The Cultural Heritage Administration of the Republic of Korea, headed by Administrator Chung Jae-suk, has announced that the rain gauge from the Chungcheong-do Provincial Office in Gongju is being designated a National Treasure. It is the only surviving example of a pre-modern rain gauge in the world. Being designated alongside it are two rain gauge supports respectively formerly installed at the Gyeongsang-do Provincial Office in Daegu and in Changdeokgung Palace. These three pieces of heritage testifying to the weather monitoring system of the Joseon Dynasty (1392–1910) are currently registered on the list of National Treasures : No.
The designation of these three heritage items as National Treasures, the title given to heritage of the greatest national importance, is a reinterpretation of their significance in the history of meteorology at the national and global level. They demonstrate the long-standing tradition of systematically crafting rain gauges and rain gauge supports and methodically measuring precipitation. The invention of a rain gauge (called a cheugugi 測雨器 in Korean) dates to 1442 during the reign of King Sejong (r. 1418–50). This is arguably the earliest known creation of a systematic precipitation-measuring device anywhere. The creation in Korea of a scientific instrument for monitoring precipitation became internationally known with its introduction in the British science journal Nature in 1911.
This rain gauge (National Treasure No. 329) was crafted in 1837 and installed at the Chungcheong-do Provincial Office in Gongju. It was transported to Japan in 1915 by the Japanese meteorologist Wada Yuji, but returned to Korea in 1971. It has since been preserved at the headquarters of the Korea Meteorological Administration in Seoul. Rain gauges were centrally fashioned by the royal court and distributed to provincial governments during the Joseon era. Among the many rain-measuring devices believed to have been crafted throughout the Joseon period, the Gongju rain gauge is the only surviving example.
The rain gauge was built in three sections with an inscription on the outer surface of the middle section that lists its production date and size. The inscription tells that the rain gauge is 31.9 centimeters in height, 14.9 centimeters in diameter, and weighs 6.2 kilograms. These proportions are a faithful reflection of the standardized dimensions established during the reign of King Sejong. An inscription carved on the underside relates that there were officials designated for the management of this rain gauge. The inscribed information on this 19th-century instrument demonstrates that the rainfall-measuring system established in the 15th-century was sustained until at least the late Joseon period.
The Joseon rain gauges are well known for their symbolic significance. The details of their production and use, however, have relatively remained obscure. To address this, the Cultural Heritage Administration and the Conservation Science Division of the National Research Institute of Cultural Heritage have been conducting scientific research on the Gongju rain gauge, which has brought to light a range of important facts about this historic precipitation-measuring instrument. It revealed signs of welding where the three individual sections were joined, purportedly for the purpose of preventing any leakage if the rainfall collected surpassed the lowest section. In addition, a precision survey of the rain gauge has confirmed that its body indeed served as a ruler. This finding calls into question the long-held understanding that the rainfall collected using the gauge was measured with a separate instrument.
The precipitation-measuring system set up in the mid-15th century was interrupted during the Japanese invasions of the late 16th century, but was revived in 1770 during the reign of King Yeongjo (r. 1724–76). At that time, rain gauges were crafted in accordance with the standards originally established during the reign of King Sejong. New dimensional guidelines were instituted for the production of the pedestals by referring to measurements applied in Sejong's era. These centrally-made rain gauges and their supports were dispatched to the provincial governments. The rain gauge pedestal (測雨臺) from the Gyeongsang-do Provincial Office in Daegu (National Treasure No. 330) is among the rain gauge pedestals crafted at this time.
Made from granite, the Daegu rain gauge support survives as an embodiment of the meteorological system from King Yeongjo's reign and pays testimony to the historic standardization of the size of the pedestals for the rain gauges.
The other rain gauge support being entered on the list of National Treasures was installed in front of the Imunwon , an office storing royal documents, within Changdeokgung Palace. It was crafted in 1782 during the reign of King Jeongjo (1776–1800). This pedestal (National Treasure No. 331) demonstrates that the practice of installing rain gauges continued at least into King Jeongjo's reign. This pedestal is represented in the painting Donggwoldo (Eastern Palaces), confirming the content of the inscribed writing on its front side regarding its placement in front of the Imunwon office. The inscription also provides information on the history of precipitation measurement during the Joseon era.
The Imunwon rain gauge pedestal serves as evidence that the precipitation measurement system from the early Joseon era was maintained well into the later period of the dynasty.
These rain gauge and pedestals were important instruments in the agricultural society of the time where recording meteorological trends and making according preparations were of great significance. The Joseon royal court collectively made rain gauges and distributed them to each province, the state-appointed governor of which measured local precipitation and reported the results back to the royal court. This centralized meteorological system is a unique Korean tradition with few parallels in the world.
The Gongju rain gauge and the two pedestals provide exact information on their production dates and origins, an eloquent testimony to the birth of a significant and enduring innovation in agricultural science. This rain gauge globally recognized as the oldest pre-modern example is expected to contribute to the appreciation of traditional Korean science within the international community.