CHAPTER XXIV
THE DANGERS OF JUMPING
HE effect of William's attempt to jump upward was, as we have said, a positive surprise to him. He had fully expected that the act jumping upward would bring the attraction of gravitation into play again, or, more properly speaking, that to rise in the car he would be obliged to overcome the earth's attractive force. He consequently calculated to be able to jump no farther in the car than he would have been able to spring from the surface of the earth; that is to say, he expected to rise two or three feet, and to be then obliged to swim up the rest of the way to the top of the car.
But he was mistaken in believing that his upward progress would be checked by the attraction of gravitation. As the bodies in the car were falling with exactly the same speed as the car itself, they no longer possessed any weight, and it was consequently just as easy to move a body upward as downward, or to one side of the car. The result of William's jump was accordingly to carry him up toward the ceiling with great rapidity; but, owing to his bent position at the start, instead of going straight up, he found himself turning a series of somersaults as he rose in the air.
In vain he tried to stop himself. The impetus he had acquired was too great, and up he went, spinning like a top. Fortunately, the trip was not long, and he soon reached the ceiling. But, to his surprise, instead of stopping there, he struck against the cushions, and then bounced back toward the floor again, still spinning quite rapidly.
Poor William was highly alarmed at this completely unexpected turn of affairs.
"Good heavens!" he exclaimed; "it looks as if I was going to keep on bouncing up and down, and spinning round and round, until I am stopped by the resistance of the air and the elasticity of the cushions! This will never do, because I already begin to feel terribly dizzy."
How matters would have ended it is impossible to say, had not our hero made one supreme effort, and managed to grasp the back of the lounge, thus stopping himself, though with no little difficulty.
"Gracious!" said he, as he pressed his hand to his throbbing temples; "it's lucky I managed to catch hold of that lounge, or I should surely have had an apoplectic stroke, with all that blood running to my head as I spun round."
The blood had, in fact, been unduly forced to his head by centrifugal force as he whirled around, and the problem now arose, how to get this, blood down into his feet again. Surely there must be some way in which this could be effected, and yet William was obliged to puzzle over the problem some little time before a solution occurred to him.
"I have it!" he exclaimed, at last. "The only way I see to get back the blood into my feet is to stand on my head! It does seem a curious remedy; but everything is so different here from what it is on the earth that in order to get the blood down into my feet I shall now be obliged to stand head downward, whereas, on the earth, to stand in this position would have just the opposite effect." 
"UP HE WENT, SPINNING LIKE A TOP."
"The thing is this," said he. "As I am falling faster and faster every second, there is every instant a slight shock which tends to throw my blood upward."
He was, of course, referring to the well-known sensation that a man going down on a very rapid elevator experiences when the elevator starts, a peculiar disturbance in the pit of the stomach—the well-known sensation of falling. The reason is that the body of the man falls a small fraction of a second before his internal organs, and these consequently seem to rise up in his abdomen.
"Here in the car," continued our hero, "as my velocity increases every instant, I must feel the same kind of a shock continuously when I am upright in the air; but when, on the contrary, I turn head downward, the shocks will be in the direction of my feet, and will therefore tend to send the blood slowly away from my head. Besides, Dr. Giles recommended an upside-down position; and the farther I go, the more I see that he knew what he was about when he put up those signs on the walls."
It seemed as though William had hit upon the true solution; but unfortunately, things are not always what they seem, especially not in our hero's case, and William's explanation, plausible though it was, was incorrect. This he soon discovered; for although he turned himself head downward for a short time, he found that this position did not relieve him in the least.
The real explanation of the matter was probably that William's internal organs were under the same conditions in his body as he himself was in the car; in other words, they tended to remain stationary at whatever point they might be. Hence whether he stood upright or head downward made no difference; even his blood would have no tendency to run more in one direction than in another. No matter how he placed himself, the flow of blood to his head would be somewhat more than normal, because gravitation no longer pulled it down into his feet as it did on the earth. In a word, his head received as much blood now as it would ordinarily upon the earth if he were lying perfectly flat.
William's surprise at not feeling in any way the increase in his velocity would have disappeared had he remembered that the earth, in its course around the sun, travels very much faster during the winter than during the summer. Yet although this increase of speed occurs every year at about the same date, no one feels any unpleasant effects from it, or even notices it.
After vainly trying to solve this puzzle, William was obliged to give it up; but it reminded him that Mr. Curtis had asked him to try two experiments during his trip.
"He told me," said William, "that as soon as bodies in the car lost their weight he would like me to try to throw something from one side of the car to the other. He claimed that I should n't be able to throw an object a single inch.
"He said that up on the earth a very light object, such as a feather, cannot be thrown far, even by a very strong man; and the lighter the body, the less distance it can be thrown. Consequently, if a body had no weight at all, he claimed, it could n't be thrown any distance. He told me that if I tried to throw a ball or any other object, no matter how hard I tried, the ball would stick to my hand as if it were glued there, and that I should n't be able to get rid of it.
"I noticed that Dr. Giles laughed, but he too told me that I ought to try the experiment; so, as I've got my jack-knife in my pocket, I'll have a try with that."
Our hero accordingly took his knife from his pocket, and, steadying himself by the handle of the lounge, he threw his cherished four-blader with all his force toward the top of the car.