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Portable Diptych Sundial Signed L.S.

L. S.

This square ivory diptych sundial is designed for a latitude of about 45 degrees. Hooks at the back hold it open; hooks at the front hold it closed. Leaf 1a has a diagram for converting equal hours; calibrated around the outside from 0 to 360 by degree, then from 1 to 12 by 1 X 2, then from 1 to 12 by 1, with this "1" near the first "6" of the middle ring. A brass pointer is at the center. Flowers are carved at the corners. Leaf 1b has a dial for planetary hours calibrated from 1 to 10 by 1 with zodiacal symbols around the edge. The symbols are labeled for declination and inclination. Below this dial is a semi-circle with names of towns and a linear scale calibrated from 10 to 120 by 2. Underneath the scale is a motto: "QUILIBET PUNCTUS SIGNAT DVO MILIARIA TEUTONICA." A string gnomon is attached to this leaf but has come loose from leaf 2a. Leaf 2a contains an inset compass with glass and needle. The 4 compass points are lettered, and the compass is calibrated from 1 to 24 by 1. The compass is offset roughly 10 degrees east for variation. Around the compass is an hour dial calibrated from 4 to 12 to 8 by 1 with lines at every half-hour point. A scale around the hour dial is calibrated by zodiac names. Below the compass is a subsidiary dial calibrated from 10 to 22 by 1. A nocturnal scale from 8 to 16 by 1 runs along the left side; daytime hours from 16 to 8 by 1 are on the right. Leaf 2b contains a lunar volvelle of gilt metal giving phases and aspects. The volvelle's interior is engraved with squares, triangles, and asterisks connected by lines (astrological aspects). The outer edge is calibrated from 1 to 12 by 1 X 2. A pointer extends from one 12:00 point. The volvelle is surrounded by two dials on the ivory face which are calibrated from 1 to 12 by 1 X 2 and from 1 to 29 by 1 in the counterclockwise direction. There is a flower in each corner. The maker's mark appears twice: "LS" in a box with a star on top. Inscriptions are in Latin. In lined hardwood case.

Date

1518

Type

sundial

Medium

overall: 4.5 cm x 17.7 cm x 18.2 cm; 1 25/32 in x 6 31/32 in x 7 5/32 in

Department

NMAH

Institution

National Museum of American History

Object number

nmah_997043