In a charming spot on the Nile, far from the noise of Fatimid Cairo and its crowded alleys and souqs, a statue of a man standing confidently with a compass in his hand seems to greet the passerby. The statue pays homage to a unique mathematician and astronomer whose legacy is celebrated in Heaven as on Earth! (There is a lunar crater carrying the Latinised version of his name: Alfraganus).
In the ninth century, about a century before Cairo was built, Al-Farghani arrived in Egypt from Iraq, commissioned by the Abbasid Caliph Al-Mutawakkil to supervise the construction of a very important building…as important as the Pharaonic structures on the Nile a millennia ago. A beautiful structure, one can still admire the building that bears his mark today at the Island of Rhoda across the Nile from Fustat. They call it Meqias al-Nil (the Nilometer), arguably Egypt’s second oldest Islamic monument after Amr ibn Al-‘As Mosque.
From his birthplace in present-day Uzbekistan, it was a long journey to Egypt; one that involved the patronage of an enlightened caliph, Caliph Al-Maamun, respected worldwide for launching a project that would lay the cornerstone for a flourishing scientific and humanist renaissance: Bayt Hikma (House of Wisdom). It was in Caliph Al-Maamun’s Baghdad that Al-Farghani studied and worked side by side with such great minds as Banu Musa ibn Shakir, Thabit ibn Qurra and others. Al-Farghani’s talent and theoretical knowledge was unquestionable, but it was his practical application of these theories that was somehow flawed in his early years in Iraq, something that we learn from an account given by Ibn Al-Daya in his book Al-Mukafaah. Ibn Abi Usaibia went even further with criticism, as he mentioned in his Uyun Al-Anbaa that "he (Al-Faghani) never completed a construction project." This would change dramatically in Egypt, where he perfected his skills while working on the Nilometer.
At the Nilometer
"Egypt was the gift of the Nile" – Herodotus
…and the gift had to be measured annually to estimate the taxes and to make sure the blessing would not turn into a curse (in the case of excessive floods). For centuries, Egyptians would wait with apprehension to know the level of the Nile water during the annual flood season. They would have a mental image of a column…a graded octagonal marble column at the heart of the Nilometer. If the water would fall below a certain mark (16 cubits) on the column, drought was surely around the corner and people would fall into despair. They would also despair if the water exceeded a certain mark, obviously because it would signal an opposite effect. Anything in between would be celebrated by the ruler and his people alike.
Ibn Khalkan and Ibn Taghribirdi attest Al-Farghani completed the Nileometer around the year 861. Prior to that, another nilometer once stood at the same spot since the Umayyad era, but was severely damaged by a flood, which is why Ibn Taghribirdi refers to Al-Farghani’s construction as Al-Meqias Al-Jadid (the New Nilometer). Much of what the visitor can see today is original, with some renovations and restorations from successive epochs (most notably by Ibn Tulun and by the Fatimid Caliph Al-Mustansir).
For art history students and fans, the interior of the Nilometer carries a massive surprise: the earliest pointed arches still surviving anywhere in the world, centuries before this type of arches would be re-baptised in Europe as ‘Gothic’. Other aesthetic elements in the Nilometer include the Kufic inscriptions, the floral motifs carved in stone, and the restored geometrical decoration of the cupola. Nevertheless, the real beauty lies in the design of the Nilometer and fitting its different parts for their functions: The large, deep pit is rectangular at its upper level, and circular at the bottom. This prevents the water that once rushed through the tunnels that connected it to the Nile from causing any damage to the base of the column. This design also helped the walls of the pit bear the pressure.
The contribution of Al-Farghani to the field of astronomy is recognised by his contemporaries as well as by historians, scientists and intellectuals centuries later. Even Dante referred to one of his works in his Vita Nouva, namely Jawami ilm Al-Nujum (A Compendium of Astronomy) in which he summarised and analysed the views of Ptolemy in his Almagest. The book, which he finished before working on the Nilometer, was translated to Latin in the twelfth century by Gerard of Carmona, gaining immediate popularity in Europe and bringing Al-Farghani into the spotlight.
At the British Museum, a thirteenth century manuscript copying the writings of Al-Farghani on the astrolabe bears witness to the importance of his contribution to improving this instrument. This manuscript is only one of many that carry different titles and that are attributed to him.
Sadly, Al-Farghani only wrote a couple of books. However, the quality of these works made them a reference for other astronomers for centuries to follow. Just like Al-Zarqali, Al-Battani and Al-Sufi, he became one of the greatest figures in the history of astronomy.
The astronomical observatory where he once worked in Iraq is long gone, but his Nilometer still stands in Cairo. It lost its function long ago as the old technology gave way to modern technology, but it never lost its charm, and one visit is enough to see it for yourself.