Science blog

4 posts categorized "Medieval history"

22 October 2020

In our Hebrew Manuscripts exhibition, "Tsurat ha-arets" by Abraham bar Hiyya

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A manuscript page written in Hebrew including a geometric diagram of circles.
A page from "Tsurat ha-arets"

Our Hebrew manuscripts exhibition continues until next year. You might not expect it to have a whole section on science, the prize of which is the manuscript numbered Or 10721, a copy of Tsurat ha-arets ("Form of the Earth") by Abraham bar Hiyya, with some additional works. It is thought to have been transcribed in the 15th century by one Joseph ben Se’adyah Ibn Hayyim. It is fully digitised at

Or 10721 was purchased in 1924 by the British Museum Library from the Romanian-British Jewish scholar, and Chief Rabbi of the English Sephardic community, the Rev. Moses Gaster, as part of a large collection known as the "Gaster Manuscripts". Bar Hiyya (1070?-1136) lived in Barcelona during the period of Moorish rule in 11th-12th centuries and was considered the foremost scientific authority of any background in Spain at the time. He probably introduced Arabic algebra into Middle Ages Europe, and his work was key to Fibonacci's introduction of the Hindu-Arabic number system into Christian Medieval Europe, which allowed modern maths to begin there. He published the first general solution of quadratic equations and wrote the oldest known mathematical work on the Hebrew calendar. His book Hegyon ha-Nefesh is considered to be the oldest surviving book on philosophy in the Hebrew language. Outside his scholarly studies, he held the government legal position "sahib al-shurta" of the Taifa of Zaragoza, a kingdom of the era that ruled a large part of Eastern Spain.

Bar Hiyya was the first major figure of Jewish scholarship to use Hebrew rather than Judeo-Arabic for scientific works. He developed a new vocabulary for science in the language and translated many existing Arabic scientific works into Hebrew, to improve what he considered to be the very poor state of mathematical knowledge among Spanish and French Jews of the era.

Tsurat ha-arets is a treatise on cosmology and geography describing the Ptolomaic or Earth-centred view of the universe, generally accepted in Middle Ages Europe. It also describes the division of the known northern hemisphere into seven "climates", or regions divided by east-west lines of latitude.

An earlier post on our Collection Care blog has described the most recent conservation of the manuscript.

Further reading:

Medieval Jewish civilization : an encyclopedia / edited by Norman Roth. London : Routledge, 2017. Available electronically in British Library reading rooms as Non-Print Legal Deposit.

04 December 2019

Oil, storms and knowing part 1: Seafarers Calm Waves with Oil

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This post is to mark the period of the 25th Conference of Parties to the UN Framework Convention on Climate Change, and is contributed by Andrea Deri, Cataloguer.

A storm at sea is one of the most feared experiences, as it often presages shipwreck. Mariners would do anything to survive tempestuous waters, from weather forecasting to casting holy oil or auspicious soil from the tomb of a Persian Sufi saint, Abu Eshaq Kazaruni (d. 1035) on the waves.

Occasionally, sailors wailing from fear were also briefly plunged into the sea: to calm them, not the waves though.

A medieval illumination showing a group of people with varied skin-tones and costumes crammed into a ship. A young boy is being dangled by his arms over the side.
A Persian pageboy is thrown overboard briefly in order to calm his fears from Saʿdī Shīrāzī, Gulistān (CE 1258), part of his collected works or Kullīyāt. IO Islamic 843, Folio 42v

Oil features prominently in K. V. Hariharan’s paper on ‘Sea-dangers in Early Indian Seafaring’, a catalogue of traditional adaptation practices to a range of marine hazards, including cyclones: ‘Seafarers seemed to have known the effect of oil to smoothen the sea surface’. As storms approached seafarers ‘covered their body and garments with oil to smoothen the surface of the water they touched on thus presenting less resistance to the wind and preventing breaking of the waves – the real dangers in wave motion’.

The sewn boats in the archipelago of Lakshadweep, South India, boats fastened with coir, not nails, have also been coated with an oily material for the same reason seafarers covered themselves with oil: making the vessels waterproof and smoothing the water around them.

In addition to coating, seafarers also poured oil directly onto the sea to prevent the waves from breaking on their vessel. Throwing oil on the waves was applied so widely that it became in idiom in Dutch (‘olie op de golven gooien’) and English (‘pouring oil on troubled waters’) with the meaning of settling a disagreement and ‘bringing about a state of calm after great anger or excitement, etc., by tact and diplomacy.’

‘Oily seas’ that appear during the stormy southwest monsoon (June-September) along the Kerala coast, however, are not caused by mariners but natural processes. According to B. Arunachalam, an authority of Indian marine navigation:

[…] such a sea-surface – the kedu neer – is believed by seamen to generate a relatively smooth surface, ideal for anchoring or drifting during foul weather in rough seas. The mudbanks of Cochin, for this reason, are treated as safe anchorages during active monsoon times. 

Kedu neer  (Tamil  கெடு நீர் ) literally means ‘bad water’. It refers to a turbid and calm marine area with almost no waves. A recent scientific study suggests the calmness of the ‘oily sea’ is linked to the wave damping effect of fine suspended matter, not oil. Mariners may have called these patches ‘oily seas’ as the water over the mud banks near Cochin, Kerala, known to generations of fishers, behave similarly to waters that have no waves because they were covered by a thin oil patch.

A close-up of a wooden boat on water, with an area of calm water immediately around it contracting with the rippling water further away
Traditional sewn fishing boat, small odam, in Agatti, Lakshadweep, India, coated with an oily substance. Photo by Andrea Deri, 23 February 2007


A simplified image of the coastlines around the Indian Ocean. The site of Cochin is highlighted.
Map of the Indian Ocean in B. Arunachalam, Heritage of Indian Sea Navigation. (Mumbai, 2002:9) YA.2003.a.26499. Cochin, where the oily seas of the mud banks provide safe anchoring during the monsoon season, is marked in South India.


A hand=drawn chart of a coastline and island
Traditional Kutchi sea chart, with east at the top, features the Malabar coast, shown as seen from the sea, with coconut palms in B. Arunachalam, Heritage of Indian Sea Navigation. (Mumbai, 2002:28) YA.2003.a.26499. The Cochin port (Kochi Bandar) played an important role in local and regional trade. South Indian ports are considered to be some of the oldest maritime centres.


It was not only in the tropical seas where mariners made use of the oil’s water calming properties. Bede, the Anglo-Saxon scholar and monk, tells us ‘How Bishop Aidan foretold to certain seamen a storm that would happen, and gave them some holy oil to lay it’ [642-645 AD] off the Kentish coast in cold North Sea, recorded in the Historia Ecclesiastica Gentis Anglorum, in the British Library at Add MS 1450.

Bede lists his sources including Utta, the priest who received the oil from Aidan, in order to add credibility to Aidan’s sea calming, revered as miracle. The credit, however, perhaps should go beyond Aiden, to local mariners anonymous to chroniclers.

As Aidan served on two islands, Iona and Lindisfarne, he spent considerable time in boats where he may have experienced and learned the practice of pouring oil on waves from local fishers and seal hunters who ferried him. Could Aiden’s holy oil be the same kind of oil local mariners used to quell waves? If so, this is an example of how local knowledge or rather adaptation practice to extreme weather became canonised.

A stylised medieval image showing three robed men in a sailing boat.
St Cuthbert (c 634-687) in a boat at sea, with two other men, from Chapter 11 of Bede's prose Life of St Cuthbert. Yates Thompson 26 f. 26 Cuthbert became a monk after his vision of St Aidan who died in 651


Nautical idioms preserve seafarers’ practices. Most of us, landlubbers, need to take a historical perspective to unpack and appreciate their meaning, and we may still ponder over their relevance today. Faced with the unfolding changes of our climate, a major concern of our time, seafarers may serve a great source of inspiration by the way they kept their knowledge alive with keen observation, tireless experimentation and sharing.

If you have an "oil on water" story, you can tell us here.

References and further reading

Arunachalam, B. Heritage of Indian Sea Navigation (Mumbai, 2002)  Shelfmark YA.2003.a.26499

Bede, The Ecclesiastical History of the English Nation (London, 1954). Book III, Chapter XV. Shelfmark 4824.m.1

Bede, Historia Ecclesiastica Gentis Anglorum; Plympton annals for the years 1066-1177, Shelfmark Add MS 1450

Hariharan, K. V. ‘Sea-Dangers in Early Indian Seafaring’. Journal of Indian History, 1956. 34 (Part III (Serial No 102)), pp.313–320. Shelfmark Ac.1928/2

Jeans, P.D. Ship To Shore: A Dictionary of Everyday Words and Phrases Derived from the Sea (Santa Barbara, 1993) Shelfmark YC.1996.b.3808

Jyothibabu., R. Balachandran, K.K., Jagadeesan, L., Karnan, C., Arunpandi, N., Naqvi, S.W.A., Pandiyarajan, R.S., 2018. ‘Mud Banks along the southwest coast of India are not too muddy for plankton’. Nature Sci. Rep. 8, 2544. Available online at [Accessed 3 December 2019].

OED, pour oil on troubled waters. [online] Oxford Dictionaries | English. 2019. Available online at: [Accessed 3 December 2019].

M. b. Otman, ‘Ferdaws al-moršediya fi asrar al-samadiya’. In: F. Meier and I.A. Afšar, eds., Die Vita des Abu Ishaq al-Kazaruni in der Persischen Bearbeitung von. (Istanbul, 1943) Shelfmark Per.D.537

Sa'di Shirazi, Gulistan (CE 1258), part of his collected works or Kulliyat. Shelfmark IO Islamic 843, Folio 42v

Subramanian, P.R. Kriyavin tarkalat Tamil akarati: Tamil-Tamil-Ankilam (Madras, 2000)

Simpson, J. A. and E. S. C. Weiner eds., Oxford English Dictionary (Oxford, 1989:749) Shelfmark OIA 423

Varadarajan, L. Sewn Boats of Lakshadweep. National Institute of ([Dona Paula], 1998). Shelfmark YP.2019.b.606

Wright, J.R. A companion to Bede: a reader’s commentary on ‘The ecclesiastical history of the English people’. (Grand Rapids, 2008) Shelfmark YC.2009.a.15214.

03 July 2019

Renaissance science works in Treasures of the British Library

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To replace the Leonardo da Vinci items that are usually in our Treasures gallery, but are now in the stand-alone "A Mind in Motion" exhibition, our Manuscripts and Incunabula curators have selected some less well-known but very interesting items dealing with the connection between art and science in the Renaissance. On the pure art side are some works by Albrecht Dürer and Michelangelo, but this post is about three volumes of Renaissance science. They sum up the way that humanists during the Renaissance sought to synthesise the existing knowledge of medieval Europeans with rediscovered Classical texts, many of which had been lost in Europe but preserved by Arabic scholars, and further advances that had been made in the Arabic world.

Manuscript page showing pictures of flowers
Depiction of edelweiss from the Codex Bellunensis.

The first item, shelfmark Add MS 41623, is the "Codex Bellunensis", a bound manuscript of herbal material in Latin with some Italian notes. Much of the content is based on De Materia Medica by Pedanius Dioscorides, a famous Greek physician of the first century CE. De Materia Medica was the single most important herbal text in Europe from its writing until the nineteenth century. "Bellunensis" refers to the town of Belluno in Italy, north of Venice, where the manuscript may have been created. The page to which the manuscript is opened in the display shows what is thought to be the first artistic representation of edelweiss, used to treat abdominal and respiratory diseases. The other herbs shown on this spread are valerian, an early sedative, eupatorium, and agrimony. The whole manuscript can be read free online .

The second item, shelfmark Royal MS 12 G VII, is a fifteenth-century Latin copy of Kitab al-Manazir, or "Optics", and another short work, by the great Arab scientist Hasan Ibn al-Haytham, known in Renaissance Europe as Alhazen. The pages on display deal with binocular vision and how the visual axes of the eyes intersect. The book was the first to empirically demonstrate that sight occurs when light reflected from an object enters the eye. Many early classical thinkers had believed that vision worked by the eye emitting some kind of "ray of sight". The book also includes "Alhazen's problem", a geometrical problem involving finding the point on a spherical mirror that a light ray from a given location must strike to be reflected to a second given location. This would not be completely solved algebraically until 1965. The copy on display comes from the Royal Manuscripts collection, a collection of manuscripts and printed books donated by King George II to the British Museum (not to be confused with the King's Library collection housed in the centre of the building, which was donated later by George IV).

Manuscript page showing artistic depiction of constellations
Illustration from the Phaenomena

The third of these items, shelfmark Add MS 15819,  is a manuscript copy of the Phaenomena by Aratus of Soli, a Greek poet of the early third century BCE. This is a long poem with one section describing the constellations of the stars, and a shorter second section on weather forecasting based on observations of the heavenly bodies and animal behaviour. You can read a public domain English prose translation of the poem at the Theoi Project, although we have two copies of the most recent English translation by Douglas Kidd in our collections. Our copy is a manuscript of the Latin translation of the poem by the Roman general Germanicus Julius Caesar, the nephew of the emperor Tiberius and father of Caligula. Our manuscript dates from the fifteenth century and once belonged to, and was probably written for, Francesco Sassetti, a senior manager in the Medici Bank.

Posted by Philip Eagle, with thanks to Eleanor Jackson, Curator of Illuminated Manuscripts, and Karen Limper-Herz, Lead Curator Incunabula and Sixteenth-Century Books.

18 December 2018

Arabic science manuscripts from the British Library

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Kitab al sirah
The beginning of Kitāb al-sīrah al-falsafīyah, an autobiographical treatise by the physician and philosopher Abū Bakr Muḥammad ibn Zakarīyā al-Rāzī (Add MS 7473, f. 1v)

Today is World Arabic Language Day, so here's a reminder of the scientific content in our Qatar Digital Library digitisation project. Our friends on the Asian and African Studies blog created two lists of major scientific works digitised in the collection, including Arabic versions of classical scientific texts, some of which were lost from Western European culture until the Renaissance, and original works by great early scientists of the Arabic-speaking world, such as Quṭb al-Dīn al-Shīrāzī, Ibn Sīnā (Avicenna), Ibn Haytham (Alhazen), and Abū Bakr Muḥammad ibn Zakarīyā al-Rāzī (Rhazes).