orms the starting point for stepping off the six points (C)
in the circle, using the dividers without resetting, after you have made
the circle. Then connect each of the points (C) by straight lines (D).
These lines are called chords. From the center draw two lines (E) at an
angle and one line (F) vertically. These are the radial lines. You will
see from the foregoing that the chords (D) form the outline of the
cube--or the lines farthest from the eye, and the radial lines (E, F)
are the nearest to the eye. In this position we are looking at the block
at a true diagonal--that is, from a corner at one side to the extreme
corner on the opposite side.

[Illustration: _Fig. 144._]

Let us contrast this, and particularly Fig. 142, with the cube which is
placed higher up, viewed from the same standpoint.

FLATTENED PERSPECTIVE.--Fig. 144 shows the new perspective, in which the
three vertical lines (A, A, A) are of equal length, and the six
angularly disposed lines (B, C) are of equal length, but shorter than
the lines A. The only change which has been made is to shorten the
distance across the corner from D to D, but the vertical lines (A) are
the same in length as the corresponding lines in Fig. 143.
Notwithstanding this change the cubes in both figures appear to be of
the same size, as, in fact, they really are.

[Illustration: _Fig. 145._]

In forming a perspective, therefore, it would be a good idea for the boy
to have a cube of wood always at hand, which, if laid down on a
horizontal support, alongside, or within range of the object to be
drawn, will serve as a guide to the perspective.

TECHNICAL DESIGNATIONS.--As all geometrical lines have designations, I
have incorporated such figures as will be most serviceable to the boy,
each figure being accompanied by its proper definition.

[Illustration: _Fig. 146._]

[Illustration: _Fig. 147._]

Before passing to that subject I can better show some of the simple
forms by means of suitable diagrams.

Referring to Fig. 145, let us direct our attention to the body (G),
formed by the line (D) across the circle. This body is called a segment.
A chord (D) and a curve comprise a segment.

SECTOR AND SEGMENT.--Now examine the shape of the body formed by two of
the radial lines (E, E) and that part of the circle which extends from
one radial line to the other. The body thus formed is a sector, and it
is made by two radiating lines and a curved line. Learn to distinguish
r