struments which have assisted to acquire, and still continue to maintain, the dominion of mind over matter.

Iron in a purely metallic form is of rare occurrence, though in different parts of the world several large masses of metallic iron are known to exist, and other similar masses have at various times been observed to fall from the atmosphere. In South America there is a mass of meteoric iron estimated at thirty-six thousand pounds weight, and one in Siberia of sixteen thousand pounds.

The iron of commerce is not found in a metallic state, but is produced from iron ore, familiarly known as ironstone. Beds of ironstone occur in various parts of the United Kingdom, especially in the south-west of Scotland, South Wales, and South Staffordshire and its neighbourhood.

The first process in the manufacture of iron is roasting the ore; which is done in kilns or furnaces, or in large heaps in the open air. The effect of roasting the ore is to drive off the water, sulphur, and arsenic, which it generally contains. It is then mixed with limestone and coke and brought to the blast furnace; which is the most important feature in an iron-work, rising to the height of from fifty to seventy feet, and lighting up the country around like a small volcano.

The coke, ironstone, and limestone, ultimately form two liquid products at the bottom of the furnace. One of these is glass, composed of the limestone in combination with the earthy impurities of the ore. This, when drawn off and left to cool, forms slag or cinder. The other product is liquid iron, combined with the carbon of the fuel.

This

As the materials gradually descend from the top to the bottom of the furnace, the ore, being thus for several hours in contact with the burning fuel, is almost saturated with carbon when it reaches the lower or hottest part of the furnace. Here the melted iron is drawn off at intervals of from eight to twelve hours. work is continued with double sets of attendants day and night, without intermission, for two or three years; for if the furnace were allowed to cool, the contents would become solid and the furnace be ruined.

Previous to each cast, a channel, called the sow, is formed in a bed of sand in front of the furnace. Branching off from the sow, at right angles to it, are a number of smaller channels called pigs. Into these the melted metal is run. The bars when cooled are in the state known commercially as pig iron. The general name of the metal in this state is cast iron.

Iron is employed in the arts in three different states: as crude or cast iron, as steel, and as wrought iron; the differences depending upon the relative amount of carbon with which the metal is combined. Cast iron contains a larger proportion of carbon than steel, and steel more than wrought or malleable iron, the best malleable iron having only a very minute portion of carbon. The presence of carbon in cast iron renders the metal more fluid when melted, and, consequently, better suited for casting in moulds.

Cast iron is extremely brittle, and for the most part of a dark gray or blackish colour. An immense variety of useful and important articles are formed of cast iron. These are made by pouring the liquid metal into moulds formed in sifted sand.

Wrought or malleable iron is produced from cast iron by a process called blooming. The cast iron is thrown into a furnace, and melted by a fierce flame which is made to play upon its surface. Here it is kept for some hours, a workman constantly stirring it, until, notwithstanding the heat, it gradually acquires consistency and congeals. A large piece called a bloom or ball is then taken out while hot, and beaten by a huge hammer worked by machinery. This treatment presses a quantity of dross out of the iron. While still at a bright red heat it is passed through massive rolling machines, till it is reduced to the thickness required. It is now very different from the pig iron used to produce it. While in the form of pig iron it was very hard, very brittle, and readily fusible; it is now a long slender bar of soft, tough, malleable iron, fusing with difficulty; and this remarkable change is supposed to be produced merely by the separation of a little oxygen and carbon from the cast iron.

Steel is produced from iron by adding a little carbon to that which wrought iron already contains. Within what is

called a cementing furnace, bars of iron are buried in earthtroughs filled with pounded charcoal. These troughs are carefully closed with clay, then a fire is lighted below, and an equable heat maintained for several days, until the iron has absorbed the quantity of carbon requisite to form the kind of steel required by the manufacturer. The carbon in common iron appears to be only mechanically mixed with the metal, but in the cementing process a chemical union between the two is effected; and thus are developed those remarkable properties which distinguish steel from iron, and adapt it to purposes for which iron is inadequate. Thus steel is so much harder than iron, that it can cut and file it. Steel can even scratch the hardest glass. It is denser than iron, has a finer grain, assumes a brighter and whiter lustre when polished, and possesses much greater elasticity. When heated it assumes various beautiful tints of colour; and if suddenly cooled, it becomes harder, more brittle, and less flexible than iron. Indeed, the chief value of steel depends upon the ease with which it can be tempered to any degree between extreme hardness and softness. And even after having been hardened it may have its softness and ductility restored by being again heated and suffered to cool slowly.

The best iron for making into steel comes from the mine of Dannemora, in Sweden. This mine yields every year about 4,000 tons of iron, which are shipped for the port of Hull; and thence a small portion is sent to London, Newcastle, and Birmingham; but by far the largest quantity goes to Sheffield, where more steel is made than in any other place in the world.

When converted into ordinary machinery, cast iron originally worth £1 becomes worth about £4; into large ornamental work, £45; into buckles and Berlin work, £600; and into buttons, £5,000.

A bar of wrought iron, originally worth £1, becomes worth about £2, 10s. when worked into horse shoes; £30 when made into table-knives; £70 when turned into needles; £650 when in the form of penknife blades; and, to crown all, it becomes worth £50,000 when manufactured into watch-springs.

THE CHEMISTRY OF A CANDLE.

"AND now, uncle," asked Harry, who was a favourite with the old gentleman, can you tell me what you do when you put a

candle out?"

"Put 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 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. Wilk

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inson.

"Troublesome? Oh, not at all. I like to hear him."

"Let us get a wax candle then, uncle. There's one on the mantel-shelf. Let me light it.”

"Take care you don't burn your fingers, or set anything 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. Look down on the top of it, 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?"

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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 capillary attraction; 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 vapour, and the vapour burns. The heat of the burning vapour keeps on melting more wax, and that is sucked up too within the flame, and turned into vapour 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?

"I dare say 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 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. What do you think is 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 vapour 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 vapour or gas from the candle will mix with the air there; and if you were to 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,