Chapter 2: Work train engine changes from 9 to 6 and back to 9.
About 2 minutes into Chapter 1, when the train crew are looking at Hell's Gate Pass scenic valley, if you look to the bottom right, you can see a man wearing a hat walking up the hill.
At the end of Chapter 1 the cable that tips the wagon over onto the train tracks can be seen.
The same Indians on horseback are shown being shot off their horse several times in the movie.