portable dial – Geographies of Time

An ivory diptych dial made soli deo gloria by Paulus Reinman (active 1575-1609), in Nuremberg around 1602, at the time an important centre of manufacturing specialised in scientific instruments, including sundials such as this one.

Pocket dials, formed by two leaves that fold flat when not in use with a string between the inner surfaces casting a shadow, were used to tell the time and, among other things, to regulate mechanical clocks, whose rapid technical development had by no means caused the abandonment of gnomon-based methods.

This dial worked at a multitude of latitudes, between Danzig and Sicily, listed on the vertical leaf. The finely decorated details and the very use of ivory for a secular luxury object indicate how it was intended for a wealthy clientele. The possibility of using it in a number of different places points to a potential user who was cosmopolitan in his or her interests, perhaps a noble with a refined aesthetic palate and friendships in various courts and cities of Europe, or perhaps a wealthy merchant with trades and interests around the Mediterranean, eager to show off his economic possibilities by surrounding himself with expensive objects.

The dial, around 11.5 x 9 cm, was to be oriented to the north by means of the compass encapsulated into the base. The string that served as gnomon had one end fixed immediately above the compass, while the other was inserted in one of six numbered holes on the vertical leaf to obtain different angles that made it usable at six different latitudes: the time was read by the shadow projected on one of the six rings on the horizontal surface. The list of cities on the vertical face indicates, for each place, the number corresponding to the hole to be used (54, 51, 48, 45, 42 and 39˚ N).

Ivory diptych dial by Paulus Reinman, detail. Photo by Geographies of Time, all rights reserved.

But this small object incorporated a remarkable plurality of functions. On the horizontal leaf the concave area with a fixed vertical pin is another sundial indicating the hour in two different systems which divided the day in 24 units: the Babylonian, beginning at sunrise, and the Italian, beginning at sunset.

On the vertical leaf two smaller sundials also constructed with fixed vertical brass pins indicated the number of hours of day-light in a given day of the year, between 8 and 16 depending by the position of the sun in the ecliptic (the one on the left, also with the signs of the zodiac represented around the edge) and the so-called “temporary” or “Jewish” hours – the division of the day in 12 parts, varying in length according to the time of the year (on the right).

On the top of the vertical surface there may be a windrose to identify the prevailing winds, and on the bottom an epact to calculate the date of Easter, such as in a very similar piece today at MAT – The Metropolitan Museum of Art in New York (accession number: 03.21.24), or perhaps a lunar volvelle with gilt-brass disc, such as in the specimen at the Whipple Museum of the History of Science, University of Cambridge (Holden-White collection no. 1935-42, accession no. 1688).

The two sundials on the vertical face are decorated with scenes of gallant life: a musician playing a string instrument with buildings in the background on the left and two lovers sitting on the right. The plants in both scenes perhaps intend to evoke the passage of time, recalling ideas of seasonality and cycles of life.

Thus, a multitude of technical and cultural trends converge in a minute object: the circulation of materials and luxury goods in Europe; the need for a standardized computation of time across geographical and political borders; the coexistence of mechanical and gnomonic systems of time calculation in the 1600s, and of different units of measurement of the year and day.

Tag: portable dial

Dialing in Early Seventeenth-Century Europe