Instruments · Altitude sundials
Cylinder sundial or 'Shepherd's dial', for use at latitude 42°. Rough construction. Made in France, 1801-1900 (see note).
- Maker / attribution
- Unrecorded in source
- Date
- 1801-1900
- Historical period
- Industrial Revolution (1850 – 1900)
- Country of origin
- France
- Place
- France, France
- Object type
- Altitude sundials
- Dimensions
- overall: 98 mm x 40 mm 20 mm, .025kg
- Holding institution
- Science Museum Group, London
- Accession / object no.
- 1934-137
- Credit line
- Thomas H. Court
- Catalogue title (original)
- Portable pillar or column sundial
Record summary
Held and catalogued by Science Museum Group, London (object number 1934-137), this is an altitude sundials, made in France, France, dated 1801-1900. The Atlas places it in the Industrial Revolution period (1850 – 1900) of its Instruments collection. Recorded dimensions: overall: 98 mm x 40 mm 20 mm, .025kg. 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
Science Museum Group description
Crude sundials of this type were used in the Pyrenees as cheap alternatives to watches until well into the 20th century.They indicate time from the sun's altitude, which is also dependent on the latitude and the season of the year. This instrument is made for a latitude of 42 degrees and it must be set to the correct date by rotating the knob on the top so that the metal gnomon lies immediatley above the symbol for the appropriate month, which is marked along the bottom of the column. To use the sundial, it is positioned so that the shadow of the gnomon falls vertically down the column. The time will then be indicated by the position of the tip of the shadow relative to the curved hour lines which are marked on the column. Altitude sundials give ambiguous results as the instrument is unable to differentiate between hours before and after noon. The ambiguity is easily resolved if the user is aware that it is morning or afternoon, otherwise a second reading must be taken some time later.
Historical context
Industrial Revolution (1850 – 1900)
American interchangeable-parts manufacture; railroad time standards; Swiss and German factory systems.
Instruments spread into industry, science and sport: stopwatches, chronoscopes, metronomes, watchmen's clocks and time recorders.
Read the period in the timelineMore instruments from this periodEarlier: Precision & Scientific 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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