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The Chemical History of a Candle Michael Faraday Public domain text from Project Gutenberg. THE CHEMICAL HISTORY OF A CANDLE A COURSE OF LECTURES DELIVERED BEFORE A JUVENILE AUDIENCE AT THE ROYAL INSTITUTION BY MICHAEL FARADAY, D.C.L., F.R.S. EDITED BY WILLIAM CROOKES, F.C.S. A NEW IMPRESSION, WITH ILLUSTRATIONS LONDON CHATTO & WINDUS 1908 PREFACE From the primitive pine-torch to the paraffin candle, how wide an interval! between them how vast a contrast! The means adopted by man to illuminate his home at night, stamp at once his position in the scale of civilisation. The fluid bitumen of the far East, blazing in rude vessels of baked earth; the Etruscan lamp, exquisite in form, yet ill adapted to its office; the whale, seal, or bear fat, filling the hut of the Esquimaux or Lap with odour rather than light; the huge wax candle on the glittering 1 altar, the range of gas lamps in our streets, all have their stories to tell. All, if they could speak (and, after their own manner, they can), might warm our hearts in telling, how they have ministered to man s comfort, love of home, toil, and devotion. Surely, among the millions of fire-worshippers and fire-users who have passed away in earlier ages, _some_ have pondered over the mystery of fire; perhaps some clear minds have guessed shrewdly near the truth. Think of the time man has lived in hopeless ignorance: think that only during a period which might be spanned by the life of one man, has the truth been…

The Chemical History of a Candle

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always present with it. There is a current formed, which draws the flame out for the flame which you see is really drawn out by the current, and drawn upward to a great height just as Hooke has here shewn you by that prolongation of the current in the diagram. You may see this by taking a lighted candle, and putting it in the sun so as to get its shadow thrown on a piece of paper. How remarkable it is that that thing which is light enough to produce shadows of other objects, can be made to throw its own shadow on a piece of white paper or card, so that you can actually see streaming round the flame something which is not part of the flame, but is ascending and drawing the flame upwards. Now, I am going to imitate the sunlight, by applying the voltaic battery to the electric lamp. You now see our sun, and its great luminosity; and by placing a candle between it and the screen, we get the shadow of the flame. [Illustration: Fig. 4.] You observe the shadow of the candle and of the wick; then there is a darkish part, as represented in the diagram, and then a part which is more distinct. Curiously enough, however, what we see in the shadow as the darkest part of the flame is, in reality, the brightest part; and here you see streaming upwards the ascending current of hot air, as shewn by Hooke, which draws out the flame, supplies it with air, and cools the sides of the cup of melted fuel. I can give you here a little further illustration, for the purpose of shewing you how flame goes up or down; according to the current. I have here a flame it is not a candle-flame but you can, no doubt, by this time, generalise enough to be able to compare one thing with another. What I am about to do is to change the ascending current that takes the flame upwards into a descending current. This I can easily do by the little apparatus you see before me. The flame, as I have said, is not a candle flame, but it is produced by alcohol, so that it shall not smoke too much. I will also colour the flame with another substance[6], so that you may trace its course; for with the spirit alone you could hardly see well enough to have the opportunity of tracing its direction. By lighting this spirit-of-wine, we have then a flame produced; and you observe that when held in the air, it naturally goes upwards. [Illustration: Fig. 5] 13

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The Chemical History of a Candle