John Greaves (1602 - October 8, 1652) was the second Savilian Professor of Astronomy at Oxford University from 1643 to 1649. He was a scholar of many languages (including ancient Greek, Arabic, Persian, and oriental languages, which he later applied to his study of ancient astronomy. He is well known as being the co-editor and translator of the Canicularia a compilation of Arabic astronomical tables, which included the Zij-i-Gurgani of Ulugh Beg. He is also well-known for his studies of ancient units of measurement, as well as his analysis of the pyramids of ancient Egypt published in his Pyramidographia. His own astronomical work included early measurements of the solar diameter.

Greaves was born in Colemore parish, Hampshire, in the south of England. He was the eldest son of Reverend John Greaves, and a Laudian. As a student, he studied classics and oriental languages at Balliol College, Oxford, from 1617 to 1621. He was appointed to a professorship of Geometry at Gresham College, London, a college which served (and still serves) to present free lectures on academic subjects to the people of London. However, he left this post (apparently without leave!) in 1637 to travel to Rome with the goal of studying ancient units of measurement by measuring the dimensions of ancient monuments. This work included measurements of Roman, Greek, and Egyptian archaeological sites, including the pyramids. He published at least two books on this subject, including his two best-known, Pyramidographia, or, A description of the pyramids in Ægypt in 1646, and A Discourse of the Roman foot and Denarius: from whence, as from two principles, the measures, and weights, used by the ancients, may be deduced in 1647. The former work was criticized, primarily because his measurements of the pyramids' dimensions were incorrect -- the bases of the pyramids were covered by several thousand years worth of sand and debris. However, the latter work was highly praised by other contemporary scholars of antiquity.

In 1643, Greaves was appointed to the Savilian Chair of Astronomy at Oxford, a position which required him to teach students the contents and theory behind Ptolemy's Almagest, along with more recent (primarily Arabic) revisions to it. During his time as the Savilian Professor, he worked to translate many works of Arabic and Persian astronomy and astrometry to Latin, as had his predecessor, John Bainbridge. He released several books on the subject, including the tables of the great astronomer of Samarkand, Ulugh Beg, and Abu al-Fida' Isma'il ibn 'Ali. Such works were very valuable to astronomy at the time, as accurate, ancient records of stellar positions and planetary motions helped later astronomers to understand the motions of stars and planets. For example, Greaves' translation of Shah Cholgii Persae Astronomica (presumably the translations of observations of a Shah(*) of Persia) were used by John Flamsteed for his Gresham Lectures, specifically Lecture 10 on the obliquity of the solar ecliptic. Greaves' work culminated with the publication of Canicularia(**) in 1648, a large work including translations of Arabic and Persian astronomical tables, and derivations of stellar positions and the Earth's precession, a work commenced by John Bainbridge.

Unfortunately, Greaves' time as Savilian Chair was short -- he was essentially sacked in 1649. One reference says this was due to his misappropriation of funds from the school. However, as Greaves was a Laudian, and since Charles I was executed that year, his removal was probably due to a purge of academia by the Cromwellians in Parliament. Apparently, Greaves knew he would be let go, and rather than be fired, he resigned his Chair and offered it to Seth Ward, who then held the Savilian Chair until 1661, when Christopher Wren succeeded him. In any case, Greaves remained in London, married, and wrote several more books on astronomy, ancient architecture, and ancient Persian grammar before his death in 1652.

(*) Gritchka suggests "Shah Cholgius" might be Il-Khan Hülegü, grandson of Genghis Khan.

(**) specifically, Iohannis Bainbrigii -- Canicularia: Una cum demonstratione ortus Sirii heliaci, pro parallelo inferioris Ægypti / Auctore Iohanne Gravio. Quibus accesserunt, insigniorum aliquot stellar longitudines, & latitudines, ex astronomicis observationibus Ulug Beigi, Tamerlani Magni nepotis (nunc primum a J. Gravio publicat).

In English, it's something like Concerning the Dog Star: one with a demonstration of the heliacal position of Sirius from lower Egypt. With stellar longitudes and latitudes from astronomical observations of Ulugh Beg, grandson of Tamerlane. Thanks again to Gritchka for helping to translate this ridiculously long title.

Francis R. Johnson, Astronomical Thought In Renaissance England, Octagon Books, NY, 1968
The Gresham Lectures of John Flamsteed, edited by Eric Forbes, Mansell Press, 1975
Yale University library catalog