The slow day's run with little wind and the long equatorial calms permitted him to penetrate a little into the mysteries of the oceanic immensity, severe and dark, that for ancient peoples had been "the night of the abyss," "the sea of utter darkness," "the blue dragon that daily swallows the sun.

The gigantic equatorial river basin is filled with an immense forest, the largest in the world, with which no other forest can be compared save those of western Africa and Malaysia.