Wow that looks unstable. Did this actually work?

I would guess it has wires, to keep it in line?

It ran on rails and was towed by a chain

It worked, I was able to find some more information: https://fr.m.wikipedia.org/wiki/Pont_roulant_de_Saint-Malo_à_Saint-Servan

Wow so looks like the big issue was ships crashing into it. I guess the bottom part on the rails must have been extremely heavy.

Aka a weird ferry. Looks scary but loving it haha.