Read it through once

Let us drop the Mississippi's physical history, and say a word about its historical history--so to speak. We can glance briefly at its slumbrous first epoch in a couple of short chapters; at its second and wider-awake epoch in a couple more; at its flushest and widest-awake epoch in a good many succeeding chapters; and then talk about its comparatively tranquil present epoch in what shall be left of the book.