KOREAN HERITAGE

A Korean sundial that was long held overseas was acquired by the Cultural Heritage Administration earlier this year. Known as the Iryeongwongu, or “spherical sundial,” it was crafted in 1890 during the reign of King Gojong (the 26th monarch of the Joseon Dynasty). The form and design of this device set it apart from other sundials both at home and abroad. Besides its rare globular shape, it is uniquely designed to indicate time by moving the gnomon from side by side. It also has a device for adjusting the latitude to allow time to be measured anywhere in the world it might be used.

Two Hemispheres Along the Same Axis

The Iryeongwongu is rendered in the shape of a globe. The sphere consists of two separate hemispheres assembled along a single axis. The globe measures 11.2 centimeters in diameter, and the entire device including the base and stem is 23.8 centimeters high. The north hemisphere, marked by Chinese characters and lines indicating time, is firmly affixed to the axis, while the south hemisphere featuring the gnomon can spin independently.

The northern hemisphere contains time markers following the same time-telling method as conventional Korean sundials. It is marked by 96 vertical lines and Chinese characters referring to the 12 double hours. During the Joseon era, the day was divided into 12 divisions (sijin), or double hours, which are known by the names of the twelve animal symbols of Earthly Branches. Each of the 12 sijin is further divided into eight sub-divisions (gak). The day was thought to consist of 96 gak, with each gak measuring 15 minutes.

A Moving Gnomon

In contrast to conventional Korean sundials with a fixed gnomon, the Iryeongwongu has a movable version. The T-shaped gnomon on the south hemisphere is supposed to be moved from east to west through the day following the apparent path of the sun in the sky. The gnomon extends from a long narrow vertical groove on the surface, under which it is attached to an axis. When the T-shaped rod is aligned with the sun, the shadow it casts disappears into the vertical groove. The sun is positioned slightly south of the gnomon, so the northernmost tip of its shadow is always cast on the surface to point at specific time lines. A user of this spherical sundial could tell the time by moving the southern hemisphere and, by extension, the gnomon, until the shadow of the rod is hidden in the groove.

Besides reading the time line indicated by the shadow of the gnomon, there is another time-telling mechanism embodied in this sundial. It is known as sipae, or “time-telling tag.” There is a circular opening below the noon marker, where the names of the 12 double hours automatically appear every double hour. Tags bearing the names of the 12 double hours are connected to the axis and designed to appear in accordance with the movement of the southern hemisphere. This automatic time-indicating device can be thought of as a shared element between the Iryeongwongu and modern digital clocks. The sipae system can also be found in other Joseon-era stationary clocks such as the 15th-century clepsydra Jagyeongnu and the 17th-century armillary clock Honcheon Sygye. This 19th-century sundial is understood as being in line with Joseon’s timekeeping traditions, but innovatively adopted a portable mode.

Sundial Setting

It was necessary to place the Iryeongwongu in the right setting before it could be used to measure time. First, the plumb line was leveled. Although the plumb bob and the string from which it was suspended are now lost, the features to accommodate the plumb line still remain, such as a hole the string must have run through and a sharp projection used to check the perpendicularity of the plumb line. The axis was then directed toward the North Pole with the help of a compass and a latitude adjuster.

This sundial could function well beyond the geographical limits of Korea. When it was deployed away from home, the latitude simply needed to be adjusted. The Iryeongwongu has a component to accommodate for the latitude of its geographical position on the globe. This Joseon-era sundial can be used in the Southern Hemisphere as well. In this case, the axis must be pointed toward the South Pole. Its potential use in the Southern Hemisphere explains why two sets of the 12 double hour names are marked on the surface in opposite directions. Given the ship and sea images appearing on the petal-shaped base, it is assumed that this spherical sundial was intended for use both on land and at sea.

Known Date and Producer

The globular body of the Iryeongwongu bears an inscription confirming its date of production. The inscription reads “Produced at the start of the seventh lunar month in the 419th year since the foundation of the Joseon Dynasty,” corresponding to 1890 (during the reign of King Gojong). The seal of its producer, Sang Jik-hyeon (1849–?), is also evident. He was a military official affiliated with the garrison known as Chongeoyeong that was responsible for escorting the king and protecting the capital. Before joining the Chongeoyeong garrison, Sang had visited Japan and China as a member of diplomatic missions dispatched by the Joseon government.

An aesthetic Scientific Artifact

The Iryeongwongu is a rare artifact embodying both creative design and precise science. This movable sundial with its unusual globular form remains in good condition. The floral base is inlaid in silver with various motifs that adds an aesthetic elegance to the timekeeping equipment. All of these qualities manifested in this unique artifact recently returned home are expected to make it a precious source of information for historical research in the country.