To be honest, Liu Che had so much fun these past two days that he almost forgot about the dragon-bone waterwheel.

When Liu Tan asked him if he wanted to see the model, he was confused for a moment. When he remembered, he asked in surprise, "So fast?"

Liu Tan smiled and said, "Of course it's fast. After all, we have the blueprints. This is still considered slow. I guess Gongshu Can didn't dare to disturb my father's leisure."

Liu Che put the document in his hand aside and said excitedly, "Let him bring it over."

When Gongshu Can came over, he was tense all over.

He originally thought that being able to meet His Royal Highness the King of the North in this lifetime was a blessing from his ancestors, but he never expected that one day he would be able to meet His Majesty the Emperor!

Before coming, he thought many times about how to greet and respond when meeting His Majesty. However, it was proved that when people become nervous to a certain extent, their brains will become blank. No matter how much he thought before, it was useless. All his actions became driven by instinct.

Seeing that Gongshu Can was so nervous that he was almost at his wit's end, Liu Tan couldn't bear to let him stay any longer. He simply waved his hand and said, "You go down first. I'll take care of this."

Gongshu Can came to his senses after hearing these words, and immediately hated himself for his poor performance just now. He missed such a good opportunity to show off.

But he was not so shameless as to say that he wanted to stay, so he had to bow and leave.

Liu Che watched Gongshu Can leave and said with some dissatisfaction, "He is not up to the task."

Liu Tan laughed and said, "It's their mechanical engineering that I'm attracted to. Other aspects don't matter. As long as they can produce what I want, that's all that matters."

Liu Che thought about it and it made sense. Liu Tan didn't expect these people to make any political achievements, so when he thought about it this way, he didn't think it was a big deal.

Putting Gongshu Can's matter aside, Liu Che began to look at the model of the dragon bone waterwheel.

The dragon-bone waterwheel was completely different from the one he had seen before. Liu Che had imagined that the dragon-bone waterwheel was also round, but he didn't expect that this one was actually long and narrow.

Gongshu Can put a lot of effort into making this model. He even made water and fields. The keel waterwheel can also be controlled, so that the usage and effects of the keel waterwheel can be demonstrated more intuitively.

Liu Che observed carefully and found that there were axles at both ends of the keel waterwheel, one end was placed in the water and the other end was placed on the field. The entire keel waterwheel was placed at an angle.

The keel waterwheel is composed of a series of sprockets, each of which has a water trough. At the top axle, there is a crank similar to a well wheel. When the crank is shaken, the sprocket of the keel waterwheel starts to transmit, transporting the water troughs one by one. The water troughs are also designed in a triangular shape, with the water outlet facing downward. When they come out of the water during the rotation process, they will be filled with water.

Then it is brought up little by little through the sprocket drive. When it reaches the top wheel axle, the trough flips down and the water in the trough will pour into the field. The whole process is clearly visible and it does look easier.

Liu Tan said as he turned the crank of the keel waterwheel, "This type of waterwheel can actually be improved to use animal power, or human power. Compared to the round-wheel waterwheel, it might waste more energy, but the advantage is that it's cheaper and suitable for many places."

Liu Tan added, "Of course, it's not easy to do it in places with a huge drop in height. In that case, it would be better to build a waterwheel or dig a canal to divert water from above."

Liu Che looked at the dragon-bone waterwheel carefully. To be honest, he was not proficient in agriculture so much that he could tell at a glance whether this thing was useful or not.

However, adhering to the principle that things from the fairy world are all good things, Liu Che has decided to find a place to promote and test it first.

Although there are not many mountains in the plains, there are still many places with height differences. If keel water wheels are used, it should be able to greatly reduce the irrigation burden.

After Liu Tan stopped, Liu Che took it curiously, turned it around a few times, and said with a smile: "This thing doesn't seem to have any connection with the waterwheel by the river. It's rare that you could think of it."

Liu Tan couldn't say this was the fruit of ancient wisdom, could he? So he could only calmly say, "It depends on local conditions. And while they may look different on the outside, they actually share many similarities. Your Majesty, you can think of the dragon-bone waterwheel as a flattened round-wheel waterwheel, where the driving force is replaced by human or animal power instead of water. Isn't that easier to understand?"

Liu Che smiled faintly and said, "Alright, go write a letter to the Crown Prince and have him send it to Chang'an as fast as he can. Also, send this miniature version of the waterwheel to Chang'an and have him consult with the Minister of Agriculture."

Liu Tan agreed immediately, turned around and asked someone to pack up the model of the keel waterwheel and the model of the water wheel that had been obtained earlier, and then wrote a letter and prepared to send someone to deliver it.

However, he thought about it and decided to send someone from Gongshujia to explain to Liu Ju in order to avoid misunderstandings in Chang'an due to insufficient details in the letter.

Gongshu Can definitely cannot go, so Gongshu Yi is more suitable.

Before Gongshu Yi left, Gongshu Can warned him to be cautious in front of the prince, not to show any weakness, and to speak well. He should not be like Gongshu Yi, who dared not say anything when he met the emperor.

Gongshu Yi felt a little helpless when his father naggled about him. To be honest, in his opinion, his father was a little... not so good.

I remember that Gongshu Can was extremely nervous when he met Liu Tan. Although Gongshu Yi was also nervous, young people are born with the courage of a newborn calf who is not afraid of a tiger. He thought much less than Gongshu Can, and the burden on his shoulders was lighter than Gongshu Can, and of course he was more free and easy.

It seems that his father can't get any benefits from the emperor, so he has to work hard.

So Liu Ju, who was far away in Chang'an, received the longest letter ever written to him by Liu Tan.

When Liu Tan writes letters, one-third is usually about official business, one-third is about family matters, and the remaining one-third is about some interesting things.

This time, Liu Tan had more things to write about, but because the matters concerning the keel waterwheel and the round-wheel waterwheel were more important, he put them first.

This was the first time Liu Ju saw a model. Even Liu Che was a little surprised when he saw such an exquisite model, let alone him.

Because he received the letter at night, he did not rush to find the Minister of Agriculture Sang Hongyang to discuss the matter. Instead, he asked someone to bring the model to him and played with it for a while.

Liu Tan was worried that what he wrote in the letter was not clear enough. In fact, what he wrote in the letter was already very clear, and Liu Ju had no problem understanding it, so after understanding the difference between the two water wheels, he knew that the keel water wheel might be the most popular one in the end.

Water wheels are beautiful and convenient, but they are too difficult to make.

After he had played with the model enough, he put it aside and couldn't wait to continue reading the letter.

If he guessed correctly, most of the letters this time were probably related to his father.

As expected, most of Liu Tan's letters were about Liu Che's whereabouts and what they did and ate.

In the letter, Liu Tan also told Liu Ju that the recipes were sent along with the letter, and if he wanted to eat it, he could just ask someone to cook it for him.

Only then did Liu Ju understand what the other thick document that came with the letter was. It turned out to be a menu?

Out of curiosity, he opened the menu to take a look, but in the middle of the night, he actually made himself hungry!

There was no other way. If it was just writing the name of the dish on a piece of paper, it would be enough, but Liu Tan not only wrote the name of the dish, he also wrote the preparation method. What's more, he even wrote down the taste and flavor!

Liu Ju guessed that his brother's literary talent was used in describing these dishes. Just looking at those adjectives made people salivate.

Liu Ju closed the menu halfway through and didn't plan to continue reading, otherwise he might have to order an extra meal in the evening.

Thinking that his father had already tasted these delicacies, Liu Ju couldn't help feeling a little jealous - being the crown prince of Jianguo was great, but looking at these dishes, he also wanted to take a trip to the Northern Border Kingdom.

However, what made him even more sad was yet to come. He watched Liu Tan write about everything from the glass house to the tree house, from the grassland to the water park. Although he didn't know what a slide was, since his father could stay in the water park for three or four days in a row, it must be something very fun.

Liu Ju suddenly felt that his recent life had become boring. Even though there was good news from the jade mine and the quality of Dunhuang jade was good, it could not comfort his wounded heart.

Liu Ju secretly decided that after Liu Che came back, he would ask Liu Che for leave and go to the northern border country for two days.

Especially the bustling Tongda City made him curious.

Think about it, his younger brother lives a very carefree life. He can do whatever he wants. I don’t know what’s going on in his little head, but he has so many new and interesting ideas.

Liu Ju, who was thinking about running to the Northern Border Kingdom, did not know that the Northern Border Kingdom was not peaceful at that time.

It may not be quite accurate to say that things were not peaceful, but the fact is that when Liu Tan was accompanying Liu Che on his travels, someone seized the opportunity and started making trouble.

The method of causing trouble was very simple, which was to spread rumors. At first, no one took this matter seriously, but when the rumors spread in the original refugee city, Huo Guang became alert.

Originally, he thought that if Liu Tan didn't come back in time, he would just arrest everyone first and deal with them first, and then report to him after Liu Tan came back.

Unexpectedly, Liu Tan came back in time, so Huo Guang ordered people to control the spread of the ballad and find the source of the ballad, while coming over to talk to Liu Tan.

Liu Tan was a little surprised: "Ballad? What's wrong with ballad?"

Huo Guang said, "Your Highness, please take a look."

As he spoke, he handed over a piece of paper. Liu Tan took it and found that it contained four lines of a ballad: "The northern border is a thousand miles away, the human world lies beneath the cloud steps." "The sound of the Qiang flute is no ordinary sound, the mountains and rivers are stained with blood."