Because Yan Xiao was leaving today, He Shiqing was not in high spirits. Yan Xiao was also trying hard to make jokes and make He Shiqing happy.

Zhou Zhi said: "Yan Shu and Mangzi are members of the country. They can't take more than a few days off each time. Fortunately, in a few days I will go to the capital of Shu, together with Shu Yi, to see you then."

"Ah?" Jiang Shuyi became nervous: "No, I went to see grandma with my dad, I didn't say I was with Zhou Zhi..."

"Another shameless person!" Feng Xueshan expressed disdain again.

"That's right." Zhou Zhi didn't take it seriously: "Shuyi, think about it, when you arrive in the capital of Shu, why don't you go and visit Vice Principal Li? Don't you go and visit Sister Xue Li? The old station director? For these people who have selflessly helped these people?

We should all use our courtesy to those who cross our path, right?"

"There are still study materials, so we have to find Zhang Weiran, Xu Hui and the others. Why don't we go together?"

"Yeah...I'm sorry Zhou Zhi, I didn't think of Zhou Zhi." Jiang Shuyi quickly apologized.

"Oh my God, are you apologizing now?" Feng Xueshan hugged Jiang Shuyi to her side: "Shuyi, you are so deceitful. You are obviously just trying to find an opportunity to get close to you, and you even end up getting close to him.

It seems reasonable."

"But...it makes sense, so you have to listen..."

"Shu Yi's attitude is the right one." Zhou Zhi nodded in agreement: "Don't ask where the truth comes from, ask yourself whether it's right or not."

"Even if it is an enemy's suggestion, as long as it is right, then we must listen to it, such as the Qin State building the Zheng Guo Canal."

"How many years did it take to build the Zheng Guo Canal? How much benefit is there?" Zhang Lu ate and asked questions without delay.

"The record in "Historical Records: Book of Rivers and Canals" is that there are more than 40,000 hectares of irrigated, marshy and brine land, which is almost 1.1 million acres, and "one hour per acre is harvested," which means that the yield per acre is almost 200 kilograms."

As a result, Guanzhong was fertile and fertile, and there were no bad years. From that time on, the floods in Guanzhong were basically controlled, and it gained the reputation of the first 'Land of Abundance'." Zhou Zhi also did not delay eating and explaining.

"The population of Qin at that time, according to Mr. Fan Wenlan's inference, was between two million and three million. The Zhengguo Canal project took about ten years and increased Qin's per capita grain possession by one hundred kilograms."

"Note that this is extra food out of thin air. Based on the amount of food carried by an average person in ancient wars, which can last for half a month during a regular march, these extra food can support a three-measure battle if they can be transported to the front line.

One hundred thousand troops, one month of war.”

"Of course it won't be so beautiful in reality, but we must also note that so much food is only an increase in one year."

"So there is no doubt that Zheng Guoqu's increase in Qin's national power was exponential."

"Is there any evidence for this data of yours?"

"Yes, there is a record in "The General Essentials of the Martial Arts": 'In the old method, a person could carry three measures of dry food, which could last for several days. If the commander was on the road and the destination was far away, and the supplies were exhausted, he would have to choose thin oxen and horses to serve as soldiers.

Use it as food for the army, so that you can use all your manpower so that you will not be trapped by thieves."

"Do you think this is liberal arts or science?" He Shiqing also became interested: "What you are doing is almost the same as doing math application problems."

"It should be analyzed across disciplines and from multiple perspectives." Zhou Zhi said: "This is the advantage we have over the ancients. We can study both arts and sciences and use all available methods to study problems."

"For example, there is the famous historical event 'Iron Lock across the River', because in Liu Yuxi's poem there is a line about 'Wang Jun's boat sailed down to Yizhou, and the King of Jinling lost his spirit sadly. Qianxun's Iron Lock sank to the bottom of the river, and a stream of flags fell out of the stone.' Sentence, I think that the incident happened in Jinling, and Sun Hao used iron chains to cross the Yangtze River in the upper reaches of Jinling, so that the warships of the Western Jin Dynasty could not go eastward, but it is actually wrong."

"If you check the information, you will find that Wang Jun, the governor of Yizhou in the Western Jin Dynasty, was ordered to build a warship in order to conquer Soochow. The wood chips produced during the shipbuilding flowed to Jianping County along with the Yangtze River. After Wu Yan, the prefect of Jianping discovered it, he picked up the wood chips. Sun Hao was submitted to Sun Hao, who believed that the Western Jin Dynasty was building warships and planned to attack Wu. He asked Sun Hao to send more garrison troops to Jianping to defend, saying that as long as Jianping did not fall, the Western Jin Dynasty would not be able to cross the river to attack. But Sun Hao would not listen. Wu Yan was helpless. They could only make iron chains and lower them at dangerous places to cross the Yangtze River; they also made large iron cones and placed them secretly in the river in an attempt to prevent the Western Jin warships from advancing eastward."

"Where is Jianping? It is now Zigui, a dangerous place in the Three Gorges. It is thousands of miles away from Jianye in Soochow."

"So the iron chain across the river actually cuts across the Three Gorges?" Zhang Lu asked.

"That's impossible." Wei Fei reacted quickly: "As you can see from our Jiachuan River, the water level of the Yangtze River differs by more than fifteen meters between dry and busy seasons. How can we stop it with an iron chain? Also, even if we cross the river there, How long is it? How much iron is consumed? How powerful can these iron materials be used to make weapons and arrowheads? Which method is more cost-effective? "

Zhou Zhi gave Wei Fei a thumbs up: "This is the idea, the science idea. Even in Jianping County, assuming that the iron chain across the Yangtze River blocked the building ship, it was not something that the national power of the Wu State could achieve at that time."

"However, history does have records. In the fourth year of Tianji (the first year of Taikang in Jin Dynasty), Wang Jun led his army to attack Wu. Most of the defenders of the cities along the river surrendered or were quickly defeated, but Wu Yan led the army to hold on to Jianping. , unable to capture it, finally Wang Jun used a large raft to remove the iron cone under the water, and burned the iron chain with fire, and then 'went down to Xiling'."

"Xiling is Yichang, and Wang Jun finally broke out of the Three Gorges."

"Then this also shows that the 'Iron Lock across the River' is indeed a thing. How should we understand this?" Zhang Lu asked.

"In fact, it can be explained from the perspective of modern military science." Zhou Zhi said: "It can be explained by understanding the iron lock across the river and the hidden iron cone as a measure to defend Jianping."

"Zigui is located in a dangerous location. At that time, Jianping was located between the Yangtze River, Xiangxi River and Mancao River. If Jianping was properly guarded, it would be a dead nail in the middle of the Three Gorges. If he could not capture it, Wang Jun would never dare Go eastward."

"This should be easy for us Jiachuan people to understand. During the Southern Song Dynasty, we had the Divine Arm City in Jiachuan and the Diaoyu City in Hechuan downstream. These two places were no different. The Mongolian army could not move eastward along the Yangtze River for decades. In the end, they had to This is the reason why we changed the route to Xiangyang."

"Yes, otherwise there will be no way out and the entire army will be wiped out." Zhang Lu nodded.

"Therefore, iron chains and iron signs are mostly measures to defend Jianping City. They can only be installed in the Xiangxi River or Mancao River around the city. They are powerful measures to prevent Wang Jun from using waterways to attack the back roads of Jianping City. The cost is Compared to crossing the Yangtze River, it is much lower and can be accomplished by a county governor."

"It would be great if I could go and take a look sometime." Zhang Lu is a fan of the Three Kingdoms. After careful analysis and Wei Fei's supplements, he realized how wrong he once believed to be the "truth":

"Based on emotion and reason, your inference is much more reasonable than the idea of ​​'iron chains across the river'."
Chapter completed!