sentences:  The Cow Tower was one of several fortifications along this stretch of the river, with the gatehouse of Bishop Bridge lying just to the south, followed by two boom towers that controlled access to the waterway a further down-river, and with another tower positioned up-river to the north.Although the Cow Tower was not directly part of the city walls, a protective timber palisade linked the tower with the line of the city wall to the north-west, and ran south to meet Bishop Bridge.The city's accounts show the details of the payments for the construction of the tower between 1398 and 1399, including charges for 36,850 bricks, stone, sand, lime, a hoist and various equipment.