Mannard bristled at him.
“I’ve been trying to reach you to tell you about an attempt on my life today! At Police Headquarters they said they’d try to find you. They implied that all my affairs were in your lap!”
Ghalil glanced at Coghlan.
“Your affairs have at least been on my mind,” he admitted. “Did not Mr. Coghlan explain the measures I took?”
“No,” said Coghlan dryly. “I didn’t. I’m going to work on this refrigeration affair. You tell it.”
He went over to the incredible patch of moisture on the wall. Laurie went with him. Behind them, Ghalil’s voice droned as Coghlan opened the suitcase of apparatus, began to fit together the induction balance. Suddenly Mannard said explosively:
“What? You shot the cup out of my hand?”
Laurie reared up in amazement.
“Go listen,” commanded Coghlan. “I’m going to work here.”
Laurie went away.
Coghlan got busy with the induction balance. There was, he soon discovered, no metal behind the wet spot on the wall. Nor above it. Nor below or on either side. There were no wires running to the place that had stayed cold “since always.” There was no metal of any sort in the wall. Coghlan sweated a little. There could not be a refrigeration apparatus without metal.
He put the induction balance away. He stuck a thermometer into the hole he’d made earlier. He moved it carefully back and forth, watching the mercury shrink. He swallowed when he saw its final reading. He hooked up the thermocouple—infinitely thin wires, of different metals, joined at their tips. He hooked on the microvoltometer. He soon found a particular spot. It was a very particular spot indeed. The tips of the wires had to be at an exact depth inside the hole. A hundredth of an inch off made the microvoltometer sway wildly. He changed a connection to get a grosser reading—millivolts instead of microvolts—and found that exact depth in the hole again. He went pale.
Laurie said:
“Tommy, I’m back.”
He turned and said blankly, “A hundred and ninety millivolts! And it’s below the temperature of dry ice!”
Laurie said wistfully, “I can’t even raise the temperature of that, can I, Tommy?”
He didn’t notice. He put down the thermocouple and brought out the alnico magnet. He wrestled the keeper off its poles.
“This doesn’t make sense,” he said absorbedly, “but if it is a field of force . . .“
He turned again to the wall and the hole he’d made in it. He put the heavy, intensely strong magnet near the opening.
The opening clouded. It acquired a silvery sheen which had the look of metal as the magnet neared it. Coghlan pulled the magnet away. The look of metal vanished. He put the magnet back, and the silvery appearance was there again.
He was staring at it, speechless, when Mannard came over with Ghalil and Duval. Mannard carried the thick, ancient volume with the battered ivory medallions in its cover—and Coghlan’s seven-hundred-year-old fingerprints on its first page.
“Tommy,” said Mannard uncomfortably, “I don’t believe this! But put one of your fingerprints alongside one of these, dammit!”
Ghalil matter-of-factly struck a match and began to make a deposit of soot on the scraping-tool which he’d used to pull down plaster. Coghlan ignored them, staring at the hole in the plaster.
“What’s the matter with him?” demanded Mannard.
“Science,” said Laurie, “has reared its ugly head. He’s thinking.”
Coghlan turned away, lost in concentrated thought. Ghalil said mildly:
“A finger, please.” He took Coghlan’s hand. He paused, and then deliberately took the bandage off the thumb. He pressed the thumb against the sooted scraper. Mannard, curious and uneasy, held up the book. Ghalil pressed the thumb down.
It hurt. Coghlan said: “Wait a minute! What’s this?” as if startled awake.
Ghalil took the book to a window. He looked. Mannard crowded close. In silence, Ghalil passed over his pocket magnifying-glass. Mannard looked, exhaustively.
“That’s hard to explain,” he said heavily. “The scar and all...”
Coghlan said:
“All of you, look at this!”
He moved the alnico magnet to and fro. The silvery film appeared and disappeared. Ghalil looked at it, and at Coghlan’s face.
“That silvery appearance,” said Coghlan painfully, “will appear under the plaster wherever it’s cold. I doubt that this magnet alone will silver the whole space at once, though—and it’s twenty times as strong as a steel magnet, at that. Apparently a really powerful magnetic field is needed to show this up.”
The silvery film vanished again when he pulled back the magnet.
“Now,” said Ghalil mildly, “just what would that be? A—what you would call a gadget?”
Coghlan swallowed.
“No,” he said helplessly. “There’s a gadget, all right, but it must be back in the thirteenth century. This is—well—I guess you’d call this the gadget’s ghost.”
VI
It grew dark in the room, and Coghlan finished clearing away the plaster from the wet spot by the light of police flashlights. As he removed the last layer of plaster, frost appeared. As it was exposed to view it melted, reluctantly. Then the wall was simply wet over colorings almost completely obliterated by the centuries of damp. At the edges of the square space, the wetness vanished. Coghlan dug under its edge. Plaster only. But there were designs when he cleared plaster away back from the edge. The wall had been elaborately painted, innumerable years ago.
Duval looked like a man alternately rapt in enthusiasm at the discovery of artwork which must extend under all the later plaster of this room, and hysterical as he contemplated the absolute illogic of the disclosure.
Mannard sat on a camp-chair and watched. The flashlight beams made an extraordinary picture. One played upon Coghlan as he worked. Laurie held it for him, and he worked with great care.
“I take it,” said Mannard after a long silence, and still skeptically, “that you’re saying that this is a sort of ghost of a gadget that was made in the thirteenth century.”
“When,” said Ghalil, from a dark corner, “there were no gadgets.”
“No science,” corrected Coghlan, busy at the wall. “They achieved some results by accident. Then they repeated all the things that had preceded the unexpected result, and never knew or cared which particular one produced the result they wanted. Tempering swords, for example.”
Duval interposed: “The Byzantine Empire imported its finer swords.”
“Yes,” agreed Coghlan. “Religion wouldn’t let them use the best process for tempering steel.”
“Religion?” protested Mannard. “What did that have to do with tempering swords?”
“Magic,” said Coghlan. “The best temper was achieved by heating a sword white-hot and plunging it into the body of a slave or a prisoner of war. It was probably discovered when somebody wanted to take a particularly fancy revenge. But it worked.”
“Nonsense!” snapped Mannard.
“Some few cutlers use essentially the same process now,” said Coghlan, absorbed in removing a last bit of plaster. “It’s a combination of salt and nitrogenous quenching. Human blood is salt. Steel tempers better in salt water than in fresh. The ancients found that human blood gave a good temper. They didn’t think scientifically and try salt water. And the steel gets a better surface-hardening still, if it’s quenched in the presence of nitrogenous matter—like human flesh. Cutlers who use the process now soak scrap leather in salt water and plunge a white-hot blade in that. Technically, it’s the same thing as stabbing a slave—and cheaper. But the ancients didn’t think through to scrap leather and salt water. They stuck to good old-fashioned magic tempering—which worked.”