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Turning Night Into Day

This '"something" is a gas which is one of the component parts of air. It is called oxygen. When the candle burns, oxygen is used up and disappears. But this still doesn't explain exactly what combustion is. We see that the candle has gone out and furthermore that something has happened to the oxygen. What is the secret of this mysterious disappearance?

The explanation is that it only seems to us that the candle flame has gone out.

If you put a drinking glass over a candle flame it will be coated inside with soot and drops of water will form in it. This shows that water is given off in the process of combustion. But besides water, which we can see, another substance is given off, an invisible gas, carbon dioxide. When we put the burning candle into the jar, a layer of this carbon dioxide collected at the bottom of the jar and the candle could not burn in this any more than it could in water.

This carbon dioxide can be poured out of the jar like a liquid. If we then put the lighted candle back into the jar it will not go out at once. It will burn until another layer of carbon dioxide has collected.

That is, when a candle burns, neither the candle nor the oxygen in the air are destroyed. They are merely changed into carbon dioxide and water vapor.

Formerly this was not known. A little more than four centuries ago there was only one man living who had figured out what combustion really was. This was the Italian artist, scientist and engineer Leonardo da Vinci.

A Lamp with a Samovar Chimney

Leonardo da Vinci even in those early days understood that soot was due to an insufficient supply of air. He came to the conclusion, too, that to supply sufficient air there must be some kind of draft like that in a stove, that a chimney must be put over the flame. Then the heated air would go off up the chimney, carrying with it the carbon dioxide and water vapor, and fresh air would come in from below with plenty of oxygen in it.

So the lamp-chimney was invented. At first it was made of tin, like the chimney of a samovar, instead of glass. And it wasn't put right on the lamp bowl, as glass chimneys are, but was placed up above the flame.

It was some two hundred years later that a French apothecary named Quinquet had the bright idea of substituting a transparent glass chimney for the original one made of tin which would not let the light out. But even he didn't realize that since the chimney was transparent it could be put lower down, right on the burner.