The Genius of Leonardo. A London exhibition lets the Renaissance artist be seen on his own terms.

A LITTLE uncertain of its capacity to stay aloft, Prof. Martin Kemp and I stand beneath the 36-foot skeletal wings of Leonardo da Vinci's ``Flying Machine,'' suspended in midair - an object of some awe. Professor Kemp, with Jane Roberts, organizer of the unique Leonardo exhibition drawing crowds to the Hayward Gallery here, intended this great birdlike affair - made of beautifully crafted beech wood, iron, brass, hemp, and coir rope, not to mention tarred marline, leather, and tallow - to be the show's climax. Which is exactly what it is.

``I fed the modelmaker with a whole series of Leonardo designs and also with details of the materials that Leonardo described...,'' says Kemp. The modelmaker was James Wink, an architectural model specialist. Translating the Renaissance artist's 500-year-old notions into tangible form in the 1980s proved to be a fascinating challenge. He thought of it as a kind of archaeology. And he concluded that the result was an ``aesthetic,'' rather than a ``scientific,'' object.

Kemp says that Leonardo was ``thinking on a large scale,'' and it was this scale that they wanted the model to capture. ``He was thinking of remaking nature. If he thought he understood nature so perfectly that he could reconstruct nature on his own account, then that would be the ultimate aim.''

A video of a smaller prototype made by Mr. Wink is shown near the full-size model. It pictures the flying machine in flight. Its wings move with the slow, hefty grace of some prehistoric bird. Never mind that the man in its harness could never have actually pedaled all that weight into the air. It's the thought that counts.

There are other models of Leonardo's conceptions in the show, a number borrowed from an earlier, quite different exhibition in Montreal. They are handsome and efficiently made but seem comparatively ``soulless'' - ``slightly like executive toys,'' Kemp suggests. The new flying machine, on the other hand, looks as if it might have been built centuries ago.

Its historical look fits the tenor of the show: Leonardo being presented, as far as possible, on his own terms rather than ours. Kemp tells me: ``I rather resist the idea of Leonardo as `the prophet of modern vision.' ... In this exhibition we're trying to get Leonardo to speak with his own voice.''

That voice, Kemp argues, is ``neither medieval nor modern. It's a highly individual voice. He speaks to us better ... in his own language, rather than [the exhibition] trying to say that he invented absolutely everything from the ... washing machine to the submarine!''

Leonardo has often been presented as a man obsessed with detail rather than possessing a general view of the world. The exhibition deliberately sets out to counter this idea.

``I think that we can look back [at Leonardo's work] and see that there is a wholeness of vision here,'' says Kemp, ``a willingness to see how different fields of endeavor connect with each other.'' Without overemphasis, Kemp does feel that the vision contains a message for us today, with our breakdown of communication among intellectual disciplines. If ``we have the humility to learn from the past,'' he says, ``then in Leonardo there is something that communicates to a modern audience.''

Something in the show that undoubtedly communicates with a modern audience is a number of screens displaying computer graphics. These relate to several aspects of Leonardo's own visual explorations: study of light effects, the use of perspective (as in his ``Last Supper'' mural in Milan), his plans for churches, and his finding of parallels between various kinds of branching structures.

Kemp says Leonardo ``wanted ultimately [his] drawings to do more than they can really do.'' He suggested movement ``marvelously ... but ultimately he can't achieve it'' in drawings. He also had an urge to explore ``remorselessly ... every variation on a theme'' in his scientific endeavors, but couldn't do so.

``It seemed to us that computer graphics could handle precisely this kind of problem,'' Kemp says, so ``Leonardo's own frustrations could be ... salved in retrospect! ... We've programmed in Leonardo's principles and ideas and seen them at work.''

The computer images move fascinatingly around three-dimensional conceptions and exhaustively explore variations of some of Leonardo's ideas.

THERE is no stinting in this exhibition, however, when it comes to Leonardo's own graphics - in ink, metalpoint, or chalk. The endless stream of visitors shifts with slow concentration from one supreme drawing to another. A large number of them are borrowed from one of the richest collections of Leonardo drawings in the world, the British Royal Collection. Most of them have been many times reproduced; but there remains a real difference between experiencing even the best reproduction and seeing the actual thing.

This is not, however, the usual run of Old Master drawings shows. It doesn't present them chronologically. Nor do you find all the drawings relating to a final painting grouped together. Kemp has tried to avoid ``starting with a scholarly concept, almost a book, and then putting it on the walls.'' Instead the idea has been to ``group objects together which seem to tell [a story] beside each other.''

Kemp points out a section of drawings under the heading ``The Vortex.'' He says, ``You have a whole series of related movements and dynamics from different areas of his activity.'' These range from ``hydraulic engineering..., the growth of plants, the turning of hair, the twisting of drapery, through investigations of perpetual motion [although Leonardo convinced himself quite rightly that perpetual motion wasn't possible], ... and then climaxing in the deluge drawing, in which these vortex movements have run wild in nature: You have a great cataclysm, where mountains, earth, trees, are all whirled up in the maelstrom of revolving lines.''

Does this suggest a move in Leonardo's thinking from the constructive to the destructive, from optimism to pessimism?

Kemp thinks so, but finds ``pessimism in his early work,'' too. ``I don't myself ... have a picture of somebody who is deeply disillusioned at the end of his life. I think he realizes that the system of knowledge he is working with has grave faults he didn't see earlier, but I think he remained optimistic. ... There was more to be discovered than he had even dreamed of at the beginning.''

All the same, the final words in the show, inscribed on the wall as visitors go out underneath the wings of the flying machine, are a translation of a rhetorical refrain that echoes throughout the manuscripts: ``Tell me if anything was ever done.''

That sounds frustrated enough. But Kemp's hope is that visitors will weigh the evidence of this one man's work, exploring such a wide range of interests, and answer: ``Yes!''

The exhibition continues at the Hayward Gallery through April 16.