In Search of a Son

  CHAPTER XII.

  AT THE CENTRE OF THE EARTH.

  Monsieur Roger, hiding his satisfaction, seemed to attach no importanceto this request of Miette under the assent given by Paul. Wishing toprofit by the awakened curiosity of his little friend, he hastened tocontinue, and said,--

  "Who wants to bring me a bit of cork and a glass of water?"

  "I! I!" cried Miette, running.

  When Miette had returned with the articles, Monsieur Roger continued:

  "I told you a moment ago that if balloons and smoke and clouds do notfall, it is because they find themselves in the midst of air which isheavier than they are. I am going to try an experiment which will makeyou understand what I have said."

  Monsieur Roger took the cork, raised his hand above his head, and openedhis fingers: the cork fell.

  "Is it a heavy body?" said he. "Did it fall to the ground?"

  "Yes," cried Paul and Miette together.

  Then Monsieur Roger placed the glass of water in front of him, took thecork, which Miette had picked up, and forced it with his finger to thebottom of the glass; then he withdrew his finger, and the cork mountedup to the surface again.

  "Did you see?" asked Monsieur Roger.

  "Yes," said Miss Miette.

  "You remarked something?"

  "Certainly: the cork would not fall, and you were obliged to force itinto the water with your finger."

  "And not only," continued Monsieur Roger, "it would not fall, as yousay, but it even hastened to rise again as soon as it was freed from thepressure of my finger. We were wrong, then, when we said that this samecork is a heavy body?"

  "Ah, I don't know," said Miette, a little confused.

  "Still, we must know. Did this cork fall just now upon the ground?"

  "Yes."

  "Then it was a heavy body?"

  "Yes."

  "And now that it remains on the surface of the water, that it no longerprecipitates itself towards the earth, it is no longer a heavy body?"

  This time Miette knew not what to answer.

  "Well, be very sure," continued Monsieur Roger, "that it is heavy. If itdoes not fall to the bottom of the water, it is because the water isheavier than it. The water is an obstacle to it. Nevertheless, it isattracted, like all bodies, towards the earth, or, more precisely,towards the centre of the earth."

  "Towards the centre of the earth?" repeated Miette.

  "Yes, towards the centre of the earth. Can Miss Miette procure for metwo pieces of string and two heavy bodies,--for example, small pieces oflead?"

  "String, yes; but where can I get lead?" asked Miette.

  "Look in the box where I keep my fishing-tackle," said Monsieur Dalizeto his daughter, "and find two sinkers there."

  Miette disappeared, and came back in a moment with the articles desired.Monsieur Roger tied the little pieces of lead to the two separatestrings. Then he told Miette to hold the end of one of these strings inher fingers. He himself did the same with the other string. The twostrings from which the sinkers were suspended swayed to and fro for someseconds, and then stopped in a fixed position.

  "Is it not evident," said Monsieur Roger, "that the direction of ourstrings is the same as the direction in which the force which we callweight attracts the bodies of lead? In fact, if you cut the string, thelead would go in that direction. The string which Miss Miette isholding and that which I hold myself seem to us to be parallel,--that isto say, that it seems impossible they should ever meet, however long thedistance which they travel. Well, that is an error. For these twostrings, if left to themselves, would meet exactly at the centre of theearth."

  "Then," said Miette, "if we detach the sinkers, they would fall, andwould join each other exactly at the centre of the earth?"

  "Yes, if they encountered no obstacle; but they would be stopped by theresistance of the ground. They would attempt to force themselvesthrough, and would not succeed."

  "Why?"

  "Why, if the ground which supports us did not resist, we would not be atthis moment chatting quietly here on the surface of the earth; drawn bygravity, we would all be----"

  "At the centre of the earth!" cried Miette.

  "Exactly. And it might very well happen that I would not then be in amood to explain to you the attraction of gravity."

  "Yes, that is very probable," said Miss Miette, philosophically. Thenshe added, "If, instead of letting these bits of lead fall upon theground, we let them fall in water?"

  "Well, they would approach the centre of the earth for the entire depthof the water."

  Miette had mechanically placed the sinker above the glass of water. Shelet it fall into it; the cork still swam above.

  "Why does the lead fall to the bottom of the water, and why does thecork not fall?"

  "Why," said Albert, "because lead is heavier than cork."

  Miette looked at her brother, and then turned her eyes towards MonsieurRoger, as if the explanation given by Albert explained nothing, andfinally she said,--

  "Of course lead is heavier than cork; but why is it heavier?"

  "My child, you want to know a great deal," said Madame Dalize.

  "Ah, mamma, it is not my fault,--it is Paul's, who wants to know, anddoes not like to ask. I am obliged to ask questions in his stead."

  That was true. Paul asked no questions, but he listened with attention,and his eyes seemed to approve the questions asked by his friend Miette.Monsieur Roger had observed with pleasure the conduct of his youngfriend, and it was for him, while he was looking at Miette, the lattercontinued:

  "Tell us, Monsieur Roger, why is lead heavier than cork?"

  "Because its density is greater," answered Monsieur Roger, seriously.

  "Ah!" murmured Miette, disappointed; and, as Monsieur Roger kept silent,she added, "What is density?"

  "It would take a long time to explain."

  "Tell me all the same."

  Monsieur Roger saw at this moment that Paul was beckoning to Miette toinsist.

  "Goodness!" said he, smiling at Paul; "Miss Miette was right just now.It is you that wish me to continue the questions!"