Madregot & Yesod Redux
With all the question flying around about Yesod I decided to really re-check the text on Brook Madregot. I felt the answers would be there and I do think I have a clearer view of what is going on now.
Tinkerbell Tzadkiel say Brook Madregot runs from Yesod to Briah. The "glory of Yesod "upstream to the "destruction of Briah downstream. Juturna confirms that it "rises in Yesod and rushes to Briah".
Severian uses Madregot (there is a meadow also) to travel four times. The first is from Tzadkiel's "skipper's quarter" to Severian's stateroom. Later he uses the Brook for time travel. We are not told which direction he moves except once. In his trip from Typhon's rule to Valeria's rule he takes 7 strides downstream. so we learn that downstream carries him to the future.
Brook Madregot doesn't represent time as much as energy and entropy. Entropy increases as you move through time, so Yesod, with higher energy, lower entropy would seem to be in the past from Briah
Dowstream is to the future, and Yesod is upstream, I think we must conclude that Yesod is in the past from Briah. I think this is confirmed by Tony Ellis' observation that the Ship travels backward in time to get to Yesod.
With regard to branching, I will speculate that Brook Madregot is a straight, single path as Severian moves (upstream) toward the past. The past, his orgin, is fixed. Severian only encounters branchings as he makes the long, future-ward journey all the way from Apu Punchau to the blossoming of Ushas.
One other feature about Brook Madregot is that tinkerbell Tzadkiel warns Severian "Don't jump across it though, or you'll end up in another place". I'm not sure what that means..perhaps that there is spatial travel involved in Madregot also and Severian doesn't want to step out onto a place in Briah which isn't Urth/Ushas.
As the Jordan-Wolfe interview clearly suggests that Urth is a past iteration of Earth
I think this rules out the guess that Yesod is our universe. Too bad. It would have been nice to get Jesus worked into the story somehow, however tangentially.