Through the Earth/Chapter XXIII
IN WHICH OUR HERO INVENTS A NEW KIND OF SWIMMING
ILLIAM was right in his surmise. The presence of air in the car afforded him a point of resistance against which he could act, and he would therefore be able to reach the side of the car without resorting to any heroic measures such as he had been considering. Had there been no air in the car, however, the only possible way for him to have reached the floor, ceiling, or walls would have been some method similar to that suggested.
Our hero's first idea was naturally to reach the floor. He accordingly turned himself head downward, and proceeded literally to swim toward the bottom of the car. But William had failed to consider, in his calculations, how slight the resistance offered by the air really is; and after making a dozen lusty strokes without appreciably advancing, he was ready to give up the undertaking in despair.
"Whew!" said he, panting, "if I can't get on any faster than this, with all my exertions, I sha'n't reach the floor in a year. Why, in swimming through water I M go ten times as fast! It seems to me that it ought to be just the contrary, and that, as air offers a much slighter resistance to my progress than water would, I ought to go faster here."
In speaking thus our hero did not take into account the fact that, although the resistance to his progress was much less, the force of impulse was correspondingly decreased. Consequently, since his advance was due to the difference between the propelling force and the resistance to his progress, the denser the medium in which he traveled, the quicker he would go, so long as the medium remained mobile. Hence he could swim through water very much faster than through air.
Another very peculiar fact which our hero noticed was that, in making these swimming motions, the speed of all his movements was greatly increased. The same fact had struck him on attempting to hit the fly. For example, even when he tried to raise his hand very slowly, it would be shot violently upward, while when he moved it normally it would travel with lightning speed. So, in his swimming movements, although he meant his strokes to be very slow and deliberate, yet his arms fairly flew through the air.
Our hero was very much puzzled at first for an explanation of this singular phenomenon; but at last it struck him that the reason his motions were so much more violent than on the earth was that, while his muscular force remained unchanged, this force produced greater effects, since his limbs now possessed no weight.
When he moved his limbs on the earth a great portion of his muscular force was consumed in overcoming the attraction of gravitation, while here no force whatever was wasted in this way; hence the same exertion would produce very much more rapid movements.
"I understand it now," said William, after considering the matter a little. "We learned at school that a force sufficient to give a weight of one pound an acceleration of one foot per second would, if the same body were placed where it would have no weight, suffice to impart to it an acceleration of thirty-two feet per second. In other words, all motions which I would make on the earth in direct opposition to the attraction of gravitation will, now that I have no weight, be made thirty-two times as fast. Of course all my motions are not of this character, but, on the whole, the average speed of my movements is considerably increased."
So far, so good. But interested though William was in explaining this curious mechanical effect, his present desire was to get to the bottom of the car as soon as possible; and his efforts, in spite of the violence of his movements, carried him but slowly forward.
"I guess I'll have to give it up!" he exclaimed, at length. "This is too slow work."
So saying, he stopped his exertions for a breathing-spell. But, to his surprise, he saw that, although he had stopped swimming, he was still slowly progressing.
"Sure enough!" he exclaimed joyfully. "I was forgetting that, now that the attraction of gravitation no longer has to be taken into account, any motion I make will continue indefinitely, or at least until it is stopped by the resistance of the air in the car. Consequently, now that I have a start, I need merely fold my arms, and I shall slowly but surely keep on advancing. Moreover, if I want to set to work and swim a little more, each stroke I take will increase my speed, so that by keeping on I could finally get up a speed of over a mile a minute."
It is safe to say that William could never have succeeded in obtaining so great a rapidity as this, since the resistance of the air would increase as the square of his velocity. Still, he could have obtained a high rate of speed had he had sufficient space to swim in. As it was, however, he was fast approaching the bottom of the car.
It was most amusing to find that when he stopped his exertions he still continued progressing at the same rate, while whenever he took a few strokes his speed increased and continued at the new rate. Finally he reached the lower part of the car, and catching hold of one of the handles on the lounge, he pulled himself down.
"This is hot work," said he, as he let go of the handle and remained lying about ten inches above the sofa. "It's hot work, but it's glorious fun! I wonder if I'll be able to swim up again. Of course, in going up, I shall have to work my way against the attraction of gravitation, and that will make it much harder for me to swim up than it was to swim down. I am really like a fish in a basket that is floating down a river. So long as the fish remains perfectly still he won't get any nearer the ends of the basket; but if he wants to swim, he will find it easier to swim down with the current to the lower end of the basket than to swim against the current to the upper end."
William's simile of the fish in the basket was perfectly correct, but there was a serious flaw in his conclusions as to what would happen in the given case, and this error was the cause of his meeting with a new experience, which might have turned out rather unpleasantly.
"It can't make very much difference, anyway," thought William; "for even if I find it too hard to swim up, I can turn around and swim down again. I shall, however, give myself a good start by jumping up from the floor with all my might, and will thus have less distance to swim."
With these words, our hero, bracing himself by the handles at the bottom of the car in order to get a good start, put down his feet against the floor, and gave himself a strong upward push.
The result of this simple action was a positive and very disagreeable surprise. Never in the world would he have imagined that such an every-day act as jumping could produce such wonderful results as it did here in the car!