Han Qian slept until the sun was high in the sky. For the first time since leaving Jinling, his taut nerves completely relaxed. He slept extremely comfortably, waking full of energy and high spirits.
He knew at this hour his father should be handling official business at the front yamen. With nothing urgent, he didn’t want to barge directly into the front yamen. After washing up and eating two meat buns, he performed a set of Stone Duke Boxing, sweat streaming down.
He took a sweat towel from Zhao Ting’er and was wiping away perspiration when he saw Gao Shao leading people to clear out a side chamber on the east side, then confine Madam Xi inside.
That morning they’d also run to the provincial prison to borrow several sets of shackles, using one set to lock Madam Xi’s feet, no longer binding her tightly with ropes.
Gao Shao and the others had all witnessed Madam Xi’s wildcat-like agile movements. Now they only needed to shackle her legs to restrict her movement and prevent her from accessing bladed weapons—her potential threat was significantly reduced.
Madam Xi’s strength ultimately couldn’t compare with masters like Gao Shao and Tian Cheng who diligently trained and conditioned their bodies daily.
Han Qian walked into the side chamber, staring at Madam Xi with considerable interest, pondering what methods to use to discipline her. At that moment, Han Laoshan entered and told Han Qian about changes within Qianyang City during the four days he’d served as hostage in Jingyun Stronghold.
Han Daoxun had already assigned Zhao Kuo to lead the purge of the jailer force.
Those planning to remain in Xuzhou with Han Daoxun, besides the eleven household soldiers and old servants like Han Laoshan, Fan Xicheng, and Zhao Kuo along with their wives and children, also included thirteen household soldier youths who had undergone over half a year of strict training from Han Qian.
At the provincial prison, besides the Prison Warden and clerks, several native-born cell chiefs had all been purged under the name of “dying in the line of duty.”
The remaining fifty-plus jailers included both guest-register Han Chinese and native-register tribal people. However, they could currently confirm these men weren’t controlled by the four families, with family members basically all residing in the city. With Zhao Kuo leading ten household soldier youths integrated into the jailer force, this jailer unit could be almost completely controlled.
Additionally, on the Hibiscus Garden side, Han Laoshan and Fan Xicheng led over ten household soldiers and household soldier youths responsible for basic defense and assisting Han Daoxun in handling official business.
The four families had also sent some offspring back to the provincial garrison, though only a small portion—currently only enough to prevent the provincial garrison from disintegrating, insufficient to pose much threat.
“…Besides Yang Qin bringing people to escort Young Master back to Qianyang and Guo Nu’er guarding the garden with some Left Division scouts, seeing the city situation wasn’t so urgent, yesterday the master ordered Lin Zongjing to lead some people out of Qianyang City to survey the surrounding topographical maps.” Han Laoshan informed Han Qian of the general situation within the city.
Han Qian nodded, indicating he understood everything.
Over seven hundred years ago, during the Western Jin, Pei Xiu had proposed the Six Principles of Cartography, using the six major principles of scale, orientation, distance, elevation, angle, and directness to calculate specific geographical information for mapping into topographical maps.
In Han Qian’s early training of household soldier youths, he’d mainly strengthened counter-reconnaissance, infiltration, and wilderness survival abilities. After the Xinchang Marquis household and Wanhong Tower clearly tasked him with establishing the Secret Bureau’s Left Division, he’d made wilderness topographical mapping a core subject for cultivating scout reconnaissance abilities, requiring all Left Division scouts to use every available moment for study, master it as quickly as possible, and put it into practice.
In Han Qian’s view, so-called enemy intelligence gathering had its most core information largely contained within geographical and topographical intelligence, which would also greatly improve the accuracy of gathered enemy intelligence.
However, this inevitably set extremely high requirements for Left Division scouts. Currently only the early household soldier youths had mastered some rudimentary surveying methods, while newly recruited scouts found it somewhat unbearable.
Although Xuzhou had been a city for six or seven hundred years, the topographical maps currently preserved by the yamen were extremely crude.
For nearly a century of military governorship and regional separatism, the central government’s control over remote prefectures and counties had greatly weakened. Topographical maps were almost never updated anymore—many places had already become unrecognizable.
Therefore, Lin Zongjing leading men out of the city to collect and survey geographical information for Qianyang, Langxi, and Tanyang counties and compile them into atlases both utilized the precious time from the eased situation for rigorous training and laid the foundation for his father to truly grasp Xuzhou’s circumstances in the future.
If Han Daoxun couldn’t even understand Xuzhou’s mountain forests and streams, terrain dangers and gentle slopes, and the distribution of native-register and guest-register civilian households, how could he possibly control Xuzhou’s overall situation?
Thinking that Guo Nu’er and the others had already mastered the traditional Six Principles of Cartography, normal surveying work didn’t require Han Qian to worry much more.
However, Han Qian also knew the traditional Six Principles of Cartography had too many defects—far from being called precise.
Not to mention establishing complete latitude and longitude coordinate systems—even mountain elevations and distances couldn’t be measured accurately.
The problem was that in the dreamscape, the person Zhai Xinping’s mind only held concepts like latitude and longitude. How to determine and measure latitude and longitude left Han Qian completely in the dark.
Han Qian stroked his chin, having forgotten about teasing Madam Xi, standing in the doorway thinking that this era’s research into trigonometry based on the Pythagorean theorem was already quite thorough. Trigonometric function values could be relatively easily calculated, allowing construction of simple angle measurers and altitude measurers.
With angle measurers, theoretically measuring the sun’s altitude differences in different regions, as long as one accepted the concept that the earth was spherical, with this era’s learning one should be able to determine latitude, right?
However, measuring longitude required knowing the precise time difference between two locations—much more difficult.
Han Qian thought for a long time, concluding that before the invention of precise timepieces, one could only establish an accurate time reference system based on the specific positions of stars and moon in the celestial dome. But the orbital trajectories of stars and moon were extremely complex. Even with an astronomical observatory for observation, it might take decades to precisely observe and determine the specific orbital trajectories of stars and moon and use this as a precise time reference.
Han Qian contemplated for a long while, not believing that measuring longitude was something he could accomplish at this time. However, even just determining latitude now could greatly improve the accuracy of this era’s maps.
At this time, Han Qian couldn’t possibly and had absolutely no ability to organize large numbers of people to conduct actual measurements in various places. However, records of gnomon solar measurements existed abundantly in documents preserved from the previous dynasty—these were actually the specific data needed to determine each location’s latitude.
Different regions, as long as located on the same latitude, would have consistent relative shadow lengths at the same time.
The shadowless location of the summer solstice sundial was the Tropic of Cancer—a fact confirmed by astronomical and calendrical masters over a thousand years ago.
The failure to form a complete latitude concept and even extend it to map surveying was mainly due to limitations in this era’s clearer understanding of the earth they inhabited.
“Young Master, what are you thinking about, standing here in a daze for so long?” Zhao Ting’er waited a long time before finally pushing Han Qian’s shoulder and asking.
Han Qian knew the entire project would be extremely complex to advance. Wanting to be lazy, he could only entrust the matter to Zhao Ting’er. He immediately explained all the involved principles to Zhao Ting’er, having her help review materials, collect data, and perform calculations.
Once they calculated the latitudes of different regions and sent people to select several locations for verification, they could formally begin correcting the Great Chu maps.
“The earth beneath our feet extends straight and vast in all directions—how could it possibly be round?” Zhao Ting’er asked puzzledly. She already understood calculations like triangular intercepts thoroughly, but had difficulty accepting the concept that the earth was spherical.
Seeing Zhao Ting’er ask this, Han Qian was slightly stunned. Could he possibly say that people in later generations could fly into space and see the earth was round?
After considering for a while, Han Qian told Zhao Ting’er:
“The Western Han’s Liu An compiled the Huainanzi Astronomical Treatise, which wrote, ‘To know the height of heaven, erect a pole one zhang high, positioned exactly north and south a thousand li apart. On the same day measure their shadows—the northern pole shows two chi, the southern pole shows one chi nine cun, meaning the shadow shortens one cun per thousand li south.’ This ‘one cun shorter per thousand li’ figure also appears identically in the Zhoubi Suanjing, but these were all calculations made by predecessors under the assumption that the earth extended flat. However, the previous dynasty’s calendrical masters Monk Yixing and Nangong Shuo organized people to conduct actual field measurements, confirming that the ‘one cun shorter per thousand li’ theoretical conclusion had extremely large errors. Specific measured data can also be found—many people find it incomprehensible. Find Monk Yixing’s measured data, then reverse-calculate using the algorithms recorded in the Zhoubi Suanjing or Huainanzi, and see if they only match under the assumption that the earth is spherical?”
“Qing Yun, Qing Yun!” Zhao Ting’er saw Qing Yun passing through the courtyard outside and quickly called to her, wanting her to go together to the study to search for actual sundial measurement data. Zhao Ting’er thought that when household master Han Daoxun traveled to Xuzhou for this assignment, what he carried most was various books he’d collected over the years—she should be able to find some actual sundial measurement data.
However, just as Zhao Ting’er was about to pull Qing Yun to run out, she saw Han Daoxun returning from outside accompanied by Fan Xicheng. She stuck out her tongue, curtsied, and retreated behind Han Qian.
Han Daoxun glanced at Madam Xi confined in the room without asking further questions. He smiled and asked the two maids Zhao Ting’er and Qing Yun, “You two little girls—what are you running around so recklessly for?”
“Young Master insists the earth is round. Ting’er wants to pull Qing Yun to the study to search for different sundial measurement data from various locations to prove Young Master is just bluffing Ting’er,” Zhao Ting’er said.
Han Daoxun carefully considered the calculation method Han Qian had told Zhao Ting’er and said, “This matter’s calculations are extremely complex. Don’t rush to do them now—keep them in mind and discuss after returning to Jinling. This angle measurer you mentioned—it would be best if you could manufacture one to leave behind before departing Xuzhou!”
Manufacturing an angle measurer for land use wasn’t particularly complex, but ensuring the instrument’s scale precision couldn’t be completely left to craftsmen below. Han Daoxun still hoped Han Qian could personally supervise the construction.
Hearing a clattering sound behind him, Han Qian glanced back at Madam Xi standing stubbornly in the corner—she’d shifted her body slightly, moving the shackle chains. Seeing her eyes full of confusion, as if pondering what he’d just said to Zhao Ting’er, he smiled inwardly. In this era, besides his father, truly few people could understand this conversation between him and Zhao Ting’er.
Fan Xicheng was completely bewildered listening.
“Does Madam Xi perhaps feel my father making an angle measurer is frivolous cunning arts, hence your face full of contempt?” Han Qian said with a smile. “Once the angle measurer is made, it can measure the specific height of a mountain peak. After measuring a mountain peak’s height, conversely one can calculate the relative elevations and differences in terrain around the mountain—this is also an essential means for excavating river channels, building water conservancy, and irrigating farmland in Xuzhou’s mountainous lands. Madam Xi, do you still wholeheartedly believe my father and I are merely extraction tyrants?”
“Madam Xi?” Han Daoxun looked questioningly at the beautiful female prisoner and asked Han Qian.
“She’s Feng Changyu’s concubine. Her brother impersonated Feng Xuan’s subordinate to monitor our movements all along the way and was killed by me. When I was in Jingyun Stronghold, she came to assassinate me. Feng Changyu ultimately handed her over for my disposal,” Han Qian said.
“Her crime is pitiable. Don’t create excessive killing karma either,” Han Daoxun said, hoping Han Qian’s murderous intent wouldn’t grow too heavy.
“She knows too many secrets. If I truly let her go, Feng Changyu won’t spare her either,” Han Qian said. “But if she can behave herself and not cause trouble, I could let her move about this courtyard wearing shackles, helping Ting’er with some tasks.”
Having said this, Han Qian looked toward Madam Xi.
Now no one wanted the fragile balance between Qianyang City and the four families broken—the four families themselves absolutely didn’t want it either. Han Qian thought that if he truly released Madam Xi, even if Feng Changyu didn’t kill her, he’d imprison her.
From the moment Feng Changyu abandoned her, Xi Ren knew Han Qian spoke truly. Regardless, even if for future convenience in escaping or continuing to find opportunities to assassinate this dog thief Han Qian, obtaining a certain degree of freedom now was extremely important. She lowered her head, showing submission before Han Qian for the first time.
Allowing a captured assassin to move about one’s living quarters, even wearing shackles, seemed too perilous to Fan Xicheng. But seeing the household master glance at the female assassin without appearing to object, he didn’t voice any opinion.