Petrus Peregrinus de Maricourt.

Petrus Peregrinus (pronounced "PEH-trus pehruh-GRINE-us") de Maricourt--also known as Peter the Pilgrim, Peter of Maricourt, and Pierre Le Pèlerin de Maricourt--was the founder of the science of magnetism in the West. He produced Epistola Petri Peregrini de Maricourt ad Sygerum de Foucaucourt, militem, de magnete (1269; Epistle of Petrus Peregrinus de Maricourt, to Sygerus of Foucaucourt, Soldier, Concerning the Magnet, 1902), commonly called Epistola de magnete or Letter on the Magnet, which was arguably the best and most systematic analysis of observations in medieval science. (The only work that is the equal of Petrus' treatise on the lodestone is the "Treatise on the Rainbow" by Theodoric of Freiburg.) All that is known for certain about Petrus is to be found in his treatise itself--the name of the author and the exact date of the treatise, August 8, 1269--and in a passage praising Petrus written by Roger Bacon, the great medieval advocate of technology and experimentation. Petrus Peregrinus was born or lived in Maricourt (or Méhaircourt) in Picardy, France. His designation "Peregrinus"--variously translated as "the pilgrim," "the traveler," "the wayfarer," and "the stranger"--suggests his travels. Unfortunately, the only one of his travels that is known for sure is his involvement in the siege of Lucera, Italy, likely as a military engineer; the date of his treatise is on the eve of the battle of Lucera. Because the compass first appeared in China and apparently traveled to Europe via a land route in Central Asia, and later by a sea route around the Middle East, Petrus' title of "the pilgrim" or "the traveler" may suggest travels to the Middle East as a pilgrim in the Holy Land. The title of "pilgrim," however, was also given to participants in the Crusades, even if the war was fought in Europe. INSET: Petrus Peregrinus de Maricourt.