too
great, as shown exaggerated in Figure 18, the body of the ink lies too
near the point and is apt to flow too freely, running over the pen-point
and making a thick, ragged line. On the other hand, if the inside faces,
between which the ink lies, are too parallel and narrow near the points,
the ink dries in the pen, and renders a too frequent cleaning necessary.
Looking at the face of the pen as at A in Figure 17, its point should
have an even curve, as shown, the edge being as sharp as it can be made
without cutting the drawing paper. Upon this quality depends the
fineness and cleanness of the lines it will make. This thin edge should
extend around the curve as far as the dotted line, so that it will be
practicable to slant the pen in either of the directions shown in Figure
19; and it is obvious that its thickness must be equal around the arc,
so that the same thickness of line will be drawn whether the pen be held
vertical or slanted in either direction.

[Illustration: Fig. 19.]

[Illustration: Fig. 20.]

The outside faces of the pen should be slightly curved, so that when
held vertically, as in Figure 20 (the dotted line representing the
centre of the length of the instrument), and against the square blade S,
the point will meet the paper a short distance from the lower edge of S
as shown. By this means it is not necessary to adjust the square edge
exactly coincident with the line, but a little way from it. This is an
advantage for two reasons: first, the trouble of setting the square-edge
exactly coincident is avoided, and, secondly, the liability of the ink
to adhere to the edge of the square-blade and flow on to the paper and
make a thick, ragged line, is prevented.

The square being set as near to the line as desired, the handle may be
held at such an angle that the pen-point will just meet the line when
sloped either as in Figure 21 or 22. If, however, the slope be too much
in the direction shown in Figure 21, practice is necessary to enable the
drawing of straight lines if they be long ones, because any variation in
the angle of the instrument to the paper obviously vitiates the
straightness of the line. If, on the other hand, the square be too close
to the line, and the pen therefore requires to be sloped as in Figure
22, the ink flowing from the pen-point is apt to adhere to the
square-edge, and the result will be a ragged, thick line, as shown in
Figure 23.

[Illustration: Fig. 21.]

[Illustratio