The length units used by modern people are millimeters, centimeters, decimeters, meters, miles, kilometers (kilometers), and the length units used by ancient people are millimeters, centimeters, minutes, inches, rulers, zhangs, citations, and miles.

There is not much superiority or inferiority between the two sets of length units, it is mainly a matter of habit, as long as you get used to one set of length units, you will not have much feeling about the other set of length units.

When choosing two sets of length units, Su Yan did not hesitate to cross out the former, leaving only the latter.

The copper ruler that is about to be made is about 60 centimeters long, and Su Yan set its length to two feet.

At the end of the first day, the construction of three brick kilns was completed.

At the end of the second day, the construction of an earthen blast furnace was completed, and three brick kilns fired a kiln of black charcoal.

On the third day, the smelting of copper ore begins.

Under the command of Su Yan, a basket of black charcoal was poured into the earth blast furnace, and finally two hundred catties of copper ore were poured in, cauterized, and there were three clansmen at the air inlet of the earth blast furnace to fan the wind in the earth blast furnace, and more air was fanned into the earth blast furnace, so that the black carbon in the earth blast furnace was fully burned, the combustion temperature was increased, and finally the copper in the copper ore was melted.

The waiting time was the longest, and through the openings around the earthen blast furnace, Su Yan could see that the inside of the furnace was red, and even the temperature around the earthen blast furnace was rising.

Finally, the copper melted, and drops of copper juice flowed towards the copper outlet at the bottom of the earthen blast furnace, only to see drops of fiery red copper juice burst into the air, and finally fell into the large thick-walled pottery bowl below the copper outlet, and finally converged into a pool at the bottom of the pottery bowl.

The fiery copper juice accumulated more and more, and seeing that the copper juice was almost collected, Su Yan shouted to Jian beside him: "Jian, do it." ”

Immediately, according to Su Yan's instructions, he stepped forward with several layers of thick linen cloth in both hands holding a large thick-walled pottery bowl, and directly held the pottery bowl with both hands and placed it under the copper outlet.

At the same time, Su Yan, whose hands were also covered with several layers of thick linen, quickly took away the pottery bowl containing the fiery red copper juice, and at the right time, Jian put down the pottery bowl he was holding in his hand, and then let go of his hand.

Su Yan took a few steps to the left with a pottery bowl filled with fiery copper juice, and a clay mold was placed horizontally on the ground.

Su Yan smoothly walked to the side of the casting mold with the pottery bowl, squatted down slightly, Su Yan aimed the pottery bowl at the casting mold, the pottery bowl was tilted, and the fiery red copper juice in the pottery bowl poured onto the casting mold, and finally the copper juice flowed in the rectangular space on the casting mold.

Su Yan took the pottery bowl and moved along the cuboid space, and soon, the cuboid space was filled with copper juice, and there was not much copper juice left in the pottery bowl.

In order to cast this copper ruler, Su Yan was afraid that he would have to use two catties of coarse copper.

Time passed slowly, the copper juice in the casting mold was cooling and solidifying, and the copper juice falling from the copper outlet of the soil blast furnace was also slowly decreasing, and finally disappeared completely.

Su Yan estimated that this furnace of 200 catties of copper ore produced nearly five catties of blister copper, maybe there is still copper in the slag that has not come out, but now it is enough, there is no need to waste time on this.

About five catties of blister copper are produced, two catties are used to cast copper rulers, and the rest of the blister copper is collected and will be used in the future.

The first time the earth blast furnace smelted copper ore, Su Yan did not find any problems, maybe the smelting times can only find the problem, of course, there may have been problems, but Su Yan did not find it.

Judging from the current situation, the earth blast furnace can only smelt one furnace of copper ore a day, and the copper ore smelted by a furnace can increase a little, about dozens of catties, according to the grade of copper ore, this earth blast furnace can only produce about five catties of blister copper a day, very little.

The copper mining area can mine 8,000 catties of copper ore in two days, and the smelting area only consumes more than 200 catties of copper ore a day, this gap is too big, if the copper ore produced every day can be consumed, the dragon tribe can produce about 100 catties of blister copper a day, and even 10,000 catties of blister copper a year, but limited by the smelting capacity of the earth blast furnace, the goal of 10,000 catties of blister copper is impossible to achieve in a short time.

There are too many copper ores mined every day to be consumed, Su Yan has no intention of reducing the manpower in the copper mining area, and the copper ore mined will be put there if it cannot be consumed, and one day they will be able to smelt them all.

Next, Su Yan plans to use this first earth blast furnace to smelt copper ore twice, if there is no big problem, then build several more earth blast furnaces of the same specification, and in the future, Su Yan will also design a higher and larger earth blast furnace, which can smelt more copper ore and produce more blister copper at a time, but before building a higher and larger earth blast furnace, Su Yan wants to solve the problem of air intake in the earth blast furnace first.

The temperature of the copper ruler had completely cooled down, and Su Yan picked up the copper ruler that was flat on three sides and slightly uneven on the other, feeling a little heavy.

After careful inspection, the surface of the copper ruler is mainly black, mixed with red and purple, and after the copper ruler is carefully polished, most of the black will be removed, revealing the purple red color of the copper.

It's only afternoon now, there is still an hour and a half before it gets dark, tomorrow the earth blast furnace will continue to open the furnace to smelt copper, you can't waste copper juice like today and wait for the copper juice to cool and solidify by itself, you should cast all the copper juice into tools, Su Yan is going to make a few casting molds with clay in the time before it gets dark and wait for tomorrow to be used.

As for the goal of casting the mold, Su Yan chose three kinds of axes, saws, and nails, and after these three tools were cast, he could try to make bellows or water drains.

The casting mold of the axe and nail is good to say, the casting mold of the saw is the most troublesome, especially the saw's sawtooth, which needs to be carefully made, and wait until the copper juice is poured to form at one time.

Five catties of coarse copper can probably cast two axes and two saws plus some nails, and Su Yan makes casting molds according to this amount.

The tribesmen mainly excavated the clay and piled the clay into several cuboids, and in the end, Su Yan had to work hard and cut out the space for axes, saws, and nails in the cuboids.

It wasn't until the sun was about to go down that Su Yan finished making these casting molds, and waited until tomorrow to cast the axes, saws, and nails, and then it would be simple to make the casting molds in the future.

Although he was a little tired, Su Yan was still very happy, the first furnace of copper had been smelted, and in the future, the Dragon Tribe would only smelt more copper, and with more copper, he could use copper to cast weapons, farm tools, and tools in large quantities.