"Someone couldn't have forged it?"
"No. Forgery, you have pen lifts and other signs. This writing is his."
Kate said, "Would he play a joke on us?"
"If he did, it isn't funny."
"What about this parchment it's written on?" Marek said. "Is it as old as the other sheets in the stack?"
"Yes," David Stern said, coming over. "Short of carbon dating, I'd say yes - it's the same age as the others."
Marek thought: How can that be? He said, "Are you sure? This parchment looks different. The surface looks rougher to me."
"It is rougher," Stern said. "Because it's been poorly scraped. Parchment was valuable material in medieval times. Generally it was used, scraped clean, and then used again. But if we look at this parchment under ultra-violet. . . . Would somebody get the lights?" Kate turned them off, and in the darkness Stern swung a purple lamp over the table.
Marek immediately saw more writing, faint but clearly there on the parchment.
"This was originally a bill for lodging," Elsie said. "It's been scraped clean, quickly and crudely, as if somebody was in a hurry."
Chris said, "Are you saying the Professor scraped it?"
"I have no idea who scraped it. But it's not expertly done."
"All right," Marek said. "There's one definitive way to decide this, once and for all." He turned to Stern. "What about the ink, David? Is it genuine?"
Stern hesitated. "I'm not sure."
"Not sure? Why not?"
"Chemically speaking," Stern said, "it's exactly what you'd expect: iron in the form of ferrous oxide, mixed with gall as an organic binder. Some added carbon for blackness, and five percent sucrose. In those days, they used sugar to give the inks a shiny surface. So it's ordinary iron-gall ink, correct for the period. But that in itself doesn't mean much."
"Right." Stern was saying it could be faked.
"So I ran gall and iron titers," Stern said, "which I usually do in questionable cases. They tell us the exact amounts present in the ink. The titers indicate that this particular ink is similar but not identical to the ink on the other documents."
"Similar but not identical," Marek said. "How similar?"
"As you know, medieval inks were mixed by hand before use, because they didn't keep. Gall is organic - it's the ground-up nuts of an oak tree - which means the inks would eventually go bad. Sometimes they added wine to the ink as a preservative. Anyway, there's usually a fairly large variation in gall and iron content from one document to another. You find as much as twenty or thirty percent difference between documents. It's reliable enough that we can use these percentages to tell if two documents were written on the same day, from the same ink supply. This particular ink is about twenty-nine percent different from the documents on either side of it."
"Meaningless," Marek said. "Those numbers don't confirm either authenticity or forgery. Did you do a spectrographic analysis?"
"Yes. Just finished it. Here's the spectra for three documents, with the Professor's in the middle." Three lines, a series of spikes and dips. "Again, similar but not identical."
"Not that similar," Marek said, looking at the pattern of spikes. "Because along with the percentage difference in iron content, you've got lots of trace elements in the Professor's ink, including - what's this spike, for instance?"
"Chromium."
Marek sighed. "Which means it's modern."
"Not necessarily, no."
"There's no chromium in the inks before and after."
"That's true. But chromium is found in manuscript inks. Fairly commonly."
"Is there chromium in this valley?"
"No," Stern said, "but chromium was imported all over Europe, because it was used for fabric dyes as well as inks."
"But what about all these other contaminants?" Marek said, pointing to the other spikes. He shook his head. "I'm sorry. I'm just not buying this."
Stern said, "I agree. This has to be a joke."
"But we're not going to know for sure without a carbon date," Marek said. Carbon-14 would enable them to date both ink and parchment within about fifty years. That would be good enough to settle the question of forgery.
"I'd also like to do thermoluminescence, and maybe a laser activation while we're at it," Stern said.
"You can't do that here."
"No, I'll take it over to Les Eyzies." Les Eyzies, the town in the next valley that was the center of prehistoric studies in southern France, had a well-equipped lab that did carbon-14 and potassium-argon dating, as well as neutron activation and other difficult tests. The field results weren't as accurate as the labs in Paris or Toulouse, but scientists could get an answer in a few hours.
"Any chance you can run it tonight?" Marek said.
"I'll try."
Chris came back to join the group; he had been telephoning the Professor on a cell phone. "Nothing," he said. "I just got his voicemail."
"All right," Marek said. "There's nothing more we can do right now. I assume this message is a bizarre joke. I can't imagine who played it on us - but somebody did. Tomorrow we'll run carbon and date the message. I have no doubt it will prove to be recent. And with all due respect to Elsie, it's probably a forgery."
Elsie started to sputter.
"But in any case," Marek continued, "the Professor is due to call in tomorrow, and we'll ask him. In the meantime, I suggest we all go to bed and get a good night's rest."