There was once a bridge which spanned a large river. During most of the day the bridge sat with its length running up and down the river paralleled with the banks, allowing ships to pass thru freely on both sides of the bridge. But at certain times each day, a train would come along and the bridge would be turned sideways across the river, allowing a train to cross it. A switchman sat in a small shack on one side of the river where he operated the controls to turn the bridge and lock it into ...