Cross-Contour Lines

Definition:

Cross-contour lines are very much an attitude about and approach to drawing. They are the lines that reflect the movement of your eye in and around what you see.

While contour lines describe edges, cross-contours describe form and volume. These lines can follow planes of form, moving around and across objects as well as through them.

Think of a topographical map--the lines move across the terrain. Cross-contour lines do the same thing.

(source)

Cross contour lines, as I've described, are as above - in addition to this, try to think of it this way:

Contour follows the outline and edges of the form, while,
Cross-Contour CROSSes over the object to contour the  surface and planes of the form.
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There are many varying ways of treading the lines in a Cross-Contour drawing.
You can vary the width of the line
You can make the line lighter
Create depth by overlapping one line to hide another
A line can be wavy
The line can be long, and gradually fade

Think about the way we expressed line in the first part of the class with the line exercises, and think about how you can bring that experience into a cross-contour drawing.
 

Examples of cross-contour line drawing: