Instruments · Pocket sundial
Sundial, China, 1770-1880
- Maker / attribution
- Unrecorded in source
- Date
- 1770-1880
- Historical period
- Precision & Scientific Horology (1750 – 1850)
- Country of origin
- China
- Place
- China, China
- Object type
- Pocket sundial
- Dimensions
- overall: 17 mm x 53 mm x 118 mm, .05kg
- Holding institution
- Science Museum Group, London
- Accession / object no.
- 1928-207
- Credit line
- Dr. H. Chatley
- Catalogue title (original)
- Chinese pocket sundial and compass
Record summary
Held and catalogued by Science Museum Group, London (object number 1928-207), this is a pocket sundial, made in China, China, dated 1770-1880. The Atlas places it in the Precision & Scientific Horology period (1750 – 1850) of its Instruments collection. Recorded dimensions: overall: 17 mm x 53 mm x 118 mm, .05kg. The record is illustrated with 4 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
Science Museum Group description
This pocket sundial from China is intended to be used facing north and has a compass that allows the user to check their orientation. This ensures the position of the sun is correct in order to accuratey read the time. This sundial is based on the Chinese solar calendar, Jiegi, and lists the 24 solar terms of the year from, Duxue meaning great snow, to Xiazhi meaing summer soltice. This sundial was intended to be adjusted throughout the year to account for the changing position of the sun as the seasons changed by altering the angle at which the sundail rests. Based on the position of the sun, the chinese day was divided into 12 equal units, or double hours, known as Shi, which range from Tzu to Hai. Each double hour was named after one of the twelve earthly branches, commonly associated with chinese zodiac. There are further divisions within this time standard such as Ke and Fen. However the exact calculations of these units have varied throughout the chinese dysnasties. China now utilises the Coordinated Universal Time (UTC) standard divsion of hours, minutes and seconds. Although some of the Chinese characters used for the previous time standard are now applied to these divisions.
Historical context
Precision & Scientific Horology (1750 – 1850)
Harrison solves longitude; Mudge invents the lever; Breguet's Paris workshop defines the modern watch.
The longitude problem was solved by the marine chronometer and lunar distance methods; dividing engines made precision scales possible, and observatories set time by transit instruments.
Read the period in the timelineMore instruments from this periodEarlier: Early Modern 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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