In 1889, a Sunday school train excursion in Armagh, Ireland, turned tragic when the train stalled while climbing a steep hill. The crew decoupled the cars, intending to climb the hill with the first few cars and then pull the remaining cars separately, but the back section had insufficient brakes and rolled down into an oncoming train. At least 78 people were killed in the crash, including many children. What had the crew put behind the wheels to prevent the train cars from rolling backwards? Discuss
Source: The Free Dictionary