A double tube passes through the body of the figure, having an ascending part, whose mouth is within the cup, and communicating with the water; and a descending part, whose mouth M, is concealed in the hollow, D C, of the vessel. When the water is poured into the vessel, it ascends the tube in the interior of the figure; but as the tube bends downwards when it reaches the level of the chin of the figure, no sooner does the water in the vessel reach that level than it begins to descend the tube to M, and so escapes, leaving the head of the figure quite untouched by the water. The tube in the figure being very small, its course cannot well be traced; but the subjoined figure (fig. 3) will shew the principle more clearly. The shorter leg of the bent Fig. 3. tube is open to the water, and when the latter ascends to the level of the bend in the tube it flows over that bend, and escapes at the exterior mouth of the tube.-S. M. THE FLAME OF A CANDLE. PART I. WHAT a pretty invention is a candle, especially a wax or a composite candle! So beautifully white, so truly rounded, and so nicely moulded into a point round the top of the wick! Let I could give you a good deal of curious and useful information about the manufacture of so simple an article as a candle; but I am now going to burn it, and to shew you a little of the chemistry of its flame. us light the candle, then. See how steadily the flame ascends, sharp and pointed, like a spear or arrow-head. Why does the flame take this form?-why might it not be round, square, or oval, or any other shape? I will tell you why. A candle cannot burn without air, any more than you can live without air. If you wish for a proof that air feeds the flame of the candle, we can easily make an experiment. A short bit of candle will do best for our purpose, about an inch long, lighted and stuck upon the table. There, now, cover it over with that large tumbler, quite over, so that the edge of the glass rests upon the table. Look how dim the flame grows—yet dimmer; it flutters, it dies! Why, it did not last for a quarter of a minute! No, nor anything like it; for if the tumbler held a full quart instead of about half-a-pint, the flame would scarcely have lasted fifteen seconds. I know this, because I have tried the experiment before. The flame goes out because it is in a confined portion of air, and the glass being close upon the table prevents any fresh air from getting in to supply the flame. But, see! the other candle burns on freely, because it can get a proper supply of air from all parts of the room; but if you stopped up the fire-place, windows, key-holes, and every crack or crevice in the room, this candle would go out just the same as that under the glass did just now, only it would be a longer time doing so, because it is in a larger portion of confined air. But as the air always rushes into a room through the crevices of the doors and windows, the candle always gets as much as it wants. Hold the lighted candle opposite the key-hole of the door. There, see how the flame is blown towards you by the air whistling through the key-hole. Well, then, the air comes about the candle to support the flame, and after it has done so, and got very hot, it ascends towards the ceiling; more air comes forward to supply its place, and so on during the whole time that the candle burns. So you see the flame is placed in the centre of an ascending draught of air, which urges it upwards into a sharp and pointed form. Chemists find that the quiet of the air is disturbed by the heat of the flame, that the hot air is lighter than colder, and that, therefore, the flame is unequally pressed upon. The pressure is stronger at the lower part, weakest towards the upper part, and, therefore, the pointed form results from this unequal pressure. The flame would be as round as a marble if it could burn without disturbing the air, because then it would be equally pressed upon from all sides at once. There are methods of shewing this form of flame; but these I do not think you would be able to understand yet, and I am sure you could not put them into practice. Look at the beautiful devices lighted with gas during public illuminations; there the gas flames, although for the most part forced out in a straight direction, bend upwards, to assume their natural position. This pointed form of flame attracted the attention of the old chemists, and in many of their curious books, instead of writing the word flame, or fire, they put a mark or sign for it, shaped like this, A,-no bad representation of the form of a flame; and as water was the element opposed to fire, they reversed the mark or sign for it like this, V; these sorts of signs were used to prevent people from understanding their curious works. Well, then, the ascent of air towards the flame is the cause of its pointed form. But now observe how nicely the melted wax remains around the wick, confined in a sort of little cup. But why should not all the wax melt and run into a mass by the heat of the flame? Why does only that portion melt which is close to the flame, and why is it there held in this regularly shaped cup? I will endeavour to explain why, as familiarly as I can; for it is a very beautiful process, and depends upon the air. See, now, the flame melts a portion of the wax; very well, the air immediately rushing upwards, as I have just told you, cools and keeps cool the wax around the outside of the candle, forming, in fact, a little circular wall, within which, as within a cup, the melted wax nearest the flame is safely kept. If I destroy this cup, I instantly spoil the burning of the candle. I will hold this red-hot poker near it, so as to melt down the wall of the cup. There, now, it melts away; and look, the flame cannot get its proper supply of fuel, for the melted wax runs away from the wick, and "gutters" all down the candle. How beautifully and how effectually, then, does the air act round a candle, not only supporting its flame, but also supporting its melted fuel. If the air could not keep the outside of the candle cold, and thus form a cup, a candle would burn very badly, and would be of very little use. In I was at a great public meeting, in a large room, the other night, and there were five or six hundred candles burning, but not steadily. They were running_and guttering, although of the very best manufacture. How was this? Why, the company and the flames of the candles had heated the air of the room so much, that it was hot enough to melt down the walls of each candlecup, and therefore they could not burn properly. the chandelier holding two or three rows of candles, the upper rows were burning languidly, and guttering away; the bottom rows were burning better, but not well. How was this? Why, they were getting the most benefit of the air, and sending it up hot and vitiated to the rows above them. You never see the branches on a chandelier set exactly over each other, but alternately, so that the hot air from the lowest row may ascend without annoying the rows above it; and this answers very well for two rows; but when there are five or six, and the chandelier is hung near the ceiling of the room, the guttering and destruction of the candles is unavoidable. The candles on the table in a hot room burn better than those in the branches around the walls, or in the chandelier at the ceiling, because they are in a cooler situation. The wick now requires notice. Why does it raise the melted wax from the cup and deliver it to be burnt in the flame? I will tell you. The wick possesses a peculiar power, called capillary attraction; I mean by this term, the rise of fluids in very small tubes,—yes, even in tubes or pipes as fine as a hair. But I will make an experiment to illustrate my meaning. There is a bit of cane, about an inch long; see, it is full of small holes; I can easily blow through it. Well, there is no difficulty in calling these holes very small tubes. Look, then, I just put the bit of cane so as to touch the surface of the water in this tea-cup. Wait a moment; and now some of the water has risen through the small holes in the cane; it is quite wet on the upper part. There is another bit of cane, and there is a tea-spoonful of turpentine; I will make a similar experiment with it. Now the turpentine has risen, and I will light it; but as it burns with a good deal of smoke, put it on the hob of the grate, that we may not be annoyed. Look now, all the turpentine is drawn out of the spoon and all burnt. But you ask me where are these little tubes in the wick of a candle? You can easily imagine that the cotton threads of the wick are laid side by side, and therefore leave little spaces between each other. Well, then, these little spaces are the tubes, and when the wax is melted they attract it upwards, just the same as the small tubes in the cane attracted up the water or the turpentine. Thus the flame is supplied with liquid fuel, and as it is burnt, the wick becomes charred and useless, forming the "snuff" of the candle. I will tell you about the hollow nature of the flame and its luminosity on the next occasion.-S. M. FAREWELL OF THE DUKE OF BUCKINGHAM. Buck. All good people, You that thus far have come to pity me, Hear what I say, and then go home and lose me. I have this day received a traitor's judgment, And by that name must die; yet, heaven bear witness, And if I have a conscience, let it sink me, Even as the axe falls, if I be not faithful! |