Luoyang Palace, Yuwen Wen, who had handled government affairs, was idle and was able to fiddle with a device in the study. The device was square, just like the size of an ordinary dressing box, with several small windows on the front, a row of knobs, and a shaking handle on the side.

Not long ago, Yuwen Wen returned from a northern tour and did not return to Chang'an. Instead, he went east to Tongguan and Luoyang, preparing to stay here with his family until next spring when the flowers bloomed.

The Luoyang Imperial Palace cannot always be empty, and Yuwen Wen does not have too many palaces, so he has to rotate in Chang'an and Luoyang every once in a while to adjust his mood and save expenses.

When he walked between the two capitals, not only his family members followed, but also civil and military officials also had to follow him. This would in itself cause a lot of expenses, but compared with the huge transportation costs of Kanto materials imported into Guanzhong, this was nothing.

Although now there are steamships and water and land transfers to avoid the dangers of the pillars, the "logistics cost" of transporting massive materials in the west is still not small, and this is the reality.

When Yuwen Wen brought civil and military officials to temporarily live in Luoyang, the massive amount of materials collected from Guandong only needed to be transported to Luoyang, saving a lot of transportation costs. Therefore, he lived in Luoyang from time to time, which was a way to save money.

Of course, this is different from the history of the Tang Dynasty emperors who had to bring civil and military officials to Luoyang to "just eat" due to the overload of the population in Guanzhong.

Yuwen Wen was concentrating on operating the device, like a child playing with a baby toy, and couldn't let go of it. Xiao Jiuniang and Yuchi Mingyue, who were helping to organize books, felt strange when they saw this.

They felt that most of the devices Yuwen Wen had fiddled with were strange and seemed to have never been used before, so they didn't know what the meaning was.

However, the device Yuwen Wen holds in his hand now has a great background, called the "hand-cranked mechanical addition and subtraction calculator", which can perform addition and subtraction calculations, and the user needs to shake the handle during calculation.

At this moment, Yuwen Wen shook the handle from time to time, and numbers kept appearing in the small window on the front of the box.

These numbers are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 in "Xiyang Mathematics". Yuchi Mingyue looked around and found that this calculator was indeed of practical value.

If, when the calculation of large-scale accumulation and subtraction is frequently performed, using this calculator to calculate is less labor-saving than using abacus to calculate the numbers.

Because of accumulation and subtraction, it is actually repeated calculations, and the calculation rules remain unchanged, as if they are shattering iron, just keep forging.

Since forging iron tools can replace human power with machinery, if the accumulation and decrement are used, people do not need to repeatedly dial abacus beads.

Yuwen Wen agrees with Yuchi Mingyue's view: "Yes, tax collectors need to do a lot of complicated but repeated accumulation or deduction when collecting taxes. Although it is okay to use calculation sheets and abacus, but with a calculator, efficiency can be improved."

"The abacus is very refreshing, but the calculation volume of complex and repeated addition and subtraction calculations will still make people tired. With the addition and subtraction calculator, which replaces the finger dialing the abacus, the calculation speed will increase."

"Of course, the application of this kind of calculator is currently mainly tax calculations. Most other industries are currently sufficient for abacus."

Xiao Jiuniang was very interested in this magical calculator. When asked about the mystery, Yuwen Wen asked the two to sit beside him and began to "popularize science": "The operating principle of this calculator is actually similar to a clock, and it is realized by rotating gears."

"A ten-tooth gear represents ten numbers. The gear rotates one circle and pulls another gear into one, which is decimal."

"The first gear represents the single position, the second gear represents the ten position, the third gear represents the hundred position, and so on."

Hearing this, Xiao Jiuniang asked: "But when the gears turn, how can you turn one round and move another gear?"

"The reason is very simple, but not simple." Yuwen Wen picked up his pen and drew it on the paper. "At the beginning, no one could think of how to achieve this rotation and carry. Later, look at this gear."

On the paper, Yuwen Wen drew a ten-tooth gear. This gear has a slightly longer tooth. After rotating for a circle, the protruding long teeth just twitched the adjacent gear.

This means "to join one", Xiao Jiuniang and Yuchi Mingyue suddenly realized after seeing it.

Yuwen Wen continued: "Forward rotation and accumulation, inversion accumulation and reduction, the structure is so simple, and there is another combination, that is, coaxial single teeth, the principle is the same, of course, it will be more complicated in practical application."

"Now, the speed measuring instruments used for rotary processing machinery such as lathes, boring machines, paddle wheels, etc. rely on this principle to count. Of course, calculating the odometer of the mileage is also achieved by recording the number of rotations of the wheels."

"Similarly, the anemometer and various flowmeters are also this structure."

Seeing Yuchi Mingyue raise his hand, Yuwen Wen asked: "What are the questions Mingyue has?"

"If this calculator is calculated..." Yuchi Mingyue took a pen and wrote a number on the paper, "If you calculate 99999+1, then you have to turn......................................................................................................................................................................................................................................

"Will these gears be shaken by excessive force?"

Yuchi Mingyue has been in charge of the accounting for so many years and often performs large numbers calculations, so she is very sensitive to this kind of calculation.

Yuwen Wen was stunned when he heard this, looked at Yuchi Mingyue, and nodded in praise: "Mingyue is right. This is the problem that calculator will encounter when actually using it. If you rely solely on cumulative carry and calculate large numbers, it will be difficult to shake. If the action is too big, the gear set may collapse."

"So, a special 'escaper' is needed to 'escape' gears of various digits as needed, and temporarily form a simple gear set for carrying, which saves effort and protects the gears."

"The principle of this escapement is a bit complicated and cannot be drawn by your husband. But if you look at the structure, you will find that the structure of this escapement is not much more complicated, but..."

"This seemingly simple structure has been realized by a watchmaker for more than 20 years. Using this escapement will cause the gear set to be unable to be reversed, that is, it can only be added or subtracted. One problem is solved, but it will cause new problems."

"In this regard, many craftsmen's solution is to design more clever devices to switch the rotation direction of the gear set, but it causes more new problems."

"The more complex the structure of engineering design, the greater the chance of error, but the simpler the structure, the greater the difficulty of design."

"The craftsmen racked their brains to solve this problem. Later, a computing-based astronomer solved it cleverly. Guess what he came up with?"

Yuchi Mingyue and Xiao Jiuniang only knew about the addition and subtraction calculator today, so how could they know how the astronomer solved the problem?

But Xiao Jiuniang roughly guessed a clue from the four words "being good at computing": "Could it be that it is changing the calculation rules?"

"That's right." Yuwen Wen nodded, expressing his admiration for Xiao Jiuniang's quick thinking. "It is not a significant addition of a new structure, but a calculation rule has been added. The principle is simple, but it is very troublesome to explain. I won't say much about it."

"The hard work of countless people, more than 20 years, has led to the release of this addition and subtraction calculator today, which is really hard to come by."

Yuwen Wen rubbed the addition and subtraction calculator, as if he was rubbing a treasure, sighing:

"Although there is only an addition and subtraction calculator at present, and it is still far from realizing addition, subtraction, multiplication and division. However, the rotating gear set connects craftsmen who are proficient in mechanical structures and scholars who are proficient in theoretical calculations. Such a combination is infinite."

"The rotating bamboo dragonflies can fly, the rotating water wheel and the windmill can lift water, push the stone mill, push the rotating transmission shaft can drive the machine, and the rotating paddle wheel can drive the ship forward."

"Spinning can achieve many incredible things. The charm of rotation is really unstoppable, Biru......"

Yuwen Wen put out a model, Xiao Jiuniang and Yuchi Mingyue looked at it, and found that it was the "ship propeller propeller" that his husband often advocated.
Chapter completed!