Zhang Dajiang and several officials, including the Commander, Cheng, and several officials from the Si Nong Division who were in charge of Han Jiacang, accompanied Wu Yanzhi, and planned to check the maintenance of the northern city wall first.

Access is strict! The guards guarding the gate carefully examined their fish charms and vouchers, and searched them to see if they were carrying ignition tools before letting them into the city.

Entering the city, Wu Yanzhi looked around and saw that the granaries where the grain was stored were all underground, and only circular mounds less than 50 centimeters high could be seen from the ground.

The diameter of the mound varies, the largest is about eleven or twelve meters, and the smallest is only five or six meters, and there are many small trees planted on the mound.

Although I knew that this granary was underground, but now that I see it with my own eyes, I still think it is very strange, why is the size of this granary still different? He couldn't figure it out!

"Wu Lang, let's go see the city wall first!" Zhang Dajiang said.

As you keep going, you will soon come to the site where the construction of the northern wall will be.

"Takerou! This northern city wall collapsed in early April, a section six feet long and about five feet wide. The maintenance construction has been carried out for a month and a half, and it is estimated that it will be completed by the end of this month! Zhang Dajiang introduced.

Wu Yan looked at it, and the city wall was still more than a meter away from completion.

This wall is made of rammed earth, not stone, otherwise the cost is too high, where can you afford it!

After looking at the city wall, Wu Yanzhi came to a large granary under repair in the east! I saw that the diameter of this granary is about 10 meters, the depth is about 9 meters, and the bottom is about six meters. The mouth is large and the bottom is small, and it is round cylinder-shaped.

He asked, "Zhang Gong?" Why are these granaries different in size? ”

"This granary must be surrounded by an earthen structure, and if you dig up a large rock, it must be covered with soil, and the silo will naturally be reduced.

It seems that Wu Lang doesn't know much about the structure of the granary, so I'll tell Wu Lang about it, after the wall of this granary is dug up, it will be dried with fire.

Then spread the ashes of the plants and trees on the bottom of the barn, and then spread the wooden planks on it, and spread the mats on the wooden planks, and then spread the mats after the chaff was laid on the mats;

The wall of the warehouse is also surrounded by two layers of mats and a layer of chaff, and then the warehouse can be filled with grain, and the place one foot from the ground is also covered with the method of "mat chaff", and then the soil is sealed, which is considered to be completed.

Wu Yanyi listened, I see! Not only can the stone not be dried, but the nearby rain may also seep into the granary along the cracks between the stone and the soil.

After the soil is tamped, it is baked with firewood, and after it is baked, it will be as strong as red bricks. Even the earthen walls are to be burned with fire to make them hard and waterproof.

Of course, when selecting a site, it is necessary to dig a well to see the water level of the groundwater, and the groundwater level must be very low, otherwise it will be impossible to store grain.

"Then why are there small trees planted on top of this granary?" Wu Yanzhi asked.

"It's actually a means of monitoring: if the grain heats up and sprouts, the trees will turn yellow. We'll take care of it! An official from Sinong Temple next to him replied.

"How long can the grain in this granary be stored without spoiling?" Wu Yanzhi asked again.

"This is not necessarily, a dry granary, can be managed for nine or ten years, there is no problem. The next granary can be stored for five or six years, and the worst granary can be stored for three years! Most of the granaries in this can be managed for more than six years without any problem! The officer replied.

"Where did you get all the food here?" Wu Yanzhi was very interested in this granary, which was located underground, and could be fireproof and anti-theft.

The big granary of his later generations often had fires that burned the grain!

The granary of the Tang Dynasty was set up underground, but it avoided these possible dangers, even if it was impossible to artificially burn it, or destroy the evidence of corruption in the empty warehouse.

The ancients were indeed smarter than we think.

"The grain here comes from Jiangnan, Hebei and other places, and almost all states with surplus grain have grain transported here!" The granary official said.

Wu Yanzhi looked down and saw that the workers below were digging and repairing! They all use a wooden reel placed on the ground and hang a rope to lift the material.

Suddenly, he became interested in the wheel, and couldn't help but walk over.

"Bad wheel! Isn't that what you learned about in junior high school physics books? I didn't expect to see the real thing now! He looked at this wheel and couldn't help but be surprised.

The structure of this differential wheel is that on the same axis, there are two rollers, one large and one small! The rope is wrapped in the opposite direction.

Turn to the right, tighten the rope of the large roller and lower the rope of the small roller. Since the two rollers are of different diameters, the object will definitely be lifted up, and vice versa.

This kind of thing is similar to the principle of "chain hoist" in later generations, which uses the principle of pulley block and lever to achieve the purpose of saving effort.

This wheel has a long handle as a bar, and the chain hoist does not have such a long handle, and at the same time uses the large wheel as a lever to drive the small wheel.

Of course, this fixed wheel is not flexible enough, and it is far from being able to compare with the "chain hoist" that can be used anytime and anywhere.

However, this reflects how high the wisdom of our ancestors was.

"What's this wheel called? Seems to work well," he asked.

"Haven't you seen it before? This wheel is called the fairy wheel, and he can improve thousands of catties of things! Of course, this wheel is too small, and it can only lift a thousand catties at most! Zhang Dajiang introduced.

It is not easy for a wooden wheel to lift such a heavy thing! Wu Yanzhi thought.

However, as a general supervisor, this thing alone is not enough, and I have to find a way to make that "chain hoist" in the future.

It's a treasure, and its engineering usefulness is indescribable.

After reading it, the official of Sinong Temple, who was in charge of taking care of the granary, said: "Wu Langzhong, please give me more opinions on the management of the granary!" ”

"Your management here is already very good, and this underground granary can be fireproof, bird-proof, and anti-theft! The only inconvenience is to leave the warehouse.

This granary is located underground, and it is very convenient to load grain into it, but it is very troublesome to transport it out! It will definitely cost a lot of manpower and material resources! "The Way of Martial Arts.

"That's true! Every time I leave the warehouse, hundreds of people have to be busy for more than ten days, and I can't transfer all the grain from a warehouse out of the warehouse! I don't know if there is a solution in Wulang? ”

Wu Yanzhi smiled slightly and said, "Of course there is a solution!" In fact, there are three ways to solve it, one of which is to add a ramp to each warehouse to facilitate the exit! But it doesn't seem to work! Your warehouse is already arranged, and most of the warehouses are impossible to add ramps.

The second is to renovate the granary, and build a special roadway from the ground to connect all the granaries. A funnel for discharging grain is set under the bottom of each silo.

This should have been taken into account when it was originally designed, and now it is very troublesome and not very economical to renovate.

This method requires relatively high-precision measurement techniques to grasp the position and bottom height of each grain silo.

However, your positions are of different depths, and it is actually difficult to deal with them in this way, unless all the positions are changed to the bottom close to the same level.

Third, it is to use a machine to come out of the warehouse from above, of course, this machine is very troublesome, not a day's work.

Only I can find manufacturing, you haven't seen it, the machine is very convenient to use! ”