Piranesi at Blackfriars by The London Archaeologist

I've mentioned my West City consultancy work, the magic shop it brought me to on a corner of Theobold's Road. The junction's with Leather Lane and the market. While there, I'd noticed what seemed to be the kind of framing effects, produced in this instance by the market stalls, that have in the past accompanied occurrences. Passing this time on my way to an exhibition, I set about to capture them.

Work with the camera's often been likened to hunting, an experience I've never had. For me, fishing's always been a clearer analogy. A world without substance, silent and still, purely of vision, devoid of taste, feel, smell, the element into which we peer through the camera is an alien one, in which we could never survive. Staring at the glistening surface, we are aware of things in there of value, and occasionally there are sufficient signs to allow us to draw them near enough to, the arm a line, perhaps, the camera a hook, with patience, waiting till the twitch, pull, snap, catch. Sometimes you draw out a rusting shopping trolley or bicycle, rotting log, sometimes it's a rare fish, and the urban waterway's long been a favoured place for disposing of a firearm.

Uncertain what they were I stocked them away. I say fishing, but of course only a lost archaeologist, strayed into an alien present, would build up the collection of discarded shopping trolleys I suspected they were, the camera no hook but a trowel, the element obscure as earth.

My plan for the afternoon was neither blogging nor work, though. I was hoping to train my eye. I was on my way, first to Sommerset House, where I hoped to illuminate my own process by that of Frank Auerbach's trowelling through paint in imitation of the London subsoil at the bomb sites. If it made sense to him, perhaps it could to me . My next stop was to be the Tate. If anything should arise on the way - as from the market stalls, for instance, I had hoped - so much the better. If they should not, perhaps that would be due to my inability to see into the alien element, and inspecting how pain

ters, who have the advantage, like Auerbach, of working in a genuinely humous medium, might have managed would certainly help me in future.

However, I left perplexed. The Auerbachs, failing to clear for me into the intensity of vision of his portraits, remained as dark, featureless and obscure as the substances they imitated. This was worrying. If my eyes were unable to draw even from these the fauna that were supposed already to have been labelled and logged, how much less so would they do so from the original element, the outside city itself. After a visit to an interesting adjunct they had on about the representation of the ruined city in art, including Piranesi Inventione, I left, I admit, slightly disappointed. Perhaps the Tate would redeem my intention of learning genuinely to uncover, see into the world I believe the previous posts have proved at least to exist.

It was an odd day, light wise, as many have been recently, clouds coming in and draining out all warmth, then parting and leaving a polished gleam, sinking in, clearing. Sometimes I blamed my lack of vision on their presence, or, in their absence, on their absence. Everywhere I could sense the element that this blog attempts to plot, repeatedly, sensing it near, I'd stick out the machine, click, bring up more waste.

Only the Tate would bring refuge, I hoped, its disused chimney a distant beacon.

On the far side of Blackfriars Bridge there was a sign. The footpath to the gallery was closed, the railway bridge was in need of repair, the station was to be expanded from its present building, among the plainest of all London's termini, to something straddling the river, which seemed a pretty impressive feat of industrialism. Impressive feat of industrialism. I was standing, of course, not only on another, but one which was itself the site of a previous other, the present one, designed by Brunel, whose statue I'd passed with hardly a thought on the way (designer of the first Thames tunnel, of course, a link to that at Greenwich), replacing it. Beneath this, I recalled, was a representation of a representation of it by a man who'd never seen it, but who was sufficiently surprised by what he'd heard about it to have copied up still other representations into an impressive print.

In fact, not only had Piranesi never seen Blackfriars Bridge, he'd never been to London. And yet he'd effected - almost indirectly built - the city's architecture more than many who had. The three strands that have fascinated the Brits have been his representations or vedutas, vedute if you prefer, particularly of ruins, where his dramatic sense of contrast and perspective appealed, perhaps via half-sensed ambivalences about imperialism, in the sublime, his imagined documentary realities, enjoyed for their whimsical eccentricity as Capricios, and, most of all, his darkest conceptions, impossible and cavernous penitentiary interiors, the Carceri di Inventione.

There's no space here to go into this, but I've decided to give it a label, surely come back to the places he's influenced, not least since one has already featured here - an acquaintance of George Dance, (the erstwhile) Newgate Prison shows his influence sufficiently for it to remain evident in Islington's (ex-)electricity substation based on it. I've recently come upon an interesting site for this sort of thing, in fact, that I'll doubtless come back to. But not only Dance did he know, but Chambers, too, of course, his fantasy evident no less in the prison than in the latter's Sommerset House. And not only architects had he influenced, of course, but painters, not least David Hepher, whose visionary series based upon them has proved more than anything else to what extent he's embedded himself in the fabric of the city, in that abstract concrete, imagination. That a great contemporary British composer should have rendered the experience into music is perhaps further testimony.

Something certainly was in the making in the way of what I'd set out to look out for. There had been yet another bridge here. Even the relevant Pevsner, a series usually more marked by sober accuracy than intensity of vision, recognises in its remains the piers 'One of the strangest sights in London, marching across the river, carrying nothing nowhere.'

The Tate would have to wait, the collection I sought there permanent. Here, the building work on the bridge would in not long be over, whatever it revealed folded back into the fabric of the city and its impenetrable air.