The limb and back plate of the mater are formed from one piece of brass. The rim of the limb has the names of seven winds. The limb has an outer scale of hours 0 to 12 twice, numbered by 1 with Roman numerals; the degree scale is used for subdivision to 20 and to 4 minutes. There is an inner degree scale 90 (at the throne) to 0 to 90 to 0 to 90, divided to 5, subdivided to 1, numbered by 5. The inside of the mater is blank. The throne is formed from two mermaids and a flower with a shackle and suspension ring.The rete has pointers for 17 named stars in a delicate tracery pattern incorporating a fleur de lys. The ecliptic band has the names and symbols for the zodiacal signs, each with a 30-degree scale, divided to 5, subdivided to 1, numbered by 5.
There are two plates. One, which is original has a geographical planisphere on a conical projection on either side, one from the north pole to the tropic of Capricorn, the other from the south pole to the tropic of Cancer. Each has a degree scale surrounding the map, 0 to 360, divided to 10, subdivided to 5 and to 1, numbered by 10. The second, later, plate is signed 'Pierre Seuin AParis' and has on one side an ordinary projection for latitude 48 degrees 52 minutes, and on the other a universal projection of the Rojas type.
The back has an outer degree scale 90 to 0 to 90 to 0 to 90, divided to 5, subdivided to 1, numbered by 5, the degree scale serving also for an inner zodiac scale with the names and symbols of the signs, each with a 30-degree section of the scale, numbered by 10. The representations of the signs are on a separate band decorated with clouds. Inside this is a calendar scale with months named in Latin, each with a scale of days divided to 5, subdivided to 1, numbered by 5 as appropriate. The first point of Aries is at 211/2 March. In the central space is a diagram of the 32 named points of the compass, a double shadow square, a table of dominical letters, the solar cycle, golden numbers and epacts for the years 1600 to 1627, and a perpetual calendar for these years. Signed and dated beneath the shadow square: 'Fr. Morillard Lugdunen. faciebat Narb. Anno M.VI c.'
There is a counterchanged alidade ('ALHIDADA') with folding vanes with a pair of sighting holes and a hole and target for alignment with the sun. There is a counterchanged rule ('OSTENSOR') with a latitude scale on one arm. There is also a later rule with sliding cursor and a blued steel articulated arm or brachiolum, all for use with the universal astrolabe plate. This later rule has an attached pin, threaded, fitting a round nut.
Jim Bennett
