Lionardo, the natural son of Messer Pietro, notary of Florence and landed proprietor at Vinci, was so beautiful of person that no one, says Vasari, has sufficiently extolled his charm; so strong of limb that he could bend an iron ring or horse-shoe between his fingers; so eloquent of speech that those who listened to his words were fain to answer "Yes" or "No" as he thought fit. This child of grace and persuasion was a wonderful musician. The Duke of Milan sent for him to play upon his lute and improvise Italian canzoni. The lute he carried was of silver, fashioned like a horse's head, and tuned according to acoustic laws discovered by himself. Of the songs he sang to its accompaniment none have been preserved. Only one sonnet remains to show of what sort was the poetry of Lionardo, prized so highly by the men of his own generation. This, too, is less remarkable for poetic beauty than for sober philosophy expressed with singular brevity of phrase.[236] This story of Da Vinci's lute might be chosen as a parable of his achievement. Art and science were never separated in his work; and both were not unfrequently subservient to some fanciful caprice, some bizarre freak of originality. Curiosity and love of the uncommon ruled his nature. By intuition and by persistent interrogation of nature he penetrated many secrets of science; but he was contented with the acquisition of knowledge. Once found, he had but little care to distribute the results of his investigations; at most he sought to use them for purposes of practical utility.[237] Even in childhood he is said to have perplexed his teachers by propounding arithmetical problems. In his maturity he carried anatomy further than Delia Torre; he invented machinery for water-mills and aqueducts; he devised engines of war, discovered the secret of conical rifle-bullets, adapted paddle-wheels to boats, projected new systems of siege artillery, investigated the principles of optics, designed buildings, made plans for piercing mountains, raising churches, connecting rivers, draining marshes, clearing harbours.[238] There was no branch of study whereby nature through the effort of the inquisitive intellect might be subordinated to the use of man, of which he was not master. Nor, richly gifted as was Lionardo, did he trust his natural facility. His patience was no less marvellous than the quickness of his insight. He lived to illustrate the definition of genius as the capacity for taking infinite pains.