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rates them from the gas which comes from the melted wax, and, as soon as they touch the air on the outside of the thin case of flame, they burn."

"Can you tell how it is that the little bits of carbon cause the brightness of the flame ?" asked Mr. Wilkinson.

"Because they are pieces of solid matter," answered Harry. "To make a flame shine, there must always be some solid-or at least liquid-matter in it."

"Very good," said Mr. Bagges,-"solid stuff necessary to brightness."

"Some gases and other things," resumed Harry, "that burn with a flame you can hardly see, burn splendidly when something solid is put into them. Oxygen and hydrogentell me if I use too hard words, uncle-oxygen and hydrogen gases, if mixed together and blown through a pipe, burn with plenty of heat but with very little light. But if their flame is blown upon a piece of quicklime, it gets so bright as to be quite dazzling. Make the smoke of oil of turpentine pass through the same flame, and it gives the flame a beautiful brightness directly."

"I wonder," observed Uncle Bagges, "what has made. you such a bright youth."

"Taking after uncle, perhaps," retorted his nephew, "don't put my candle and me out. Well, carbon or charcoal is what causes the brightness of all lamps, and candles, and other common lights; so, of course, there is carbon in what they are all made of.”

"So carbon is smoke, eh? and light is owing to your carbon. Giving light out of smoke, eh? as they say in the classics," observed Mr. Bagges.

"But what becomes of the candle," pursued Harry, “as it burns away? where does it go?"

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"Nowhere," said his mamma, " I should think. It burns to nothing."

66 Oh dear no!" said Harry," everything-everybody goes somewhere."

"Eh?—rather an important consideration that," Mr. Bagges moralised.

"You can see it goes into smoke, which makes soot for one thing," pursued Harry. "There are other things it goes into, not to be seen by only looking, but you can get to see them by taking the right means,—just put your hand over the candle, uncle."

"Thank you, young gentleman, I had rather be excused." "Not close enough down to burn you, uncle; higher up. There,—you feel a stream of hot air; so something seems to rise from the candle. Suppose you were to put a very long slender gas-burner over the flame, and let the flame burn just within the end of it, as if it were a chimney,— some of the hot steam would go up and come out at the top, but a sort of dew would be left behind in the glass chimney, if the chimney was cold enough when you put it on. There are ways of collecting this sort of dew, and when it is collected it turns out to be really water. I am not joking, uncle. Water is one of the things which the candle turns into in burning,-water coming out of fire. A jet of oil gives above a pint of water in burning. In some lighthouses they burn, Professor Faraday says, up to two gallons of oil in a night, and if the windows are cold the steam from the oil clouds the inside of the windows, and in frosty weather, freezes into ice."

"Water out of a candle, eh? exclaimed Mr. Bagges. "As hard to get, I should have thought, as blood out of a post. Where does it come from?"

"Part from the wax, and part from the air, and yet not a drop of it comes either from the air or the wax. What you make of that, uncle?"

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"Eh? Oh! I'm no hand at riddles. Give it up.'

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"No riddle at all, uncle. The part that comes from the wax isn't water, and the part that comes from the air isn't water, but when put together they become water. Water is a mixture of two things, then. This can be shown. Put some iron wire or turnings into a gun-barrel open at both Heat the middle of the barrel red-hot in a little furnace. Keep the heat up, and send the steam of boiling water through the red-hot gun-barrel. What will come out at the other end of the barrel won't be steam; it will be gas, which doesn't turn to water again when it gets cold, and which burns if you put a light to it. Take the turnings out of the gun-barrel, and you will find them changed to rust, and heavier than when they were put in. Part of the water is the gas that comes out of the barrel, the other part is what mixes with the iron turnings, and changes them to rust, and makes them heavier. You can fill a bladder with the gas that comes out of the gun-barrel, or you can pass bubbles of it into a jar of water turned upside down in a trough, and, as I said, you can make this part of the water burn."

"Eh?" " cried Mr. Bagges. "Upon my word! One of these days we shall have you setting the Thames on fire." "Nothing more easy," said Harry, "than to burn part of the Thames, or of any other water; I mean the gas that I have just told you about, which is called hydrogen. In burning, hydrogen produces water again, like the flame of the candle. Indeed, hydrogen is that part of the water, formed by a candle burning, that comes from the wax. All

things that have hydrogen in them produce water in burning, and the more there is in them the more they produce. When pure hydrogen burns, nothing comes from it but water, no smoke or soot at all. If you were to burn one ounce of it, the water you would get would be just nine ounces. There are many ways of making hydrogen, besides out of steam by the hot gun-barrel. I could show it you in a moment, by pouring a little sulphuric acid mixed with water into a bottle upon a few zinc or steel filings, and putting a cork in the bottle with a little pipe through it, and setting fire to the gas that would come from the mouth of the pipe. We should find the flame very hot, but having scarcely any brightness. I should like you to see the curious qualities of hydrogen, particularly how light it is, so as to carry things up in the air; and I wish I had a small balloon to fill with it and make go up to the ceiling, or a bag-pipe full of it to blow soap-bubbles with, and show how much faster they rise than common ones, blown with the breath."

"So do I," interposed Master Tom.

"And so," resumed Harry, "hydrogen, you know, uncle, is part of water, and just one-ninth part."

"As hydrogen is to water, so is a tailor to an ordinary individual, eh?" Mr. Bagges remarked.

“Well, now then, uncle, if hydrogen is the tailor's part of the water, what are the other eight parts? The iron turnings used to make hydrogen in the gun-barrel, and rusted, take just those eight parts from the water in the shape of steam, and are so much the heavier. Burn iron turnings in the air, and they make the same rust, and gain just the same in weight. So the other eight parts must be found in the air for one thing, and in the rusted iron turnings for another, and they must also be in the water; and now the question is, how to get at them?"

"Out of the water? gested Mr. Bagges.

Fish for them, I should say," sug

"Why, so we can," said Harry. "Only, instead of hooks and lines, we must use wires-two wires, one from one end, the other from the other, of a galvanic battery. Put the points of these wires into water, a little distance apart, and they instantly take the water to pieces. If they are of copper, or a metal that will rust easily, one of them begins to rust, and air-bubbles come up from the other. These bubbles are hydrogen. The other part of the water mixes with the end of the wire and makes rust. But if the wires are of gold, or a metal that does not rust easily, air-bubbles rise from the ends of both wires. Collect the bubbles from both wires in a tube, and fire them, and they turn to water again; and this water is exactly the same weight as the quantity that has been changed into the two gases. Now then, uncle, what should you think water was composed of?" "Eh? well-I suppose of those very identical two gases, young gentleman."

"Right, uncle. Recollect that the gas from one of the wires was hydrogen, the one-ninth of water. What should

you guess the gas from the other wire to be?”

"Stop-eh ?-wait a bit-eh ?-oh!-why, the other eight-ninths, to be sure."

"Good again, uncle. Now this gas that is eight-ninths of water, is the gas called oxygen that I mentioned just now. This is a very curious gas. It won't burn in air at all itself, like gas from a lamp, but it has a wonderful power of making things burn that are lighted and put into it. If you fill a jar with it—”

"How do you manage that?" Mr. Bagges inquired.

"You fill the jar with water," answered Harry," and you stand it upside down in a vessel full of water too.

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