Shef nodded again, reflecting on how the monks of Saint John or Saint Peter would have appreciated such an addition to their income. He saw the potential of the device. But he could not understand Udd’s interest: it was notorious that the little man cared for nothing but metal. Best not to rush him.
Silently Udd led his king out and down the slope to a second shed. “This is like rung two,” he said, with a glance at Shef’s ladder-emblem. “And this is down to us. See, ever since last year the priests here have been fascinated by what they heard of our catapults. Cwicca and his mates have already built a couple, to show ’em how we do it. But they’d already got the idea of the little wheels: the cog-wheels, you know. And the priest who was working with the mill, he got the idea of using real big cog-wheels not to wind a catapult but to make a different mill.”
The pair approached the second building. On one wall of it, another big wooden wheel with paddles, exactly like the first one: but set vertically in the snow-choked ravine, not horizontally. Clearly the water would turn this even better, with a better purchase. But what use would an axle be turning two vertical millstones? The corn would run straight through them and never be ground at all. It was the weight of the stone that did the grinding.
Still silently Udd led Shef in and pointed to the gearing. At the end of the millwheel-axle an immense iron cog-wheel stood vertical. Its teeth meshed into a matching horizontal cog, fitted over a stout oak axle. Below it, on the same axle, the two familiar stone wheels. Above them, a hopper showed where men could stand to pour in sacks of kernels.
“Yes, lord, it’s well-done. But what I wanted to say was there’s something to do with this that these folk haven’t thought of yet. See, lord,” Udd dropped his voice, though there was no-one near, no-one within a furlong of them. “What’s our problem with iron? With making it, like?”
“Beating it out,” said Shef.
“How many days does it take a man to get fifty pound of iron out of, say, five times that amount of ore?”
Shef whistled, remembering the hours he had spent pounding out the slag for his first home-made sword. “Ten,” he guessed. “Depends how strong the smith is.”
“That’s why smiths have to be strong,” agreed Udd, looking down at his own puny frame. “I couldn’t ever be one. But then I thought, if this mill does the work of forty grinding-slaves, women that is, could it not do the work of, say, twenty smiths?”
Shef began to feel a familiar warning itch in his brain. Many minds were working here, as they had worked to make the catapults, the pulley-wound crossbow. Some priest of the Way had thought of the water-mill. Some long-dead Roman had left behind the cog-wheels. Shef and his crewmen had rebuilt the catapults. And from hearing about that alone, some other priest had worked out how to transfer the force in the flow of a river to the task he needed in a different dimension. Now Udd had returned that thought to his own obsession. It was as if people too were cog-wheels, the one fitting into the other, one brain turning the next.
“How could stone wheels grind iron?” he asked cautiously.
“Well, lord, what came to me was this.” Udd dropped his voice even further. “What everyone’s always thought in this line is, a wheel drives a wheel. But I thought, what if it doesn’t? What if it drives something a different shape? And much, much bigger? See, axle turns here. Turns a shape like this. The shape turns, and all the time it’s turning, it’s lifting a heavy weight, as heavy as a millwheel. Only not a millwheel, a hammer. But when it gets to this point here—it stops lifting. The hammer drops instead. A really heavy hammer, a hammer six smiths couldn’t lift, not even if they were as strong as Brand! And hammering as fast as the axle on this millwheel turns. How long would it take to beat out fifty pounds of iron then? Five hundred pounds?”