How does Mark Twain use imagery in Roughing It?

Imagery:

"He dropped his ears, set up his tail, and left for San Francisco at a speed which can only be described as a flash and a vanish! Long after he was out of sight we could hear him whiz."

"The cayote is a long, slim, sick and sorry-looking skeleton, with a gray wolf-skin stretched over it, a tolerably bushy tail that forever sags down with a despairing expression of forsakenness and misery, a furtive and evil eye, and a long, sharp face, with slightly lifted lip and exposed teeth. He has a general slinking expression all over. The cayote is a living, breathing allegory of Want."

"Nothing helps scenery like ham and eggs. Ham and eggs, and after these a pipe—an old, rank, delicious pipe—ham and eggs and scenery, a "down grade," a flying coach, a fragrant pipe and a contented heart—these make happiness. It is what all the ages have struggled for."