Read it through once

The big Buttocks of the land closed round upon us, and the river narrowed, and then we entered the immense width of a forest-track, and slowly felt our way among the trunks. The sun went down: a heavy, sluggish heat settled upon the water. The great river, brown with its own muddy life, rolled on, and the bank on either side was a wall of sombre vegetation. Nothing moved but the boat and the gulls which fluttered and screamed above us.