tside, because the wick is large;
but if, as Argand did so cleverly, I open a passage to the middle of the
flame, and so let air come in there, you will see how much more
beautifully it burns. If I shut the air off, look how it smokes; and why?
We have now some very interesting points to study. We have the case of the
combustion of a candle; we have the case of a candle being put out by the
want of air; and we have now the case of imperfect combustion; and this is
to us so interesting, that I want you to understand it as thoroughly as
you do the case of a candle burning in its best possible manner. I will
now make a great flame, because we need the largest possible
illustrations. Here is a larger wick [burning turpentine on a ball of
cotton]. All these things are the same as candles, after all. If we have
larger wicks, we must have a larger supply of air, or we shall have less
perfect combustion. Look now at this black substance going up into the
atmosphere; there is a regular stream of it. I have provided means to
carry off the imperfectly burned part, lest it should annoy you. Look at
the soots that fly off from the flame: see what an imperfect combustion it
is, because it cannot get enough air. What, then, is happening? Why,
certain things which are necessary to the combustion of a candle are
absent, and very bad results are accordingly produced; but we see what
happens to a candle when it is burnt in a pure and proper state of air. At
the time when I shewed you this charring by the ring of flame on the one
side of the paper, I might have also shewn you, by turning to the other
side, that the burning of a candle produces the same kind of
soot--charcoal or carbon.

But, before I shew that, let me explain to you--as it is quite necessary
for our purpose--that, though I take a candle and give you, as the general
result, its combustion in the form of a flame, we must see whether
combustion is always in this condition, or whether there are other
conditions of flame; and we shall soon discover that there are, and that
they are most important to us. I think, perhaps, the best illustration of
such a point to us, as juveniles, is to shew the result of strong
contrast. Here is a little gunpowder. You know that gunpowder burns with
flame--we may fairly call it flame. It contains carbon and other
materials, which altogether cause it to burn with a flame. And here is
some pulverised iron, or iron filings. Now, I purpose burning th