However, usually the mine can not be dug so deep, often halfway to the digging, there is a permeable phenomenon, you have to give up, after all, once it is found that there is water in the mine, with the current technical conditions, it is impossible to drain the water in the well.

Moreover, in some places, the water was so strong that the entire mine could be flooded in just a few breaths, and the Huns who were working in it were sometimes drowned without having a chance to escape.

Cao Liang is not surprised by this phenomenon, after all, the coal mining industry is by no means a high-risk industry, in this kind of mining without technology and experience, it is completely normal for people to die.

In ancient China, the Ming Dynasty, coal mining technology has been greatly developed, Song Yingxing's "Heavenly Works" in the process, there is a detailed record of the process flow of coal mining, Cao Liang remembered that he had read this book before, but unfortunately he could not fully remember the content of it, who did not let himself not Cai Yan Zhang Song as unforgettable ability.

However, although he did not remember all the contents, Cao Liang still remembered some sporadically, he sorted out the contents of the memory, combined with some specific situations at the moment, Cao Liang wrote a coal mining construction manual, as the most basic operation specifications, requiring the coal mining teams in the ravines to learn and master.

Of course, this can only provide theoretical guidance, and the specific operation has to be constantly explored in practice.

In each ravine, more than a dozen points were selected at the same time for excavation, and after dozens of days of continuous digging, more than 95 percent of the wells were abandoned, either because of permeability or collapse, or because they dug to the specified depth, and did not find the coal seam, so they were forced to give up.

However, in the remaining five percent of the mines, there was good news that the Huns had finally dug up this "black stone".

The first basket of charcoal dug out was sent to Jinyang by the fast horse overnight, Cao Liang looked at these "familiar" things with emotion, it was not easy, and finally let him mine successfully.

Everyone was very curious, they didn't know what Cao Liang was doing holding this black stone, it seemed that this thing was much lighter and more brittle than ordinary stones.

And this thing is obviously inedible, neither food nor hard, but looking at Cao Liang's solemn appearance, everyone is a little confused, could it be that this thing really has a special purpose?

Cao Liang smiled without saying a word, and asked his soldiers to bring an ordinary stove, the ignition material of these stoves was firewood, which was flammable and had a high flame, but it lasted for a short time.

Cao Liang instructed his soldiers to light the fire with firewood, and when all the firewood was ignited and a fire was a foot high, Cao Liang personally put these black stones into the fire.

Everyone was very curious, and they all came forward to watch, thinking that there would be some miracle, but when they saw that the flames in the furnace were completely suppressed, they couldn't help but feel disappointed, it seems that there is nothing unusual about these black stones, except for the color of ordinary stones, there is nothing special.

Cao Liang didn't say anything, but signaled everyone not to worry, take your time, wait for a while, those black stones were burned red, and after a while, the furnace was already red, although the burning flame was not as high as the firewood, but obviously the temperature was much higher, standing in front of it, everyone could feel its pressing heat.

"This thing is called coal, in ancient times the mountains and seas called it stone, like a stone is not a stone, speaking of which these coals are quite complicated to form, but you remember that these coals can be burned instead of firewood, and the firepower is sufficient, it lasts for a long time, this winter, we are counting on it for the winter." Cao Liang didn't explain too much, the formation of coal will go through hundreds of millions of years of geological changes, and people of this era are also incomprehensible, anyway, they just know that coal and stone can be burned.

In the end, it was found that about ten ravines had dug up coal in dozens of ravines, so Cao Liang ordered those ravines that had not dug coal to give up, and all the personnel concentrated on the ten ravines that produced coal.

Exploration work has made great progress so far, and the next step will be to enter the substantial coal production phase, with countless quantities of coal being loaded into baskets from underground and transported to the surface.

The harsh working environment caused a large number of Huns to die, almost every mine, there will be Huns die in it, there is a landslide accident, more than a dozen Huns were buried alive in an instant, even the grave does not need to be dug again.

By the time coal production began in earnest, nearly a third of the Huns had died, and the truly severe test had just begun.

Dozens of mines in ten valleys produce coal at the same time, although the speed of this manual coal digging is not too fast, but dozens of mines are running at the same time, and a lot of coal and stone can still be produced.

After the coal mining was on the right track, Cao Liang sent a special person to supervise, and he could finally breathe a sigh of relief, after all, as the general of Bingzhou Assassin Shi Pingbei, he still had a lot of things to do, and he couldn't just stare at the coal mining.

The Huns who fled to Jiuyuan were the focus of Cao Liang's greatest attention, and in the Battle of Dongguan, the Huns were severely damaged, and they could not recover in a short period of time, and it was difficult for them to attack Jinyang City again.

After the merger of the Pingbei Army with the Bingzhou Army, the strength of the army increased greatly, from the original 10,000 to 25,000, and the increase in personnel also meant the improvement of combat effectiveness.

Deng Ai Yanghu and the others have not been idle at all, and have been seizing the time to conduct drills, and integrate the Bingzhou Army into the combat rhythm of the Pingbei Army as soon as possible.

Under the cultivation of Tian Yu, the Bingzhou army also has a combat effectiveness that is different from that of ordinary county soldiers, which has a great relationship with the fact that they have been under the threat of the Xiongnu Xianbei Hu people for a long time, and the Bingzhou soldiers have extremely high combat quality, and can even be compared with the most elite Chinese army in the imperial court.

This made Cao Liang feel like he had picked up a treasure, it seems that Tian Yuguo is an extraordinary person, and he has made considerable contributions in Bingzhou over the years, and Jinyang City has not been lost, which is enough to prove that Tian Yu's efforts are successful.

Just when Cao Liang was thinking about when to march to Jiuyuan, Luoyang's home suddenly sent someone to deliver a letter. Because he didn't want Cao Liang to be distracted, Yang Huiyu rarely wrote letters to Cao Liang, but this family letter had a different and extraordinary significance, and Cao Liang just finished reading it, and a smile appeared on his face.