Sentence:  If a person hires a ship and loads her or not entirely, and wishes to unload her, before she sets sail, he shall pay half the ship's freight. But if the ship has sailed a <WSD>kenning</WSD>'s way seawards, he shall pay the shipmaster his full freight. ["Footnote": <WSD>"kenning</WSD>" ... This phrase is applied in the Rutter of the Sea to signify the distance from one headland to another in sight. Vol. I., p. 115.] 
Meaning of the word marked with <WSD> tags:  The range or extent of vision, "especially" at sea;  a marine measure of approximately twenty miles.