China was the first country in the world to invent a humidity-surveying instrument, as the Records of the Great Historian mentioned that clay and charcoal were placed on either side of a scale to observe the rise or fall of the end where charcoal was placed.

Later, another historical book, Huai Nan Zi, pointed out the meaning in the rise or fall thereof, "if the weather is dry, the charcoal will be light, and if the weather is humid, it will be heavy." The book also said, "In case the humidity is to increase, though invisible, the charcoal will turned heavier." This shows the humidity-surveying instrument could also play a part in measuring the invisible vapor.

During the Song Dynasty (960-1279), a monk named Zan Ning related in his book, "Put the clay and charcoal on either side of a scale, and balance it. Then, hang the scale in a room. If it is to rain, the charcoal will be heavier, and if it turns clear, the charcoal will be lighter." The record shows the humidity-surveying instrument had been used for weather broadcast by the Song Dynasty.

During the reign (1662-1722) of Emperor Kangxi of the Qing Dynasty (1644-1911), Nan Huanren, a missionary from the West, made a bowstring thermometer with a fawn's tendon to examine the humidity of the air.

Author: Jessie