Jets
At the opening of the film we see jets flying over Jack as he lays in the desert. They are a symbol of the new, faster-paced world colliding with Jack's old west, slower-paced life.
Chained
Jack chains his horse by it's ankles in the opening scene. This is a symbol that his horse is wild to the bone and the only way to keep it still is to chain it down. In the same way, the horse is Jack.
Horse in Rearview
Crossing the major road on his horse we see Jack mounted on the horse in the rearview mirror of a man's car. It symbolizes that Jack's old west way of living is being left behind in this new world where everyone is moving faster because of the machine. There's no place for them on this road.
Phone Call
Jack is told that he has a phone call by the police officer in charge of the prison. This phone call is a symbol of the beating the officer is about to give him for testing the cop on his first day in jail.
Campfire
The Sheriff finds a burned down campfire while looking for Jack. This is a symbol that he is close on the cowboy's heels and is close to catching him.