Yi

Mountain 9 of the twenty-four mountains (luopan) is Yi, one of the eight Heavenly Stems placed on the ring, occupying position E3, east sector, 97.5 to 112.5 degrees. Yi is Yin Wood, and its classic image is the grass, the flower, the climbing vine. In Four Pillars astrology, where a person's chart is read from the stem and branch of the year, month, day and hour, a Yi Day Master, the stem governing the day of birth, is described as gentle, sociable and quietly persistent, able to bend where the rigid tree would snap, though it may lean too much on others.

Ten Heavenly Stems exist in the full sexagenary system, one yang and one yin stem for each of the five elemental phases, but only eight reach the compass ring: the pair for Earth, Wu and Ji, is withheld from the perimeter and reserved to the centre, following the same five-phase logic recorded elsewhere in this atlas under which Earth's own direction is the pivot rather than any one of the eight compass points. Because ten stems and twelve branches do not share a common factor larger than two, a given stem does not return to a given branch until the combination has cycled sixty times, the sexagenary count (jiazi) that names years, months, days and hours across the traditional Chinese calendar; a mountain's own stem or branch name is therefore also, in a different context entirely, a recurring building block of that sixty-term cycle.

Yi sits directly opposite mountain 21, Xin, twelve positions and a hundred and eighty degrees around the ring, the pairing compass school feng shui reads as a sitting-and-facing set for a building or a grave, back toward Yi and front toward Xin. Stephen Skinner's account of the luopan places the stem ring between the branch ring below it and the outer rings above, functioning as a finer division that lets a practitioner distinguish three fifteen-degree mountains within the thirty degrees a single branch alone would otherwise cover undivided; Yi is one of the two stem mountains flanking its sector's branch, sharing the sector's general direction while carrying its own distinct element and, through the Day Master reading, its own distinct temperament.

Because the eight stems on the ring pair up by element, Yi's own element partner sits in the mountain immediately across the same sector from it rather than opposite across the full circle, a closer, same-sector relationship compass school treatments keep distinct from the sitting-facing opposition proper. Compass school practice treats the fifteen-degree seam between one mountain and its neighbour as a genuine hazard rather than a rounding error: a sitting or facing line falling exactly on that boundary, called an empty or straddling line, is read as drawing on the qi of both adjacent mountains at once rather than cleanly on one, and Stephen Skinner's account of the luopan treats avoiding a seam-line reading as one of the instrument's basic disciplines, checked before any of the finer rings above the twenty-four mountains are consulted at all.