The first straight tube represents one end in water, and the level at A is raised to S in the tube; the second straight tube represents a tube lifted out of the water, and the formation of a drop of that fluid at the bottom part of the tube. This drop is formed by the attraction of gravitation, which draws all bodies down to the earth; but in this case the drop will not fall, because the capillary attraction is superior to that of gravitation. In the third straight tube the level, S, is higher than in the other cases, because the tube is supposed to be narrower.

Capillary attraction is of vast importance in nature. By its means the sap ascends the trees, and at some seasons of the year the force of the ascent is so great that if a bough be cut off from a vine, for example, and a bladder be firmly tied to the mutilated stump, it will in a few hours become full of sap, and even burst if not removed. It has been remarked that timber trees which are cut during spring or summer, when the sap is in action, yield very bad timber, which would have been good if cut in the winter; the reason probably is, that the sap decomposes, and thus injuriously affects the wood. Capillary attraction also influences the distribution of the animal fluids, and it extends its influence over mineral bodies, and greatly assists in their decomposition, and in the formation of soils. We see, then, that a small force, which is almost unnoticed and unknown by the great mass of mankind, becomes, when developed by the inquiries of science, one of the most important processes in the three kingdoms of nature.-S. M.

THE FLAME OF A CANDLE.

PART II.

I WILL now point out to you a very curious matter about the flame of a candle.

Let the candle burn steadily. Now, look at it attentively. Do you see that dull pointed spot in the middle of the flame? There, just above the middle of the wick. Well, that is what I am now going to speak about.

The vapour is burning all round the wick, but that

which rises exactly over its centre does not burn, because it can get no air, the flame which envelopes it prevents any from getting in; therefore the middle of the flame remains unburnt, and gives no light, but forms a dull spot in the centre of a bright flame.

I think you will understand me better if I resort to a familiar example. Here is an almond in its shell; see how closely it resembles the pointed shape of the flame. Well, now imagine the shell to be the outside (the burning or light part of the flame), and the kernel to be the inside (the unburnt or dark part). This will give you a very correct idea of the structure of the flame of the candle; it is a sort of a natural model of it.

I can shew you, in a very decided way, that the inside or kernel of the flame is unburnt vapour. I take this piece of very thin window-glass. It is about four inches square. I place it thus on the point of the flame, and lower it down very quickly upon the wick. Now, look down upon the glass before it gets smoky; quick! You see a dark central spot, with a luminous ring round it.

Now, if the whole of the vapour of the flame was burning, there would be no dull spot in the flame, it would be equally light throughout; but, as I have just now told you, the vapour in the middle cannot burn, because of the thin shell of flame around it preventing the access of air.

In further illustration of this curious matter, I will make a very simple, yet a very pretty experiment. I will cut a little strip off this thin card, about two inches long and one-sixteenth of an inch wide; and now, when the candle burns steadily, I hold it across the flame

near the wick (which, you see, I have snuffed rather short). I hold it only for an instant. I take it out. There, now look at the card, it is only scorched where the outside of the flame has touched it; the inside of the flame has had no effect upon it, because there is no fire there.

Try the experiment. Perhaps you may fail once or twice, for it requires some little dexterity, and so does the next I am about to mention; but you will be sure to succeed in both, after a few patient trials.

Here is a bit of glass-tube, about four inches long and one-eighth of an inch in the bore, it is open at both ends. I will just warm it first, by moving it gently through the flame of the candle two or three times, for perhaps it would break if too suddenly heated. This being done, I now hold it slanting upwards in the flame, so that one end may be completely in the dark part. Watch the result. Look, the unburnt vapour rises up the tube. There, now it is coming out at the top. Quick! Put a light to it, but do not agitate the air as you move your hand. See! the vapour kindles; and thus we get a second flame by leading away the inside unburnt portion of the first-a beautiful experiment.

Such, then, is the curious structure of a candle-flame, and all flames fed by a bunch of wick have dark spots in their centres. The same thing is seen in the flames of torches, links, or flambeaux, and also in the flame of coal-gas, when it is burnt at the end of a pipe, after the manner in which you so often see it blazing away in butchers' and greengrocers' shops about London.S. M.

THE YOUNG CHEMIST.

I HAVE another pretty experiment, to shew you that there is no fire in the centre of the flame of a candle, and it is one that you can very easily make.

Here is half a sheet of writing-paper. I will hold it flat down upon the flame of this wax candle, so as very nearly to touch the wick, only for a moment, then take it away; now, look how the paper is scorched in the form of a ring—the shell of the flame has done this; but the paper is not a bit scorched in the middle of the ring, because there is no fire in the kernel or centre of the flame.

I now wish to tell you something about the heat of the flame. This candle has been burning for about half an hour, and it therefore has a very long "snuff." I will now blow it out with a sharp and sudden puff of breath.' See, the snuff remains red-hot, and the vapour of the wax rises plentifully for a little while.

What does this prove? Why, it proves that the heat of the snuff or wick, although it is quite (nay, more than) sufficient to make the wax into vapour, yet it is not hot enough to fire the vapour so as to make flame. Whilst this wick remains red-hot and glowing, if I gently blow upon it, or still better, if I take the candle in my hand and suddenly raise it in the air, the chances are that I light it again;-look, I have succeeded! What is the reason of this? Why, the breath, or the air, has caused the wick to become much hotter than a red heat (just the same as if I blow or fan this bit of red-hot tinder, it becomes very much hotter), and this greater heat is strong enough to make the vapour catch fire and burn.

On a foggy night when the flame of a torch is accidentally blown out, if the end of the torch happens to keep red-hot, you see it easily lighted again by the link-boy whirling it quickly in the air.

I can do the same thing with this bit of stick or roll of brown paper, if I light them and let them burn a little while, then blow them out and whirl them rapidly round and round.

Look at those dying embers in the fire-grate, they are scarcely visibly red-hot; I put some fresh sticks of wood upon them, which only become scorched, not. burnt, with the flame. I now use the bellows and

blow gently; the embers get much hotter; now they are hot enough to kindle the vapour of the fresh wood; it bursts into flame. The same observations hold good in regard to a fire of coals.

You very frequently hear of thatched buildings, or ricks, being accidentally set on fire from the spark from a steam-engine wafted to them. The spark is not hot enough to do this immediately, but by remaining in the thatch or hay for a little while it is fanned into flame by a gentle breeze, and sad destruction of

course ensues.

It must be evident to you, from these very familiar and every-day examples, that the heat necessary to produce flame is very great. See, I cannot light the candle with this dull ember. I blow upon it so as to

make it hotter, and I get a light directly; a dull and red-hot cinder will not light the candle, a bright red-hot one will do so easily. In his laboratory or work room, where a furnace is almost constantly at work, the chemist is in the habit of lighting a candle or lamp with a bright red-hot coal from the fire; and when the vapour of the wax or the oil is once fairly kindled, the flame rapidly gains a little white heat by the air rushing around it, fanning it, as it were.

HEAT.

In the present state of our knowledge, it is impossible to determine whether heat should be regarded as a substance endowed with extraordinary powers, by which it penetrates and infuses itself along the particles of every other element, or as a quality inseparable from matter, and dependent on certain conditions for those unceasing fluctuations which constitute its most remarkable phenomena.

The resistless energies of this omnipotent and allpervading agent are in constant operation. There is