water; and a gas, such as I can let off from this gas-jet by
turning the tap. And yet any child can make a picture of this in
his mind if only it has been properly put before him.

All matter in the world is made up of minute parts or particles;
in a solid these particles are locked together so tightly that
you must tear them forcibly apart if you with to alter the shape
of the solid piece. If I break or bend this wood I have to force
the particles to move round each other, and I have great
difficulty doing it. But in a liquid, though the particles are
still held together, they do not cling so tightly, but are able
to roll or glide round each other, so that when you pour water
out of a cup on to a table, it loses its cuplike shape and
spreads itself out flat. Lastly, in a gas the particles are no
longer held together at all, but they try to fly away from each
other; and unless you shut a gas in tightly and safely, it will
soon have spread all over the room.

A solid, therefore, will retain the same bulk and shape unless
you forcibly alter it; a liquid will retain the same bulk, but no
the same shape if it be left free; a gas will not retain either
the same bulk or the same shape, but will spread over as large a
space as it can find wherever it can penetrate. Such simple
things as these you must learn from books and by experiment.

Then you must understand what is meant by chemical attraction;
and though I can explain this roughly here, you will have to make
many interesting experiments before you will really learn to know
this wonderful fairy power. If I dissolve sugar in water, though
it disappears it still remains sugar, and does not join itself to