Early observations of electric and magnetic phenomena were purely qualitative. The affinity of lodestone for iron and that of freshly rubbed amber for small objects were noted at least as early as the Golden Age of Greece, but no systematic study was recorded. Much later investigation of magnetism was stimulated by practical use of the mariners’ compass, a device introduced in the west probably during the eleventh century. The epistle of Peter Peregrine 1 (Peter the Pilgrim) on the magnet, written in 1269, revealed considerable clarity in the concepts of polarity and magnetic fields, and William Gilbert 2 in De Magnete (1600) noted the impossibility of isolating magnetic poles. Gilbert also emphasized the ubiquity of electrics (materials on which a charge could be produced by friction) and gave the first known description of an electrical measuring instrument, a primitive electroscope, but electrical repulsion was overlooked until its discovery by Nicolo Cabeo 3 (1629).