250 THE MONTESSORI METHOD
one of the guiding lines, and leave, sometimes that on the right, sometimes that on the left, finally taking away this last line and at last, the dots, beginning by erasing the one at the top which indicates the starting point of the line and of the hand. The child thus learns to draw a vertical without material control, without points of comparison.
" The same method, the same difficulty, the same means of direction are used for the straight horizontal lines. If, by chance, these lines begin well, we must await until the child curves them, departing from the centre and proceeding to the extremity as nature commands him, and because of the reason which I have explained. If the two dots do not suffice to sustain the hand, we keep it from deviating by means of the parallel lines or of the rulers.
" Finally, have him trace a horizontal line, and by uniting with it a vertical ruler we form a right angle. The child will begin to understand, in this way, what the vertical and horizontal lines really are, and will see the relation of these two ideas as he traces a figure.
" 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 Seguin 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