Yes, the biggest reason that hindered the Central Plains Dynasty from completely eliminating the nomads and controlling the grasslands was that the land here was too barren for large-scale agriculture, and the cold climate made most of the migrated population unwilling to settle down for a long time.

It's like an enclave.

Even if it can occupy it in a short period of time and drive away all the Hu people above, once the army leaves, it won't be long before another nomadic people will rise.

From the Xiongnu to the Khitan, from the Jurchens to the Mongols, this is the case.

Unless it is to make this place suitable for Han people to live in, otherwise, no matter how strong the Central Plains Dynasty is, it can only guarantee temporary peace. When the day comes, it will still be the same as before, constantly suffering from the invasion of nomads.

Nanshan is well aware of this.

Just the average physical fitness of about 10 points does not mean that the human body can get rid of the shackles of the environment and be free from the cold. Maybe when it moves, ordinary people in this world who are close to the level of professional extreme athletes on the earth can endure low temperatures of dozens of degrees below zero, but once they are still, even if their physical fitness has reached the level of a military general, they can't prevent the heat of their bodies from being taken away in large quantities in a state of frost.

In fact, every winter, tens of thousands of people quietly freeze to death in the cold nights..... Slaves who lacked warm clothing, or shepherds who were old and frail and abandoned outside.

This is true even for the nomadic people who have lived in the northern steppes for generations, not to mention the Han people who mainly live in the south and do not suffer from the cold.

Only if you have actually lived here can you understand how long and difficult the winter is every year, from October to April of the following year, the snow will fall heavier and the food will become less and less.

Therefore, after taking out high-yield crops such as potatoes, corn, and sweet potatoes, Nanshan took out several other things that are conducive to taking root in the grassland to improve the living environment.

And what he brought Liu Bei and others over to see was one of them.

It's just that as soon as they approached their destination, these people who were ready to see the world almost didn't have to cover their mouths and noses.

"What's the smell so rushed?"

Including Liu Bei, many people with good perception frowned. For from afar, they smelled a distinct stench, which seemed to emanate from a cellar-like underground structure, and a combination of rotten rotten eggs, as if it were filled with excrement. Not to mention why such a smelly thing is placed in a place like the "cellar", what is even more unbearable is that it is not dug in some remote corners, but placed not far from the houses in the living area, close to the road.

Seeing the strange expressions of these people who wanted to ask but didn't know what to say, Nanshan's bad taste came out, and it was directly a meal of professional terms.

"There is no doubt that this is the reason for the frequent fires on the grassland, the flammable gas obtained by the fermentation of livestock manure, because it is a reaction that occurs in an anaerobic environment, so it will not be affected by conditions such as damp rain, but will be due to the action of dewdrops, water vapor and other concentrated strong light, so that the produced methane, hydrogen sulfide and other combustible gases suddenly burn under the induction of heat, thus causing a fire. Now I'm going to collect them and use them together. ”

Well, the person who heard it said he didn't figure it out at all.

They have never heard of flammable gases, anaerobic reactions, strong light focusing and other unclear words, let alone explain them with livestock manure.

But this did not prevent Nanshan from using an example to prove it, in front of everyone, he used his spiritual force field to wrap some gas floating out of the cracks in the wooden planks covering the "cellar", and then, he took an ice brick from the building next to him, made it into a shape like a magnifying glass, and placed it on top of the gas, facing away from the direction of direct sunlight.

It can be seen that the color of these encapsulated gases is very light, close to transparent, only some people with the best eyesight can see clearly, they are actually a little cyan, under the action of the focused light spot, constantly circulating and floating, just for a while, it suddenly banged, burned, the rising flame is two meters high, obviously not ordinary fierce.

"It's ......"

Liu Bei, who was staring at this scene intently, was stunned for a moment, and then seemed to think of something, and suddenly had a flash of inspiration.

That's right, he'd played with it before.

Piling up the collected fresh dung and then digging a hole in the middle and lighting it with something like a flint or a fire fold is exactly one of the favorite games of many bear children - "fried cow dung", which can blow up the smelly cow dung everywhere to see who is the most unlucky and can't avoid it.

It has to be said that the wisdom of the ancient working people is infinite, maybe they do not understand the truth behind this, but they can understand how to use it from some similar life phenomena.

Among them, Zhang Fei, who is a heavy drinker, even thought that the fermentation process, which seems to be the same as winemaking, is to put the raw materials in a sealed container, and after a period of time, they will be transformed into another substance, and at the same time produce a smell, but the thing in front of him is smelly.

Nanshan, who noticed everyone's reaction, stopped selling off the door and began to show its true effect.

"It's called a biogas digester, and it produces a large amount of flammable gas, which can be connected to the surrounding houses through tunnels, and can be used to cook rice, boil water, and keep indoor insulated. Because it weighs less than the air we breathe, it is safe to use as long as we are careful not to expose ourselves to the air......"

Nanshan said, took them to visit the surrounding houses, and also showed Liu Bei and others the underground air passage paved with bricks, rice milk and wooden planks and straw near the kitchen and bedroom, among which there is also an existence that northerners like to attach to the most in later generations - the Northeast Fire Kang.

This simple structure, consisting of a stove, a kang and a chimney, can use the heat emitted to maintain the indoor temperature while cooking and boiling water. Even if it is in the grassland with a cold climate and sprinkling water into ice, there is no need to worry about being cold and freezing, as long as you lie on it and cover a quilt, it is definitely the supreme enjoyment of the cold winter.

In this regard, a group of ancient people who have never seen the world remain in a state of confusion throughout the whole process.

They never thought that it would be so simple to solve the problem of large-scale settlement of Han people in the north!

I'm afraid it's not a lie, right......

However, after sitting inside for a while, a few people couldn't help but take off the robes they were wearing outside, because they were no longer needed, and Liu Bei, who was the leader, was holding a cup of boiling hot water, squinting on the kang and not preparing to come down, it was really comfortable.