De revolutionibus orbium coelestium have begun work on his new system by that time. Most historians believe that he wrote the "Commentariolus" after his return from Italy, possibly only after 1510. At this time, Copernicus anticipated that he could reconcile the motion of the Earth with the perceived motions of the planets easily, with fewer motions than were necessary in the "Alfonsine Tables", the version of the Ptolemaic system current at the time. In particular, the heliocentric Copernican model made use of the Urdi Lemma developed in the 13th century by Mu'ayyad al-Din al-'Urdi, the first of the Maragha astronomers to develop a non-Ptolemaic
Paris in the 16th century art, did not come until the very end of the century with the reign of Henry IV. Through the 16th century, there were only four bridges across the Seine, two on each bank, insufficient for the growing city and the amount of traffic they carried. The Paris bridges at the beginning of the 16th century were largely made of wood, and were frequently washed away in floods or knocked down by ice on the frozen river. The most important bridge was the Pont au Change, which had been built in 1304 under Philip le Bel, and was site where the