Joe Theobald, age 14, of Concord, N.H., for his question:
WHAT DID BEN FRANKLIN'S KITE DO?
Benjamin Franklin was one of the first men in the world to experiment with electricity. He conducted his most famous electrical kite experiment in Philadelphia in 1752.
Franklin literally brought electricity out of the sky with a kite, a string and a key. He hoped to show that nature's tremendous displays of electricity in lightning were the same thing as the feeble electric sparks scientists of the day were producing in their labs.
Franklin made a square kite by using two sticks of equal length which he crossed at their centers and covered with a large silk handkerchief. To the stick which formed one of the upper corners he attached an iron wire. He then flew the kite with a hemp string, but at the ground he attached a long silk ribbon to serve as an insulator.
Near the knot by which the line and ribbon were joined, Franklin tied a large brass key. The kite rose into the dark thunderstorm and soon he noticed that the strands of the string were beginning to bristle with electricity.
As rain wet the string, it conducted more electricity. Franklin stood in the shelter of a shed, keeping the silk ribbon dry for self protection, then cautiously reached out his knuckle to touch the key. A series of sparks jumped from the metal key to his finger.
Franklin thus proved that lightning and electricity are the same. His experiment was dangerous because the lightning definitely might have injured him seriously.
Kites have long been a favorite with scientists. Three years before Franklin's famous experiment, Alexander Wilson and Thomas Melvill of Scotland fastened thermometers to kites to record the temperature of clouds.
In 1883 in England, a man named Douglas Archibald attached an anemometer or wind meter to the line of a kite and measured wind velocity 1,200 feet up in the air.
During the early 1900s, the kite played an important part in forecasting weather for the United States weather bureau.
The U.S. Weather Bureau used the Hargrave Kite, or box kite, invented about 1892 by Lawrence Hargrave of Australia. The bureau's kites were made of spruce wood and covered with cloth.
Three more large Hargrave kites were flown in a train strung along a line of piano wires. The highest kite recorded barometric pressure, temperature, wind velocity and humidity by means of a small instrument called a meteorograph.
Kites helped a number of persons in their efforts to design successful airplanes. One was Alexander Graham Bell, inventor of the telephone. He made a large and improved Hargrave kite which carried a U.S. Army lieutenant to a height of 175 feet. Bell and a group of engineers went on to design a number of aircraft, several of which made successful powered flights between 1907 and 1909. When Guglielmo Marconi first successfully sent a radio signal across the Atlantic Ocean in 1901, he used a kite to elevate the antenna at the receiving station in Newfoundland.