Poetry in motion.

Kinetic art is one of the most stimulating inventions of the twentieth century, yet it is rarely examined extensively. A new exhibition in London attempts to reassess the mobile's legacy.

The trouble with kinetic art is that you can't photograph it properly, and somehow videos and films of a kinetic work tend to reduce it from three dimensions to two. Perhaps this is why it is so little seen in museums and galleries: it's difficult to make posters and postcards from moving objects. And of course, for curators, there are all the electric motors and electromagnets: devices that need a good deal of attention, and which are prone to stopping unpredictably and occasionally emitting sparks and bursting into flames.

Yet kinetics is one of the great twentieth-century contributions to the continuously developing corpus of artistic invention. And the Hayward Gallery in London is to be congratulated on mounting a show in which classics have been brought together (or remade) to form a stirring, sometimes disturbing and even hilarious sequence of often rowdy and flickering events. Almost the first thing you see, is Marcel Duchamp's rotorelief of a disc with slightly eccentric circles of hatched red, black and white. Pressing the button to make the thing revolve causes it to create in your mind the impression of a three-dimensional spherical object. It is caused by an interaction between the machine and your physiology and psychology which is completely impossible to reproduce in the two dimensions of the page and, I suspect, in movies. Duchamp's continuing fascination with movement, which he tried so hard to incorporate in his famous works like The Bride Stripped Bare..., reached an apotheosis in these discs, but they are ver y little known because of the difficulty of showing them, except in reality.

All the early masters of kinetic work are represented: Calder (wonderfully elegant, but a bit rough in execution), Moholy-Nagy (a much better mechanic, but inclined to fussy effects), to Yves Klein (whose fire paintings certainly illustrate that the artist was very busy, but do little to recreate the action in your mind). The show, which started in the Museu d'Art Contemporani de Barcelona, has a strong and stimulating injection of South American and Mediterranean work, for instance, the three dimensional wire space-knitting of Gego (Gertrud Goldschmidt), who emigrated to Venezuela, and in her old age produced the most delicate, space-modifying creatures that tremble as you approach them. And Julio le Parc from Argentina who arranges thin semitransparent/semi-reflective discs on strings and simply shines light up at them to make a continuously changing pattern of strange reflections on the darkened walls of the booth in which the installation is housed -- the alterations are caused by convection from the lam ps and the air movements of your body.

Such simple and humanly responsive work is rare in the exhibition, which covers the history of kinetic art from the '20s to the early '80s. Many of the mechanisms involved could have been used in a Second World War bomber: big and heavy electric motors seem to power most of the exhibits; in some cases they and their clumsy wiring become part of the object. The most high tech (in ourterms) objects are the glassfibre sculptures of Pol Bury, where light flickers from the ends of waving strands. Because of the chronological restrictions, even Jean Tinguely is represented by clanking early stuff, a long way from the sparkling, funny, colourful waterworks at Pompidou.

Induction motors, photoreceptors, thyristors, diodes, even computers, the whole world of electronics (as opposed to the technology of electro-magnetism) have been missed out. It's easy to understand why -- technology has been completely transformed in the last couple of decades, and the potential of electronics is so astonishing that recent efforts would have been very difficult to marry with the great works of the mid-century, which still remain extraordinarily fresh, cheerful, and optimistic of dynamic future. An excellent subsequent show on electronic art is clearly possible. It will, like this one, have much to teach us all about relationships of the body, mind, machine and the phenomenal world in motion.