**Johannes Campanus** was an Italian mathematician who published a Latin edition of Euclid's Elements. He also wrote on astronomy.

- Panteléon was elected pope on 29 August 1261, becoming Pope Urban IV, and he made Campanus one of his chaplains He also made him Rector of the Church of Savines in the diocese of Arles in 1263 and gave him a canonicate in Toledo's cathedral in 1264.
- Campanus also held other benefices being chaplain during 1263-64 to Ottobono Fieschi, the cardinal deacon of Saint Adrian's and papal legate to England.
- Through Fieschi's influence, Campanus was made parson of Felmersham in Bedfordshire, England, some time before 1268.
- Urban IV died on 2 October 1264 but Campanus had other leading ecclesiastical figures as his patron so continued to be able to devote his time to scholarship.
- One should not think that because Campanus held benefices in France, Spain and England, he must have travelled widely.
- Roger Bacon, writing in 1267, stated that Campanus was one of the four greatest contemporary mathematicians but, despite some historians believing that Bacon knew Campanus personally, this looks very unlikely.
- If Campanus did indeed visit Ottobono Fieschi while he was in England then a meeting with Roger Bacon would be quite likely but, as we have just explained, this probably did not happen.
- Campanus wrote a Latin edition of Euclid's Elements in 15 books around 1260 and it was the standard Euclid for 200 years.
- Most of Campanus's writings were on astronomy.
- In this work Campanus describes the construction and use of an equatorium, the first to be described by a European.
- Campanus, using Ptolemy's data, calculated the dimensions of the universe including a calculation of the area of the sphere of the fixed stars.
- Another astronomical work by Campanus is Computus maior which was a treatise on time-reckoning based on solar and lunar cycles.
- Campanus also wrote the important text Tractatus de Sphaera which was an elementary astronomy book describing celestial phenomena seen during the 24 hour rotation of the heavens.
- Campanus also published his own set of astronomical tables.
- Campanus determined the time of each planet's retrograde motion and gave precise instructions on using the tables.
- Let us now look a bit further at Campanus's mathematical contributions.
- we have in the commentary by Campanus, considering its respectable strength, occasionally its remarkable strength, additional evidence of the promising beginning of science which was made in the thirteenth century ...
- The edition by Campanus relied to some extent on Adelard of Bath's Latin translations of Euclid's Elements from Arabic sources.
- Campanus, however, borrowed most of his definitions, axioms, postulates and enunciations from this work by Robert of Chester.
- Campanus shows that he is familiar with the work of Arab mathematicians and, in Book V, he quotes from Gherard of Cremona's Latin translation of Ahmed ibn Yusuf's treatise on ratio and proportion.
- In 1485 Campanus's Euclid became the first printed edition of Euclid's Elements when it appeared in Venice, and it was in fact the first printed mathematical book of any importance.
- Between its first printing in 1485 and 1560 fourteen editions of Campanus's text were printed.
- Two further mathematical texts are thought with a high degree of certainty to be by Campanus, although a slight doubt remains.
- We explained above that Campanus borrowed material from De elementis arithmeticae artis by Jordanus Nemorarius.
- Other mathematical work has been attributed to Campanus, but for most the attribution must be considered rather speculative.
- Finally we should mentions Campanus's contributions to astrology.
- His contribution here was a major one and most people today who have heard of Campanus know of him because of his 'house system' of dividing the horoscope into twelve houses.
- Certainly Urban IV made Campanus his chaplain so that he could advise him on astrological and medical matters.
- However, Campanus used his mathematical skills to develop his 'house system' which is still used by astrologers today.
- Campanus's house system provided a method of determining a plane through the celestial sphere which could be used to make twelve equal divisions called houses.

Born 1220, Novara (now Italy). Died 13 September 1296, Viterbo (now Italy).

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Astronomy, Origin Italy

Epochs: 1

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive