Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. For the benefit of those who, for the first time, may meet new terms and expressions in this manual, the following vocabulary, with definitions, is appended:

Altitude. Vertical height.

Angle. Space between two intersecting lines.

Apex. Point where converging lines meet.

Apices. More than one apex.

Arc. Any part of the circumference of a circle.

Area. Surface in units of measurement.

Bisect. To cut in two equal parts.

Bisector. A line which bisects.

Chord. The line connecting any two points of an arc of a circle.

Circumference. The boundary of a circle.

Circumscribe. To draw around.

Convention. Customary method or symbol used in producing a drawing.

Decagon. Figure of ten sides and ten angles.

Degree. One 360th part of a circle.

Diameter. The distance measured across the center of a circle or a line drawn through the center terminating in the circumference.

Element. A part which goes to make up the whole.

Elevation. A view of an object looking at the front or side.

Elliptical. Pertaining to the shape of an ellipse.

Equilateral. Equal-sided.

Frustum. Remaining portion of a cone or pyramid when the top has been removed parallel to the base.

Hemisphere. Half a sphere.

Heptagon. Figure of seven sides and seven angles.

Hexagon. Figure of six sides and six angles.

Horizontal. Parallel to the horizon.

Hypotenuse (spelled also Hypothenuse). The diagonal distance between opposite angles of a rectangle or the side opposite the right angle.

Isometric. Of equal measurement.

I

For the benefit of those who, for the first time, may meet new terms and expressions in this manual, the following vocabulary, with definitions, is appended:Altitude. Vertical height.Angle. Space between two intersecting lines.Apex. Point where converging lines meet.Apices. More than one apex.Arc. Any part of the circumference of a circle.Area. Surface in units of measurement.Bisect. To cut in two equal parts.Bisector. A line which bisects.Chord. The line connecting any two points of an arc of a circle.Circumference. The boundary of a circle.Circumscribe. To draw around.Convention. Customary method or symbol used in producing a drawing.Decagon. Figure of ten sides and ten angles.Degree. One 360th part of a circle.Diameter. The distance measured across the center of a circle or a line drawn through the center terminating in the circumference.Element. A part which goes to make up the whole.Elevation. A view of an object looking at the front or side.Elliptical. Pertaining to the shape of an ellipse.Equilateral. Equal-sided.Frustum. Remaining portion of a cone or pyramid when the top has been removed parallel to the base.Hemisphere. Half a sphere.Heptagon. Figure of seven sides and seven angles.Hexagon. Figure of six sides and six angles.Horizontal. Parallel to the horizon.Hypotenuse (spelled also Hypothenuse). The diagonal distance between opposite angles of a rectangle or the side opposite the right angle.Isometric. Of equal measurement.Isosceles Triangle. A triangle with two sides of equal length and base angles equal.Lateral. Side.