e able to see plainly if the work is proceeding evenly
and equally, for if one-half of the pen is thicker at the point or edge
than the other, it will show a brighter line. This is especially the
case with instruments that have become dull by use, for in that case the
edges will be found quite bright, and any inequality of thickness shows
plainly.

[Illustration: Fig 33.]

[Illustration: Fig. 34.]

It follows, from what has been said, that the needle-point and pen-point
should stand vertical when in use, and to effect this the instruments,
except in the smallest sizes, are provided with joints, such as shown at
A and B in the bow-pencil or circle-pencil, in Figure 33. These joints
should be sufficiently stiff that they will not move too easily, and yet
will move rather than that the legs should sensibly spring without
moving at the joint. The needle-point leg should be adjusted by means of
the joint, to stand vertical, and the same remarks apply equally to the
pen-leg; but in the case of the pencil-leg it is the pencil itself and
not the leg that requires attention, the joint B being so adjusted that
the pencil either stands vertical, or, what is perhaps preferable, so
that it stands inclined slightly towards the needle-point. In
sharpening the pencil the inner face C may be made concave or at least
vertical and flat, and the outer convex or else bevelled and flat,
producing a fine and long edge rounded in its length of edge. In using
the circle-pencil and circle-pen it will be found more convenient to
rotate it in the direction of the arrow in Figure 34. It should be held
lightly to the paper, and the learner will find that he has a natural
tendency to hold it too firmly and press it too heavily, which is
_especially to be avoided_.

If in drawing a small circle the needle-point slips out of the paper, it
is because the pencil-point is too long; or, what is the same thing, the
needle-point does not protrude far enough out from the leg. Or if the
instrument requires to be leaned over too much to make the pencil or pen
mark, it is because the pen or pencil is not far enough out, and this
again may cause the needle-point to slip out of the paper.

[Illustration: Fig. 35.]

[Illustration: Fig. 36.]

In Figure 35 is shown a German instrument especially designed to avoid
this slipping. The peculiarity of this instrument consists in the
arrangement of the centre point, which remains stationary whilst the pen
or penci