loosing my mind

I watched a documentary back in the 80s that was so good I cant forget it and cant find it anywhere.
I know it was about silent era westerns but dont remember the name of it.
What I do know was they were talking about some of the best angles ever filmed in a western and some of the best riding ever in a western, William S. hart was one of the best riders and was the best angle in "Tumbleweeds"
Also I remember a scene in which I believe to be Lillian Gish laying on a chunk of ice and being saved at the last minute from going over a waterfall, And I especially remember a group of men battling crocodiles from a canoe in search of a rare butterfly.
Thats about all I remember but I loved the way it was all put together and the music.
If anyone has any idea of what I'm talking about please answer and point me in some direction where I may be able to locate this film.