Part First
Lesson First Lines
Note to the Teacher.—In all the development-lessons, the pupils are to be occupied with the diagrams, and not with the printed matter.
See Note A, Appendix.
Refer to Diagram 1, and show that
What are here drawn are intended to represent length only.
They have a little width, that they may be seen.
They are called lines.
A line is that which has length only.
Points
Show that
Position is denoted by a point.
It occupies no space.
It has some size, that it may be seen.
The ends of a line are points.
A line may be regarded as a succession of points.
The intersection of two lines is a point.
A point is named by placing a letter near it.
A point may be represented by a dot. The point is in the center of the dot.
A point is that which denotes position only.
A line is named by naming the points at its ends.
Read all the lines in Diagram 1.
Crooked Lines
See Note B, Appendix.
Does the line m n change direction at the point 1?
At what other points does it change direction?
It is called a crooked line.
A crooked line is one that changes direction at some of its points.
Curved Lines
The line o p changes direction at every point.
It is called a curved line.
A curved line is one that changes direction at every point.
Straight Lines
Does the line i j change direction at any point?
It is called a straight line.
A straight line is one that does not change direction at any point.
Other Lines
The line q r winds about a line.
It is called a spiral line.
The line w x winds about a point.
It also is called a spiral line.
A spiral line is one that winds about a line or point.
The line 7 81 looks like waves.
It is called a wave line.
What kind of a line is a b?
Why? What is a straight line?
What kind of a line is 11 16?
Why? What is a crooked line?
What kind of a line is o p?
Why? What is a curved line?
What kind of a line is s t?
Why?
What kind of a line is 9 10?
Why? What is a spiral line?
What kind of a line is w x?
Why?
Notes
1. To be read seven, eight, not seventy-eight.