Liu Tan did not wait for the water in the small copper basin to completely freeze before taking it out. There were ice chips and a little water in it at this time, which was a mixture of ice and water.

However, the more this situation is, the easier it is to convince people.

Liu Tan held the small copper basin in front of Liu Che and said with a smile, "Father, look, if I say I don't need it, then I don't need it, right?"

Liu Che looked at Liu Tan in surprise and suspicion. Although he had many guesses in his mind before, he had never seen Liu Tan perform magic in front of him. What happened today?

When Liu Tan saw Liu Che's expression, he was shocked: It's over, this is too much.

He quickly cleared his throat and said, "Ahem, let me tell you the truth. What makes water freeze is saltpeter. The water in this basin is saltpeter dissolved. With it, you can make ice anytime, anywhere. If you don't believe me, you can try it."

The best way to break feudal superstition is to let people do it themselves. When something loses its mysterious attribute and becomes something that can be done casually, the so-called magic of immortals will naturally collapse on its own.

Liu Che watched Liu Tan ask people to prepare things, and then he threw the saltpeter into the water in the large copper basin with his own hands as Liu Tan said, and then placed the small copper basin in the large copper basin, and saw the water in the small copper basin freeze little by little again.

Liu Tan held his chin up and smiled, "How was it? Wasn't it quite fun?"

Liu Che waited until all the water in the small copper basin had frozen solid. Then he looked up at Liu Tan and asked, "Did you do anything with the saltpeter?"

Liu Tan was stunned: "No, it's just ordinary saltpeter."

Liu Che was full of disbelief. How could it be possible that just throwing ordinary saltpeter into water could make another basin of water freeze into ice?

Liu Tan, not knowing whether to laugh or cry, explained, "Saltpeter...it's like that. When you put it in water, it absorbs heat. The temperature of the water in the small copper basin keeps dropping, so of course it'll freeze in the end."

Liu Che calmly asked, "How do you prove that this is ordinary saltpeter?"

Liu Tan: ????

How could he prove it? Did he have to go and mine it now? No, it would be useless even if he went to mine it. It would be wrong to ask someone else to mine it. Even if someone else mined it, if Liu Che insisted that he had tampered with it and cast a spell, there would be no way to explain it.

Whose magic needs to be handled by others?

Liu Tan felt that he was being fooled by Liu Che, and for a moment he couldn't think of any particularly good explanation.

But saltpeter has just such a reaction when it comes into contact with water. How can he explain it?

This is another disadvantage of not having a formalized scientific and technological system. He only knows the answers and results, but there is no more solid theory to support them. Not to mention that he has now forgotten the reaction formula for the dissolution of saltpeter in water. Even if he knew it, what would it matter? Could he really write it down directly?

Liu Tan looked devastated. If he had known this would happen, he would not have teased Liu Che. Well, this time he was really in trouble.

Liu Che looked at his dazed expression and couldn't help but smile secretly.

He somewhat believed what Liu Tan said, but this phenomenon was so magical that he found it difficult to accept it for a while.

But no matter what, if this can be done without Liu Tan casting a spell in secret, it will be much easier to get ice in the future.

Liu Che used himself to give Liu Tan a vivid lesson, making him thoroughly understand that he should not play tricks casually, otherwise it would be troublesome if he couldn't explain it clearly.

Fortunately, there is nothing to be mysterious about next. After all, there is no other high-tech to be demonstrated along the way.

Liu Tan and Liu Che did not often sit in the carriage, and would occasionally go out for horseback riding to get some fresh air.

Anyway, the carriage is there and you can get in anytime when it gets hot.

In fact, Liu Tan prefers being outside to being in the car. Although it is hot, he feels a sense of accomplishment.

Yes, it’s a sense of accomplishment.

The route they took was arranged by Huo Guang. Our Northern Frontier Kingdom's Prime Minister was very thoughtful in arranging places that could showcase the work of the Northern Frontier Kingdom in recent years.

For example, the wasteland where saltwood is planted. Since the planting of saltwood began, the Huns have basically never stopped in the past few years. Wherever they go, they plant it. At a glance, there are spots of green on the barren land.

It is said that these dots of green can reduce the extent of flying sand in the wind. In the past, when there was strong wind, the sky would basically be covered with sand and dust.

There is still a lot of dust now, but it is a little clearer than before.

Liu Che had never seen saltwood before, so he was quite surprised to find that there was a plant that could grow tenaciously in the Gobi Desert and grow quite well.

After learning why Liu Tan planted salt trees, Emperor Wu of Han asked, "Will the Yellow River stop changing its course so frequently in the future?"

Liu Tan shook his head and said, "The Yellow River frequently changes course because it carries too much silt. Of that silt, very little is actually produced within the northern borders. Most of it is concentrated in the Loess Plateau, where the land is also barren. If we want to calm the Yellow River, we have to control it there as well."

Liu Che didn't say anything. The Loess Plateau is not small in area. The most important thing is that there are no vassal states there, or even if there are vassal states, they may not be willing to put in the effort to govern it.

But now the Han Dynasty's treasury has just breathed a sigh of relief, and has invested a lot in the management of the Yellow River over the years.

The reason why the Northern Border Kingdom was able to start planting salt trees on a large scale so quickly was ultimately because Liu Tan had a lot of Xiongnu captives under his command. These Xiongnu people had no land of their own, and planting salt trees could provide them with a living. If they performed well, they could even obtain Han household registration and be allocated land, so they worked extremely hard.

There are no such conditions in other places. The people are busy cultivating their own land, so how can they have time to grow salt?

It was also unrealistic to ask Liu Tan to transport Xiongnu prisoners there. After all, that place was already considered the heartland of the Han Dynasty. If so many Xiongnu prisoners were brought there and these people rebelled, it would probably threaten Chang'an.

Liu Che couldn't help but sigh. If it wasn't really inappropriate and the distance between the two sides was not too far, he would even want to give that piece of land to Liu Tan as a fiefdom.

Anyway, as long as the Yellow River can be managed well, Liu Tan can do whatever he wants.

But this is just a thought. If all the land over there is really given to Liu Tan as a fiefdom, the entire Han court will never agree. That area, together with the Northern Border Kingdom, basically occupies more than 30% of the land of the Han Dynasty.

Now Liu Tan has been targeted and rumors have begun to spread, let alone what will happen afterwards.

As soon as Liu Tan saw Liu Che's expression, he knew what he was worried about. After thinking for a while, he said, "Father, there are actually some people who are more useful than the Xiongnu prisoners."

Liu Che asked, "Who is it?"

"Refugees."

Liu Che was surprised: "Refugees?"

Liu Tan nodded. "Yes, refugees. Most refugees today are in the mountains. They fled there to escape the war. They may not know the war is over. Even if they did, they have no household registration and therefore no land. If they came out, they would be slaves. That's why they stay in the mountains and refuse to come out. If the court recruits them and promises them land after they plant a certain number of trees, they will surely be willing to come."

Liu Che asked, "Since you said the refugees have become accustomed to life in the mountains, why did they come out?"

Liu Tan smiled faintly. "There are plenty of supplies in the mountains, but even if there are plenty, they can't be completely self-sufficient. For example, take salt. They have to find ways to trade with the outside world. And if I'm right, they must be extremely short of salt. Then there's food. Living in the mountains means farming is very difficult. As for hunting... if hunting was that easy, why would the refugees be living so poorly?"

Liu Che said thoughtfully, "That's one way. You can go back and write a plan and give it to the Crown Prince, and let him carry it out."

Liu Tan: ...

This was the second time he told the prince his idea, and then the prince went to work.

Let them do all the work, Dad, what are you doing?

Liu Che looked at Liu Tan's expression and raised an eyebrow and said, "Why? Don't you want to?"

Liu Tan smiled bitterly and said, "Of course not. It's just that such an important matter always requires your supervision. It's just that there are always omissions between the two of us."

Liu Che taunted, "You two? You're just the one coming up with the idea. Let the prince discuss the rest with everyone else!"

Liu Che was in the Northern Border Country, but the entire Han Dynasty's power structure was still operating in Chang'an. According to the current situation, let alone Liu Che being away for a few months, it would be fine even if he didn't go back for a year!

Of course, it is impossible not to go back for a year. After all, there are two major festivals, the Winter Solstice and New Year's Day, and Liu Che also has to go back to worship his ancestors.

After passing this relatively desolate area, fields gradually began to appear.

After a lot of effort, he finally saw green everywhere, with fields of crops everywhere. Of course, Liu Che couldn't help but run out to ride his horse.

Looking around as he walked along the road, he asked in surprise, "Didn't you just think of this keel waterwheel?"

Liu Tan followed his gaze and saw a keel waterwheel already standing by the field. He couldn't help but smile and said, "Yes, I thought of this when I heard that the round-wheel waterwheel was expensive. After I made the model, I asked Huo Guang to arrange it. He's quite quick on his feet."

Liu Che was deeply shocked by the efficiency of the Northern Border Kingdom. It would not be surprising if dragon-bone water wheels began to appear around Shuofang City.

After all, it is the royal capital, so it is easier to promote it.

But this place is already within the boundaries of Xi'anyang County, at least a hundred and eighty miles away from Shuofang City. How long has it been? Less than a month and already this place has been used?

For the first time, Liu Che was curious about how the Northern Border Kingdom operated and couldn't help but ask, "How did they manage to get so many people using dragon-bone water wheels in such a short period of time?"

Liu Tan looked at Liu Che without saying anything. Liu Che didn't hear any answer and turned to look at him: "What is there to hide?"

Liu Tan smiled bitterly: "It's not that I want to hide it, it's mainly because... I don't know either."

Liu Che: ????

What happened to the King of the North who was said to have absolute power in the Northern Kingdom?