Yan Zhang specially came to tell Yan Yan that the emperor saw the drawings drawn by Lu You, and also saw the arithmetic books on the bookcase, most of which were to ask about these related things.

And the reason why Yan Zhang noticed this was because he was concerned about his father's battle situation on the front line, and he wanted to know if these things were going to be sent to the front line to help his father fight the enemy.

Yan Yan had to put down the dishes and chopsticks when he heard this, and touched Yan Zhang's head, "How many times has the eldest sister told you, you are still young, these things are to worry about the emperor and the ministers of the court, what you can do now is to study hard, learn more things, and help your uncle in the future." ”

"Okay, I know that the eldest sister can help my father, just because the eldest sister has read a lot of books, eldest sister, or I will follow you to learn something when I have time in the future, you still teach me and my second brother more as before." Yan Zhang also saw that the emperor's eldest grandson was going to worship Yan Yan as a teacher, and he also moved this thought.

"Okay." Yan Yan agreed to him.

The main reason is that she also knows that Yan Zhang doesn't have much leisure time when she enters the academy, and the original owner has not instructed Yan Zhang a few times before, so she didn't say anything to refuse.

After the meal, Yan Yan returned to the upper room, only then did he know that everyone had entered the study to watch Master Yun play the piano, and when Li Sui was about to pull Yan Yan to play again, Li Cong left her, and the two went into the next room to talk, and it was quieter over there.

Li Cong still had those design drawings in his hand, he had already asked Lu You, Lu You said that this painting method was taught to him by Yan Yan, and what Li Cong wanted to know was where Yan Yan learned about this painting method, at least he had not seen it.

This question is easy to answer, Yan Yan first mentioned that charcoal should be used to draw when embroidering, and in addition, she now knows that building a house in this time and space also requires architectural drawings, and it is also used to mark the size with a boundary ruler.

As for the calculation formula of the Kong Ming lantern and the kite, Yan Yan also gave an explanation, why some objects can fly to the sky, some cannot, why some things can float in the water but some cannot, there must be some correlation here, and this so-called correlation is nothing more than a kind of force to support or pull, this force should be greater than the weight of the object itself.

Li Cong had a bit of a hard time understanding this, Yan Yan had to give up first, and changed to another example, "Let's put it this way, why can wooden planks of the same size float on the water, but iron cannot, so people will think of using wood to build ships, in the same way, paper kites made of wood and bamboo and Kong Ming lanterns can fly into the sky, and iron blocks must not work." Does this mean that if two things of the same size, the light one can float on the water, but the heavy one cannot. In the same way, things that want to fly into the sky are the same. ”

"Everybody knows that." Li Cong didn't understand what such a simple truth had to do with what Yan Yan said before.

Everyone understands the truth, but no one can say why it is related. Because Chen's brother-in-law said that the paper kite can drive a child if it is done, I was inspired after listening to it, and it is not safe to use children to do experiments after all, so I changed to a stone to calculate, there must be a correlation or law in the middle, but I have not yet found out what this correlation and law is, so I am studying the arithmetic book these days. ”

In this way, these arithmetic books also came in handy, she didn't want to admit that she was learning to read, but she knew that with the emperor's temperament, most of them had already asked Lu You, and Lu You, a layman who had never been taught, how could he understand these esoteric arithmetic books?

In fact, Yan Yan also knew that arithmetic in ancient times was still quite developed, and there were all kinds of Pythagorean theorems and fraction operations, but they were not as simple as Arabic numerals in later generations, but expressed in words.

"You mean you can read these esoteric arithmetic books?" Li Cong was also very surprised to see Yan Yan take the initiative to admit it.

He had already asked Li Ji and the others about those arithmetic books, and they all shook their heads, except for some simple addition, subtraction, multiplication and division calculations, they couldn't understand anything else, and they couldn't even read it.

"To be honest, it was difficult at first, but the more I looked at it, the more I felt that the mystery was endless, and it stimulated my interest, the emperor must also know the allusion of Cao Chong's elephant, I didn't understand the trick at first, and I pondered carefully for several days before I realized that if the weight of the same ship is the same, the power it receives in the water must be the same, so there will be the same scale, in other words, the power of this lifting is related to the weight of the object, but what is the connection? On the other hand, the weight of what the paper kite can drive when it flies into the sky must also be related to the size of the paper kite and the wind or something, but I haven't found out what this correlation is. Yan Yan explained half-truthfully.

These words really blinded Li Cong, and after thinking about it, this is indeed the truth, so he asked Yan Yan again about the progress of Kong Minglan's research.

This Yan Yan is not afraid, this matter is Lu You's credit, so Li Cong called Lu You over again.

After listening to Lu You's explanation, the group followed to the back garden, but fortunately, there was nothing else in the back garden at this time except for a few trees, so Lu You lit two Kong Ming lanterns on the spot, one can be placed very high, and there is more pine oil in it, and the other is planned to fly over the city, which is to drift and rise with the help of some wind.

It's a pity that the weather was sunny and there was no wind at this time, so Yan Yan had to order a few mothers-in-law to take fans and fan them against Kong Ming Lantern for a while, and Yan Yan breathed a sigh of relief when he saw that Kong Ming Lantern was really staggering and shifted by two or three zhang.

The rest of the follow-up explanation was handed over to Lu You, but it was necessary to calculate the height of the Kong Ming lantern, the time it fell, and the required pine oil, etc., which could not be explained in one or two sentences, nor could they be grasped so easily, so Lu You said that it was gradually reduced according to the test results, and he couldn't say what the law was.

But this is enough for Li Cong, he knows that there are many such skilled craftsmen in the Ministry of Industry, and he can hand over the next problems to the Ministry of Industry.

And Li Cong is a person who does what he says, he didn't stay for dinner that day, and after coming out of the back garden, he took Li Ji back to the palace.

And the first thing he did when he returned to the palace was to order someone to call several officials of the Ministry of Industry to the south study.

Because this day is the tenth day of the first lunar month, there are still ten days before the official opening of the official seal, and it has not yet reached the Lantern Festival, the emperor hurriedly summoned so many personnel from the Ministry of Industry into the palace, and people naturally felt that something was wrong.