SCULPTURE / Teetering on the edge: They were not intended for public gaze, but they are among the best sculptures of the 19th century. Tom Lubbock on Degas at the Burrell

The Glasgow exhibition is called 'Degas in Bronze', and the title is chosen advisedly. It's not, for example, 'Degas's Bronzes'. For the 75 bronze statues on show are - with one famous exception - in a state in which Degas never knew them, or ever envisaged they would be seen. Indeed, these are works so far from anything that the artist intended that you might doubt how far they should be called works of art, or works by Degas, at all.

What happened was this. During his lifetime, from perhaps the mid-1860s onwards, Degas began making quite small models in wax, to be used to study the body in the round, as an aid to his picture- making. They were familiar Degas subjects: some equestrian studies, dancers, bathers. But they weren't meant for exhibition, and they weren't maquettes for larger sculptures.

Degas's attitude to most of them seems to have been casual and practical, bending their limbs around to try out different poses, bashing the wax out and starting again when things didn't work, and leaving them lying around with no particular thought for their preservation. Unlike the well-known Little Fourteen-Year-Old Dancer in her real tutu - the exception mentioned above, which Degas did exhibit - these were, in effect, a private, three-dimensional sketchbook.

After the artist's death about 150 of these models were recovered from his studio, in the state in which he'd left them. Half of them were deemed to be in too bad a condition to be saved. The rest were cast in bronze, in 20 editions, though most of those have now been dispersed and you find the odd figure or two turning up all over the place.

But five complete editions have been kept together, one being at the Museu de Arte in Sao Paolo, Brazil, and it's this that's now on loan to the Burrell Collection. Still, saying 'complete' is, of course, misleading. Ideas like 'the full series' and 'finished state' simply don't apply. What we have is a chance selection of working models given an arbitrary permanence.

But we're very lucky to have them, and not just for any insight they offer into Degas's working methods. They stand by themselves beautifully. They're among the best things Degas did. They're among the best sculptures of the 19th century. And, though there's no way of knowing what the lost figures were like, what remains does reveal an independent plan. The female figures - they are the great majority - fall clearly into groups, sometimes as variations on a single pose, sometimes as if they were different stages of the same action, like three-dimensional Muybridge. That's how they're shown at the Burrell, and that seems right.

If there's a problem with this exhibition, it's to do with the size of the figures. They are for the most part around 2ft high, and they need ideally to be seen at head height. The display cases here set them too low down. To get the best from them, viewers of average stature will need to go round much of the show on their knees - quite the wrong attitude to take before these least monumental of works.

Their size is important. One visitor to Degas's studio described them as 'strange dolls - dolls if you will, but dolls modelled by a man of genius'. But dolls none the less, and this is not only a matter of dimension, it's the way they are still visibly objects made to be played with. The bronze-casting does not disguise the evidence of Degas's wax activities. You notice the working of his fingers. You notice where he's bent a limb into a new position and made the hardened wax crack. What's now frozen was just a stage in a continuing modelling process.

This gives the figures a double aspect. You can take them, representationally, as figures doing something, or trying to do something. Or you can take them, object- wise, as figures having something done to them, worked by the modeller into these often strenuous, sometimes impossible, postures. Holding a position, being made to hold a position: you can see it both ways. And this double aspect declares, or mimes, Degas's essential interest in the human figure. The body acts and performs and shows grace and self-command - but at the same time it's put through its paces, being subject to physical disciplines (like ballet dancers) or to social codes (costume, conventional body-language) or simply to its own anatomical limits (those bathers trying to dry inaccessible parts of themselves). The 'bronzes' put these pressures in their purest form.

They exist at the level of pure action or pure function. Their surfaces are finished to varying degrees, but there's always most interest and most finish in the anatomical centre, the stomach, shoulders, upper arms and legs, the places where the body's central directions and tensions happen. Hands and feet are left very sketchy, the heads are little more than blobs. You can't tell what kind of people they are, nor often whether an individual figure should be strictly classed as ballerina or bather. And though they're probably all meant to be naked, this isn't much of an issue either (they're not overtly sexy). Just bodies.

Women's bodies, of course, and that's pertinent. Degas would no doubt not have felt happy making such physical examples of men, putting the male body through these exercises. Women were, to him, more pure instances of the body, more essentially physical. But, on the other hand, I don't think those who see Degas as a cold taxonomist of anatomies, or as a voyeur - in this case perhaps a 3-D voyeur, touching up his little dolls - have got it more than half right. He isn't that removed from the bodies he's doing. Making these models, he's trying their positions himself. The figures are not primarily about looking or touching, but about feeling what it's like.

It comes down, so often, to a question of balance: standing up and falling over. And about sculpture and balance there are two simple facts to be borne in mind. One is that a statue, if firmly stuck to a base and maybe supported by internal splints, can hold positions that an unpropped person couldn't hold without falling over. The other is that, conversely, a person with normal powers of balance can often keep upright in positions where it would be very hard to get a statue - if set merely on its own feet or foot - to stay standing.

Degas presents many cases of doubtful balance, one leg on the ground as a pose is struck, a stocking pulled on, a foot examined. They're especially doubtful because one is never sure whether the statue's base is substituting for normal human sure- footedness, or whether it's lending unrealistic stability to an unbalanced stance. And the business is sometimes complicated by another uncertainty: is the figure holding a position that is basically still, or is it just a captured instant of movement, where different balance factors apply?

These are questions that can't be easily answered, but they must have arisen practically in the making: the waxes would often have been bending under their own weight, or toppling over. It's another aspect of their 'unfinished' and literally experimental nature, the way these creatures, perhaps only half-art, almost conform to the condition of life.

Burrell Collection, Glasgow, to 13 March

Tom Lubbock has been awarded the 1993 Hawthornden Prize for art criticism

(Photographs omitted)