'Given at Pavia on August 18th, in the year of our Lord, 1502, and the second of our reign in Romagna.
'Cæsar, dux Romandiolæ.'
So ran Leonardo's new credentials.
These were the years in which Cæsar Borgia was gradually recovering for Alexander VI. the ancient States of the Church, said to have been conferred on the papacy by Constantine the Great. He had taken the town of Faenza from the eighteen-year-old Astorre Manfredi; and Forlì from Caterina Sforza. The lad and the woman had been confided to his protection. He threw them both into the Castle of St. Angelo. He concluded a fraudulent treaty with the Duke of Urbino, and in 1502 planned a campaign against Bologna. He was intent upon making himself sole and absolute ruler of Italy. In September his enemies, including the dukes of Perugia and Siena, as well as other important personages, assembled at Mugione, and concluded a secret alliance against him. Vitellozzo Vitelli swore the oath of Hannibal, that within a year he would slay, imprison, or exile the common foe. Report of this alliance having been bruited abroad, it was joined by some of the greater princes. Urbino rose in revolt; Cæsar's own troops mutinied; the King of France was slow in coming to his help; he seemed on the verge of ruin. Nevertheless he still had resources, and his enemies were dilatory. The opportunity was let slip, and presently these, his allied enemies, entered into negotiations with the usurper. He overreached them, contriving to set them at variance with each other; by profound dissimulation and courteous manners converted them to a more or less favourable attitude; and presently made an urgent appointment to meet his foes in parley at the newly-conquered town of Sinigaglia.
Leonardo had quickly become a prominent personage at Cæsar's court. The duke employed him in adorning the various towns with palaces, libraries, schools, barracks, and canals. He constructed engines of war, made military maps, and was present at all Cæsar's bloodiest exploits.
Leonardo did not wish to see too clearly, or to know too accurately, what was taking place around him. He eschewed politics. He confined himself almost entirely to observations on physical and social phenomena: the manner of planting orchards, the machinery for ringing the bells at Siena Cathedral, the low music of the falling water in the fountain of Rimini, the dove-cot in the Castle of Urbino. He noted how the shepherds at the foot of the Apennines placed their horns in the narrow openings of deep hollows, so that echo should increase the volume of their sound. For whole days he stood on the desolate shore of Piombino, watching the falling of the waves; and while all around him the laws of human justice were being broken, mused on the invariability of nature, and found deep-seated joy in the eternal justice of the Prime Mover.
On a day in June the corpses of the young Astorre and his brother were found in the Tiber, stones tied round their necks. The crime was universally attributed to Cæsar. But that day Leonardo noted—
'In Romagna four-wheeled carts are used, the front wheels small, the back large: the construction is faulty, for all the weight rests on the front.'