1269

Chinese south-pointing spoons and needles are earlier. European sailors were already using magnetic needles by the late twelfth and early thirteenth centuries. What had not survived in Latin is a systematic experimental account.

He says he writes so that Sygerus may understand the stone. Behind the courtesy is a practical world: direction-finding, military engineering, and a thirteenth-century hunger to make hidden virtues visible by trial.

A Picard master of military engineering, known from his own letter and from Roger Bacon’s praise of a 'dominus experimentorum.' He writes to a fellow soldier, Sygerus. Almost nothing else of his life is securely known. The name Peregrinus likely marks pilgrimage or crusading service, not a surname in the modern sense.

Petrus Peregrinus de Maricourt (Pierre de Maricourt) · Sygerus of Foucaucourt · Charles of Anjou · Roger Bacon (later witness to his reputation)

He wrote Epistola de magnete: how to find the poles of a lodestone, that like poles repel and unlike attract, how to make a magnetized needle turn on a pivot, and (more speculatively) a magnetic perpetual wheel. The lasting act is the experimental letter, not the wheel.

He tells the reader to shape the stone, mark it, float it, present iron to it, and build a dry pivoted instrument. The method is the point: do not only cite authorities, try the stone.

The hinge is a dated letter from a camp, in which an invisible virtue is given poles, rules, and an instrument that can be rebuilt.

A military camp outside Lucera in Apulia. The writer is fortifying, mining, and building engines. The magnet work is done in that noise, not in a quiet study. The letter is dated 8 August 1269, from the siege. Lucera, a Muslim colony under Hohenstaufen then Angevin pressure, fell that same August.

8 August 1269 · The Angevin camp at Lucera, Apulia

He knew lodestones, needles, and the practical compass. He used the word polus for the magnetic pole. He did not have a theory of Earth’s magnetic field.

William Gilbert’s De magnete (1600), terrestrial magnetism as a science, declination as a mapped quantity, or the later pairing of electricity and magnetism.

Epistola de magnete (manuscripts; first printed 1558)

A short Latin letter. Manuscripts survive. The first printed edition appeared at Augsburg in 1558, more than two centuries later.

The object survives.

The letter itself is the first record. Roger Bacon, writing around the 1260s, praises an experimenter from Picardy who is widely taken to be this man, but Bacon does not date the magnet letter.

The letter circulated in manuscript. Early modern readers, including the 1558 editor, treated it as a founding text before Gilbert.

Popular history sometimes says Peregrinus 'invented the compass' in 1269. He did not. He described and improved an instrument already in use, and he wrote down an experimental grammar for the stone.

This does not prove that 1269 caused magnetism to be understood, or that years ending in 69 favor discovery. It proves that this letter is dated 1269.

Does not make 69 a magnetic number, and does not assign Peregrinus the invention of the compass.

It entered the test because a primary source carries the year, the object, and a question about unseen direction. That is enough.

How can something invisible give direction?

1. 1. Petrus Peregrinus de Maricourt. Epistola de magnete. Letter dated 8 August 1269, Lucera. First printed Augsburg, 1558. English: The Letter of Petrus Peregrinus on the Magnet, A.D. 1269. Translated by Brother Arnold. New York: McGraw, 1904. See the record
2. 2. Institution of Engineering and Technology. Archives biographies: Pierre de Maricourt, 'Peter Peregrinus.' See the record
3. 3. Roger Bacon. Opus tertium. c. 1267. Contains praise of an experimenter from Picardy, commonly identified with Peregrinus.

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