extract from this "academy of childish ingenuity"! (5/6.)

At this time he was undertaking the education of his own children. His
chemistry lessons especially had a great success. (5/7.) With apparatus of
his own devising and of the simplest kind, he could perform a host of
elementary experiments, the apparatus as a rule consisting of the most
ordinary materials, such as a common flask or bottle, an old mustard-pot, a
tumbler, a goose-quill or a pipe-stem.

A series of astonishing phenomena amazed their wondering eyes. He made them
see, touch, taste, handle, and smell, and always "the hand assisted the
word," always "the example accompanied the precept," for no one more fully
valued the profound maxim, so neglected and misunderstood, that "to see is
to know."

He exerted himself to arouse their curiosity, to provoke their questions,
to discover their mistakes, to set their ideas in order; he accustomed them
to rectify their errors themselves, and from all this he obtained excellent
material for his books.

For those more especially intended for the education of girls he took
counsel with his daughter Antonia, inviting her collaboration, begging her
to suggest every aspect of the matter that occurred to her; for instance,
in respect of the chemistry of the household, "where exact science should
shed its light upon a host of facts relating to domestic economy" (5/8.),
from the washing of clothes to the making of a stew.

Even now, to his despair, although freed from the cares of school life, he
was always almost wholly without leisure to devote himself to his chosen
subjects.