However, if you want to see what Abbey is really made of, check out his wonderful sketches and studies.
Note in the drawing above how Abbey draws with his eraser as much as his charcoal, in order to create the right values.
I prefer these studies to most of his finished drawings. They are very revealing and they have a powerful, mystical feeling to them.
Very few people ever see these studies. Many are locked up in the Yale University collection. However, I think they are almost as important as the Boston murals themselves when it comes to appreciating Abbey as an artist.