阅读理解 In 1752, three years after two Scotsmen, Alexander Wilson and Thomas Melville, fastened thermometers to kites to record the temperature of clouds, Benjamin Franklin made his famous experiment with a kite, a string, and a key. Franklin 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 laboratories. He built a square kite to which he attached an iron wire. He flew the kite with a hemp string(麻线), and near the base of the string he tied a large brass key. The kite rose into a dark thundercloud, where the iron wire picked up electrical charges. Franklin noticed that the strands of the string(绳串) were beginning to stand up with electricity. As rain wet the string, it conducted more electricity. Standing in the shelter of a shed, Franklin cautiously reached out his Finger to touch the brass key. A series of sparks jumped from the key to his finger. He thus proved that lightning and electricity are the same. We now know that this experiment was a dangerous one, for Franklin might have been killed by a bolt of lightning.