After a night's thoughtful deliberation, the mechanism Lori came up with for the carpenters to make was a box. The shape had to be simple so it could be efficiently made from planks with a minimum of wood. While they could theoretically leave her Dungeon now to fell trees for wood again, in practice the snow made that difficult. Best to work within the resources they had stockpiled that required a minimum of processing. Technically she could have designed something that could be made with the metal from their dragon scales, or even just their copper, but that wasn't as easily replaced as wood.

The box was an elongated cubic tube, with accelerated air meant to pass though one end and out the other. On one of the faces was a hinged flap that could drop down and block the tube at an angle, diverting the accelerated air out through the new opening that had just been uncovered. A lever mechanism would keep the flap pushed up and shut, as well as give the operator the leverage to overcome the force of the accelerated air to push the flap back up once it had dropped.

"I don't see a locking mechanism," Rian said as he perused her diagram. "How to we keep the flap from falling down?"

"The intention is that someone is holding the lever to keep the flap closed at all times," Lori said. "Otherwise the flap will drop down and the accelerated air will divert upwards, removing the sled's source of thrust and causing it to slow. This way, if there is no one on the sled to apply force to the lever, it will just stop."

"Ooh, clever!" Rian said. "I wish I'd thought of that! This is so simple! And here I was trying to think of how we'd put together sliding wooden blocks."

"Far too heavy and big," Lori said dismissively. "A simple design is a lighter design, and is more likely to be something an air jet can actually push to any appreciable speed. Give this to the smiths and carpenters and tell them to start planning on how to build it but not to begin construction yet."

"Eh? Why not?"

"We need to find out how much thrust is needed to move the sled," Lori said. "That will depend on how much air is being accelerated, and that will depend on how wide the tube anchoring the bindings accelerating them will be."

"Not necessarily," Rian said. "If you put something like a funnel at the end of the tube, you can collect more air, especially if the tube is already moving forward and meeting the oncoming air head-on."

Lori tilted her head thoughtfully. "Hmm… an interesting idea… yes, I can see how it could work."

"Might work for the water jet too," Rian said. "Something to consider in future."

Lori waved her hand, wiping the thought away. "Well, remember to bring it up when we're talking about water jets. We're discussing air jets at the moment."

"Right, sorry. So… does that mean you're going to try to ride the sled? It's really fun!"

"No, Landoor is going to ride the sled. I will be building the tube that will be mounted to the sled and the binding to accelerate it."

Rian blinked. "Why Landoor?"

"I don't care if anything happens to him in the course of testing the air jet."

"Wow. What a terribly harsh and very Lori thing to say. You know nobody actually needs to be riding it, right? It doesn't have a steering mechanism, it'll just go straight. We can just put snow or rocks on it to simulate the weight of a person."

"Ah. Then do that instead."

"… You know, Landoor is a very nice person once you get to know him."

"That sounds like a 'dealing with people' matter. I leave that nonsense to you."

Rian rolled his eyes. "Fine, fine, I'll drop it. Though try not to get the man killed, all right? He's a hard worker and has a naturally cheerful and pleasant disposition. Infinitely preferable to the inverse of either, don't you think?"

Lori waved a hand dismissively. "Eh, I suppose," she said.

Rian suddenly frowned. "Huh. Something just occurred to me. The mechanism will only redirect the air and stop the acceleration, right? It won't actually slow the sled down?"

"Yes…?"

"So… how do we actually slow it down if we want to stop?"

Lori gave him a bland look, and pointed significantly to one side. "I suggest consulting an expert."

Rian brightened. "Oh, right! Silly me." He turned to Riz, sitting next to him. "Hey Riz, how do you know how to get a moving sled to slow down?"

––––––––––––––––––

For building the sled's air jet, she needed building material, and her options were very limited. Wood was in limited supply and would need the carpenters to shape. Stone was too heavy and while ice was plentiful, it was still weighty and unless reinforced would be easily damaged. While she knew that with reinforcement it would be adequate to the task, as the Coldhold had proven, reinforcing it would add more weight.

So, bone it was. Lori had already tunneled and excavated the snow from the bone pit before today, since she had needed it for material for making the original air jets. Getting the material was merely a matter of going there and picking it out, and months of eating seels and beasts had given them a healthy supply. Some of the bone was, according to Rian, ground down and used as fertilizer for the fields, but she still had her pick.

Few of the bones were still whole. Some had been broken open to access the marrow, which was added to their stew. Others had come apart, and a few looked like they had been gnawed on by chokers. Still, some where set aside because they made for good material for her, such as skulls and jaws. Lori had long since stopped collecting all the teeth and claws, since she had a healthy stockpile, but that just meant other people got them to make buttons, small blades, arrowheads…

And just because the bones were broken didn't mean they weren't useful. After all, she could just make them whole again. It increased the overall weight, since some of the porousness was lost, but the material was still decently strong.

To shape it into a tube, however, she had to do so in several steps. First she got a plank from the carpenters that seemed the right dimensions for what she wanted. Then she went outside and gathered snow to create a block of ice, which she bound solid. The smithy was empty, so she took the block there and pressed her plank down into the ice, deforming it through the binding of waterwisps as she went. When she managed to pry out the plank, on the ice was left a plank-shaped mold.

After that, it was a simple matter of putting bones into the shape, then carefully filling in the gaps using bone made fluid by a binding of earthwisps to fill the mold. This allowed her to retain some of the porousness of the bone, allowing it to be both relatively strong and lightweight, until she had several planks of bone to use. They weren't completely uniform, but that was fine.

The material preparation took her most of the morning, and she had no intention of not expanding her demesne, so actually putting the tubes together had to wait until the following day. Putting the bone planks together was a simple matter, since they were all made of the same substance. Lori had considered making them in the shape of square tubes, after her design, but decided against it, opting for a triangular tube shape instead. It would make fitting in the mechanism a bit more difficult, but having it be a triangle made the structure more resistant to deformation. Given the planks were all as wide as her hand was long, there would be plenty of space in the tube for air. She made two, both a pace and a half long.

Once that was finished, the two tubes for the air jet needed to be secured to Lori's Boat. They needed to be mounted on the arms that usually connected to the boat's outriggers, where she used more softened bone to bond it to the wooden spars.

"Don't step on it or lift with it," Lori told Rian sternly as he directed the men who would be carrying the boat back out into the snow for her to test whether it could even be propelled by air. She stood on a plank that had been placed in the snow, mostly to keep herself from sinking in, because she wasn't sure her boots weren't leaking and she didn't want to have wet socks. "It's not made to be load bearing like that."

"Will it be able to provide thrust without breaking, then?" Rian asked as the boat was gently set down on the snow and slid back and forth a few time to make sure it would move.

"We shall see," Lori said. She stayed where she was as she bound airwisps, anchoring them to the earthwisps on the bone. That would transfer the force of the thrust to the bone tubes, and from there to the boat-turned-sled.

"Should we weigh it down?" Rian said as a rope was tied to one of the arms, with several men holding the other end, standing to one side. It would be their job to slow the sled down if it moved.

Lori shook her. "Not yet. We're still trying to find out how much force is needed to move the boat. We'll start with that as a minimum, and work upwards from there."

"Huh. Given the utter lack of testing the water jet underwent, I was afraid you'd just slap these things one the boat and then tell me to get going and figure it out as I went."

"I'd made a water jet before when I was a student," Lori shrugged. "I knew it would work."

"But not an air jet, presumably." Rian said.

"Not for the purposes of propelling something, in any case," Lori said. "It's known but considered impractically dangerous. To have enough expanding air for decent thrust, one usually needs to rely on some sort of alchemical combustible or steam, which leave residue that is burning hot, cloying, harmful, and the combustible itself is usually costly to make."

"Unless you happen to have the raw power of a bored Dungeon Binder, presumably," Rian said.

"Unless that," Lori agreed.

"You're really bored with nothing to really do, aren't you?"

Lori ignored him and his stupid smile as she began to properly assemble the binding, giving it directionality to propel the air down the tube. She made sure that both bindings were formed the same way so that they would have the same output. It wouldn't do for one side to have greater output than the other and make it list to one side, after all. Then she simply had to heavily imbue both sides.

Once both sides were imbued, she activated both bindings simultaneously.

Snow was blasted into the air behind the sled as the tubes suddenly began to thrust air through them. It was surprisingly loud, something that Lori should have expected from the smaller air jet tubes they used for snow clearing, but hadn't really been prepared for. The tubes shook in their mountings as the bindings began to consume their imbuement.

The sled, annoyingly, didn't move.

Lori frowned. "Annoying, but not unexpected," she said, mostly to herself. She got ready to increase the air jets' output.

"Wait a moment," Rian said thoughtfully.

Lori glanced at him as more snow was blown. Her lord had a thoughtful look on his face. "What?" she said.

"Let me try something first," he said.

She watched, curious and bemused as Rian moved behind the sled, raising one hand over his face to, probably futilely, keep the snow out of his face until he was standing directly behind the sled. Then he put two hands on the back of the sled and pushed. One step, two steps, and suddenly the sled was moving on its own, leaving Rian behind. It was moving barely faster than walking pace, but it was moving.

Rian was nodding in satisfaction as he walked back towards her, his nose not so much running as streaming and—ugh, yes, RIAN, STOP USING THE TOWEL OVER YOUR MOUTH TO WIPE YOUR NOSE, IT'S DISGUSTING! "Friction," he said in a self-satisfied tone. "We had to overcome the friction of the snow first before it would start moving. The snow's not wet, so the friction isn't reduced yet."

"So I see," Lori said, watching the sled slowly progressing away from them. Obvious, in hindsight. "Still, it would still need to be faster than this. This is without people weighing it down. As it is, when it is occupied it will move even slower."

"Can you get it going that fast?"

"Oh, undoubtedly," Lori said. "The question is whether a reasonable speed will be achieved with a reasonable amount of imbuement consumption. Air is a far less efficient propellant than water because of its lack of density…"

Lori paused, then looked down.

When she looked up again, she saw Rian had also been staring down at the snow.

Their eyes met.

"Water is denser than air," he said, a slow smile growing on his mouth. It was a new smile, one of mounting delight and realization.

"It does not even need to be water," she said. "Snow in any state is far denser than air."

"We'll have to mount the tubes lower down so that they're closer to the snow," Rian mused. "And need some sort of scoop to scrape up the snow… "

"That would add needless friction," Lori said, her tone also musing. "Besides, if there was a receptacle, that could just be filled up with snow and the receptacle opened to drop snow down into the binding…"

"Snow to water to steam… that would result in air far denser than just sucking it up…"

"Only one end would need to be opened, and since it's reliant on water, the air jet can technically be deactivated by cutting off the flow… and if I use vaporous waterwisps instead of airwisps, the binding wouldn't activate completely to common air, simplifying the control mechanism…"

The two of them stared at the sled, which was being pulled to a stop by its rope. Lori absently deactivate the bindings.

"I need to design a different mechanism and tube structure," she muttered. "And a new means of mounting it to the boat."

"I'll see if I can find something lightweight for the snow receptacle," Rian said. "Maybe some kind of sack, that will be lighter than a wooden box or anything like that."

Lori nodded absently, and they both looked towards the boat.

"We should probably figure out how to steer," Rian added. "Otherwise our magic-powered sled is going to be steered by someone in front with a stick pushing it left and right. Which is probably stupidly dangerous."

Yes, a method of steering would be needed…

…

But after this afternoon's demesne expansion!