Petrus Peregrinus
Petrus Peregrinus is known for writing the "Epistola de magnete" in 1269 which must be seen as the first scientific treatise ever written. He performed a series of remarkable experiments with spherical pieces of lodestone. He defined the concept of polarity for the first time in Europe, discovered meridians, distinguished and named the north and south poles of the magnet and observed that the magnetic force is strongest and vertical at the poles. He described how iron when touched by lodestone becomes magnetized, explained how a piece of magnetized iron can easily be remagnetized in the opposite direction and was the first to formulate law that poles of opposite polarity attract while poles of the same polarity repel. Unlike his contemporaries Petrus Peregrinus used his experiments rather than preexisting speculations to draw conclusions.