon had been made many years previously, and that the intrepid Martians who undertook the hazardous journey, never returned.  Although their aerenoid carried enough oxygen to supply them for many days after they had left the atmosphere of Mars, it was decided later that they had been lost in space, unable either to reach the moon or return to Mars.  The gravity of so small a body would be insufficient to draw them to it, unless they traveled straight in its direction, and, as the moon was moving rapidly around Mars, the chances of this were admittedly small.  Moreover, once out of the atmosphere of Mars, it would be impossible to propel the aerenoid, and, having missed the moon, they would travel on and on through endless space.  Had they reached the moon they could have returned, as the repelling force on a body with so little gravity, would be greatly increased, and would have hurled them into the gravity of Mars again, as soon as they exposed the repelling metal.  There could be no doubt that they had never reached the moon, and their terrible fate resulted in a safe limitation of this dangerous metal upon all aerenoids.