Clapper Bridge

"Since our last letter... we have driven to some of the places on Dartmoor that are of interest.  Clapper bridges dot the moors and are made of huge flat stones set on stone pillars to provide crossing of small rivers for wagons and pack horses.  We have also visited the ruins of one of the earliest castles in the area, Okehampton.  Though solidly built of stone, without ongoing maintenance, even solid castles become ruins.  Of course stone was often taken for other structures when there wasn't a resident nobleman."