CHAPTER XV.
DROPS OF RAIN AND HAMMER OF WATER.
"I am very willing to show you that," answered Monsieur Roger; "but Imust have a candle."
Miette ran to the kitchen and succeeded in obtaining that article whichwas once so common, and which is now so rare, known as a candle.Monsieur Roger lit the candle and placed it under the glass globe of theair-pump. Then he asked Paul to make a vacuum. At the end of a fewminutes the candle went out. Monsieur Roger then told Paul to stop.
"Why has the candle gone out?" asked Miette.
"Because it needs air. Master Paul has just exhausted the air necessaryto the combustion of the candle; but the wick still smokes, and we aregoing to see if the smoke which it produces will rise or fall."
Everybody approached the globe, full of curiosity.
"It falls," cried Miette, "the smoke falls."
And in fact, instead of rising in the globe, the smoke lowered slowlyand heavily, and fell upon the glass disk of the air-pump.
"Well," said Monsieur Roger, "you see that I was right. In a vacuumsmoke falls: it falls because it no longer finds itself in the midst ofair which is heavier than it and forms an obstacle to its fall. In thesame way the cloud in the sky above the chateau would fall if we couldexhaust the air which is between it and us."
"I am very glad that we cannot," cried Miette.
"And why are you very glad?" asked Madame Dalize.
"Because, mamma, I don't wish any rain to fall."
"Does Miss Miette think, then," said Monsieur Roger, "that if the cloudfell rain would fall?"
"Certainly," answered Miss Miette, with a certain amount of logic. "Whenthe clouds fall they fall in the form of rain."
"Yes; but supposing that I should exhaust the air which is between thecloud and us, the cloud would not fall in a rain, but in a single andlarge mass of water."
"Why?"
"Clouds, you doubtless know, are masses of vapor from water. Now, whenthese vapors are sufficiently condensed to acquire a certain weight,they can no longer float in the atmosphere, and they fall in the form ofrain. But they fall in rain because they have to traverse the air inorder to fall to the ground. Now, the air offers such a resistance tothis water that it is obliged to separate, to divide itself into smalldrops. If there were no air between the water and the ground, the waterwould not fall in drops of rain, but in a mass, like a solid body; and Iam going to prove that to you, so as to convince Miss Miette."
Among the various instruments unpacked from the box, Monsieur Rogerchose a round tube of glass, closed at one end, tapering, and open atthe other end. He introduced into this tube a certain quantity of waterso as to half fill it. Then he placed the tube above a little alcohollamp, and made the water boil.
"Remark," said he, "how fully and completely the vapors from the water,which are formed by the influence of heat, force out the air which thistube encloses in escaping by the open end of the tube."
When Monsieur Roger judged that there no longer remained any air in thetube, he begged Monsieur Dalize to hand him the blowpipe. MonsieurDalize then handed to his friend a little instrument of brass, which wascomposed of three parts,--a conical tube, furnished with a mouth, ahollow cylinder succeeding to the first tube, and a second tube, equallyconical, but narrower, and placed at right angles with the hollowcylinder. This second tube ended in a very little opening.
Monsieur Roger placed his lips to the opening of the first tube, andblew, placing the little opening of the second tube in front of theflame of a candle, which Monsieur Dalize had just lit. A long andpointed tongue of fire extended itself from the flame of the candle.Monsieur Roger placed close to this tongue of fire the tapering and openend of the tube in which the water had finished boiling. The air, forcedout of the blowpipe and thrust upon the flame of the candle, bore tothis flame a considerable quantity of oxygen, which increased thecombustion and produced a temperature high enough to soften and melt theopen extremity of the tube, and so seal it hermetically.
"I have," said Monsieur Roger, "by the means which you have seen,expelled the air which was contained in this tube, and there remains init only water. In a few moments we will make use of it. But it is goodto have a comparison under your eyes. I therefore ask Miss Miette totake another tube similar to that which I hold."
"Here it is," cried Miette.
"Now I ask her to put water into it."
"I have done so."
"Lastly, I ask her to turn it over quickly, with her little hand placedagainst its lower side in order to prevent the water from falling uponthe floor."
Miss Miette did as she was commanded. The water fell in the tube,dividing itself into drops of more or less size. It was like rain inminiature.
"The water, as you have just seen," said Monsieur Roger, "has fallen inMiss Miette's tube, dividing itself against the resistance of the air.In the tube which I hold, and in which there is no longer any air, youwill see how water falls."
Monsieur Roger turned the tube over, but the water this time encounteredno resistance from the air. It fell in one mass, and struck the bottomof the tube with a dry and metallic sound.
"It made a noise almost like the noise of a hammer," said Paul Solange.
"Exactly," answered Monsieur Roger. "Scientists have given thisapparatus the name of the water-hammer." And looking at Miette, who inher astonishment was examining the tube without saying anything,Monsieur Roger added, smiling, "And this hammer has struck Miss Miettewith surprise."
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