Superseded by the Birmingham Accords of 1967 where natural waterway usage is allowed, but with a penalty of a loss of turn - a return to a more pure form of the game. Overland portage is, of course, right out unless playing under Victorian rules where it is allowed on odd Tuesdays and the Queen’s Birthday (it’s lost to antiquity as to whether it’s Victoria only or any prior or subsequent Queen).
Okay, I’ll stop.