It did not take the Black Bear very long to pass the green islands near the delta.  The river there looks like an ocean.  In fact, the main branch of the Amazon is from fifty miles to two hundred miles in width.  Some of the tributaries are a hundred miles wide.  It is from fifty to two hundred feet deep.  The water is always dark colored because of the wash brought down from the uplands.  For a long time it did not seem possible to the boys that they were sailing on a river instead of an ocean.