John Somer was a contemporary of Geoffrey Chaucer (ca. 1340 -1400). He was probably born
in the 1340s and the last record of his receiving a grant was 10 October 1409, so he probably
died in that year.
Somer seems to have entered the order of the fratum minorum, Franciscan friars, in the friary
at Bridgwater. There were Somers in Bridgwater who were of some standing and who
leased or owned property in Friarn Street. John Somer is a witness to a document in 1307,
but this must be perhaps our man's father. John Somer appears in the Borough Archives in the
1330s and 1340s along with an Alice Somer (d 1352); perhaps his wife. Thomas Somer,
co-executor of Alice's will may be her son. Later archives tell of Margaret, daughter of John
Somer, in Bridgwater in 1405. Another John Somer appear in the archives in 1374, 1376, and
1379, but is not given the style friar, so perhaps not the same man.
Our John Somer, the author of a Kalendarium and other works, might be related to this family,
It is safe to assume that Fr. John Somer was in Oxford by 1380, when he wrote his kalendar ad meridiem Oxonie (for the meridian of Oxford). He was still a member of the Greyfriars convent in Oxford in 1394 and 1395, where he was recognised as an astronomer.
At Oxford, Somer would have had access to the Merton school of astronomy. He would have
found instruction and resources to stimulate his scientific investigations and resulted in the
production of his Kalendarium. Chaucer, in his Treatise on the Astrolabe, makes reference to
the kalendar of the "reverent clerk Frere J Somer".
By 1380, Somer had established a reputation as an astronomer . The Kalendarium was produced for Joan of Kent, the Princess of Wales, and mother of Richard II. The Princess died in 1399,
and he then received a royal grant from the new king, Henry IV. He continued writing
astronomical and astrological treatises and updating the charts accompanying the
kalendar thorough the 1390s. His reputation as an astronomer survived well into the fifteenth
century and the horoscope figure and a copy of Tabula Planetarum where still being ascribed
to him in the sixteenth century.
The Kalendarium is in four parts: a prologue, including instructions for use of the tables; the
monthly kalendar; additional tables containing Zodiac Man and explanatory text; and eclipse
tables. 43 manuscripts containing the kalendarium or parts of it survive.
Somer wrote a Chronicle, identified in a manuscript in the British Library Chronica quedam brevis fratris Johannis Somour ordinis S Francisci de conventue ville Briggewater. In this,
are listed every year from AD 1001 to 1532 and tabulated are the historical, religious,
astronomical and political entries, probably in Somer's own hand between 1348 until 1402,
when a great thunderstorm was noted in Taunton, and the Walsingham comet noted in the same
year. Probably after Somer's death, the Chronicle records the laying of the foundation stone of
the new church of the friars minor at Bridgwater between 9 and 10 o'clock in the morning of
4th March 1411.
It seem that John Somer was one of the leading , if not the leading, astrologer of his day.
William Worcestre said he met a old man in 1478, Fr. John Wells, in Bridgwater then a tanner,
who said he had been servant to John Somer.
John Somer left 40 marks for the library at the Bridgwater friary, and 200 marks for the new friary church .
Other works attributed to Somer are
Of Ille Days of the Yere (Days to be avoided in the year)
Canones pro veris motibus habendis planetarum : a perpetual calendar
Regule ad sciendum nati vitam secundum Johannem Somer ordinis minorum
Tabula medii motus solis in singulis 24 horis
Tabula proportionis diversitatis aspectus
Verus Motus Ultimo Decembri 1393 completus
A figure for casting a horoscope (in the Corpus Christi Library, Cambridge).
Mooney, L R, ed The Kalendarium of John Somer, The Chaucer Library, Athens: University of
Catto, J and Mooney, L R, The Chronicle of John Somer, Camden Miscellany XXXIV, 5th
series Volume 10, 1997, pp201-285
Dilks, T B, Bridgwater Borough Archives, Somerset Record Society, 1933, 48.