Decan 1 of Libra

This is the first ten-degree segment of Libra, the cardinal air sign, spanning 0 to 10 degrees. Its ruler in the Chaldean order of faces is the Moon, following the continuous sequence of the seven planets around the thirty-six decans. The decans are the oldest stratum of astrology, beginning as thirty-six Egyptian stars whose risings marked the ten-day weeks of the year and were absorbed into the Greek zodiac as ten-degree subdivisions of the signs only later.

The Golden Dawn of 1888 assigned the thirty-six minor arcana to the decans in order; this segment bears the Two of Swords, titled Peace or Peace Restored, its Moon-in-Libra planet taken from the face ruler, the balanced air sign and the twos of the mental suit matching the card's image of a tense, held equilibrium. That tarot correspondence is a modern Western overlay on the far older decan scheme, not a feature of the Egyptian or Hellenistic decan material.

The first decan of Libra runs from 0 to 10 degrees of the sign and is ruled, in the scheme this atlas records, by Moon.

The card on the decan

In the Golden Dawn's assignment this decan carries the Two of Swords. The mapping is one to one and exhaustive: the thirty-six small cards numbered two to ten across the four suits match the thirty-six decans exactly, taken in order from the Two of Wands at the first decan of Aries. The suit follows the sign's element, so Libra is a Air sign and takes a card of Swords, and the rank follows the position in the sequence, which puts the two here.

Two ruler schemes, and which one this is

Two schemes for decan rulership are in circulation and they disagree. The one recorded here runs the seven planets in Chaldean order continuously round the circle. The other, the triplicity scheme, gives a sign's three decans to the rulers of the three signs of its own element in order, so the rulers stay inside the element and restart at every sign. Both are attested in the tradition, neither is a corruption of the other, and a reader comparing two books will find them differing here without either being wrong.

What the atlas is recording

The degrees and the ruler are the attributions this atlas holds for this decan, and the card is the Golden Dawn's. All of them are traditions with variants rather than settled facts, and the decan itself, as a ten degree segment of a sign, is the only part that is simply arithmetic.