The Vivero Letter

I took the mirror from Halstead and laid it flat on the table. This is how it works. Forget the gold trimmings and concentrate on the mirror itself. All early Chinese mirrors - were of metal, usually cast of bronze. Cast metal doesn't give a good reflective surface so it had to be worked on with scrapers to give a smooth finish. Generally, the scraping was done from the centre to the edge and that gave the finished mirror its slight convexity.'

Fallon took a pen from his pocket and applied it to the mirror, imitating the action of scraping. He nodded and said briefly, 'Go on.'

I said, 'After a while the mirrors began to become more elaborate. They were expensive to make and the manufacturers began to pretty them up a bit. One way of doing this was to put ornamentation on the back of the mirror. Usually it was a saying of Buddha cast in raised characters. Now, consider what might happen when such a mirror was scraped. It would be lying on its back on a solid surface, but only the raised characters would be in contact with that surface -- the rest of the mirror would be supported by nothing. When scraper pressure was applied the unsupported parts would give a little and a fraction more metal would be removed over the supported parts.'

'Well, I'll be damned!' said Fallon. 'And that makes the difference?'

'In general you have a convex mirror which tends to diffuse reflected light,' I said. 'But you have plane bits where the characters are which reflects light in parallel lines. The convexity is so small that the difference can't be seen by the eye, but the short wavelengths of light show it up in the reflection.'

'When did the Chinese find out about this?' queried Fallon.

'Some time in the eleventh century. It was accidental at first, but later they began to exploit it deliberately. Then they came up with the composite mirror -- the back would still have a saying of Buddha, but the mirror would reflect something completely different. There's one in the Ashmolean in Oxford -- the back says "Adoration for Amida Buddha" and the reflection shows Buddha himself. It was just a matter of putting a false back on the mirror, as Vivero has done here.' Halstead turned over the mirror and tapped the gold back experimentally. 'So under here there's a map cast in the bronze?'

'That's it. I rather think Vivero re-invented the composite mirror. There are only three examples known; the one in the Ashmolean, another in the British Museum, and one somewhere in Germany.'

'How do we get the back off?'

'Hold on,' I said. 'I'm not having that mirror ruined. If you rub a mercury amalgam into the mirror surface it improves the reflection a hundred per cent. But a better way would be to X-ray them.'

'I'll arrange it,' said Fallon decisively. 'In the meantime we'll have another look. Switch on that projector.' I snapped on the light and we studied the vague luminous lines on the screen. After a while Fallon said, 'It sure looks like the coast of Quintana Roo. We can check it against a map.'

'Aren't those words around the edge?' asked Katherine Halstead.

I strained my eyes but it was a bit of a blurred mish-mash nothing was clear. 'Might be,' I said doubtfully.

'And there's that circle in me middle,' said Paul Halstead 'What's that?'

'I think I've solved that one,' I said. 'Old Vivero wanted to reconcile his sons, so he gave them each a mirror. The puzzle can only be solved by using both mirrors. This one gives a general view, locating me area, and I'll lay ten to one that the other mirror gives a blown-up view of what's in that little circle Each mirror would be pretty useless on its own.'

'We'll check on that,' said Fallon. 'Where's my mirror?'

The two mirrors were exchanged and we looked at the new pattern. It didn't mean much to me, nor to anyone else. 'It's not clear enough,' complained Fallon. 'I'll go blind if we have much more of this.'

'It's been knocked about after four hundred years,' I said 'But the pattern on the back has been protected. I think that X-rays should give us an excellent picture.'

'I'll have it done as soon as possible.'

I turned off the light and found Fallon dabbing at his eyes with a handkerchief. He smiled at me. 'You're paying your way, Wheale,' he said. 'We might not have found this.'

'You would have found it,' I said positively. 'As soon as your cryptographer had given up in disgust you'd have started to wonder about this and that -- such as what was concealed in the bronze-gold interface. What puzzles me is why Vivero's sons didn't do anything about it.'

Halstead said thoughtfully, 'Both branches of the family regarded these things as trays and not mirrors. Perhaps Vivero's rather obscure tip-off just went over their heads. They may have been told the story of the Chinese mirrors as children, when they were too young to really understand.'