06:40:22

"Good Sir André, I pray you come this way," Guy de Malegant said with a gracious bow and a wave of his hand.

Marek tried to conceal his astonishment. When he had galloped into La Roque, he fully expected that Guy and his men would kill him at once. Instead, they were treating him deferentially, almost as an honored guest. He was now deep in the castle, in the innermost court, where he saw the great hall, already lit inside.

Malegant led him past the great hall and into a peculiar stone structure to the right. This building had windows fitted not only with wooden shutters but with windowpanes made of translucent pig bladders. There were candles in the windows, but they were outside the pig bladders, instead of inside the room itself.

He knew why even before he stepped into the building, which consisted of a single large room. Against the walls, gray fist-size cloth sacks stood heaped high on raised wooden platforms above the floor. In one corner, iron shot was piled in dark pyramids. The room had a distinctive smell - a sharp, dry odor - and Marek knew exactly where he was.

The arsenal.

Malegant said, "Well, Magister, we found one assistant to help you."

"I thank you for that." In the center of the room, Professor Edward Johnston sat cross-legged on the floor. Two stone basins containing mixtures of powder were set to one side. He held a third basin between his knees, and with a stone mortar, he was grinding a gray powder with a steady, circular motion. Johnston did not stop when he saw Marek. He did not register surprise at all.

"Hello, André," he said.

"Hello, Professor."

Still grinding: "You all right?"

"Yes, I'm okay. Hurt my leg a little." In fact, Marek's leg was throbbing, but the wound was clean; the river had washed it thoroughly, and he expected it to heal in a few days.

The Professor continued to grind, patiently, ceaselessly. "That's good, André," he said in the same calm voice. "Where are the others?"

"I don't know about Chris," Marek said. He was thinking of how Chris had been covered with blood. "But Kate is okay, and she is going to find the-"

"That's fine," the Professor said quietly, his eyes flicking up to Sir Guy. Changing the subject, he nodded to the bowl. "You know what I'm doing, of course?"

"Incorporating," Marek said. "Is the stuff any good?"

"It's not bad, all things considered. It's willow charcoal, which is ideal. The sulfur's fairly pure, and the nitrate's organic."

"Guano?"

"That's right."

"So, it's about what you'd expect," Marek said. One of the first things Marek had studied was the technology of gunpowder, a substance that first became widely employed in Europe in the fourteenth century. Gunpowder was one of those inventions, like the mill wheel or the automobile, that could not be identified with any particular person or place. The original recipe - one part charcoal, one part sulfur, six parts saltpeter - had come from China. But the details of how it had arrived in Europe were in dispute, as were the earliest uses of gunpowder, when it was employed less as an explosive than as an incendiary. Gunpowder was originally used in weapons when firearms meant "arms that make use of fire," and not the modern meaning of explosive projectile devices such as rifles and cannon.

This was because the earliest gunpowders were not very explosive, because the chemistry of the powder was not understood, and because the art hadn't been developed yet. Gunpowder exploded when charcoal and sulfur burned extremely rapidly, the combustion enabled by a rich source of oxygen - namely nitrate salts, later called saltpeter. The most common source of nitrates was bat droppings from caves. In the early years, this guano was not refined at all, simply added to the mixture.

But the great discovery of the fourteenth century was that gunpowder exploded better when it was ground extremely fine. This process was called "incorporation," and if properly done, it yielded gunpowder with the consistency of talcum powder. What happened during the endless hours of grinding was that small particles of saltpeter and sulfur were forced into microscopic pores in the charcoal. That was why certain woods, like willow, were preferred; their charcoal was more porous.

Marek said, "I don't see a sieve. Are you going to corn it?"

"No." Johnston smiled. "Corning's not discovered yet, remember?"

Corning was the process of adding water to the gunpowder mixture, making a paste that was then dried. Corned powder was much more powerful than dry-mixed powder. Chemically, what happened was that the water partially dissolved the saltpeter, allowing it to coat the inside of the charcoal micropores, and in the process, it carried the insoluble sulfur particles inside, too. The resulting powder was not only more powerful but also more stable and long-lasting. But Johnston was right; corning was only discovered around 1400 - roughly forty years from now.

"Should I take over?" Marek said. Incorporating was a lengthy process; sometimes the grinding went on for six or eight hours.

"No. I'm finished now." The Professor got to his feet, then said to Sir Guy, "Tell my Lord Oliver that we are ready for his demonstration."

"Of Greek Fire?"

"Not precisely," Johnston said.

In the late afternoon sun, Lord Oliver paced impatiently along the massive wall of the outer perimeter. The battlement was more than fifteen feet wide here, dwarfing the row of cannon nearby. Sir Guy was with him, as well as a sullen Robert de Kere; they all looked up expectantly when they saw the Professor. "Well? Are you at last prepared, Magister?"

"My Lord, I am," the Professor said, walking with two of his bowls, one under each arm. Marek carried a third bowl, in which the fine gray powder had been mixed with a thick oil that smelled strongly of resin. Johnston had told him not to touch this mixture on any account, and he needed no reminding. It was a disagreeable, reeking goo. He also carried a bowl of sand.

"Greek Fire? Is it Greek Fire?"

"No, my Lord. Better. The fire of Athenaios of Naukratis, which is called `automatic fire.' "

"Is that so?" Lord Oliver said. His eyes narrowed. "Show me."

Beyond the cannon was the broad eastern plain, where the trebuchets were being assembled in a line. They were just out of shot range, two hundred yards away. Johnston set his bowls on the ground between the first two cannon. The first cannon he loaded with a sack from the armory. He then placed a thick metal arrow with metal vanes into the cannon. "This is your powder, and your arrow."

Turning to the second cannon, he carefully poured his finely ground gunpowder into a sack, which he stuffed into the cannon mouth. Then he said, "André, the sand, please." Marek came forward and set the basin of sand at the Professor's feet.

"What is that sand for?" Oliver asked.

"A precaution, my Lord, against error." Johnston picked up a second metal arrow, handling it gingerly, holding it only at each end and gently inserting it into the cannon. The tip of the arrow was grooved, the grooves filled with thick brown acrid paste.

"This is my powder, and my arrow."

The gunner handed the Professor a thin stick of wood, glowing red at one end. Johnston touched the first cannon.

There was a modest explosion: a puff of black smoke, and the arrow flew onto the field, landing a hundred yards short of the nearest trebuchet.

"Now my powder, and my arrow."

The Professor touched the second cannon.

There was a loud explosion and a blast of dense smoke. The arrow landed alongside a trebuchet, missing it by ten feet. It lay in the grass.

Oliver snorted. "Is that all? You will forgive me if I have-"

Just then, the arrow burst into a circle of fire, spitting blobs of flame in all directions. The trebuchet immediately caught fire, and men on the field ran forward, carrying the horses' water bags to put it out.