An Irishman's Diary

Chances are you've never heard of Pierino da Vinci. I discovered him only recently in a footnote to Norman Davies's epic book, Europe: a History of Europe. As the name hints, he was a relative of Leonardo - his nephew. But perhaps more interestingly, he was also the result of a breeding experiment.

Pierino's father, Bartolomeo, was only a half-brother to the great man. Even so, after Leonardo had passed on, he thought he could reproduce him. With this in mind, he went back to the village of Vinci - where Leonardo had been born the illegitimate son of a peasant girl - and sought out a woman with a similar profile. Their joint project was duly conceived and, as soon as he was old enough, hot-housed in one of the great art studios of Florence.

It was a crude experiment. As the people at Coolmore Stud could tell you, there is no guarantee that a Derby winner will produce a Derby winner, even when the bloodlines are meticulously documented. Yet Pierino was talented enough for some of his work to be misattributed to Michelangelo. He died young, sadly, before the full extent of his abilities emerged.

Leonardo himself left no offspring, as far as we know. He was so repelled by "the act of procreation and anything that has any relation to it" that he thought it a marvel the human race did not die out. There is much speculation that he was homosexual. Certainly, he seems to have had few female friends. But he kept his personal life very private. So there is no evidence if his legendary curiosity extended to experiments with women.

The best thing about the Leonardo exhibition now running at the Chester Beatty Library is that it offers the thrill of proximity to the original Renaissance man. Despite the gallery's helpful notes, his 72 pages of reflection on such subjects as "the drainage of swamps" is not particularly accessible. Even if you're a hydrologist who reads early Italian, there remains the problem that the whole thing is written backwards, in Leonardo's famous mirror-script.

Nobody knows why he wrote this way (except perhaps Dan Brown). Maybe it was to protect his ideas, although it would hardly have taken a genius to decipher the code. There is a theory that he was dyslexic and found it easier to write in reverse. But Leonardo was a fiercely rational man. So I prefer to think that, being left-handed, it was the only way he could avoid smudging all his pages with ink.

In any case, the Codex Leicester is, as the promotional literature says, a window on to an extraordinary mind. And if the glass is somewhat opaque, the exhibition also features - separately - some of the furniture. The dimly-lit codex is surrounded by a complementary display of books and manuscripts that Leonardo would have read - some of them Arabic and Chinese, which may be where he got the idea of writing from right to left.

It is intriguing to think what Leonardo would be doing if he lived today. Perhaps he would hire his services to that modern-day prince, Bill Gates, who now owns the codex. Then again, he might be more at home in California, with Steve Jobs. As well as inventing the next generation of Apple Macs, iPhones, and machines we haven't thought of yet, he could direct beautiful animated films for Pixar. No doubt he would still have enough spare time to correspond with Nasa, offering his latest ideas on space exploration.

But we live in an age of specialists now, so Leonardo might not fit in easily anywhere. Even in his own lifetime, there were those who thought he had too many ideas for his own good and that he needed to focus. Pope Leo X was one such critic. "This man will never do anything," he said of him, late in Leonardo's life, "for he begins to think of the end before the beginning."

Certainly, Leonardo's career is littered with projects that were not quite finished or - in the case of his flying machine, because it was so far ahead of its time - never begun. Even some of the works he did complete suffered from his endless experimentation. No sooner had he painted The Last Supper, for example, than it began to fall off the wall. The struggle to preserve it continues to this day.

His younger contemporary, Michelangelo, openly taunted Leonardo over one of his most public failures: the great bronze horse commissioned by the Duke of Milan. It was to be the biggest equestrian statue ever built. But Leonardo envisaged the horse rearing on its hind legs and, after making the model, never solved the practical problem of how two legs would support its enormous weight. A compromise, non-rearing design was never made either.

Art was only a sideline, of course. When he first presented his CV to the duke, he placed painting well down the list of his skills, albeit adding, modestly: "I can do everything possible, as well as any other." Revisionists of the Leonardo cult argue that most of his scientific and engineering ideas went nowhere. But as the thousands flocking to Dublin Castle over the next two months may show, Leonardo's greatest exhibit was his mind itself.