VISUAL AND AUDITORY DISTINCTIONS 179
of these containers being indentical in form and colour with the
insets themselves comes into view when the framed shapes are
deposited there and the insets are taken away.
For the first exercise I used a frame having a rectan-
gular area of the same dimensions (inside the rim) as the
frames described; the dark blue interior is surrounded by a
raised border about 6 mms. deep and 2 cms. wide. On this
frame is hinged a frame-cover made from strips about two
centimetres thick, crossed in such a way that they form a rim
which fits exactly over the lower structure, and is divided into six
equal squares by one transverse and two longitudinal bars. This
lattice-work cover turns on a small hinge and is fixed in front with
a small stud.
Into the blue background can be fitted exactly six square
frames of 10 cms. sides and 6 mms. thick, which are kept in
position by the cover when it is closed, because every spar forming
the grating is superposed on the extreme sides of the adjacent
plaques; the latter thus remain securely in place and the whole
can be handled as a single piece.
In addition to the advantage offered by the other pieces
described, this frame makes it feasible to have all the com-
binations possible with the geometrical figures by changing the
plaques, as well as that of keeping the individual frames in place.
The border and the external and internal outlines of the
frame are enamelled yellow; the pieces to be imbedded (the fiat
geometrical figures) are blue like the bottom of the frame.
I had provided also four flat plaques of the same yellow
colour, because by employing these one can adapt the frame to
take only one, two, three, four or five geometrical figures instead
of six. It is more helpful, in the first lessons, to work with only
two or three contrasting figures, or which at least differ a great
deal in shape (e.g., a circle and a square; or a circle, a square and
an equilateral triangle).
In such ways we may multiply the possible combinations.
A cabinet with six drawers is also provided; it may be of