Read it through once

The chosen date being come, and all things in readiness, the two great steamers back into the stream, and lie there jockeying a moment, and apparently watching each other's slightest movement, like sentient creatures; flags drooping, the pent steam shrieking through safety-valves, the black smoke rolling and tumbling from the chimneys and darkening all the air. People, people everywhere; the shores, the house-tops, the steamboats, the ships, are packed with them, and you know that the borders of the broad Mississippi are going to be fringed with humanity thence northward twelve hundred miles, to welcome these racers.