The next day, he got two letters. The general store clerk said, "You're becoming popular!"

"I can hardly wait to start getting ten letters a week offering financial scams and slight discounts on groceries."

He read the two battered, slightly water-stained messages there in the shop because the weather was starting to get chilly and the Centaur lady considered gossip part of her payment. Lacking envelopes, they'd been packaged with similar techniques to Selen's method: folding several times before sealing with wax. One of them added a string wrapped around the whole thing for a sort of tamper-evident cord. Vonn pried it open and his ears perked up. "This is from the wizard Ralator in the east. We've been talking with him about magic theory and the dungeon problem."

The master spellcaster had proposed a date to meet just a few weeks from now, mentioning wanting to see "your sister and your owlish friend". He corrected a misconception Vonn had about Mana, and suggested a new practice exercise. Nothing about the dungeon, though. Odd.

The other letter had no sender name either, only "To Engineer Vonn of Shieldpoint". He began reading and said, "Firefern, from way south!"

"Who?"

"He makes machines, like me. You'll probably hear more about him. Already has a mechanical boat, I hear. Oh, and he's a Centaur."

"Is he single?"

"Ha. That I don't know."

In a rough hand it said, "Hello. So you're an inventor too? Nice to meet you. If you really did build a flying machine, I want to see it! Doesn't seem like the engine you described would really lift that much weight. But you obviously know what you're on about. Those 'valves' you mention are a good idea; my wife and kid worry we'll blow ourselves up. As for the steam engine, yes, I'm trying out a cart on land. Just not so big as the one you drew. What do you think of this idea?"

There followed a sketch of a modified version of Vonn's frostfire engine. At first it looked like the Centaur had misunderstood, but then Vonn grinned. Firefern didn't quite have the idea right, but he'd proposed a variant where lamp oil leaked into the cylinder and burned to create pressure inside it, pushing it outward. He had, in other words, one-upped Vonn's steam wagon concept and almost invented the internal combustion engine. Easier said than done, of course. But it was far better than lugging a giant kettle around, the external method.

"Well, he's probably going to be rich if he doesn't explode."

The letter said, "Keep in touch. Tell Miss Selen she's on the right path, trying to use math and alchemy to make these things work better. I'm at a point where banging parts together without a plan is more dangerous than productive. By the way, a friend of mine requests some space, so look for the other letter in this one."

Vonn blinked and flipped the paper over. Part of it had been written on in a tight, swooping style that had been hidden by the folding.

"Hello, Vonn. I help manage the finances of Firefern and others in Liiros. I'm Riz, Merchant 4 and Artist 3. I've only been using the System for three years; what about you? You sound accomplished. We heard about some dreadful dungeon near your town. And what's this about a flying machine? And an Aves friend with mystical visions of some sort? You either have a lot of silly rumors swirling around you, or quite a story to tell. You should visit if you can. Firefern is more enthusiastic than he might let on. He lets me turn a wrench once in a while so that I have some idea what he does."

The Artist had done a tiny sketch with a fine brush, showing a Vulin girl in profile with a feathered hat. If the faintly smiling fox with her eyes glancing off to one side was a self-portrait, Vonn had another reason to want to visit.

The shopkeeper loomed over his shoulder, leering. "That's one strange machine design."

Vonn folded the letter hastily. "Hey!"

#

He had never been farther south than the villages and docks on the south bank of the Little Star. Travel downstream on the Starry River would be pretty quick, but he had no swift route back. The good news was that a reply might get to that town quickly.

"What's wrong?" asked Tazo, back in the shop.

He looked up from pacing uselessly. "I heard back from Master Ralator and the steam inventor. The wizard wants to meet with you again." He handed over that letter.

Tazo read, looking vain. "Glad to have his attention! I have things to tell him. And what's that other one say?" She reached for it.

Vonn froze. "Um, that's basically a discussion of engine designs."

Birb had looked from another angle. "What's that picture?"

"Peeky bird! Look, they've got an Artist working with the guy. Here is his actual message." Vonn spread the letter out on a table and weighed down one edge with a homemade wrench.

Everyone came over to read it. Tazo looked at him strangely but said, "He's willing to share ideas. Looks like one of those fuel-burning engines you mentioned."

"Right. We'd benefit from working with his team. I want to send a more detailed letter discussing machine tools among other things; maybe he's got something we haven't thought of."

Ashfall said, "Aren't you worried about competition?"

"They're serving different customers, and our total impact will be greater if we cooperate." He pointed to the wizard's letter. "Same here."

#

After work, Vonn and company composed a reply to Firefern. They talked about their own shop's capabilities and more details on the frostfire engine. Vonn discussed the internal combustion concept in more detail, too. "Unlike my device, yours gets its energy from the power of the burning fuel. Potentially more powerful per weight. You could have one of these explosion cylinders, or one or more pairs of them in tandem." He sketched the zigzag shape of an automotive engine crank-shaft, held and turned by piston rods as though by hands grasping a bike's pedals. While he was at it he drew the "rack and pinion", a gear attached to the side of a long screw. It was a key part of a steering mechanism.

About the combustion engine itself he said, "I believe the efficiency will be related to the difference in temperature between the hot and cold parts of the engine's actions, and that we can start thinking of these machines in terms of charts showing a 'cycle' of repeated motions. The 'Firefern Cycle', maybe?" The Earth names for the concept honored inventors like Otto and Diesel.