Kites and Flying Dragons

Kites are an excellent example of Chinese ingenuity; there were experiments in manned flight, too

The kite, milvus lineatus, is a large carnivorous bird that gave its name in English to the aerial toy from China that was introduced to Europe sometime before Giambattista della Porta wrote Magia Naturalis in 1589, the earliest literary notice of kites. The Chinese characters above, chih yuan, mean 'paper kite' where 'kite' is indeed the bird. From now on, 'kite' means the toy, not the bird, in this paper. Chinese kites were often fashioned to look like birds or dragons. Although unknown in the West, kites were common in Southeast Asia. Their origin, which is apparently not Chinese, is ancient and unknown. In some areas, they were used in religious rites, and were taboo to women. The Chinese are said to have used them to carry fish-hooks away from boats to help fool the fish. They even carried men, since it is written that some drunkard or vagrant was tied to a large bamboo mat serving as a kite, and flown as high as possible when it was desired to find out whether a sea voyage would be successful. If they got the man in the air, the voyage would be prosperous. One emperor tied such mats to prisoners and had them thrown from a tower to see if they could fly. They could not. Kites were used to get propaganda leaflets inside a beseiged town, and as signals. Some kites had aeolian chimes that would sound as they flew. A game was played with kites in which glass chips were glued to the upper parts of the strings, and the idea was to cut the cords of competitors' kites.

A kite is a light framework (of bamboo, for example) covered by paper, with a string attached for flying it. The forces acting on the kite are its weight, the pressure of the air on it, and the tension in the string. The attitude of the kite must be maintained so that the force of the air is upward, which can be done by attaching the string correctly, or by hanging a weight from the end of the kite that should be down. A kite is launched by running with the string and paying it out as the kite rises. At altitude, the stronger wind takes over to keep the kite aloft, so the kite-flyer can stop running.

In 1749, Alexander Wilson used kites to carry a thermometer into the sky for measuring air temperatures up to 3000 ft altitude. In 1752, Benjamin Franklin flew a kite with a conducting string in the strong electrical fields near a thunderstorm to show that atmospheric electricity and static electricity had the same properties, and were, in fact, the same. The box kite was invented by Lawrence Hargrave in 1893. This form of kite gave greater stability and lift, and suggested the biplane. Aircraft are closely related to kites, producing their wind by pulling themselves through the atmosphere, which proved more practical than flapping wings.

The Chinese also had a propeller toy that would rise in the air when rotated and let go. It is not known when this originated, but it was noticed in Europe in the 18th century and called the Chinese Top. It was a 'bamboo dragonfly' in China. Needham reports stories, apparently as credible, that eggs could be made to fly like balloons by emptying them and causing water to evaporate in them, or by using tinder to make hot air. This was also claimed in Europe as an Easter trick. [An eggshell weighs about 7 grams dry; the weight of the air its 70 ml displaces is 91 mg at STP. It misses takeoff by a factor of about 80. So much for credulous academics. Modern commentators are not a lot more reliable than Pliny, and have less excuse.] There were definitely small paper dragon balloons that would fly when heated by a small fire below them. There are also stories of people jumping from towers with the aid of umbrellas, but this would require rather sturdy umbrellas.

Joseph Needham, Science and Civilisation in China (Cambridge: Cambridge University Press, 1965), Vol. 4, Part II, pages 568-599.

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Composed by J. B. Calvert
Created February 2000
Last revised 23 February 2000