River Mole in 1613. In John Speed's 1611 map of Surrey this stretch of the river is denoted by a series of hills accompanied by the legend "The river runneth under". However the river's name is unlikely to have derived from this behaviour: The "Oxford Dictionary of English Place Names" suggests that "Mole" either comes from the Latin "mola" (a mill) or is a back-formation from "Molesey" (Mul's island). In John Rocque's 1768 map of Surrey, the name "Moulsey River" is used. In common with much of the rest of the Weald, the earliest evidence of human settlement along the Upper Mole
River Mole the Pipp Brook, a tributary draining the northeastern slopes of Leith Hill. Between Dorking and Leatherhead the Mole cuts a steep-sided valley (the Mole Gap) though the North Downs, carving a river cliff on the western flank of Box Hill and a smaller cliff at Ham Bank in Norbury Park. The sudden change from impermeable Wealden Clay to permeable chalk and the increased gradient of the river (which drops in the stretch between Brockham and Leatherhead, compared to in between Horley and Brockham) allow the water table to drop below the bed of the river. Water is able to flow