A physician of the Middle Ages. Under the name of "Magister Petrus de Maharne-curia, Picardus", he is quoted by Roger Bacon in his "Opus Majus" as the only author of his time who possessed an exact knowledge of perspective. According to Bacon he came from Picardy, and the village of Maricourt is situated in the Department of the Somme, near Péronne. He has left a remarkable treatise on the magnet, "Epistola Petri Peregrini de Maricourt ad Sygerum de Foucaucourt, militem, de magnete"; Syger de Foucaucourt was a friend and neighbour of the author, his domain bordering on that of Maricourt, It is dated 8 August, 1269, and bears the legend: Actum in castris, in obsidione Luceriœ (done in camp during the siege of Luceria), whence we know that the author was in the army of Charles of Anjou, who, in 1269, laid siege to the city of Lucera or Nocera, the only detail of his life known. The sobriquet "Pilgrim" would lead us to suppose, in addition, that he was a crusader, The "Epistola de magnete" is divided into two parts. The first, a model of inductive reasoning based on definite experiences correctly interpreted, sets forth the fundamental laws of magnetism. His part seems to have been, not the discovery of these laws, but their presentation in logical order. In the second division less admirable, an attempt is made to prove that with the help of magnets it is possible to realize perpetual motion, From medieval times the work was exceedingly popular; in 1326 Thomas Bradwardine quotes it in his "Tractatus de proportionibus", and after his time the masters of Oxford University make frequent use of it. The manuscripts containing it are very numerous, and it has been printed a number of times. The first edition was issued at Augsburg, 1558, by Achilles Gasser. In 1572 Jean Taisner or Taisnier published from the press of Johann Birkmann of Cologne a work entitled "Opusculum perpetua memoria dignissimum, de natura magnetis et ejus effectibus, Item de motu continuo", In this celebrated piece of plagiarism Taisnier presents, as though from his own pen, the "Epistola de magnete" of Pierre de Maricourt and a treatise on the fall of bodies by Gianbattista Benedetti, The "Epistola de magnete" was later issued by Libri (Histoire des sciences mathématiques en Italie, II, Paris, 1838; note v, pp. 487-505), but this edition was full of defects; correct editions were published by P. D. Timoteo Bertelli (in "Bulletino di bibliografia e di storia delle scienze matematiche e fisiche pubblicata da B. Boncampagni", I, 1868, pp. 70-80) and G. Hellmann ("Neudrucke von Schriften und Karten über Meteorologie und Erdmagnetismus, No. 10, Rara magnetica", Berlin, 1898). A translation into English has been made by Silvanus P. Thompson ("Peter Peregrinus of Maricourt, Epistle to Sygerus of Foucaucourt, Soldier, concerning the Magnet", Chiswick Press, s. d.), also by Brother Arnold ("The Letter of Petrus Peregrinus on the Magnet, A. D. 1269", with introductory note by Brother Potamian, New York, 1904).

BERTELLI, Sopra Pietro Peregrino di Maricourt e la sua Epistola de Magnete in Bulletino publicata da B. Boncompagni, I (1868), 1-32; IDEM, Sulla Epistola di Pietro Peregrino di Maricourt e sopra alcuni trovati e teorie magnetiche del secolo XIII, ibid., 65-99, 319-420; IDEM, Intorno a due codici Vaticani della Epistola de magnete di Pietro Peregrino di Maricourt ed alle prime osservazioni della declinazione magnetica, ibid., IV (1871), 303-31; BONCOMPAGNI, Intorno alle edizioni della Epistola de magnete di Pietro Peregrino de Maricourt, ibid., 332-39.

PIERRE DUHEM.