Economists talk with graphs (too much, I think, but that's another post), and the ability to draw a good graph is part of the skill set econ professors have to develop. I am fond of using four-quadrant diagrams to draw IS and LM curves for my intermediate macro students. I can't hold a candle to one of my colleagues however, who teaches microeconomic theory with a personal cache of colored chalk. We have plenty of classrooms with computers and projectors and the like, but he needs none of these.

PZ Myers calls my attention to this article on the decline of blackboards at the U of M, and offers this reminiscence.

Although�there is one place where I would favor the chalkboard. One of my pleasantest memories of my undergraduate education was my comparative anatomy course. I and many of my fellow students would always show up early for class, because Professor Snider would come in 10 or 15 minutes before it started, armed with his own personal box of colored chalk. And then he would start drawing. He�d sketch in these elaborate diagrams�skull bones of reptiles, birds and mammals, a hindlimb with the muscles pulled apart to show their attachments, a time-series of kidney development. One thing you can do with chalk that is impossible to do well with a dry erase marker is shading, and he�d carefully color-code all the parts he was planning to talk about that day. It was like watching a good sidewalk artist at work. And all of us students would be sitting at our desks with our collections of colored pens and pencils, filling in the pages of our notebook before he started talking, because we knew that once he started explaining things there wouldn�t be time to draw.

And at the end of class, he�d take an eraser and quickly destroy all of his work. It was a marvel. The ability to blithely obliterate a beautiful creation because one can create it quickly and at will is a real talent.

I never took biology in college -- chemistry was my only science, and I wish I had taken another science as well -- but I can tell you this is right. Not all economics is susceptible to chalk-and-talk, and indeed the best parts you can express with words alone. But watching someone draw out third-degree price discrimination on a board is to witness something elegant.