Archives biographies: Pierre de Maricourt 'Peter Peregrinus'

Peter the Pilgrim

In 1269 Pierre de Maricourt, more usually known as Petrus Peregrinus or Peter the Pilgrim, was part of a French army besieging Lucera in southern Italy.  He was in charge of fortifying the camp, laying mines and constructing machines to hurl stones and fireballs into the besieged city.  While engaged on these activities, he had spare time which he occupied with an attempt to solve the problem of perpetual motion.  

He devised a diagram to show how a wheel might be driven round forever by the power of magnetic attraction.  Excited by his discovery, he wrote a treatise in the form of a letter on the properties of the lodestone which he had discovered during his experiments.  His letter was given the title Epistola de Magnete.

The Epistola de Magnete

The Epistola is a remarkable document.  In it, Peregrinus was the first to assign a position to the poles of a lodestone.  He proved that unlike poles attract, while like poles repel; established by experiments that every fragment of a lodestone, however small, is a complete magnet, and determined the position of an object by its magnetic bearing as is done today in compass surveying.  

Basing a perpetual machine on the power of magnetic attraction - although ultimately doomed to failure - showed remarkable foresight, anticipating the operating principles of the modern electric motor.   

During the next few centuries, various manuscript copies of the Epistola were made, and today about thirty versions are extant. The first printed edition was prepared by a physician of Lindau, Achilles Gasser, who had studied mathematics, astronomy, history and philosophy.  It was printed in Augsburg in 1558.  

The title-page is illustrated above, with its woodcut hand coloured border. The work attracted little attention until William Gilbert mentioned it frequently in his De Magnete of 1600.

The fourteenth-century manuscript

S P Thompson, the past president of the Institution, a great book collector and a scholar of Gilbert, noticed Gilbert's references to the Epistola. Thompson was delighted to acquire a manuscript of it in one of the sales of books of the nineteenth-century megalomaniac manuscript collector, Sir Thomas Phillipps.  

The Phillipps manuscript, on vellum, dates from the fourteenth century and is bound with several other manuscripts, including a contemporary copy of Geoffrey Chaucer's work ' On the Astrolabe'.  Later Thompson acquired another manuscript version, also on vellum, dating from the fourteenth century.  

This version was formerly in the collection of an Italian nobleman, Prince Baldassarre Boncompagni, who had a library containing over 900 manuscripts and 20,000 books relating to his interests in the development of physics and mathematics.  Both manuscripts and two copies of the printed version are now held in the IET Archives. 

The Epistola is one of the most significant treatises of the Middle Ages.  It was the first work devoted solely to magnetism.  Moreover, it provided empirical rules on magnetic polarity and induction which influenced William Gilbert's great work on magnetism over three hundred years later.