Instruments · Nocturnal and sundial
Nocturnal and sundial by Girolamo della Volpaia, Italy, 1567
- Maker / attribution
- Girolamo della Volpaia (maker)
- Date
- 1567
- Historical period
- Renaissance Horology (1400 – 1600)
- Country of origin
- Italy
- Place
- Florence
- Object type
- Nocturnal and sundial
- Materials / technique
- brass
- Dimensions
- diameter 97 mm
- Holding institution
- Museo Galileo, Florence
- Accession / object no.
- Inv. 3811
- 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. 3811), this is a nocturnal and sundial by Girolamo della Volpaia, made in Florence, Italy, dated 1567. The Atlas places it in the Renaissance Horology period (1400 – 1600) of its Instruments collection. Materials and techniques recorded by the source: brass. Recorded dimensions: diameter 97 mm. The record is illustrated with 2 photographs.
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
This nocturnal consists of three overlapping disks of different diameters: the largest shows the zodiacal calendar; the middle one carries the hours and the rotating index; the smallest—a toothed disk—has a long index arm and the inscription "Horologium nocturnum." On the back are the signature of Girolamo della Volpaia and the date (1567), the solar quadrant, and the disk for determining the Sun's position in the zodiac signs. The instrument is set for latitude 43°44' (Florence). Similar to items inv. 2503 and inv. 1286.
Historical context
Renaissance Horology (1400 – 1600)
Spring power makes clocks portable; Nuremberg and Augsburg produce the first watches; the Prague Orloj is built.
Instrument-making flourished in Nuremberg, Augsburg, Louvain and London: ivory diptych dials, astronomical compendia, astrolabes and nocturnals for wealthy patrons, navigators and scholars.
Read the period in the timelineMore instruments from this periodEarlier: Medieval Period
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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