It was the doctor himself who gave the name Space Fever (now so generally adopted) to the peculiar malady from which he suffered in that long period when weight was very slight or nothing at all. A little reflection on the physiological bearings of the conditions we were passing through, will serve to explain the illness.

For the period of a month, owing to the impossibility of effort, there was scarcely any wasting of our bodily tissues, and very little need for oxydization of the blood. The limbs, which the heart really works hardest to serve, did scarcely any labour and needed very little blood. But the heart had its stubborn habits the same as the other muscles. It is a high-pressure engine, and there is no way of slowing it down materially. It kept up its vigorous pumping and driving just as if the great muscles of the limbs had wasted and needed building up, and just as if it had the task of forcing the blood through those parts of the body usually compressed by its weight or strained by the effort of carrying it. The result was much the same as if your heart now should suddenly begin to beat much too fast, the blood was heated into a state of fever, which naturally increased as we lost weight, culminated at the dead-line and began decreasing as soon as we commenced having a weight toward Mars. It was only my fortunate invention of a method of exercise, and my religious adherence to it, which saved me from a similar attack.

But many things happened before the doctor recovered consciousness. The Moon had re-appeared on the other side of the Earth-spot, the light about us had grown less dazzling than sunlight on Earth, and the temperature had fallen to four degrees. It was perhaps two days after passing the dead-line that, as I was gazing carefully out of the forward window, I saw far to the right of us a large circular patch of faintly redder light in the general curtain of white. Its size quite startled me, for it was rather larger than a full moon, and I had expected Mars to re-appear as a very bright star before we could distinguish any disc with the naked eye. This misapprehension probably arose from the fact that I had thought the dead-line about half way between the two planets, which upon reflection I saw to be impossible, as it must be much nearer the smaller planet.

The outline of the planet was not clearly visible yet, but I could not have missed seeing that red glow long before, had it been more directly in front of us. Evidently we were steering much ahead of the planet, which indicated that we were arriving before opposition. I immediately changed our course so as to go more nearly toward it, but yet to keep a little ahead. Then I hastily brought the telescope back to the forward compartment, which was now the bottom of the projectile. The lenses easily pierced the curtain of light that seemed to be hung in front of the new planet, and I could distinguish the outline of the greatly magnified orb very clearly.

Judging from appearances, it could not be farther from us than twice the distance of the Moon from the Earth. I resorted to the scales at once, and found that weight was beginning slowly to return, for I weighed a little less than an ounce. From a rule the doctor had explained to me, I calculated that this indicated a distance from the planet of about four hundred thousand miles, if it really was Mars. But I had some doubts about its really being that planet; for a clear white, irregular-shaped spot upon it, which I had noticed as soon as the telescope was focussed, did not appear to move at all, as it should have done had it been upon a rotating planet. Upon closer observation, I detected a dull, greenish spot, just coming upon the lower edge. But when I looked again a bright white and perfectly circular spot had appeared in the same place and covered it up. But this new white spot travelled much more rapidly, and soon uncovered the greenish spot, which seemed to move in the same path, but much more slowly. This was something I could not understand. The white circle was too bright and regular to be a cloud, yet if they were both on the surface how could one travel faster over the same path?

Very soon the white circle passed entirely across the greater orb, and then I was surprised to see it detach itself from the planet and remain for a few moments as a separate small orb in the sky! Could this be another freak of refraction? But before I could determine, the little orb disappeared behind the greater disc and was gone. The greenish spot, which I judged to be truly on the surface and caused by an ocean or great sea, was about three times as long in crossing the disc. I next turned my attention to the immovable and irregular white spot, and discovered that its edges seemed to be revolving slowly around its centre. Then it occurred to me that this spot must be located at one of the poles and be caused by polar ice and snows. The doctor had expected such on Mars, and I no longer doubted that this was our objective planet.

It was like a great holiday for me when the doctor regained consciousness. Almost as soon as his fever abated he was well enough to perform his customary duties. His illness had not made him appreciably weak, because as yet scarcely any effort was required to move about. He was quite as anxious to hear all my experiences as I was eager to relate them. I gave him a full account of my struggle passing the dead-line, of my discovery of Mars, and the various spots I had noted.

"From the time it took the greenish spot to cross, I should judge a Martian day to be about fifty hours long," I said.

"Then you must have been very lonely," he replied. "For a Martian day is just forty-one minutes longer than an Earthly day, unless a great number of our scientists have continually made the same mistake in observing him."

"When we arrive, we shall be able to determine the point exactly if our watches commence running again," I answered. "But I think I know one reason why I have misjudged the time. Ever since you have been ill I have slept very little. I have hardly felt the need of rest since I lost my weight. I have been growing more and more wakeful, and I rarely sleep more than an hour at a time. That seems quite sufficient to refresh me."

"As we regain our weight we shall feel the need of sleep again," he said. "But on Mars we may need but one-third as much as we had on Earth, unless we exert ourselves proportionately more."

Then I told him about the circular spot which had seemed to slip off the upper edge of Mars, and asked his explanation of it.

"That must have been Phobos, one of the moons of Mars," he said.

"One of his moons!" I exclaimed; "I didn't know he had any."

"You are an American, and say that!" he answered in surprise. "It is one of the astronomical glories of your people that they discovered the two moons of Mars, during the favourable opposition of 1877."

"This is the first case I remember where we have left it to a foreigner to tell us how great we have been!" I laughed.

"These two moons of Mars also furnish a most interesting example of how fiction may forestall and pre-figure actual scientific discovery. Dr. Swift made Gulliver, in his wonderful travels, discover two moons of Mars, revolving at a speed which he must have thought ridiculously fast. Many years afterward the American telescopes really found two moons, but actually revolving more rapidly than Dr. Swift had dared to boast! If your white circle was really Phobos, you have seen the freak among satellites. She is the smallest, swiftest moon ever discovered, and travels so much more swiftly than the revolution of her primary that she appears to go opposite to everything else in the Martian sky, rising where the Sun sets and crossing the heavens from west to east!"

"What I saw did travel in the same direction as the rotation of the planet, and much more rapidly," I exclaimed.

"Then it was Phobos without a doubt, and she is due to appear again in the west in three hours and fifty minutes after she sets in the east. We must watch closely, for I wish to land upon her and make a flying trip all around Mars with her. Do you realize what a glorious view we shall have of the great planet, sailing around him on this satellite in a period of a little over seven and a half hours, and at a distance of only about four thousand miles? There will be no night, for if one side of the little moon is heavier than the other, the heavier side will always be turned toward Mars. Therefore, when the Sun does not shine on Phobos, Mars will do so, and keep her continually illuminated, except for the brief period of the regular eclipse during each revolution. And one-fourth of the entire heavens, as seen from Phobos, will be filled with the glowing orb of Mars! The great planet will exhibit to us at a near range all the configurations of his surface, his oceans and his clouds. We will survey and photograph him to our hearts' content."

The doctor was justly enthusiastic on this subject, and I felt that such a landing would, in some measure, compensate for my disappointment in not being able to visit the Moon.

As I watched carefully, the satellite finally came into view, but very much more distant from Mars than before. Also, it moved very slowly now, and seemed to grow larger as it approached the disc. I pointed it out to the doctor, and remarked that it was acting quite differently. Just as it entered upon the orb of Mars, another moon, somewhat smaller, mounted hurriedly from the under side of the planet and began hastily ploughing her way over the ruddy disc.

"That last one is the one I saw before, that is my Phobos!" I cried excitedly.

"Then the other slow one is Deimos, the outer moon. She appears the larger to us now, because her greater distance from Mars makes her nearer to us, but she appears to the Martians as the smaller. We must observe closely, and we may discover some new and lesser satellites which Earthly telescopes have never found."

"Time enough for that when we land on Mars," I answered. "If we get in past these two without being hit, I shall be satisfied. You dare not venture in front of that Phobos, and I don't see how you can ever overtake her if you approach from behind."

"That reminds me to slacken speed, for we must be getting very near," he said. "Please weigh yourself every few minutes and note your increasing weight. You should weigh seventy-two pounds on Mars, and eight pounds at the distance of Phobos."

He immediately reversed currents, and when I reported that I weighed almost a pound, it frightened him, and he turned in the full power of the negative currents to overcome our momentum. And it proved that the repelling power of Mars at the distance of 15,000 miles, which this indicated, was not at all strong against the great velocity we had been daily acquiring. I hung upon the scales every few minutes, and reported a steadily increasing weight up to three pounds.

"That shows a distance of eight thousand miles," he figured. "Almost exactly in the orbit of Deimos, but she has safely passed, and will not return for thirty hours. We must turn the rudder hard over to the right, and sail around the planet in a circle until Phobos overtakes us; then, if we approach her travelling in the same direction at almost the same rate of speed, her gravitational attraction will pick us up and draw us safely ashore."

Mars was already an enormous orb ahead of us, and many of his features, such as oceans, ice-caps, and continents, could easily be distinguished; but we paid little attention to them, being occupied with making a safe landing on Phobos, and expecting to make a systematic study of him from there.

"We must not attempt a landing on the outer side of the satellite," the doctor reflected, "for we should have no way of getting around to the inner side to make our observations. We must go within her orbit, and then as she comes past allow her attraction to draw us gently toward her."

We had quickly overtaken and passed Deimos, far within her orbit. I was keeping a close watch for Phobos out of the rear window as we circled about Mars at a distance which we calculated, from my weight on the scales, must be within the path of the satellite. We were circling in the same direction that the great planet was rotating, and yet we passed by things on his surface, which proved that we were travelling faster than his rotation. The doctor noticed, with his telescope, a brilliant snow-capped peak of a great mountain towering up from a small island. The contrast of the snow peak, with the darkish green waters all around it, was the most pronounced thing visible on the great planet, and he decided this must be the white spot detached from the polar ice which our astronomers have frequently observed at about twenty-five degrees south latitude, and to which they have given the name Hall's Island.

"I am afraid we have not appreciated the speed at which we have been travelling," remarked the doctor. "Phobos is very slow in overtaking us;" and he was just beginning to slacken speed still more, when he suddenly cried out,—

"Here she is ahead of us now! We have overtaken her, instead of waiting for her to catch us!"

And, true enough, we were gradually approaching a small brownish mass, feebly illuminated on its outer half by the sun, and more faintly still on its inner half by reflected light from Mars.

And how shall I describe that queer little toy-world which we were gradually overtaking? Imagine, if you can, a little island, less than a third the size of the Isle of Wight, tossed a few thousand miles into space, and circling there rapidly to avoid falling back upon the greater sphere. Imagine that flying island devoid of soil, of trees or vegetation, of water or air, of everything but barren, uncrumbled, homogeneous rock, and you have some idea of the unadorned desolation of Phobos, into which we were slowly sailing, or falling. There was not even the slightest trace of sand or scraps of rock, such as time must have abraded from even the hardest surfaces, but the reason for this soon became apparent.

The doctor feared steering directly against her as we approached, lest we should land with a crash. We had already reached her and were travelling along her inner side. Although we were very near her, she seemed to have very little attraction for us. Then he turned very much closer, but as soon as the influence of the rudder was released, we seemed to leave her instead of falling upon her as we expected. We were still travelling faster than she was, and had we steered directly against her, we would have crashed and bumped against her protuberances. Still there seemed to be no other way to make a landing. In order to estimate the amount of such a shock, the doctor calculated, from the best information he had of her size and a guess at her density, that she would attract the projectile and its entire load with a force of only two pounds. That was not enough to cause any very great shock, and he decided to take chances at once, before we had entirely passed her. He turned the rudder hard over toward the satellite, and we came against her with scarcely any crash, but with a bumping and grating that continued until the rudder was eased back. Then, to our great surprise, we did not remain on the surface, but rose from it and sailed inward towards Mars.

"Something wrong here!" exclaimed the doctor. "She has no attraction for us."

"Well, how do you explain this?" I asked. "You say the whole projectile weighs only two pounds toward Phobos, when, just a short time ago, I weighed nearly eight pounds myself on the scales."

"True enough!" he cried; "the gravity of Mars must be dominant." He began figuring rapidly, and then exclaimed: "We weigh one hundred and thirty pounds toward Mars, and only two pounds toward the satellite. Small wonder that we could not make a landing, with Mars pulling us away sixty-five times harder than Phobos attracted us! But this is very strange! I remember no mention of this in any of the astronomical writings, and it is as easily calculable on Earth as it is here. Moreover, this must cause everything that is loose upon Phobos to fall upon Mars. The great planet is tugging at everything the satellite has with a force sixty-five times stronger than her own!"

"Now, I am afraid those figures won't do, Doctor," I put in. "For, if what you say is true, what prevents the whole satellite from tumbling into Mars at once?"

"She would do so were it not for centrifugal force. The speed with which she whirls around the planet must just balance the force with which he attracts her, and thus she is kept in her orbit. But stones and loose things on this side of her centre are attracted more strongly by Mars than they are repelled by the whirling, so they must all have fallen to the planet. That is why the surface was perfectly barren. If Phobos always keeps the same side turned toward Mars, there may be rocks and soil on the outer side, and we could land there with a positive current; but we could not see the great planet, as I had hoped."

"I have had quite enough of this moon-chasing," I said; "let us be off for the large game at once!" and the doctor agreeing, we turned directly toward Mars.