while the two men helped themselves to some more of the green wine , he told them about the circumfence , the great effort that had been made to build it , and the ancient and wise kingdom of krull which had constructed it several centuries before , and the seven navies that patrolled it constantly to keep it in repair and bring its salvage back to krull , and the manner in which krull had become a land of leisure ruled by the most learned seekers after knowledge , and the way in which they sought constantly to understand in every possible particular the wondrous complexity of the universe , and the way in which sailors marooned on the circumfence were turned into slaves , and usually had their tongues cut out .