61

The names of regular polygons 62

The angles of regular polygons; the ellipse 63

Form of a true ellipse 69

The use of a trammel for drawing an ellipse 72

To draw a parabola mechanically 73

To draw a parabola by lines 74

To draw a heart cam 75

CHAPTER IV.

SHADOW LINES AND LINE-SHADING.

Section lining or cross-hatching 77

To represent cylindrical pieces one within the other; to represent a
number of pieces one within the other 78

To represent pieces put together and having slots or keyways through
them. 79

Effects of shading or cross-hatching 80

Lines in sectional shading or cross-hatching made to denote the material
of which the piece is composed--lead, wood, steel, brass, wrought
iron, cast iron 81

Line-shading 82

The shade line to indicate the shape of piece; representation of a
washer 83

A key drawn with a shade line; shade line applied to a nut; a German
pen regulated to draw lines of various breadths 84

Example of line-shading in perspective drawing, shown in a pipe threading
stock and die 85

A cylindrical pin line-shaded; two cylindrical pieces that join each
other; a lathe centre; a piece having a curved outline 86

Line-shading applied to a ball or sphere; applied to a pin in a socket
shown in section 87

A piece of tube, where the thickness of the tube is shown; where the
hollow or hole is seen, the piece shown in section; where the body is
bell-mouthed and the hollow curve shown by shading 88

Example of line-shading to denote the relative distances of various
surfaces from the eye 89

Line-shading to denote that the