Accession No
6198
Brief Description
“A.L.” chronohelion, dyptych dial (simple sundial), by E. J. Arnold and Son Ltd., English, early 20th Century
Origin
England; Leeds and Glasgow
Maker
E. J. Arnold and Son Ltd.
Class
dials
Earliest Date
1900
Latest Date
1930
Inscription Date
Material
wood (pine); metal (brass; steel); paper (card)
Dimensions
[in card box] length 270mm; width 225mm; height 30mm
Special Collection
Provenance
Purchased from www.eBay.co.uk on or before 10/2007.
Inscription
THE “A.L.” CHRONOHELION (A SIMPLE SUN-DIAL)
Description Notes
The “A.L.” chronohelion, dyptych dial (simple sundial), by E.J. Arnold & Son, early 20th century.
Dial comes in unmarked brown card box.
Dial consists of two rectangular pieces of pine wood attached at a hinge. Both sides of both pieces of wood have printed paper pasted onto surface.
Inside surfaces of the two plates contains the printed sun-dial (one side with “vertical dial” the other with “horizontal dial”). The vertical dial surface also contains the name of the instrument, while the horizontal surface contains the equations tables for converting from solar time to local and Greenwich mean time, plus the makers name. The horizontal dial contains a small magnetic compass embedded in its surface. The horizontal dial also contains a section which says “The longitude of the School is “, with a blank space for writing it in. As such, the dial appears to have been produced specifically as a teaching aid.
The vertical dial is held at 45 degrees to the horizontal dial by the insertion of a separate triangle of pine wood, which attaches into both surfaces by small brass pins that fit into holes in the surfaces. This triangle also serves as the gnomon.
The reverse side of the horizontal dial plate contains instructions for using the dial, including a diagram of how to set it up and an example calculation of local and Greenwich mean time.
The reverse side of the vertical dial plate contains a map of the British Isles from which the user can approximately ascertain their latitude.
Condition: Fair (large crack in middle of vertical dial plate).
References
Events
Description
Diptych Dial
Diptych dials were made popular by the instrument makers in Nuremberg during the sixteenth and seventeenth centuries. They are usually made of ivory with brass fittings. They are called diptych dials because they are made of two leaves hinged together.
Diptych dials normally carry a large number of different instruments. The lower leaf has a typical horizontal dial, and also a small bowl-shaped dial, which is used for telling the time the hours from sunset or sunrise.
The main dial on the upper leaf is a standard vertical dial which uses the string gnomon, just like the horizontal dial. In the centre of the vertical dial is a brass disc carrying the markings for an equinoctial dial. This dial would have a short pin gnomon which could be stuck into the centre to cast a shadow on the brass plate. At the top of the upper leaf is a small dial which is used to find the position of the sun in the zodiac (i.e. what time of year it is, according to the zodiac scale). It can also be used to calculate the length of daylight and night.
Other things that might be included on a diptych dial are tables of latitude, for setting the horizontal dial to the correct position to tell the time. There might also be a lunar volvelle which could be used to convert a reading taken by the light of the moon to the correct time of night.
FM:46668
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