Folding pocket compass and sundial in boxwood case made by Henry Sutton, Threadneedle Street, London, 1650-1665.

Record summary

Held and catalogued by Science Museum Group, London (object number 1928-942), this is a magnetic compass; sundial by Sutton, Henry, made in Threadneedle Street, London, Greater London, England, United Kingdom, dated 1650-1665. The Atlas places it in the Early Modern Horology period (1600 – 1750) of its Instruments collection. Recorded dimensions: overall: 24 mm x 131 mm x 129 mm, .285kg. 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

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.

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