Chartres Cathedral

The Chartres Cathedral – Cathedral of Our Lady of Chartres – is widely considered one of the finest examples of French Gothic architecture, and the building has indeed several aspects in its appearance and history that guarantee a special place among mediaeval cathedrals in Europe.
It was common in the Middle Ages that a building had been constructed through subsequent periods and completed only centuries after the beginning, but the majority of Chartres Cathedral was built with unusual speed (cca. 1198-1260) resulting in a remarkably consistent design and realization. Compared to other mediaeval churches the building has seen only relatively minor changes since the consecration in 1260. Most mediaeval cathedrals in France were looted and destroyed several times during the Wars of Religion and the Revolution, but Chartres Cathedral was spared the damage, even during World War II. Thanks to that, most of the original 13th century architectural details – even the huge stained glass windows and the sculptures and carvings of the portals and the interior – survived intact, the majority preserved in excellent condition. One of the many peculiarities of the cathedral is the numerous portrayals of the Zodiac signs on various architectural elements.

PORTAIL ROYAL: labours of the months and Zodiac signs (1142-1150)
The Portail Royal on the west facade has always been the main entrance of the cathedral. Apart from the crypts under the cathedral surviving from two earlier churches standing on this site, the west facade together with the two towers is the oldest part of today’s building – they are remnants of the earlier, partly Romanesque cathedral destroyed by a fire in 1194, incorporated into the current building. The Romanesque cathedral was built in more phases from 1020 until 1155, the Royal Portail dates from around 1140-50, representing a transition to the new Gothic style. It has three portals: a larger central portal accompanied with two smaller side portals, all of them with sculptures and lintels displaying a complex visual and theological scheme: the End of Time (Judgment Day) on the central, the infancy of Christ on the right, his second coming on the left portal. The Portail Royal derived its name from the tall statues on the doorjambs representing kings and queens of the Old Testament.

The archivolts on the left portal contain carvings of the Zodiac signs mingled with the labours of the associated 12 months – a common element appearing on many mediaeval churches in various forms, representing the cyclical nature of time and the wholeness of the Creation.

However, in this case the depiction has some very unusual characteristics: there are 12 labours of the month carvings on the archivolts but only 10 signs are portrayed. The most probable – albeit somewhat prosaic – explanation for this unusual arrangement is that the plans were changed while construction and there was not enough place left for the carvings originally intended. Thus, the two twin signs, Pisces and Gemini got a separate place at the bottom of the right portal’s inner left archivolt, and while the iconography of Gemini is standard, Pisces is rather unorthodox. There’s only one fish depicted, representing water, one of the four ancient elements, surrounded by the symbols of the other three: small flames (fire) under the fish’s belly, trees (earth) standing behind it with perching birds (air).
There’s also a less known Zodiac cycle on the Portail Royal: nested into the meandering ornament on the doorjambs  of the central portal delicate carvings portray the Zodiac sings.

NORTH TRANSEPT PORCH: labours of the months and Zodiac signs (1198-1217)
The transept (crossing) – just as the largest part of the cathedral – was built in the main construction period (1198-1260), according to the new design made after the 1194 fire. The deep, three-portal north and south porches were completed around 1215.
As usual for northern European cathedrals, the iconographical themes of the northern facade focus on Christ’s early life and Old Testament stories: the glorification of Mary on the center, the incarnation of Christ on the left, Job and the Judgment of Solomon on the right portal of the porch. The two outer archivolts of the right portal contain labours of the months and Zodiac signs carvings, in this case without any deviation from the common characteristics.

chartres cathedral north portal zodiac signs labours of the month mediaeval gothic architecture
chartres cathedral north portal zodiac signs labours of the month mediaeval gothic architecture

The arrangement of the signs and the monthly rural activities on the arches follows the path of the Sun throughout the year: the cycle starts with January from the left bottom, continues until June, pictured at the top of the arch, as daylight increases until the summer solstice, then the cycle ends with decreasing daylight until the winter solstice in December, at the right bottom of the arch. The two extra carvings at the bottom of the outmost arch depicting the Zodiac signs portray Winter and Summer: a men’s figure dressed appropriately to the season.

SOUTH AMBULATORY WINDOW: labours of the months and Zodiac signs (1215-1218)

chartres cathedral zodiac signs stained glass window labours of the month south ambulatory mediaeval gothic architecture France chartres blue
chartres cathedral zodiac signs stained glass window labours of the month south ambulatory mediaeval gothic architecture France chartres blue

One of the most distinctive features of Gothic cathedrals is the new combination of architectural elements like pointed arches, clustered columns and flying buttresses, making the insertion of huge colored windows possible on every level of the building.
In Chartres Cathedral most of the 176 windows were filled with stained glass, extensively using a new, very bright, sodium cobalt colored blue developed on the site of the Saint Denis Basilica. The windows cover a total area of  cca. 2600 m2, the majority of them made and installed between 1205 and 1240, with a few lancet panels surviving from the Romanesque building destroyed by the fire. The depicted scenes include panels of the Virgin and the Child, Biblical stories from the Old and New Testament, the Lives of the Saints and some prominently displayed coats of arms of donors of some windows.
One of the south ambulatory windows repeats again the labour of the months and Zodiac signs cycle featured on the west and north facades. For the man of the Middle Ages the Zodiac signs symbolized not only the passing of time in a cycle of a year, or of life and death. The agricultural labours associated with the 12 months and the corresponding signs were presented as work blessed by God, imposed on Adam and his descendants to find their way to salvation (Vincent de Beauvais).  The top quartrefoil of the roughly 8.1m high and 2.2m wide lancet window portrays Christ with the Alpha and the Omega, as the beginning and ending of the cycles. The labours of the months are depicted on the left side, the associated Zodiac signs on the rights side panels, 8 month/sign individually, four pairs sharing the four central quatrefoils. The two bottom panels are signature panels of the window donors.
There are some odd inconsistencies in the order and pairing of the months and the signs: May/Gemini proceeds April/Taurus, July and June (paired with Leo) are interchanged, the caption November is missing and December occurs twice.

ASTRONOMICAL CLOCK: Zodiac sings on the dial (>1407-1528)
Common people’s everyday life in the Middle Ages was determined by the daily routine and the annual cycles of the agricultural tasks rather than the days of the calendar. However, to calculate the exact date of major religious ceremonies and feasts and the time of the daily prayers had been paramount, thus keeping track of time and date had been the duty of the church. For hundreds of years the easiest way to tell local time was to use a sundial – meridian sundials had been used even after the invention of the mechanical clock to determine local noon for the public and for adjusting the clocks.
The oldest sundial of Chartres Cathedral dates probably to the 13th century, and the first mention of an astrological clock on the cathedral displaying not only the hours but also the period of the year with Zodiac signs comes from 1407. According to the description it is probably the same clock we can see today, with subsequently installed additions and adjustments of the mechanism and the dial in the 16th century. Although most of the mechanism was disassembled and used to forge pikes during the Revolution, the clock went through restoration in 2006 and the dial is still preserved in the choire on the north side.

chartres cathedral astronomical clock zodiac signs dial
chartres cathedral astronomical clock zodiac signs dial

The 105 cm diameter dial of the clock is formed of four independent plates assembled by a central axis. The outmost ring shows the twenty-four hours of the day with a needle indicating the local time, the next ring – an azure blue background decorated with golden stars – displays the lunar day and the phases of the moon, the central plate with the painted Zodiac signs moving one degree every day indicates the course of the sun in the ecliptic. A small sun moving along a slit in the needle indicates the height of the sun relative to the horizon, showing also the hours of sunrise and sunset. The clock was adjusted every noon with a sundial.


Jean-Yves Cordier

images © Philippe Giron 

Persian astronomy and astrology – Ulugh Beg

In the roughly 14 hundred years from Ptolemy writing The Almagest in the 2nd century until the invention of the telescope made more accurate astronomical observations possible at the beginning of the 1600s, many transcripts and transcripts of transcripts were made of his star catalogue by astronomers of the mediaeval East and Europe, but only a few of them contributed to the original work with additions or corrections based on their own observations. One of these astronomers was Mīrzā Muhammad Tāraghay bin Shāhrukhbetter known as Ulugh Beg, Timurid ruler of the region of Samarkand in the 15th century.

Ulugh Beg became governor of Samarkand in 1409, when his father Shah Rukh finally managed to take possession of the eastern portion of the empire established by his father Timur (Tamerlane) and moved his capital to Herat. Coming from an educated family – his parents were patrons of art and science, his mother’s efforts had even made the education of woman acceptable for a short time – his intension was to turn the city into an intellectual center.
In 1417 he began to build a madrasah – an institute for higher education – in Samarkand for studying different disciplines of secular science from astronomy and mathematics to medicine and poetry.

The two-story building-complex arranged around a rectangular courtyard with an imposing entrance portal and two minarets at the front facade included dormitory cells and rooms for the scholars and students, four lecture rooms at the four corners and a mosque at the west wall of the courtyard. Ulugh Beg invited the best scholars he could find as lecturers, and the Ulugh Beg Madrasah soon became the leading center of Islamic education in Central Asia. Today the building is still standing at the Registan, the center of Samarkand, with two other madrasahs built in the 17th century on two other sides of the square.

Although educated and active on many fields, Ulugh Beg’s main interests – inspired probably by a childhood visit to the remnants of the Marāgha Observatory, where Persian astronomer al-Tusi and his team completed around 1270 the star catalogue called the Ilkhanic tables (Zīj-i Īlkhānī) – had always been mathematics and astronomy. In 1420 he started to build the enormous observatory Gurkhani Zīj near Samarkand, with huge structures used as instruments to increase the accuracy of astronomical observations and measurements to the maximum. The observatory was unparalleled in its time.

‘Its circular main building, beautifully decorated with glazed tiles and marble plates, had a diameter of about 46 m and three stories reaching a height of approximately 30 m above ground level. The north–south axis of the main building was occupied by a huge sextant with a radius of 40 m (called Fakhrī sextant after that of Khujandī). On the scale of this instrument, which partially lay in an underground slit with a width of half a meter, 70 cm corresponded to 1° of arc, so that the solar position could be read off with a precision of 5″. On the flat roof of the main building various smaller instruments could be placed, such as an armillary sphere, a parallactic ruler, and a triquetrum. Among other instruments known to have been used in Samarqand are astrolabes, quadrants, and sine and versed sine instruments.’

source: Benno van Dalen © Springer International Publishing AG

Around this time Ulugh Beg was already working together with numerous scholars he invited to join his madrasah, among them renowned scientist Qāḍī Zāda al-Rūmī and the excellent Islamic astronomer and mathematician Jamshid al-Kāshī, author of an updated star catalogue called Khaqani Zīj. With a team of about 60-70 fellow scientists, based on systematical observations and computations carried out between 1420 and 1437 they completed an astronomical handbook with tables called Zīj-i-Sultani. 

The catalogue includes the coordinates of 1018 stars, the listing is based on Abd al-Rahman al-Sufi‘s Kitab al-Kawakib al-Thabita – The Book of Fixed Stars from the late 10th century, an augmented and improved version of Ptolemy’s Almagest.
As Ulugh Beg explains in the preface:

“Determination of the Places of the Fixed Stars in Longitude and Latitude.

Before the time of Ptolemy 1,022  fixed stars had been observed. Ptolemy has given them in a catalogue in the Almagest. The stars are distributed in six magnitudes; the largest are of the first and the smallest of the sixth magnitude. Each magnitude is divided into thirds, and in order to recognize the stars, 48 figures or constellations have been imagined, of which 21 are north of the ecliptic, 12 in the Zodiac, and 15 south of the ecliptic. The larger number of the stars are within the figures, the others are in the neighborhood, and are designated as unformed stars of the constellation.

Abd Al Rahman Sufi composed a treatise on the stars which all learned men have received with gratitude. Before determining by our own observations the position of these stars, we have laid them down on a sphere according to this treatise, and we have found that the greater part of them are situated differently from their appearance in the heavens. This determined us to observe them ourselves with the assistance of Divine Providence, and we have found that they were advanced from the epoch at which Sufi’s work was written, so that on giving them, according to this general observation, their absolute positions, we no longer found any difference from their appearance to the eye.

It is on this principle that we have reobserved all the stars already determined, with the exception of 27 which are too far to the south to be visible at the latitude of Samarkand (…) and we have taken these 27 stars from the work of Abd Al Rahman Sufi, taking account of the difference of epoch.

Besides these there are 8 stars mentioned by Abd Al Rahman Sufi in his book, of which Ptolemy gives the positions, but which Abd Al Rahman Sufi could not find, and which notwithstanding all our researches, we have been unable to discover. For that reason we do not indicate those stars in the present catalogue.(…)

In our catalogue we have given the position of the stars for the beginning of the year 841 of the Hegira, so that at any time we may be able to find the place of any stars on the supposition that they advance one degree in seventy solar years.”


The preface to the tables consists of four parts. The first three parts contain methodical descriptions of different astronomical measurements and calculations e.g. determining the length and initial days of years and months, the equation of the Sun and Moon, positions and characteristics of the stars and the seven planets, calculating eclipses, Moon phases and determining the position of the twelve celestial houses: the Zodiac signs. The fourth part of the preface is about astrology: horoscopes and nativities. Ulugh Beg, like many other Persian rulers, believed in astrology and fortune‐telling.
The catalogue also includes sheets of the motions and eclipses of the Sun, the Moon and the planets, longitude and latitude of several cities in various countries, trigonometric tables etc.

In 1449 Ulugh Beg was killed by his oldest son Abdal-Latif Mirza on his way to Mecca, his observatory was demolished by religious extremists, the library was looted, the scholars were forced to flee. Ali Qushji, a former student and leading astronomer at the observatory managed to take a copy of the original manuscript with him. This manuscript was translated from the original Farsi to Arabic and later to Latin, French and English – today, all known versions of the Zij-i-Sultani are translations.
The observatory buildings were excavated in 1908 by Russian archaeologist V. L. Vyatkin. Foundations of the three story cylindrical structure and underground sections of the giant marble sextant can be seen on site.

The work of Ulugh Beg and his colleague astronomers may not be ‘revolutionary’ in the sense of creating something absolutely new, but the accuracy of collecting, reobserving, recalculating, updating and correcting the data of existing catalogues, and listing altogether 1018 stars make Zij-i-Sultani one of the most important star inventories in the history and a highly influential work of Persian astronomy and astrology, that continued to be used in the Islamic world until the 19th century.

Heather Hobden
Benno van Dalen © Springer International Publishing AG

1. ©Francisco Anzola CC BY 2.0

2. ©Mr Hicks46 CC BY-SA 2.0
3. source: Christies
4-5. source: National Education Ministry of Bursa
6. ©Leon Yaakov CC BY-NC 2.0                             
7. ©Adam Baker CC BY 2.0


The publishing of the Gutenberg Bible – the first book prepared with a printing press with movable type – was not only an important technological breakthrough in history but also the beginning of an intellectual revolution that made books available to a wide range of people who had no access to knowledge before due to the fact that until the mid -15th century manuscripts were solely copied with years long tedious work by hand, thus books were precious and rare possessions of monarchs, monasteries, universities or very wealthy individuals.

In Europe, Johann Gutenberg (1400-1468, Mainz, Germany) is considered as the inventor of the method that made the mass-producing of books possible. He conceived the technique of combining letters to create text on paper using type cast in molds, a new, oil-based ink and a wooden printing press borrowing elements from the local Rhineland winepresses. In China, engraved wooden blocks had been used with a similar printing method to mass-produce books since the 9th century, but the results were rather poor in quality. Contrary to that, the prints made with Gutenberg’s technique were so precise, neat and elegant that the process spread swiftly across Europe and prevailed until the 19th century.

It’s very difficult to establish the exact date when the first edition of the Gutenberg Bible was completed. We know from the letters of Pope Pius II that in March 1455 he saw an example of the book displayed in Frankfurt to promote the edition. Sources also differ on the number of copies produced, but most probably there were about 180 finished copies, 3/4 of them on paper, the rest on vellum. Today, 49 of these are known to exist in whole or in part.

The chart is set to 12.00 on 23 February 1455, the day traditionally considered as the publishing date of the Gutenberg Bible.