In the long history of global civilization.

Water source.

Is a keyword that no civilization can do without.

The waterwheel and water hammer in Huaxia, and the Archimedean screw pump in the West, are tools created by ancient people for water supply.

But all of these tools, without exception, are huge in size, and most of them need to work at the water source.

And their main use is actually mostly to transport water from low to high places.

Throughout the entire ancient world history, almost no civilization could achieve flat land water transport without relying on gravity.

Whether it's the Roman aqueduct system, which shocked the world, or the Tang Dynasty's water facilities in Chang'an, they are unrelated to flatland water transportation.

For instance, the Roman water supply system was composed of the old Anio aqueduct, the new Anio aqueduct, the Marcia aqueduct, the Tepula aqueduct, the Julia aqueduct, the Virgo aqueduct, the Antonine aqueduct, and so on.

The core technology of these aqueducts was the siphon or communicating vessel principle, meaning there had to be a height difference or liquid pressure.

This is also why the water brought into Rome was first supplied to fountains, because you couldn't clog it...

So Rome's water resources were indeed rich, but this referred to the fountains and taps everywhere on the streets, which were public facilities.

Residents could easily carry a bucket to fetch water, making it naturally very convenient.

But indoor and outdoor water supply were clearly two different matters.

Except for Emperor Augustus, who danced on the top of Palatino Hill, not many people could comfortably use water at home in Rome.

The Tang Dynasty was no different; the so-called convenience ended outside the door.

So Xu Yun was previously very puzzled about how Old Su could use water from the well over at the main house.

Clearly, both the siphon and communicating vessel principles had an unexplained bug:

That was the insufficient volume of injected water.

A water pipe over a hundred meters long and nearly thirty centimeters in diameter could only be filled to one fifteenth with twenty buckets of water.

Additionally, there was a very critical issue, and that was labor cost.

In this era, the cost of a servant carrying a bucket a hundred meters back and forth ten times was not high.

Therefore, the solution Old Su chose must have been low cost, meaning with the mindset of "saving the servants some trouble with little cost," something was devised; otherwise, it would be better to give a little extra silver as a subsidy.

And now, following Zhang San's words, Xu Yun's doubts were finally resolved:

Good heavens, Old Su actually came up with a self-priming pump!

A self-priming pump is a self-suction centrifugal pump.

The so-called self-priming means that without adding water, it can automatically draw water up.

It is essentially like sitting down and moving by itself.

Its working principle is to first fill the pump casing with water before starting the pump. Once started, the impeller rotates at high speed, causing the water in the impeller channel to flow towards the volute.

At this point, a vacuum is formed at the inlet, causing the intake check valve to open, allowing air in the suction pipe to enter the pump and reach the outer edge via the impeller channel.

This kind of pump does not need a foot valve because the self-priming pump's inlet usually has a built-in check valve, which we commonly call a one-way valve.

Therefore, after the pump stops, the liquid within the pump body cannot return to the original pool and is stored within the pump body, so there is no need to refill it with liquid the next time it is used.

Very simple principle, also easy to understand.

As for the appearance of the self-priming pump, imagine the air cannon from Doraemon:

Enlarge the air cannon about 1.5 times and position a brick randomly at one end, then it's about the same as a self-priming pump.

"That's not right..."

Thinking about this, Xu Yun suddenly furrowed his brows and asked Zhang San:

"Third Brother, how fast is that donkey turning the millstone?"

"Huh?"

Zhang San subconsciously responded, unsure of what Xu Yun meant:

"It's just an ordinary donkey grinding, probably slower than usual walking?"

Upon hearing this, Xu Yun's expression grew even more confused.

There are many types of self-priming pumps on home ground, but the ones currently used are mostly powered by electricity or high water pressure.

In addition to these, hand-cranking, foot-pedaling, or even water hammers could drive a self-priming pump.

But regardless of which mode is used above, a specific instantaneous power is required.

Theoretically, the work done by a donkey grinding grain is enough, but the duration is somewhat long.

In terms of unit time—say, within one or two seconds—the power from grinding doesn't seem sufficient to turn the impeller.

Contemplating to this point, a hypothesis emerged in Xu Yun's mind:

The working principle of that self-priming pump might not be as simple as just the impeller pumping water...

The prescribed breakfast time for servants at the Su Mansion was from five forty-five to seven-thirty in the morning.

Each servant was allotted fifteen minutes to eat.

After breakfast.

The 'Qing' and 'Dai' grade servants could rest for another fifteen minutes, then they had to perform laborious tasks like chopping wood, running errands, and delivering goods.

For example, poor Zhang San was assigned by Old Chief Steward to fetch goods from a silk shop.

'Li' level and above servants could rest for two quarters of an hour, and their subsequent tasks were relatively light.

Such as accompanying the mansion's young masters to play in the courtyard or go out, or following the master to visit other houses, or even pruning plants, etc.

However, although Xu Yun currently had the treatment of 'Qing' grade, he wasn't assigned any tasks.

Whether it was considering that he was not strong (being a male actor) or his lack of registration status, Old Chief Steward's attitude seemed somewhat vague.

In his words, he simply instructed him to quickly recover and just fetch some water during the day.

The rest were cryptic instructions like 'do not sit for long' and 'try to lie on your side.'

Of course.

The necessary surveillance wasn't relaxed.

Then, accompanied by several servants heading to chop wood, Xu Yun once again returned to his little courtyard.

Cre-eak cre-eak—

Just as he entered the courtyard.

Xu Yun saw a black donkey with its eyes covered, slowly pulling a millstone.

The area beneath the millstone was simply modified. As the millstone turned, a thick rope was being pulled continuously from a corner of the wall and wound around the stone support below the millstone.

Xu Yun thought for a moment upon seeing this, glanced at the servants accompanying him, then turned towards the corner of the wall, the bells on his feet jingling.

The servants did not stop him but instead busied themselves with preparing tools for work.

After all, this courtyard wall was nearly a zhang high, and next door was the mansion's inner courtyard.

Unless Xu Yun could perform the wall-passing technique, he had no possibility of escaping under everyone's watchful eyes.

Upon reaching the wall corner, Xu Yun spotted a device about the size of a domestic computer host.

The rope he saw on the millstone earlier was being slowly pulled from one side of this device.

Besides this.

The device kept making a clicking sound.

This sound wasn't unfamiliar to Xu Yun,

It seemed like...

"A balance wheel hairspring?"

...

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