Just beneath was a pretty little blue lake, walled in with great forest trees some of which must have been over a hundred feet high.  A short way beyond was an immense field covered with what they were sure must be sugar-cane, and in which they could see dark-skinned men at work with queer carts and clumsy oxen.  At the right, a mere thread of silver, was a river, hedged with tropical vegetation.  This swept around toward their front, enlarging as it came, and at what seemed no farther than five miles away, poured its waters out into a great sea of apparently limitless expanse.