Ok, I couldn't find Mr. Williams bit on Marathon Running, but this little ditty on Gaaahf, explains pretty well how Mountain Ultras are to running track.
It's not just running.
It's not just running a long way.
It's not just running a long way over, through, around and in stuff.
It's running a long x 100 way, over mountains, over boulders, in the dark, through mud, around and through bodies of water, AT ALTITUDE.
Oh, great sport Andy! What this sport was taken?
As the late great Mr. Richard Pryor said in this town, "You aint the smartest M'F'er in the world."
No Richard I'm not!