Decan 1 of Sagittarius

This is the first ten-degree segment of Sagittarius, the mutable fire sign, spanning 0 to 10 degrees. Its ruler in the Chaldean order of faces is Mercury, 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 only later.

The Golden Dawn of 1888 assigned the thirty-six minor arcana to the decans in order; this segment bears the Eight of Wands, titled Swiftness, its Mercury-in-Sagittarius planet taken from the face ruler, swift Mercury in the far-shooting fire sign matching the card's image of arrows in flight and rapid motion. That tarot correspondence is a modern Western overlay on the far older decan scheme, not a feature of the Egyptian or Hellenistic decan material it was laid upon.

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

The card on the decan

In the Golden Dawn's assignment this decan carries the Eight of Wands. 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 Sagittarius is a Fire sign and takes a card of Wands, and the rank follows the position in the sequence, which puts the eight 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.