"In the sequence of the development of lines, it would seem that the study of the oblique should immediately follow that of the vertical and the horizontal, but this is not so! The oblique which partakes of the vertical in its inclination, and of the horizontal in its direction, and which partakes of both in its nature (since it is a straight line), presents perhaps, because of its relation to other lines, an idea too complex to be appreciated without preparation."
Thus Séguin goes on through many pages, to speak of the oblique in all directions, which he has his pupils trace between two parallels. He then tells of the four curves which he has them draw to right and left of a vertical and above and below a horizontal, and concludes: "So we find the solution of the problems for which we sought--the vertical line, the horizontal, the oblique, and the four curves, whose union forms the circle, contain all possible lines, _all writing_.
"Arrived at this point, Itard and I were for a long time at a standstill. The lines being known, the next step was to have the child trace regular figures, beginning of course, with the simplest. According to the general opinion, Itard had advised me to begin with the square and I had followed this advice _for three months_, without being able to make the child understand me."
After a long series of experiments, guided by his ideas of the genesis of geometric figures, Séguin became aware that the triangle is the figure most easily drawn.
"When three lines meet thus, they always form a triangle, while four lines may meet in a hundred different directions without remaining parallel and therefore without presenting a perfect square.
"From these experiments and many others, I have deduced the first principles of writing and of design for the idiot; principles whose application is _too simple_ for me to discuss further."
Such was the proceeding used by my predecessors in the teaching of writing to deficients. As for reading, Itard proceeded thus: he drove nails into the wall and hung upon them, geometric figures of wood, such as triangles, squares, circles. He then drew the exact imprint of these upon the wall, after which he took the figures away and had the "boy of Aveyron" replace them upon the proper nails, guided by the design. From this design Itard conceived the idea of the plane geometric insets. He finally had large print letters made of wood and proceeded in the same way as with the geometric figures, that is, using the design upon the wall and arranging the nails in such a way that the child might place the letters upon them and then take them off again. Later, Séguin used the horizontal plane instead of the wall, drawing the letters on the bottom of a box and having the child superimpose solid letters. After twenty years, Séguin had not changed his method of procedure.