Accession No

1702

Brief Description

ivory diptych dial, French, 17th century

Origin

France

Maker

Class

dials

Earliest Date

1600

Latest Date

1700

Inscription Date

Material

ivory; metal (brass, steel); glass

Dimensions

length 66 mm; breadth 51 mm; height 15 mm

Special Collection

Holden-White collection

Provenance

On loan from The Fitzwilliam Museum, University of Cambridge. Donated by Charles Holden-White to the Fitzwilliam Museum. Holden-White Collection no. 1935-56.

Inscription

Description Notes

Ivory diptych dial with brass hinges and hook fasteners.
Leaf Ib: Gold decoration on a blue and red background. Inset circle with a scale of latitudes divided 40˚ - 50˚, subdivided to 1˚. Sprung brass leaf keeps the gnomon taut, the gnomon running through an index sliding beside the latitude scale. List of towns and latitudes (see history file). Brass levelling pendulum bob.
Leaf IIa: horizontal dial calibrated for 3 latitudes (48˚, 45˚, 42˚); hour scale divided V - XII, I - VII, numbered by I, subdivided to 30 minutes. Inset compass with paper card in black ink on gold ground. 8-point rose with 16 named (8 named (?)) points. (Needle and glass not original.) Leaf decorated as Ib.

Condition: fair (gnomon broken); incomplete (needle and glass replacements).

References

Events

Description
The Diptych dial is a common form of portable multi-function sundial. 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, and are often elaborately decorated. The name of the device derives from the Greek diptychos for a pair of folding writing tablets, which the instrument resembles.

Diptych dials consist of two leaves hinged together, with a string ‘gnomon’ stretched between the inner surfaces of the leaves for casting a shadow. To use the device as a sundial the lower leaf must be placed parallel to the horizon and the upper leaf must be at a right angle vertically to it. The gnomon must then be aligned with the meridian of the place where it is being used by using the inbuilt magnetic compass. Time can then be read from the horizontal or vertical dial by the location of the shadow cast by the string gnomon.

In addition to the horizontal and vertical dials, diptych dials normally carry a number of other features, such as equinoctial dials, windroses, tables of latitude for adjusting the string gnomon for different locations, epact tables, lunar volvelles for telling time at night by the moon, and various pin-gnomon dials for telling the time according to Babylonian or Italian hours, or for calculating the position of the Sun in the zodiac.
27/05/2009
Created by: Joshua Nall on 27/05/2009

FM:43289