The Roda Island Nilometer

The Roda Island Nilometer was built to measure water levels in the River Nile, which were necessary for a good agricultural season. The measurement taken was used as a basis for the taxes that the Egyptian province had to pay to the Caliphate.

This Nilometer was one of a number of constructions that began in Egyptian antiquity. The term itself comes from the Greek Nilometer, which was made up of neilos (Nile), and metron, ‘measure’. From the Umayyad period, the new masters of the region had also constructed a Nilometer in Halwan, which consisted of a graduated wall. The hydraulic works, of which the Nilometer is part, are works of public utility that the leaders of the Islamic world often constructed, as the problems related to water supply were important and even crucial in the regions concerned. One can observe the presence of water conduit systems described precisely and illustrated in treatises on mechanics written from the ninth century[1].

The building, constructed in finely carved stone, is located south of Roda Island. It takes the shape of a well, linked to the river by three tunnels arranged on three floors, which function according to the principle of connected containers. The well has a lower circular plan and a rectangular one on the upper section. A large, marble column is located at the centre of the cavity. It stands on a stone base and is surmounted with a beam in Acacia wood inscribed with Kūfic writing[2]. The shaft of this column, with its Corinthian capital, has markers that correspond to a Roman cubit (54cm). A stone stairway provides access to three on the same floor. The inside walls contain niches with ressauts with slightly pointed arcatures supported by narrow columns. This kind of arch seems to have originated in the eastern regions of the Islamic world. The Abbasid brick architecture provides several examples of this, like the door of Baghdad in Raqqa (Syria, ninth century) and the base of the minaret of the Great Mosque of Samarra (Iraq, AD 847–961) .

After the Mosque of ‘Amr (AD 642) the Nilometer is the most ancient Islamic structure in Egypt: it was made in 861[3], according to the double inscription of the northern and eastern sides of the well that mention the name of the Works foreman. The end of the dedicatory inscription, which possibly mentions the Abbasid Caliph al-Mutawakkil, was probably effaced by Ahmad ibn Tūlūn in 872 according to Creswell, and replaced with  Qur’anic inscriptions that evoke water, vegetation, and prosperity. They stood out originally in yellow on a blue ground, according to a common principle in Islamic art where the divine word is associated with the light. While these inscriptions provide us with important historical information, they are also remarkable because they represent the most ancient example of monumental inscriptions in Islamic Egypt. The bands of simple Kūfic script, which are made from carved wood, are stylistically typical of Tulunid Egypt, even if a relative koine existed at this time in the field of writing, up until the tenth century. In the upper area of the Mosque of Ahmad ibn Tūlūn, built in new Cairo (al-Qatai) in 876–879, there is a wooden frieze with bevelled carving that is reminiscent of Abbasid decorations in Samarra, which developed Qur’anic verses that had stylistic similarities with the inscriptions on the Nilometer[4].

[2] Qur’an 2:255: ‘Allah! There is no god but He,-the Living, the Self-subsisting ... His Throne doth extend over the heavens and the earth, and He feeleth no fatigue in guarding and preserving them for He is the Most High, the Supreme (in glory).’

[3] The facing is  modern.

[4] The Louvre Museum holds a fragment of this inscribed frieze in Scots Pine: AD 876–879, Cairo, Egypt, store of the National Institute of Eastern Languages and Civilizations (1948), inv. HI 10.