The Leicester Codexof Renaissance genius Leonardo da Vinci comes to the Chester Beatty Library next week, offering a unique window on his work, writes Arminta Wallace.

'What I'd like people to take away from this exhibition," says the director of the Chester Beatty Library, Dr Michael Ryan, "is the idea that Leonardo da Vinci was an extraordinary genius. Maybe a peculiar genius in some ways, in that he did too much and rarely finished anything. But he wasn't a spaceman or a Roscrucian or a descendent of Mary Magdalene or a chap who was plugged directly into the secrets of the Earth. He made the kind of meticulous observations, with the naked eye and the pencil, which other people didn't come even close to for several centuries afterwards. And he had a background - an intellectual context. That's what I'd like people to take away with them."

The Chester Beatty's Leonardo exhibition in Dublin will go to great lengths to set its subject, like a glowing jewel, into that historical and artistic background. It will feature displays devoted to the way movers and shakers operated in Renaissance cities, and the kind of books he had in his library.

The undisputed star of the show, however, will be the Codex Leicester. The codex (an ancient manuscript in book form) is a series of loose-leaf drawings, notes and musings about the nature and properties of water - as well as observations on a diverse range of subjects, from hydraulics to canalisation, astronomy to atmosphere, geology to palaeontology - in Leonardo's famous back-to-front handwriting.

"Leonardo kept notebooks for much of his life. But where his early notebooks are random collections of stuff, the Codex Leicestershows a real attempt to organise the information into distinct subject headings," Ryan explains. Thus the 15 sections of the codex deal with such topics as "water in itself", "the sea", "the surface of water", "canals" and so forth. Even so, the impulsive nature of Leonardo's approach to life is obvious on every page. And organised, he ain't. "You'll find him talking at length about, say, the volume and gravity of sea water - and then, at the bottom of a page, he'll go 'Oh, and here's how you can propel a ship'," Ryan says.

Shortly before the exhibition is due to open, the Chester Beatty Library is bristling with electricians, carpenters and people bearing large boxes of mysterious mechanical equipment. It's the sort of ambience Leonardo - a notoriously last-minute operator who rarely completed a project, and certainly never ahead of time - would have loved. He would have been fascinated by the new hi-tech floor-to-ceiling display cases which will show the codex to stunning effect; he might even have suggested a couple of newer, higher-tech modifications ahead of the opening day on June 13th.

The 18 double sheets of the codex - each of which was folded in two to create four pages - will be lit in groups of three for three minutes at a time, with lights fading in and out in a complex switching sequence. The precious manuscript can't, obviously, be subjected to too much light for too long. But the current banging and hammering isn't just a matter of re-arranging the furniture in honour of the Codex Leicester. The entire exhibition gallery is being revamped, and the changes will be permanent. "When we moved in here in the year 2000 we ran out of time and money," Ryan explains.

"So although we did our best, and the gallery has been very successful and highly praised and all the rest of it, we ended up - in the actual exhibition space - with tacky temporary walls, a very oppressive low industrial ceiling and a lighting system which never worked to our satisfaction." A raised ceiling and new lighting track has given the room a lighter feel, which will be further enhanced in due course by glass walls and additional showcases.

Ryan advises visitors to come as often as you can - and just bask in the sheer beauty of the thing.

"The thing I like best about the Codex Leicester," according to Ryan, "is his insight into the long history of the Earth. Leonardo was wrong about a lot of things, but his sense that you could verify processes which took place long, long ago in the history of the planet by studying natural phenomena changed the way we look at the world forever."

• The exhibition runs at the Chester Beatty Library from June 13th to August 12th 2007. Admission is free but visitors are strongly advised to obtain timed tickets which are available to download and print-out from the library's website http://www.cbl.ie The Chester Beatty Library is in the Gardens of Dublin Castle. For information, tel: 01-4070750