This striking armillary sphere is built according to the Ptolemaic model, depicts the earth at the centre of the solar system. These models of the cosmos, either Ptolemaic (earth centric), or Copernican (heliocentric), were used as teaching aids for European nobility, and can often be seen in portraits of the time to denote the breadth of the sitters learning.

This particular example, somewhat unusually, rests on a compass with screw feet so that it can be levelled, and although the work is neither signed or dated, the small volutes that connect the barrel to the compass as well as the engraving of the compass can be compared to table clocks and compasses from the Augsburg region; one of the major centre of scientific instrument production of the sixteenth and seventeenth century.

Construction

At the centre, the terrestrial globe is engraved with, the polar circles, the tropics, the equator, and the circle of the zodiac. The four continents are named: AMERICA, EUROPA, AFRICA, ASIA.

The globe is surrounded by five parallel rings: (from top to bottom) the Arctic Ring, Tropic of Cancer, The Equator, Tropic of Capricorn, the Antarctic Ring. The equator ring isslighly larger than the rest and bears a scale from 0 to 360 subdivided into units which mark every 5° and 10°.

A sixth ring or wide band, the Ecliptic, encompasses the Tropics of Cancer and Capricorn is graduated from 10 to 30, and shows the signs of the zodiac.

The horizon ring also depicts the signs of the zodiac (the inner edge), with each divided into into 30 degrees. Each sign is accompanied on the right by its Latin name: ARIES, TAURUS, GEMINI, CANCER, LEO, VIRGO, LIBRA, SCORPIUS, SAGITTARIUS, CAPRICORNUS, AQUARIUS, and PISCES. The centre is engraved with a calendar divided into days, with the names of the months in Latin: IANUARIUS, FEBRUARIUS, MARTIUS, APRILIS, MAJUS, IUNIUS, IULIUS, AUGUSTUS, SEPTEMBER , OCTOBER, NOVEMBER, DECEMBER as well as the inscription of the names of saints and religious holidays. The outer edge indicates the cardinal points accompanied by the fourteen winds also named in Latin (Vulturnus, Eurus, Aquilo, Zephyrus…).

The circle of the horizon is supported by four arms attached to the barrel resting on three volutes connected by screws to the silver brass compass with central decoration of a wind rose indicating sixteen directions. It is engraved on the rim with the cardinal points MERIDIES, ORIENS, OCCIDENS and SEPTENTRIO surrounded by a circular scale divided and numbered twice from 0 to 90 on either side of a fleur-de-lys.