Instruments · Nocturnal and sundial
Nocturnal and sundial by Georg Zorn, Germany, 1613
- Maker / attribution
- Georg Zorn (maker)
- Date
- 1613
- Historical period
- Early Modern Horology (1600 – 1750)
- Country of origin
- Germany
- Place
- Augsburg
- Object type
- Nocturnal and sundial
- Materials / technique
- gilt brass
- Dimensions
- 126x126
- Holding institution
- Museo Galileo, Florence
- Accession / object no.
- Inv. 2498
- Credit line
- Museo Galileo, Florence
- Catalogue title (original)
- Nocturnal and sundial (English)
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Record summary
Held and catalogued by Museo Galileo, Florence (object number Inv. 2498), this is a nocturnal and sundial by Georg Zorn, made in Augsburg, Germany, dated 1613. The Atlas places it in the Early Modern Horology period (1600 – 1750) of its Instruments collection. Materials and techniques recorded by the source: gilt brass. Recorded dimensions: 126x126. The record is illustrated with 1 photograph.
Assembled from the source record's structured fields. Dates and attributions are given as the source states them; where a field is missing the Atlas leaves it blank rather than estimating.
Catalogue description
Catalogue description — Museo Galileo
Disk with folding index arm rotating on a square plate carrying fixed sights for altitudes. The diurnal hours and night hours are marked for several latitudes. There are also markings for the climates. On the back are a nocturnal and sundial, a 90° quadrant with a shadow square, and the sine scale. Made by Georg Zorn, about whom we have no information. Brought to Florence from Germany by Prince Mattias de' Medici in the first half of the seventeenth century.
Historical context
Early Modern Horology (1600 – 1750)
Huygens' pendulum and balance spring transform accuracy; English makers develop the anchor and deadbeat escapements.
Pocket sundials, Butterfield dials and sandglasses remained essential companions to imperfect clocks; navigators used sandglasses and the log line; observatories began to combine telescopes with pendulum clocks.
Read the period in the timelineMore instruments from this periodEarlier: Renaissance Horology
Atlas type guide
Sundials and solar time-finders
A sundial tells time from the position of a shadow cast by a gnomon or style. Because the sun's apparent motion depends on latitude, every fixed dial is laid out for a particular latitude, and portable dials either carry a latitude scale or are made for one region. Sundials show local apparent solar time, which drifts against mean (clock) time by up to about sixteen minutes over the year — the equation of time.
Portable dials were the pocket instruments of the sixteenth to eighteenth centuries. Nuremberg and Augsburg workshops produced folding ivory diptych dials with inset compasses; English and French makers sold brass horizontal dials, ring dials and the Butterfield type; Japanese and Chinese makers had their own traditions of compass dials. After mechanical watches became reliable, dials remained in use for setting them, and nineteenth-century heliochronometers were built to correct directly for the equation of time.
What to look for
- The latitude engraved on the dial plate or a latitude arc on the gnomon — it shows where the dial was meant to be used.
- The type of hour lines: equal (equinoctial) hours, Italian or Babylonian hours counted from sunset or sunrise, or unequal temporal hours on early and Islamic instruments.
- An inset magnetic compass and whether a magnetic-declination mark is drawn on its card — a useful dating clue because declination changes over time.
- Maker's signatures and town marks: Nuremberg compass-makers (Kompassmacher) often struck a personal mark and the town's punch.
- Additional scales such as lunar volvelles, wind roses, perpetual calendars or lists of cities with their latitudes.
Dating clues
- Ivory diptych dials are characteristic of Nuremberg between about 1500 and 1700.
- Butterfield-type dials with a bird-shaped adjustable gnomon point to Paris workshops from the late seventeenth century onward.
- Equation-of-time tables engraved on the plate became common after the mid-seventeenth century, once pendulum clocks made the difference between solar and mean time obvious.
General guidance written by the Atlas editors about this kind of object. It is not a statement about this particular piece; for that, rely on the source record above and on physical examination.
Read next:The history timeline
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