Song Dynasty: Yuan Dynasty, you didn't expect this, did you? I'm still alive.

With the penguin's help, Zhao Chang finally survived.

Although I couldn't meet the legendary goddess like King Mu of Zhou, the trip was still worthwhile.

Zhao Chang was powerless against the cute black and white penguins, and since the penguins had saved his life, he instantly became a loyal follower of penguins.

The discovery of Antarctica represents the discovery of the last continent on Earth by the Song people.

The Age of Geographical Discovery has thus come to an end.

The world belongs to the pioneers, and it also belongs to the Song people.

. . .

While the Song people were preparing for war, Zhu Di did not slack off.

It took Shen Lian, a centurion of the Embroidered Uniform Guard, three months to use all the Embroidered Uniform Guard's secret agents along the Ming coast and to bribe hundreds of laborers and sailors working at the docks to piece together the second intelligence report.

That was an introductory book called "New Compilation of Natural History".

This includes a sketch of a steam engine.

With the help of this rough map, Shen Lian finally returned to the realm of a thousand households.

After all the twists and turns, he felt utterly bored.

He seemed to have done something, but also seemed not to have done anything.

Three months later, the Ordnance Bureau.

In front of Zheng Yong was the second-generation "steam engine" that had been replicated at great expense of manpower and resources.

It doesn't look as exquisite as the last one, but it is a steam engine that the Ming Dynasty developed "independently".

Zheng Yong personally lit the ignition material inside the furnace door.

Half an hour later, the water in the boiler began to boil.

Steam seeped from the pipe joints, hissing like a snake flicking its tongue. The flywheel trembled, then trembled again, and then began to turn slowly—not with the thunderous roar one might imagine, but with a listless, creaking turn, like an old ox pulling a cart stuck in the mud.

The flywheel spun three times and then stopped.

The water in the boiler was still boiling, and the steam was still hissing, but the flywheel remained completely still.

Zheng Yong's face turned pale.

"Increase the firepower."

Basket after basket of charcoal was added, the flames inside the furnace door turned from red to white, the outer wall of the boiler began to glow red, and the steam at the pipe joints changed from a hissing sound to a shrieking sound.

The flywheel shuddered again, then suddenly started spinning—this time much faster than before. The belts on the edge of the flywheel crackled under the centrifugal force, as if they were about to be flung off at any moment.

"It...it moved!" Zheng Yong's voice trembled.

He stared at the machine, his gaze moving from the flywheel to the cylinder, and from the cylinder to the pipes.

He saw a cloud of white steam continuously emanating from the connection between the cylinder and the pipe; it wasn't the hissing sound of seeping out, but a continuous, powerful jet.

The color drained completely from Zheng Yong's face.

It's leaking air.

As the foremost craftsman of the Ming Dynasty, he knew what this meant.

"That's impossible. The seal at the connection between the cylinder and the pipe... I used asbestos rope and lead powder, which should have been enough to seal it..."

The flywheel is still spinning, but its speed has begun to decrease.

From fast to slow, from slow to trembling, from trembling to stopping.

The whole process took less than the time it takes to drink half a cup of tea.

The drill ground was so quiet that you could hear the crackling of charcoal in the furnace.

Zheng Yong hurriedly walked to the machine, squatted down, and looked at the clump of asbestos rope at the connection between the cylinder and the pipe, which had been shredded by steam.

Zheng Yong personally led the craftsmen to dismantle the machine.

When the cylinder head was removed, a plume of white smoke billowed out, carrying a pungent, burnt smell. Zheng Yong leaned closer for a look.

The inner wall of the cylinder is not smooth.

Deep grooves stretched from top to bottom, like someone had scratched the muddy ground with an iron nail. The deepest one was almost deep enough to fit a chopstick.

He reached out and touched the inside of the cylinder. When his fingertips touched the deep marks, he recoiled as if he had been burned.

"It was...it was the piston that scraped it."

When the piston was pulled out of the cylinder, Zheng Yong saw the whole picture of the problem.

It was a cast iron cylinder, its surface also covered with scratches.

To make matters worse, the piston was supposed to have a series of grooves—Zheng Yong had seen on the drawings that the Song Dynasty's steam engine pistons had three grooves, with some kind of material embedded in them.

He couldn't tell what the material was, so he took it upon himself to stuff oil-soaked cotton rope into the groove.

The cotton rope had been worn through, and the fragments mixed with iron powder clung to the piston surface, forming a black, sticky substance.

Zheng Yong stared at that layer of material and remained silent for a long time.

"Why?" he asked himself.

He had spent his entire life making firearms, casting bronze cannons, forging iron guns, and assembling gunpowder, considering himself the foremost craftsman of the Ming Dynasty. But this thing before him was beyond the boundaries of his knowledge.

He didn't understand what "tolerance" was, what "thermal expansion" was, or what "lubrication" was.

All he knew was that he had built it exactly according to the blueprints, with the dimensions perfect, not a single rivet missing, and even extra copper hoops added. But it just wouldn't move; if it moved, it would stop, and if it stopped, it would break.

Fortunately, Zhu Di did not come to inspect the situation in person this time; otherwise, it would have been questionable whether he could have saved his head.

The best craftsmen in the Ordnance Bureau were gathered together to study the replica steam engine day and night. They used files to grind the inner walls of the cylinders, polished the pistons with oilstones, and tested the engine again and again, only to have it jammed again and again.

The foreman, Master Tan, was the most experienced. He conducted an experiment: he coated the inner wall of the cylinder with ink, inserted the piston, rotated it once, and then removed it. Some areas of the piston surface were covered with ink, while others were not—indicating that the cylinder and piston were not completely in contact.

Old Craftsman Tan reported to Zheng Yongping: "Sir, I have discovered a problem. The inner wall of this cylinder is not round. The difference is slight, not noticeable to the naked eye. But when the steam pressure is high, the non-round part gets stuck on the piston."

Zheng Yong asked, "Why are the gas cylinders in the Song Dynasty round?"

Old Master Tan remained silent for a long time, thinking to himself, "You're asking me? Who should I ask?"

The only answer I could give was, "No matter how you file it, you can't make it that perfectly round."

The parts they manufactured were of very poor precision.

"How did the Song people create these? Were they all master craftsmen?"

Zheng Yong then reported the progress to Zhu Di, and the problem then fell on Shen Lian.

Find out why the precision of Song Dynasty parts was so high.

a few days later.

The "Shunfeng" ship, a sister ship of the "Shunchang", docked at Quanzhou Port.

Shen Lian sat on the dock and couldn't help but sigh.

Those who know the Imperial Guards would think he's the emperor's personal guard, while those who don't would think he's a laborer doing the job on the side.

I haven't done anything for the past few months.

They were too busy doing hard labor for the Song people.

Damn it, what's even more infuriating is that in order not to alert the thugs, he has to endure the exploitation by the thugs at the docks.

Shen Lian once again disguised himself as a laborer and boarded the ship. This time, his goal was clear: to find out why the Song people's parts were so precise.

He searched for a long time but couldn't find it.

But he discovered something else.

During a maintenance operation in the engine room, a part was damaged.

The Song Dynasty technician didn't repair it; he simply took an identical new part from the spare parts box and replaced it. In less than the time it takes to drink a cup of tea, the machine was running again.

Shen Lian was shocked. In the Ming Dynasty, when machine parts broke, craftsmen had to repair them on the spot—filing, grinding, hammering, and forging—and repairing a single part could take a whole day. But in the Song Dynasty, parts were simply replaced. This meant that their parts were "interchangeable"—all parts of the same model were exactly the same size.

He risked stealing two discarded old parts and brought them back to the capital.

Zheng Yong received the parts and measured them repeatedly, his expression growing increasingly serious.

He reported to Zhu Di: "Your Majesty, the dimensions of these two parts are exactly the same. They are within the margin of error of a single hair."

Zhu Di didn't understand. It was just a difference of a single hair. Humans can conquer nature. As long as the craftsmen worked hard, even the smallest error could be corrected.

Then he asked, "What does this mean?"

Zheng Yong replied, "This means that the parts manufactured in the Song Dynasty were not made one by one, but in batches. Any two parts from the same batch can be interchanged. In my fifty years of life, I have never seen such a manufacturing method."

Zhu Di remained silent for a long time before asking, "What is needed to manufacture this kind of part?"

Zheng Yong replied, "The only possibility is a machine that can precisely control the dimensions."

Zhu Di closed his eyes: "Investigate. Investigate that machine."

Shen Lian was stunned. "Your Majesty, or your subject?"