CHAPTER X
SOME CURIOUS SPECULATIONS
ITH bated breath our three friends watched the instruments in the doctor's office during the last mile of the digging. Car-load after carload of matter was removed; and as the two boring-screws approached each other the sounds made by the New York screw could be distinctly heard through the telephone on the Australian side of the tube.
Finally the two tubes came so close together that the doctor stopped the New York instrument, and continued the work on the Australian side only. The speed of revolution was also gradually slackened, until it seemed to the excited watchers as though the auger were not moving at all; but when it did finally scoop up the last bucketful of matter, and the Australian tube touched the New York tube with a shock that set them both vibrating, the enthusiasm of the spectators was intense.
The doctor had succeeded! He had successfully carried out a piece of engineering work such as had never been dreamed of before, and whose difficulties can be realized only by those who have made a lifelong study of mechanics. This last triumph of making the two tubes meet together in the center of the earth, with a discrepancy well within the margin of error allowed for by the doctor, in itself entitled him to a high rank as a civil engineer.
Of course there had been many minor accidents in the course of his stupendous task; but now that victory had crowned the efforts of the intrepid doctor, he felt amply repaid for all the sleepless nights he had passed. Even James Curtis, skeptical as he was, was forced to acknowledge that the word "impossible" was one which deserved to be stricken from the dictionaries of the twentieth century. As for his daughter Flora, she danced about with delight at the success of the undertaking.
"Well, doctor, when does the first car start?" asked Mr. Curtis, hardly five minutes after the tubes had met in the center of the earth.
"Not for many days yet," laughed the doctor. "The worst of the job is over, I'll admit, but there's still plenty to do. It will be over a week before the last car-loads of matter reach the surface here, and in the mean time I must set about welding the two tubes together in the center."
"H'm!" commented Mr. Curtis, "that will indeed be a delicate job. I suppose you will have to send a gang of workmen down into the tube to attend to that."
"Not on any account," returned Dr. Giles, quickly. "Up to the present moment, as you know, I have not been obliged to send workmen down to any distance below the surface of the earth, and even now this will not be necessary. I purposely prepared the bottoms of the tubes so that I can, when I so desire, weld them together electrically, without any one being obliged to go down into the tube. By merely pressing certain buttons here in my office the proper connections will be made."
"I am glad of that, for the sake of the workmen," said Mr. Curtis; "but in some ways it is a pity that no one will go down into the tube, for it would be quite a novel sensation to be down at the center of the earth, where there is no attraction, and where consequently bodies have no weight."
"Why, father, what do yon mean?" asked Flora. "Would n't bodies weigh anything at all at the center of the earth?"
"Not an ounce," replied her father. "If you were down there, Flora, you would float around like a feather; is n't that so, doctor?"
"Yes," assented Dr. Giles; "there is not the slightest doubt about it."
"Oh, then, doctor, you'll let me go down in the first car, won't you?" cried the young girl, eagerly.
"My cars won't stop at the center of the earth, Flora," replied Dr. Giles. "As I told you, they will go right through to New York."
"Still," said Mr. Curtis, surprised, "I hardly see how that can make any difference. When the car reaches the center of the earth, even if it does n't stop there, the passengers will have no weight, will they?"
"I am not so sure about that," replied Dr. Giles, thoughtfully. "On the contrary, I feel inclined to think that at the center of the earth my passengers will have weight, though not their normal weight, by any means. Instead of being able to float about like a feather, Miss Flora would probably find it nearly as hard to ran about, and would hurt herself almost as much if she tumbled down, as she does here."
"Well, I declare! That passes my comprehension!" exclaimed Mr. Curtis. "Time and again have I heard it said that at the center of the earth there would be no attraction of gravitation whatever. Consequently I can scarcely credit what you say."
"Understand me," said Dr. Giles. "What I say is that if a body were standing still at the center of the earth it would indeed weigh nothing. But the objects that will be in my car will, I am convinced, have a certain amount of weight at the moment when they reach the center of the earth."
"Ah, I see; you mean to say that the car will be moving so fast that the bodies will not remain a single second at the very center of the earth, and consequently the passengers will not have time to feel the effects of the loss of weight."
"No," said Dr. Giles, "that is not where the trouble lies. The difficulty is that I shall not be able to produce a perfect vacuum in the tube. Even with all the appliances I have devised for removing the air, there will still be a small amount left—enough to keep the car from coming to within about a mile of the surface at the New York end of the tube. It is this air which will make all the trouble."
"What in the world has the air in the tube to do with the weight of the passengers in the car?" asked Mr. Curtis, astonished.
"It has everything to do with it," said Dr. Giles. "But that's a subject I do not wish to speak of yet. I myself have no clear idea of how nearly perfect a vacuum I shall be able to produce, and hence my calculations are only the roughest kind of approximations at present."
"Well," said Mr. Curtis, "it will be a great pity if the passengers do not lose their weight. Just imagine, Flora, how you would feel floating around at the center of the earth, like a feather. If you had a tennis-ball in your hand, you could n't throw it anywhere, because the ball would have no weight; and if you brought down your fist with all your might on the most delicate glass vase, you could n't possibly break it, because your hand would have no weight and so would just bounce back."
Dr. Giles laughed heartily. "That's news to me," said he, "I must confess; but then, you know, we all of us learn something new every day. I We studied physics all my life, but it's to-day for the first time that I learn that a body which has no weight cannot be thrown around, or that it cannot break a glass vase if thrown with sufficient force."
Mr. Curtis looked a little sheepish at this burst of sarcasm, but he felt so sure of his position that he replied:
"Why, doctor, the same thing happens here on earth with bodies that have little or no weight. Give a feather to the strongest man alive, and, because it has little or no weight, he will only be able to throw it a few inches, even though he exerts his utmost strength, whereas he could throw a heavy base-ball quite a distance."
"That's true enough," said the doctor.
"Well, now let the same man take that feather and throw it down with all his might against the most delicate glass vase, and yet he won't be able to harm the vase in the least."
"That is also true," said Dr. Giles; "but the reason is not, as you seem to think, because the feather has little or no weight."
"What is it, then?"
"It is because the feather has almost no mass."
"Why, I always thought that mass and weight were the same thing."
"Not a bit of it," said the doctor. "Mass is the amount of matter a body contains. I weigh a hundred and fifty pounds. Put me at the center of the earth, and I would weigh nothing at all; and yet my body would still contain the same amount of matter. My mass would remain unchanged, though my weight would disappear. Consequently, if Miss Flora were at the center of the earth, she would have no trouble in throwing a ball; in fact, she could throw it much farther than she can here. And if she brought her fist down with all her strength on a glass vase, delicate as her fist is, it would shatter that vase into a thousand pieces."
"What a pity it is," said Mr. Curtis, "that your passengers will not be able to stop at the center of the earth. There would be so many curious experiences for them to undergo."
"Their experiences," said Dr. Giles, smiling, "would not be one whit more interesting if they stopped at the center of the earth than they will be as it is. You would be astonished if you knew what curious phenomena are in store for the first man who drops through my tunnel. I have calculated a large number of them, but every day I think of something new. I can tell you this much, though: that from the very moment of the start to the instant when the car arrives in New York, there will be a continuous succession of surprises for my passengers!"