One night, a little before nine o'clock, Dr. Johnson was answering a telephone call. He was asked to go and give an operation to a very sick boy at once. The boy was in a small hospital in Glens Falls, sixty miles away from Dr. Johnson's city—Albany. The boy had hurt himself in a traffic accident. His life was in danger, but his family was so poor that they could not pay the doctor anything. After he heard all this, Dr. Johnson was driving carefully. He thought that he could get to the hospital before 12 o'clock. A few minutes later, the doctor's car had to stop for a red light at a crossing. Suddenly a man in an old black coat opened the door of the car and got in. 'Drive on' ,he said. 'I've got a gun(枪). ' 'I'm a doctor,' said Johnson. 'I'm on my way to a hospital to operate on a very sick... ' 'Don't talk,' said the man in the old black coat. 'Just drive. ' A mile out of the town he ordered the doctor to stop the car and get out. Then the man drove on down the road. The doctor stood for a moment in the snow. A half hour, Dr. Johnson found a telephone and called a taxi (出租车). At the railway (铁路) station he learned that the next train to Glens Falls would not leave until 12 o'clock. It was after two o'clock in the morning when the doctor arrived at the hospital in Glens Falls. Miss Clarke, a nurse, was waiting for him. 'I did my best,' said Dr. Johnson. Miss Clarke said. 'The boy died an hour ago. ' They walked into the waiting room. There sat the man in the old black coat, with his head in his hands. 'Mr. Shute,' said Miss Clarke to the man,' this is Dr. Johnson. He had come all the way from Albany to try to save your boy. ' From the story we know it took Dr. Johnson ______ to get to the hospital.