The eighth hexagram, Bi ("Holding Together" or Union), places Kan (Water) above Kun (Earth). Water flowing over the earth draws together into rivers and seas, the image of things joining around a common center. It follows The Army in the King Wen sequence, moving from disciplined force to willing union.
Bi stands 62nd of 64 in the xiantian, or Earlier Heaven, arrangement, the binary ordering devised by Shao Yong in the eleventh century and traditionally ascribed to Fu Xi, a position distinct from its eighth place in the King Wen sequence traced above. This was the ordering Joachim Bouvet, a Jesuit in Beijing, sent to Gottfried Wilhelm Leibniz in 1701, letting Leibniz read the broken and unbroken lines as his own binary 0 and 1.
Read from the bottom, the six lines of Holding Together run yin, yin, yin, yin, yang, yin. A later interpretive layer absent from the original Zhou Yi, the nuclear hexagram (hu gua), treats lines two through four as a lower trigram and lines three through five as an upper one; here they combine as Gen over Kun, forming hexagram 23, Splitting Apart (Bo), a hidden figure first associated with the Han-dynasty scholar Jing Fang, whose Yijing commentary of the first century BCE is credited with the earliest appearance of nuclear trigrams. Holding Together's King Wen partner is hexagram 7, The Army (Shi); most of the sixty-four pair this way, related by turning the whole figure upside down, while the eight hexagrams built from a single doubled trigram pair instead by inverting every line. Mawangdui (1973) orders hexagrams by trigram, not King Wen; names here follow Wilhelm and Baynes, 1950, not Legge, 1882.