Translator: DragonRider

Meanwhile, an arrow shot over from the other side .

Sticking right in the ground at Cao Poyan's feet . Zhang Xiaojing leaped into the courtyard, and then quickly rolled to an open area thirty steps away from Cao Poyan . Early Shen, Jan . 14, the third year of Tianbao period (744 DC) .

Guangde Fang, Chang'an County, Chang'an .

Xu Bin leafed through records, his fingers running through the rough edges of the paper, and lines of ink writing jumped into his eyes .

Sicheng Li's angry words “check out everything that can be lit” inspired Xu Bin: oil was not the only fuel to cause a fire .

There were at least hundreds of kinds of supplies brought into Chang'an every day, and many of them could be set on fire . Following the direction, Xu Bin brought recent customs date and checked the cla.s.sification list to see if there were suspicious bulk flammable goods .

A long time pa.s.sed, he found nothing .

Not that there were no flammable goods or few block trade, but Xu Bin mulled them over and found these were impractical: firewood took up too much s.p.a.ce; gra.s.s paper was flammable but easy to be out; bamboo was difficult to transport; the cost of candle, cloth, silk and hemp was too high . Setting fire with these fuels was a piece of cake, but burning the entire Chang'an in a short time was a too difficult thing .

In the physical simulation before, Jing'an Department found that oil, and only oil, was the best fuel to rapidly cause large-scale fires . It was easy to undercover transport, flowable, flammable, and had strong power . If the Turks intended to burn Chang'an tonight, oil was their only option .

Advertis.e.m.e.ntThis was an earlier conclusion of Jing'an Department .

Frustrated, Xu Bin pushed the files away and rubbed his sore eyes, feeling himself was sheer crazy for promotion . He was about to call the servant to take the files away, while his raised elbow knocked the ink stone off the desk, and it smashed into pieces . The ink splashed everywhere .

Xu Bin stared at the ground, suddenly clapping his head and seizing the servant's arm . He rattled off a series of numbers and asked the servant to quickly retrieve the corresponding file . Xu Bin kneeled down; instead of picking up the ink stone, he fingered the ink on the floor, and soon his fingertips were black . Xu Bin's lips couldn't help turning up, and his eyes lit up .

The files in Jing'an Department were put orderly, easy to access . Shortly afterwards, the servant brought the scroll he need . Without untying the book belt, he tore the scroll open and scanned it . Soon he was delighted to find what he wanted, then surprised, to later his face became grim .

He hurried out of his seat to the sand table with scroll in his hand . Li Bi still stood frowning at the sand table, constantly s.h.i.+fting the fly-whisk from the left hand to the right hand, then reverse .

Xu Bin bowed, “Sicheng Li . ” Li Bi said without lifting his head, “What's wrong?”

“Your humble servant probably has…eh…guessed what the Turks are up to . ” Xu Bin said less than confident, but did not reduce the excitement in his tone .

It finally hit Li Bi, and he turned to Xu Bin, “Go ahead!”

*

From a distance came the dub-dub of drums, then the same rhythm sounded in turn from watchtowers, gradually getting closer . The distinctive sound, which was deep and clear, spread very far . These drums were made of lizard skin specially imported from Persia for Jing'an Department to transfer message, impossible to be confused with sounds of Jie drums, street drums, and Deng Wen drums and etc .

As if feeling something, Zhang Xiaojing's single eye flew open . News came in with long drumming, which was unusual .

Cui Qi and the Lubi Army were now spreading out searching, and only Yao Ru'neng was left by Zhang Xiaojing's side . Hearing the drums, he, as a translator, rose quickly focusing on the sounds .

The message this time being unusually long, Yao Ru'neng had to write it on the ground with his feet while listening . Fortunately, each message was repeated three times so as not to miss anything .

The messages from watchtowers in Chang'an had two forms: one was fixed sound . For example, three rapid and one slow drumbeats represented “reinforcements are on the way”, five rapid and two slow drumbeats were “standby”, and so on; another was the rhyme, which was based on “Tang Yun” (rhyme) written by Sun Mian after the 20th year of Kaiyuan period, and was compiled according to the volumes, rhymes, and characters . Such as 2066, which stood for the sixth character of the sixteenth rhyme in volume 2, was the word “Tian” in “Tang Yun” .

The fixed form was the fastest, but its content was limited; rhyme could transfer a little complicated message; the delivering of more complicated message had to depend on Delivery Riders .

A moment later, a melodious horn sound came from the watchtower, indicating that the message was over . The yellow ground was already full of numbers . Yao Ru'neng took a brochure of “Tang Yun” out of his waist and quickly translated the numbers into text:

“Today, there were Yanzhou stone greases being declared into Chang'an as ink materials, and then disappeared . ”

Glancing at the text, Zhang Xiaojing's face changed . Yao Ru'neng was a little puzzled, immediately asked him what happened, what the stone grease was .

Zhang Xiaojing said, “I saw a kind of water when I was a soldier in the Northwest . It flows out of the crevices, covered with a layer of black oil, sticky like fat grease, so it is called stone grease . The locals collect the floating greases with gra.s.s dustpan and use them for lighting, which was extremely bright . ”

Yao Ru'neng was surprised, “It can be lit?”

“The stone grease is non-flammable, and must be refined through secret method, and then ignite it with lard or castor oil . Once catching fire, it will never die out . When we defended the city gate in the western regions, pouring a can of stone grease could kill dozens of lives . If the greases stick the fire to your body, whatever you do cannot shake it off, or put it down . I've never seen more ferocious fuel . So, it's called “Ghost Fire” in the army,” explained Zhang Xiaojing .

Even persevering as Zhang Xiaojing would be moved, that could indicate how miserable the scene was on that day . Yao Ru'neng gasped, immediately turning pale, “Have the Turks already brought such dangerous things into Chang'an?” Zhang Xiaojing nodded heavily .

If there were a large amount of stone greases, burning Chang'an overnight was entirely possible . It was probably the “Que Le Huo Duo” that the Turks talked about .

“How could city guards allow such dangerous goods free in?” Yao Ru'neng shouted .

Zhang Xiaojing said, “The stone grease is only native to Jiuquan, Yumen and Yanzhou, etc . , and is known only to the natives and garrison . People in Guanzhong area, such as you, may not even have heard the name . Moreover, the Turks used a trick to import them… . ” He pointed at the words “ink materials” .

“Ink materials?” Yao Ru'neng was puzzled .

“The black flue from the burning stone grease is heavy . In local Yanzhou, the remaining smoke mosses are used to make Yan ink, which is very famous . ”

Knowing doc.u.ments very well, Yao Ru'neng soon understood . The stone grease could burn, and also could make ink, so the wolf guards deliberately declared it as “ink materials” when they entered the city . According to regulations in Chang'an, raw materials and finished products should be included in the same category . Therefore, these stone greases were officially cla.s.sified among the ink in the customs records .

Jing'an Department was desperately tracing oils and other fuels, but ignored ink . Ink didn't burn!

With this blind spot the Turks skillfully made things look all right . Even if someone wanted to check, it was difficult to detect the trick from the customs clearance records .

“These guys were so cunning that they came up with such a sinister trick . ” Yao Ru'neng gritted his teeth with rage . Zhang Xiaojing heard his sigh and frowned, feeling a hint of incongruity . He had been the commandant of the Indecent for many years, always sensitive to contradictions .

But now was not the time to think about these, the priority was to find out wolf guards' hiding place .

“As you said, the stone grease is black sticky grease, so it will be noticeable when spattered on the floor? How about searching the tracks on the nearby road?” Yao Ru'neng advised .

Zhang Xiaojing shook his head . Since the Turks had succeeded in bringing the stone greases in, they must have preparation for this . Some layers of hays under the sealed barrels could easily prevent oil from spilling .

“So, what should we do?”

Zhang Xiaojing patted the dog on the head, “The stone grease has a pungent smell, which is even stronger when burning . So, it's useful for outdoor lighting rather than burning indoors as candles or firewood . That's too strong . We can try to trace the odor around . ”

Yao Runeng's eyes lit up, and soon he wondered, “The dog must have a reference before searching . Where are we going to find stone grease for it?”

Zhang Xiaojing pointed toward west, “Jin'guang Gate . ”