term, therefore, though in ordinary language limited to common salt, is applied in chemistry to all combinations of acids with alkalies.

2. That common article, soap, is formed by the union of an alkali with the fatty acid of some oily substance; and hence soap itself may be considered one of the chemical salts. The alkali most frequently used is the common ley of wood ashes, which is essentially the same as pearlash or potash dissolved in water. It is well known that oil and water have no disposition to unite; but the alkali has a strong affinity for both, and in uniting with them brings about a mutual combination differing from either of the ingredients. The principles displayed in this process are well illustrated in the following

3.

EASY LESSON IN CHEMISTRY.

"Some water and oil

One day had a broil,

As down in a glass they were dropping,

And would not unite,

But continued to fight,

Without any prospect of stopping.

Some pearlash o'erheard-
As quick as a word,

He jumped in the midst of the clashing;
When all three agreed,

And united with speed,

And soap was created for washing."

4. The commonness of an article is apt to induce us to overlook its importance; a truth which is perhaps nowhere more fully exemplified than in the case before us. Liebig says, "The quantity of soap consumed by a nation would be no inaccurate measure whereby to estimate its wealth and civilization." According to Pliny, the invention of soap must be ascribed to the Gauls, by whom, he says, it was composed of tallow and ashes, and was probably at first an accidental combination. Homer had long before described the washing of the royal robes in the "limpid streams;" but we have reason to suspect, from the known absence of soap on that occasion, that the picture of their "snowy lustre" is overdrawn.

They seek the cisterns where Phoacian dames
Wash their fair garments in the limpid streams;
Where, gathering into depth from falling rills,
The lucid wave a spacious basin fills;

Then, emulous, the royal robes they lave,
And plunge the vestures in the cleansing wave:
The vestures cleansed o'erspread the shelly sand,
Their snowy lustre whitens all the strand.

POPE's Odyssey, b. vi.

LESSON XII.—THE CHEMISTRY OF A CANDLE.

(Adapted from Dickens's Household Words.)

THE Wilkinsons were having a small party-it consisted of themselves and Uncle Bagges-at which the younger members of the family, home for the holidays, had been just admitted after dinner. Uncle Bagges was a gentleman from whom his affectionate relatives cherished expectations of a testamentary nature. Hence the greatest attention was paid by them to the wishes of Mr. Bagges, as well as to every observation which he might be pleased to make.

"Eh! what? you sir," said Mr. Bagges, facetiously addressing himself to his eldest nephew, Harry-"eh! what? I am glad to hear, sir, that you are doing well at school. Now-eh? now, are you clever enough to tell me where was Moses when he put the candle out ?"

"That depends, uncle," answered the young gentleman, "on whether he had lighted the candle to see with at night, or by daylight to seal a letter."

"Eh? Very good, now! 'Pon my word, very good," exclaimed Uncle Bagges. "You must be lord chancellor, sirlord chancellor, one of these days."

"And now, uncle," asked Harry, who was a favorite with the old gentleman, "can you tell me what you do when you put a candle out ?”

"Clap an extinguisher on it, you young rogue, to be sure." "Oh, but I mean, you cut off its supply of oxygen," said Master Harry.

"Cut off its ox's-eh? what ?"

"He means something he heard at the Royal Institution," observed Mrs. Wilkinson. "He reads a great deal about chemistry, and he attended Professor Faraday's lectures there on the chemical history of a candle, and has been full of it ever since."

"Now, you sir," said Uncle Bagges, "come you here to me, and tell me what you have to say about this chemical, eh? -or comical; which?-this-comical chemical history of a candle."

"Harry, don't be troublesome to your uncle," said Mr. Wilkinson.

Let

"Troublesome? Oh, not at all. I like to hear him. him teach his old uncle the comicality and chemicality of a farthing rush-light.”

"A wax candle will be nicer and cleaner, uncle, and answer the same purpose. There's one on the mantel-shelf. Let me light it."

"Take care you don't burn your fingers, or set any thing on fire," said Mrs. Wilkinson.

"Now, uncle," commenced Harry, having drawn his chair to the side of Mr. Bagges, "we have got our candle burning. What do you see?"

"Let me put on my spectacles," answered the uncle.

"Look down on the top of the candle around the wick. See, it is a little cup full of melted wax. The heat of the flame has melted the wax just round the wick. The cold air keeps the outside of it hard, so as to make the rim of it. The melted wax in the little cup goes up through the wick to be burned, just as oil does in the wick of a lamp. What do you think makes it go up, uncle?"

"Why-why, the flame draws it up, doesn't it' ?"

"Not exactly, uncle. It goes up through little tiny passages in the cotton wick, because very, very small channels, or pipes, or pores, have the power in themselves of sucking up liquids. What they do it by is called cap-something." "Capillary attraction, Harry," suggested Mr. Wilkinson.

Yes, that's it; just as a sponge sucks up water, or a bit of lump sugar the little drop of tea or coffee left in the bottom of a cup. Now I'll blow the candle out; not to be in the dark, though, but to see into what it is. Look at the smoke rising from the wick. I'll hold a bit of lighted paper in the smoke, so as not to touch the wick. But see, for all that, the candle lights again. So this shows that the melted wax sucked up through the wick is turned into vapor, and the vapor burns. The heat of the burning vapor keeps on melting more wax, and that is sucked up too within the flame, and turned into vapor and burned, and so on till the wax is all used up and the candle is gone. So the flame, uncle, you see, is the last of the candle, and the candle seems to go through the flame into nothing, although it doesn't, but goes into several things; and isn't it curious, as Professor Faraday said, that the candle should look so splendid and glorious in going away ?"

"How well he remembers, doesn't he?" observed Mrs. Wilkinson.

"I dare say," proceeded Harry, "that the flame of the candle looks flat to you; but if we were to put a lamp-glass over it, so as to shelter it from the draught, you would see it is

What

round-round sideways, and running up to a peak. It is drawn up by the hot air; you know that hot air always rises, and that is the way smoke is taken up the chimney. should you think was in the middle of the flame ?" "I should say fire," replied Uncle Bagges.

"Oh no. The flame is hollow. The bright flame we see is something no thicker than a thin peel or skin, and it doesn't touch the wick. Inside of it is the vapor I told you of just now. If you put one end of a bent pipe into the middle of the flame, and let the other end of the pipe dip into a bottle, the vapor or gas from the candle will mix with the air there; and if you set fire to the mixture of gas from the candle and air in the bottle, it would go off with a bang."

"I wish you'd do that, Harry," said Master Tom, the younger brother of the juvenile lecturer.

"I want the proper things," answered Harry. "Well, uncle, the flame of the candle is a little shining case, with gas in the inside of it and air on the outside, so that the case of flame is between the air and the gas. The gas keeps going into the flame to burn, and when the candle burns properly none of the gas ever passes out through the flame, and none of the air ever gets in through the flame to the gas. The greatest heat of the candle is in this skin, or peel, or case of flame."

"Case of flame!" repeated Mr. Bagges. "Live and learn. I should have thought a candle-flame was as thick as my poor old noddle."

"I can show you the contrary," said Harry. "I take this piece of white paper, look, and hold it a second or two down upon the candle-flame, keeping the flame very steady. Now I'll rub off the black of the smoke, and-there-you find that the paper is scorched in the shape of a ring, but inside the ring it is only dirtied, and not singed at all."

"Seeing is believing," remarked the uncle.

"But," proceeded Harry, "there is more in the candle-flame than the gas that comes out of the candle. You know a candle won't burn without air. There must be always air around the gas, and touching it like, to make it burn. If a candle hasn't got enough air it goes out, or burns badly, so that some of the vapor inside of the flame comes out through it in the form of smoke, and this is the reason of a candle smoking. So now you know why a great clumsy dip smokes more than a neat wax candle: it is because the thick wick of the dip makes too much fuel in proportion to the air that can get to it."

"Dear me! Well, I suppose there is a reason for every thing," exclaimed the young philosopher's mamma.

"What should you say, now," continued Harry, "if I told you that the smoke that comes out of a candle is the very thing that makes a candle burn with a bright light? Yes; a candle shines by consuming its own smoke. The smoke of a candle is a cloud of small dust; and the little grains of the dust are bits of charcoal, or carbon, as chemists call it. They are burned the moment they are made, and the place they are made in is in the case of flame itself, where the strongest heat is. The great heat separates 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 quick-lime, 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?"

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