Origin 433 BCE
The fourteenth mansion closes the northern palace with stars in Pegasus and Andromeda. Linked to libraries, literature and the storing of knowledge, it is auspicious for study, writing and construction. It shares its romanised name with the nineteenth lodge, the Net, though the two are written with different characters. The association with books plays on the lodge's name rather than resting on any observation, and wordplay of that sort runs throughout the almanac meanings attached to the set. The lodge is also unusually wide, closing the northern palace across a long and thinly populated stretch of sky.
Facts
Identity
Equatorial Extent (Du)9 du (about 8.9 degrees of equatorial arc) 2Tradition: Han-era Shi Shen tradition (Kaiyuan Zhanjing) Du: the arc-degree unit of the classical Chinese calendar, where a full circle equalled 365 and a quarter du (about 0.9856 modern degrees per du). This width is the Han-era figure standardized under the Taichu calendar and preserved in the Tang-dynasty Kaiyuan Zhanjing's Shi Shen star table; later dynasties recorded small revisions as precession shifted the determinative stars, so this is one epoch's figure, not a timeless constant. It measures the mansion's extent along the celestial equator (right ascension), the coordinate system Chinese astronomy actually used, not a position on the ecliptic (tropical zodiac); the atlas has no sourced mapping from this equatorial system onto a start point in ecliptic longitude, so this figure alone cannot be substituted into a start-end boundary range the way the equal Arabic-mansion spans are. Determinative StarGamma Pegasi 2Tradition: Han-era Shi Shen tradition (Kaiyuan Zhanjing) Origins
Origin Period433 BCE 1Tradition: Chinese equatorial astronomy Origin PeriodThe full set of twenty-eight lunar mansions is attested together for the first time on the lacquer box from the tomb of Marquis Yi of Zeng, sealed in 433 BCE, the earliest surviving object to record the complete list of names. 1 Origin of the NameThe English "lunar mansion" is borrowed from the Indian nakshatras and the Arabic manazil and misdescribes the xiu. A xiu is a lodge marked by a determinative star and measured in right ascension along the celestial EQUATOR; it is not a division of the Moon's ecliptic path, and the three systems are not variants of one scheme. 2 Attributions
PalaceBlack Tortoise of the North 1 Learn More
The Lunar Mansion Bi (Wall)
Bi (Wall) is the fourteenth of the twenty-eight xiu, the lunar mansions of traditional Chinese astronomy. Each xiu is a segment of the sky marked by a group of stars near the celestial equator, and together they divide the heavens into the belt through which the sun, moon and planets appear to move.
Palace, animal and place in the sky
This mansion belongs to the Black Tortoise of the North, the quadrant of the sky lying toward the north, one of the four symbolic creatures among which the twenty-eight are shared out seven to each. In the later scheme that pairs every mansion with a creature, Bi is assigned the Porcupine.
The twenty-eight mansions are among the oldest elements of Chinese sky-lore, attested well before the common era and used to track the nightly progress of the moon and to fix the calendar. The system is described here as that documented astronomical and calendrical tradition, from which its astrological uses later grew.
Bi, the Wall of the Black Tortoise
Bi, the Wall, is the fourteenth of the twenty-eight xiu and the last mansion of the northern palace, the Black Tortoise, one of two mansions romanised Bi, this one meaning wall. It is identified with the remaining stars of the Great Square of Pegasus and Andromeda, and it was anciently associated with libraries and writing. In the later astrological tradition its animal totem is the Porcupine. As one of the twenty-eight lunar mansions it closes the seven of the northern palace. These are the conventions of the Chinese astronomical and calendrical tradition, in which the twenty-eight xiu order the heavens into four palaces; with the Wall the Black Tortoise of winter gives way to the White Tiger of the west and autumn.
Bi the Wall closing the northern palace shares its transliterated name with the nineteenth mansion, Bi the Net, in the western palace, another instance of the accidental romanisation collisions that recur across the twenty-eight xiu; the two are entirely different Chinese characters, contexts and asterisms, and the coincidence is worth flagging precisely because it has misled more than one modern popular account that treats the repeated spelling as evidence of a deliberate structural pairing rather than an artefact of transliteration.
Cross-Tradition Connections
Contained In
One of the seven lunar lodges of this palace.
Originates in Language
Sources
1. Astrology and Cosmology in Early China: Conforming Earth to Heaven
David W. Pankenier, Cambridge University Press, 2013On the twenty-eight lodges and the Zeng Hou Yi lacquer chest
2. Science and Civilisation in China, Volume 3: Mathematics and the Sciences of the Heavens and the Earth
Joseph Needham, Cambridge University Press, 1959Vol. 3, the section on astronomy: the hsiu (lunar mansions), the equatorial system and the du measureQuote, Vol. 3, the section on astronomy: the hsiu (lunar mansions), the equatorial system and the du measure
The twenty-eight lodges are equatorial divisions bounded by determinative stars and so of unequal width, measured in du on a circle of 365.25 parts; their relation to the Indian and Arabic lunar mansion systems is unresolved.
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