which joining with the water drives its
parts further asunder, and makes it take another form, that of vapour
or steam. He may apply this knowledge to the separation of the sugar
and water; he may turn the water into steam, and the sugar will be
left in the vessel in a solid form. If, instead of evaporating the
water, the boy had added a greater quantity of sugar to the mixture,
he would have seen, that after a certain time, the water would have
dissolved no more of the sugar; the superfluous sugar would fall to
the bottom of the vessel as the sand had done: the pupil should then
be told that the liquid is _saturated_ with the solid.

By these simple experiments, a child may acquire a general knowledge
of solution, evaporation, and saturation, without the formality of a
lecture, or the apparatus of a chemist. In all your attempts to
instruct him in chemistry, the greatest care should be taken that he
should completely understand one experiment, before you proceed to
another. The common metaphorical expression, that the mind should have
time to digest the food which it receives, is founded upon fact and
observation.

Our pupil should see the solution of a variety of substances in
fluids, as salt in water; marble, chalk, or alkalies, in acids; and
camphire in spirits of wine: this last experiment he may try by
himself, as it is not dangerous. Certainly many experiments are
dangerous, and therefore unfit for children; but others may be
selected, which they may safely try without any assistance; and the
dangerous experiments may, when they are necessary, be shown to them
by some careful person. Their first experiments should be such as they
can readily execute, and of which the result may probably be
successful: this success will please and interest the pupils, and will
encourage them to perseverance.

A child may have some spirit of wine and some camphire given to him;
the camphire will dissolve in the spirit of wine, till the spirit is
saturated; but then he will be at a loss how to separate them again.
To separate them, he must pour into the mixture a considerable
quantity of water; he will immediately see the liquor, which was
transparent, become muddy and white: this is owing to the separation
of the camphire from the spirit; the camphire falls to the bottom of
the vessel in the form of a curd. If the child had weighed the
camphire, both before and after its solution, he would have found the
result nearly the same