The Fairy-Land of Science | Page 6

plainly, was standing one morning near the bedroom
window and she noticed the damp trickling down the window-pane.
"Auntie," she said, "what for it rain inside?" It was quite useless to
explain to her in words, how our breath had condensed into drops of
water upon the cold glass; but I wiped the pane clear, and breathed on it
several times. When new drops were formed, I said, "Cissy and auntie
have done like this all night in the room." She nodded her little head
and amused herself for a long time breathing on the window-pane and
watching the tiny drops; and about a month later, when we were
travelling back to Italy, I saw her following the drops on the carriage
window with her little finger, and heard her say quietly to herself,
"Cissy and auntie made you." Had not even this little child some real

picture in her mind of invisible water coming from her mouth, and
making drops upon the window-pane?
Then again, you must learn something of the language of science. If
you travel in a country with no knowledge of its language, you can
learn very little about it: and in the same way if you are to go to books
to find answers to your questions, you must know something of the
language they speak. You need not learn hard scientific names, for the
best books have the fewest of these, but you must really understand
what is meant by ordinary words.
For example, how few people can really explain the difference between
a solid, such as the wood of the table; a liquid, as 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 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