Did Leonardo da Vinci Apply for a Job in Istanbul?
In 1500, after the French invaded Milan and imprisoned Leonardo’s patron, Ludovico Sforza, Leonardo found himself out of favor and unemployed. He left Milan and traveled east to Mantua and Venice, and worked for a while in Venice as a military engineer. There he came in contact with the circle of merchants trading with the Ottomans. Sometime in 1503 Leonardo applied for a position in the court of Sultan Bayazid II, the son of Sultan Mehmet Fatih and an enlightened ruler known for welcoming into Ottoman lands Jews expelled by Spain in 1492.
In his letter Leonardo proposes four separate projects to the Sultan:
• “I have a design for a gristmill powered by wind, without the need for running water.” (Not exactly ground-breaking; centuries earlier Heron of Alexandria had designed a working windmill.)
• “I have developed a bilge pump to remove water without the use of ropes and pulleys,” (Here he had a hydraulic apparatus in mind, and drawings exist for that purpose among his notebooks.)
• “I, your faithful servant, understand that it has been your intention to erect a bridge from Galata to Stambul (from that Greek name comes Istanbul) across the Golden Horn (Haliç), but this has not been done because there were no experts available. I, your subject, have determined how to build the bridge. It will be a masonry bridge as high as a building, and even tall ships will be able to sail under it.”
• “I plan to build a suspension bridge across the Bosporus. By the power of God, I hope you will believe my words. I will be at your beck and call at all times. — Architect/engineer Leonardo da Vinci”
In an inventory of its holdings published in 1938 the Topkapi lists the letter as E-6184. Leonardo’s sketches for the bridge are found in Manuscript L, a small Codex stored in the Institut de France, Paris. Only in 1952 the German scholar von Franz Babingen unequivocally established the connection between the letter in the Topkapi Archives and the drawing in the Institut de France.
Just below the bird’s eye view drawing (ref. drawing) appears the graceful silhouette of the bridge, the smooth curve of its runway set atop a parabolic arch, a masterpiece combining form and function! The specs are given in units of braccia, where 1 braccia = 2.1 ft. The bridge is meant to span the 400 braccia (800 ft) wide Golden Horn, with its parabolic arch rising to 70 braccia (146 ft) above the water. Its runway is extended to a length of 600 braccia (1200 ft) on facing shores; and is tapered in its width at its peak to 40 braccia (80 ft). The mathematics for the parabolic support for a bridge was not worked out as a structural engineering problem until the 19th century, but Leonardo appears to have intuitively realized that this shape provided the best support for the bridge!
The drawing stands as a work of timeless genius because the issues it solves are eternal. In a few pencil strokes, Leonardo da Vinci drew a major architectural and technical solution. The two lateral, curved parabolic arches are unique because they provide the necessary resistance to lateral winds.
The Golden Horn (Haliç to Turks) is an inlet, an estuary on the European side of the Bosporus measuring 10 km in length and 800 ft in width at its entrance. On the other hand the Bosporus measures 30 kms in length and 3.329 kms in width at the northern entrance and 2.8 kms at the southern entrance. Thus the 4th project in Leonardo’s letter, a suspension bridge over the Bosporus, would have been entirely impractical at a time before high tensile steel cables could be produced in the 20th century. A pair of suspension bridges were built in 1973 and 1988, respectively. A third combined rail and road bridge was recently opened.
Leonardo failed to secure an appointment to the court, never got to see Istanbul, the Bosporus or the Golden Horn, or to offer precise specs for the bridge based on his own measurements!