Dr Joyce shrugs. 'Well, readers lose library books -' he begins in a reasonable voice.

'Oh for God's sake man! A whole library? There were tens of thousands of books in it - I checked. Real books, and bound journals, and documents and maps and ...' I am aware I am starting to sound upset. 'The Third City Records and Historical Materials Library, missing presumed lost for ever; it's listed as being in this section of the bridge, there are countless references to it and cross-references to the books and documents it contained and even reminiscences of scholars who went there to study; but nobody can find it, nobody has ever heard of it except through those references. They're not even looking for it especially hard. My God; you'd think they'd send out some sort of search party of librarians or bibliophiles or something. Remember the name, doctor; give me a call if you ever come across it.' I sit back, folding my arms. The doctor makes some more notes.

'Do you feel that all this information you are seeking is, or has been, deliberately hidden from you?' He lifts one eyebrow in interrogation.

'Well, that would give me something to fight against, at least. No; I don't think there's any malice behind it all, just muddle, incompetence, apathy and inefficiency. You can't fight that; it's like trying to punch mist.'

'Well then,' the doctor smiles glacially, eyes like ice gone blue with age, 'what did you discover? Where did you stop, give in?'

'I discovered the bridge is very big, doctor,' I tell him. Big, and rather long; it disappears over the horizon in both directions. I have stood on a small radio tower atop one of its great summits and counted a good two dozen other red-painted peaks hazing off into the blue distance towards both the City and the Kingdom (both invisible; I have seen no land since I was washed up here, unless one counts the small islands which support every third bridge section). Tallish, too: at least fifteen hundred feet. Six or seven thousand people live within each section, and there is probably room - and over-designed strength in the primary structure - for an even greater density of population.

Shape: I shall describe the bridge with letters. In cross-section, at its thickest, the bridge closely resembles the letter A; the train deck forms the cross-bar of the A. In elevation, the centre part of each section consists of an H superimposed over an X; spreading out on each side from this centre are six more Xs which gradually reduce in size until they meet the slender linking spans (which have nine small Xs each). Linking the extremities of each X, one to another, then produces a reasonable silhouette of the general shape: hey presto! The bridge!

'Is that it?' Dr Joyce asks, blinking. '"It's very big," is that all?'

'It's all I needed to know.'

'But you still gave up.'

'It would have been the act of an obsessive to go on. Now I'm just going to enjoy myself. I have a very pleasant apartment, a quite reasonable allowance from the hospital, which I spend on things which amuse me or which I find beautiful; I visit galleries, I go to the theatre, concerts, the cinema; I read; I have made some friends, mostly among the engineers; I play sports, as you might have noticed; I'm hoping to be admitted to a yacht club ... I occupy myself. I wouldn't call that rejecting anything; I'm right in there, having a great time.'

Dr Joyce gets up, surprisingly quickly, throwing the notebook onto his desk and going to pace up and down behind it, oscillating between book-clogged bookcases and glowing blinds. He cracks his knuckles. I inspect my nails. He shakes his head.

'I don't think you're taking this seriously enough, Orr,' he says. He goes to one of the windows and draws the blinds back, revealing a bright sunny day; blue sky and white clouds.

'Come here,' he says. With a sigh and a small oh-all-right-if-it'll-keep-you-happy smile, I join the good doctor at the windows.

Straight ahead, and almost a thousand feet down, the sea; grey-blue and ruffled. A few yachts and fishing boats speckled about; seagulls wheel. The doctor points to the side, though (one side of his office juts out, so he can look along the side of the bridge).

The hospital complex of which the doctor's offices form a part stands slightly proud of the main structure, like an energetically growing tumour. From here, at such an acute angle, the bridge's elegant grace is obliterated, and it appears merely cluttered and too solid.

Its sloping sides rise, russet-red and ribbed, from the granite-plinthed feet set in the sea nearly a thousand feet below. Those latticed flanks are slabbed and crammed with clusters of secondary and tertiary architecture; walkways and lift shafts, chimneys and gantries, cableways and pipes, aerials and banners and flags of all shapes, sizes and colours. There are small buildings and large ones; offices, wards, workshops, dwellings and shops, all stuck like angular limpets of metal, glass and wood to the massive tubes and interweaving girders of the bridge itself, jumbled and squeezed and squashed between the original structure's red-painted members like brittle hernias popping out between immense collections of muscles.

'What do you see?' Dr Joyce asks. I peer forward, as if asked to admire the detail brushwork on some famous painting.

'Doctor,' I say, 'I see a fucking great bridge.'

Dr Joyce pulls hard on the cord, snapping it at the top and leaving the blinds open. He sucks his breath in; he goes to sit behind his desk, scribbling in his notebook. I follow him.

'Your trouble, Orr,' he says, as he writes, 'is that you don't question enough.'

'Don't I?' I say innocently. Is this a professional opinion or just a personal insult?

At the window a window-cleaner's cradle is lowered slowly into view. Dr Joyce does not notice. The man in the cradle taps at the window.

'Time to have your windows cleaned, I think, Doctor,' I tell him. The doctor looks up briefly; the window-cleaner is tapping alternately at the window-pane and his wrist watch. Dr Joyce goes back to his notebook, shaking his head.

'No, that's Mr Johnson,' he tells me. The man in the cradle has his nose pressed against the glass.

'Another patient?'

'Yes.'

'Let me guess; he thinks he's a window-cleaner.'

'He is a window-cleaner, Orr, and a very good one; he just refuses to come back in, that's all. He's been on that cradle for the last five years; the authorities are starting to worry about him.'

I gaze at Mr Johnson with new respect; how agreeable to see a man so happy in his work. His cleaning cradle is worn and cluttered; there are bottles, cans, a small suitcase, a tarpaulin and what may be a camp-bed at one end, balancing a variety of cleaning equipment at the other extremity. He taps on the glass with his T-shaped wiper.

'Does he come in to you, or do you go out to him?' I ask the good doctor, walking over to the windows.

'Neither; we talk through an open window,' Dr Joyce says. I hear him putting the notepad away in a drawer. When I turn he is standing looking at his watch. 'Anyway, he's early; I have to go to a committee meeting now.' He mimes something like this to Mr Johnson, who shakes his wrist and holds the watch up to his ear.

'And what of poor Mr Berkeley, upholding the law even as we speak?'

'He'll have to wait, too.' The doctor takes some papers from another drawer and stuffs them into a thin briefcase.

'What a pity Mr Berkeley doesn't think he's a hammock,' I say, as Mr Johnson hoists himself up out of sight, 'then you could keep them both hanging around.'

The good doctor scowls at me. 'Get out of here, Orr.'

'Certainly, doctor.' I head for the door.

'Come back tomorrow if you have any dreams.'

'Right-oh.' I open the door.

'You know what, Orr?' Dr Joyce says seriously, clipping his silver propelling pencil back into his breast pocket. 'You give in too easily.'