First, greatest and outermost is Oceanus, which winds about the earth and the sea with nine rings, but is also a subterranean river. The river Styx (river of Hate), which is a primordial figure too (daughter of Oceanus), is a branch of Oceanus and a tenth part of his water is allotted to her.
So Styx, which flows out from a rock, is the tenth ring, though some say that Styx itself corrals the souls in the Underworld with nine rings.
Download ebooks on http://www.frenchtheory.com/
See that post with different algorithms in metabole
See the journal French Metablog with today different posts