of this arrangement before Tristan was at comparative peace. Dr. Grosnoff effected an examination by slacking off the ropes until Tristan lay a couple of feet clear of the bed, then himself lay on the mattress face up, prodding the patient over.

The examination concluded, he informed us that Tristan's symptoms were simply those of a general physical shock such as would be expected in the case of a man standing close to the center of an explosion, though from our description of the affair he could not understand how my brother had survived at all. The glimmering of an explanation of this did not come until a long time afterward. So far as physical condition was concerned, Tristan might expect to recover fully in a matter of weeks. Mentally—the doctor was not so sure. The boy had gone through a terrible experience, and one which was still continuing—might continue no one knew how long. We were, said the doctor, up against a trick played by the great Sphinx, Nature, and one which, so far as he knew, had never before taken place in the history of all mankind.

"There is faintly taking shape in my mind," he said, "the beginning of a theory as to how it came about. But it is a theory having many ramifications and involving much in several lines of science, with most of which I am but little acquainted. For the present I have no more to say than that if a theory of causation can be worked out, it will be the first step toward cure. But—it may be the only step. Don't build hopes!"

Looking Alice and me over carefully, he gave us a each a nerve sedative and departed, leaving us with the feeling that here was a man of considerably wider learning than might be expected of a small-town doctor. In point of fact, we learned that this was the case. The specialist has been described as a "man who knows more and more about less and less." In Dr. Grosnoff's mind, the "less and less" outweighed the "more and more."

Tristan grew stronger physically; mentally, he was intelligent enough to help us and himself by keeping his mind as much as possible off his condition, sometimes by sheer force of will. Meantime, Dr. Grosnoff, realizing that his patient could not be kept forever tied in bed, had assisted me in preparing for his permanent care at home. The device was simple; we had just taken his room, remodeled the ceiling as a floor, and fitted it with furniture upside down. Most of the problems involved in this were fairly simple. The matter of a bath rather stumped us for a while, until we hit upon a shower. The jets came up from under Tristan's feet, from the point of view of his perceptions; he told us that one of the strangest of all his experiences was to see the waste water swirl about in the pan over his head, and being sucked up the drain as though drawn by some mysterious magnet.

My brother and I shared a flat alone, so there was no servant problem to deal with. But he was going to need care as well as companionship, and I had to earn my living. For Alice, it was a case where the voice of the heart chimed with that of necessity; and I was best man at perhaps the weirdest marriage ceremony which ever took place on this earth. Held down in bed with the roped sheet, all betraying signs carefully concealed, Tristan was married to Alice by an unsuspecting dominie who took it all for one of those ordinary, though romantic sick-bed affairs.

From the first, Tristan felt better and more secure in his special quarters, and was now able to move about quite freely within his limits; though such were his mental reactions that for his comfort we had to refinish the floor to look like a plaster ceiling, to eliminate as far as possible the upside-down suggestions left in the room, and to keep the windows closely shaded. I soon found that the sight of me, or any one else, walking upside down—to him—was very painful; only in the case of Alice did other considerations remove the unpleasantness.

Little by little the accumulation of experience brought to my mind the full and vivid horror of what the poor lad had suffered and was suffering. Why, when he had looked out of that window into the sky, he was looking down into a bottomless abyss, from which he was sustained only by the frail plaster and planking under his feet! The whole earth, with its trees and buildings, was suspended over his head, seemingly about to fall at any moment with him into the depths; the sun at noon glared upward from the depths of an inferno, lighting from below the somber earth suspended overhead! Thus the warm comfort of the sun, which has cheered the heart of man from time immemorial, now took on an unearthly, unnatural semblance. I learned that he could never quite shake off the feeling that the houses were anchored into the earth, suspended only by the embedment of their foundations in the soil; that trees were suspended from their roots, which groaned with the strain; that soil was held to the bedrock only by its cohesion. He even dreaded lest, during storms, the grip of the muddy soil be loosened, and the fields fall into the blue! It was only when clasped tight in Alice's arms that the horrors wholly left him.

All the reasoning we might use on his mind, or that he himself could bring to bear on it, was useless. We found that the sense of up and down is ineradicably fixed by the balancing apparatus of the body.

Meanwhile, his psychology was undergoing strange alterations; the more I came to appreciate the actual conditions he was living under, the more apparent it seemed to me that he must have a cast-iron mental stamina to maintain sanity at all. But he not only did that; he began to recover normal strength, and to be irked unbearably by his constant confinement. So it came about that he began to venture a little at a time from his room, wandering about on the ceiling of the rest of the house. However, he could not yet look out of windows, but sidled up to them with averted face to draw any blinds that were up.

As he grew increasingly restless, we all felt more and more that the thing could not continue as it was; some way out must be found. We had many a talk with Grosnoff, at last inducing him to speak about the still half-formed theory which he had dimly conceived at the first.

"For a good many decades," he said, "there have been a few who regarded the close analogies between magnetism and gravitational action as symptomatic of a concealed identity between them. Einstein's 'Field Theory' practically proves it on the mathematical side. Now it is obvious that if gravitation is a form of magnetism—and if so it belongs to another plane of magnetic forces than that which we know and use—then the objects on a planet must have the opposite polarity from that of the planet itself. Since the globe is itself a magnet, with a positive and negative pole, its attraction power is not that of a magnet on any plane, because then the human race would be divided into two species, each polarized in the sign opposite to its own pole; when an individual of either race reached the equator, he would become weightless, and when he crossed it, would be repelled into space."

"Lord!" I said. "There would be a plot for one of your scientific fiction writers!"

"I can present you with another," said Dr. Grosnoff. "How do we know whether another planet would have the opposite sign to our own bodies?"

"Well," I chuckled, "they'll find that out soon enough when the first interplanetary expedition tries to land on on of 'em!"

"Hmf!" grunted the medico. "That'll be the least of their troubles!"

"But you said the polarity couldn't be that of a magnet; then what?"

"Don't you remember the common pith ball of your high school physics days? An accumulation of positive electricity repels an accumulation of negative—if indeed we can correctly use 'accumulation' for a negativity—and it is my idea that the earth is the container of a gigantic