10 months are fast by! Tu Sui advanced quickly, advancing the border between Hunan and Guangxi. As a result, Tu Sui counterattacked in an all-out counterattack by the South Vietnamese coalition forces, and half of the soldiers died in the mountains, and Tu Sui himself died in the mountains.

Li Tangshan and Wu Rui came to Quanling City, which was full of unkempt and disheveled soldiers, normal people with well-developed limbs, and all kinds of disabled people. Some knelt on the ground and kept making waves to pedestrians, and some lay on the side of the road and stretched out their dirty hands, all of them with dirty faces, and when they saw pedestrians, they reached out to ask for money, and if they didn't give it, they jumped up and hugged each other's thighs. gives people a miserable and pitiful feeling, and Li Tangshan is also full of pity and sympathy for the sergeants. Li Tangshan's greatest realization in his heart is that the beautification of war is a crime against the people.

After Li Tangshan and Wu Rui returned to Quanling, there was no good news for a single day, and every day there was all kinds of troublesome news from the front line. The wounded soldiers were constantly defeated and retreated from the front line, and the only good news was that the child of Li Tangshan and Mei Hong was also born, named Li Lujia. The name comes from the Ming Dynasty thinker Li Zhen's "Zhuge is only cautious in his life, Lu Duan is not confused about big things", I hope that children will not be confused about big things like Lu Duan, the prime minister of the early Northern Song Dynasty, and be a person with high emotional intelligence, and even hope that children can be better than Lu Duan!

Li Tangshan was not happy for long, so he ordered all the troops to retreat to the Lingling area.

The border between Hunan and Guangxi of the Qin army was strongly blocked, and the damage of the Qin army was already more than half, especially the difficulty of replenishing grain and grass, so Li Tangshan and Mei Juan helped find a way. After receiving the letter, Li Tangshan called back all the people in the other groups to discuss how to solve the problem of resupplying grain and grass. Shi Lu suggested that Emperor Li Tangshan could build a small canal on the border between Guangxi and Hunan. The difficulty of construction is not very large, and water transportation can solve the problem of resupplying grain and grass on a large scale and quickly. Is it feasible to build an artificial canal connecting the Xiangjiang River in Hunan Province and the Lijiang River in Guangxi? Mao ** said: "Without investigation, there is no right to speak." Li Tangshan was overjoyed when he heard this, and led Shi Lu and them straight to the scene.

After Li Tangshan and Shi Lu arrived at the scene, they found that the water levels of the two rivers were different, and there was a hill in the middle, which was still very difficult to construct at the current level of water conservancy projects in Qin. Qin also did not have any precedent for developing a canal to refer to, and although Li Tangshan was very confident in opening up this waterway, many practical problems were in front of him. How high is the difference between the water level of the Haiyang River and the Darong River? Where do you start and where do you finish? Li Tangshan does not have modern surveying tools in his hands, and he even has problems with the calculation of a topographic map?

Li Tangshan shouted: "Lu Yique, do you have any way?" ”

Lu Yique shook his head and said: "I am familiar with wood structure, and I am really not good at earthworks. ”

Li Tangshan turned to Shi Lu and said, "Shi Lu, you are familiar with this area, what do you suggest?" You're in charge of this project. ”

Shi Lu wanted to refuse in his heart, but Li Tangshan resolutely made himself responsible, there must be his intentions, so he nodded and said, "Okay!" I'll take care of this project! But my knowledge level is limited, and I need everyone's cooperation. ”

Li Tangshan said to Shi Lu: "Shi Lu, you get out of this mountain-shaped landform first, and then we all decide what to do?" Crossing the river by feeling the stones. ”

Shi Lu nodded.

Shi Lu and they quickly figured out the topography, and after Li Tangshan made a on-site comparison, the error was still relatively large, only the river and the mountain direction, and there was no horizontal equivalence. Li Tangshan and Shi Lu walked again, and Li Tangshan asked everyone to measure the distance between the two rivers with their feet several times, and after conversion, it was about 37-40 miles (about 20 kilometers). Li Tangshan also compared Shi Lu's map and found that the horizontal distance was about the same, with an error of about 5 miles. Li Tangshan misses the days when there were GPS and barometers, these half-day efforts are all the work of getting data, Li Tangshan and Shi Lu have been doing this for more than two days, and the data is still a question mark in Li Tangshan's heart?

Li Tangshan believes that the map that Shi Lu measured with his feet should be able to be used as an original project. Now the problem is that the horizontal path is out of the way, and altitude measurement is still a big problem. Li Tangshan and Shi Lu discussed how to measure the difference in water level, but Li Tangshan found that Shi Lu and his understanding of physics were 2,000 years apart, and modern physics knowledge was linked one by one, and they could explain each other. A small physical phenomenon, Li Tangshan has to use all his strength to analyze it, but they still can't understand it.

Li Tangshan thought that if this continued, he would have to change his career, and he would become a physics teacher, and it would be a few years before Li Tangshan taught them, and the engineering project could not wait, and every extra day, the front line was a group of Qin army brothers to sacrifice.

Li Tangshan decided to let them learn by doing, and Li Tangshan brought the most perceptive Lu Yiqi to Shi Lu as an assistant.

No one can help Li Tangshan with these problems, and Li Tangshan can solve them by himself. Li Tangshan went to the Yangyang River to see the scene and see if there was any way to solve it, and the original tools could be used to quickly measure the water level and height.

Li Tangshan sat next to the Ocean River and looked at the beautiful scenery, and several children were playing in the river, a peaceful and stable scene. Li Tangshan missed the lively and lively Lu Duanlai at home very much, so he stood up and walked towards the children.

"What are you waiting for?" Li Tangshan asked with a smile and waved his hand to the children.

"Uncle, my fish catcher" The tall boy looked at Li Tangshan and explained calmly, and in a blink of an eye, he instructed his children to build a mud dam to form a fence.

The tall child instructed the other children to drain the water of the small waterhole with a small foot basin, and soon the small waterhole was almost dry, and the children caught a lot of fish at once, and they all dispersed happily. Gao Ren left alone to make a small opening in the mud dam, and the water in the river quickly filled the small waterhole along the small opening.

"Do you want to put water in?" Li Tangshan asked curiously, a tall child.

"Every day, there are fish to catch." Gao personally explained seriously.

"What's your name?" Li Tangshan nodded and asked.

"My name is Cai Jingzhong, Minglun, uncle!" Cai Jingzhong replied.

Li Tangshan said in his heart: "Cai Jingzhong, Cai Lun, is the same name as Cai Lun, who invented papermaking, but Cai Lun is a person from the Eastern Han Dynasty."

Li Tangshan really stepped on the iron shoes and found nowhere to find it, so he really made his wish come true, and told Cai Lun to go to the military tun area tomorrow to find him. Li Tangshan found that Cai Lun was in a very good mood, and when he saw Cai Lun's small pool full of water and catching fish, he liked this kid more and more and decided to accept him as an apprentice. Suddenly seeing a few small fish swimming into Cai Lun's small pool, Li Tangshan was overjoyed, patted his thigh and said: "The U-shaped tube principle, I have thought of a way to solve the problem of measuring height, I have studied the principle of barometer in Beihang before,"

Li Tangshan shouted to Shi Lu as he walked: "Shi Lu, come quickly, I have a wonderful method to solve the dilemma."

Li Tangshan explained the principle of U-shaped pipe in the most simple and easy-to-understand way how to measure the height, and the pipeline had no way to extract all the metal, so it could only be replaced by local materials and bamboo in the south. Li Tangshan asked Shi Lu to make bronze joints of bamboo and bamboo. Everyone worked together, and those who received the task went to work on their own materials.