es; if, indeed, a little child of three may achieve as
his maximum the repetition of an act forty times in succession, the
child of six is capable of repeating two hundred times an act which
interests him. If the maximum period of continuous work on the same
object may be half an hour for the child of three, it may be over two
hours for the child of six.

Hence, to establish systematic tests for a certain purpose, such as
that of preparing children to write, without taking their ages into
account, is valueless. For example, my system of writing is based upon
the direct preparation of the movements which physiologically concur
to produce writing: _i.e._ manipulation of the instrument of writing
and the tracing of the letters of the alphabet. The children, filling
in the contours of the insets with innumerable parallel strokes in the
one case, and touching the sand-paper letters in the other, fix the
two muscular mechanisms so perfectly, that the final result is an
"explosion" of "spontaneous writing" extraordinarily uniform in all
the children--because, as if all molded to a common form, they have
fixed the necessary movements by touching the same alphabet, and
therefore reproduce its forms faithfully. To bring this about, to
establish a real motor-mechanism, it is essential that the exercise
should be repeated over and over again. Now the children who take most
interest in filling in the figures with parallel strokes, and, above
all, in touching the letters, are, at most, between four and five
years old. If we offer the same material to a child of six he will not
touch the letters often enough, and he will always write imperfectly,
in comparison with the child who has begun the exercise at a suitable
age. This applies also to all the other details of the system. It is
therefore possible to determine experimentally, with, I believe, a
precision not hitherto attained, what is the mental attitude of the
child at various ages, and hence, if the fitting material for
development be offered, what will be the average level of
intellectual development according to age.

Here we have an indication of the possibility of _determining_ the
means of development so exactly as to establish a true correspondence
between internal needs and external stimuli, just as actual as the
correspondence which exists between the insect and the flower.

He who has all this material ready to his hand has an easy task in
bringing about the natural