Date of this Version
One simple phenomenon of electricity was known to the ancients: that when a piece of amber was rubbed, it acquired the property of attracting small pieces of paper and other light particles. Records show that Thales of Miletus (circa sixth century B.C.) knew of this property of amber; the Greek word for amber is elektron, hence the name electricity. There was practically no further development of this subject until about the seventeenth century. Otto von Guericke (1602-1686) of Magdeburg built a large sulphur sphere, which, when rotated about an axis and rubbed with his hand, gave off electric sparks. In the eighteenth century it was found that there were two kinds of electricity, one similar to the kind acquired by amber when rubbed with wool, and the other similar to that acquired by glass when rubbed with silk, called resinous and vitreous electricity, respectively. They are now known as negative and positive electricity, names first introduced by Benjamin Franklin (1706-1790). Franklin made many important contributions to the subject, experimentally and philosophically. He showed the electrical character of lightning and designed lightning rods for the protection of buildings. The subject of electricity was put on a firm mathematical foundation as a result of the experiments of Coulomb (1785) on the law of force between electrically charged bodies.