the water. I have only to let the cup stand till the water
dries, and the sugar will remain at the bottom. There has been
no chemical attraction here.

But now I will put something else in water which will call up the
fairy power. Here is a little piece of the metal potassium, one
of the simple substances of the earth; that is to say, we cannot
split it up into other substances, wherever we find it, it is
always the same. Now if I put this piece of potassium on the
water it does not disappear quietly like the sugar. See how it
rolls round and round, fizzing violently with a blue flame
burning round it, and at last goes off with a pop.

What has been happening here?

You must first know that water is made of two substances,
hydrogen and oxygen, and these are not merely held together, but
are joined to completely that they have lost themselves and have
become water; and each atom of water is made of two atoms of
hydrogen and one of oxygen.

Now the metal potassium is devotedly fond of oxygen, and the
moment I threw it on the water it called the fairy "chemical
attraction' to help it, and dragged the atoms of oxygen out of
the water and joined them to itself. In doing this it also
caught part of the hydrogen, but only half, and so the rest was
left out in the cold. No, not in the cold! for the potassium and
oxygen made such a great heat in clashing together that the rest
of the hydrogen became very hot indeed, and sprang into the air
to find some other companion to make up for what it had lost.