According to Li Ke's estimates, if all these factors are taken into account, the average sea speed of a large modern sailing ship with a pointed bottom can reach a speed of at least 15 kilometers per hour, which is about 8 knots.

At this speed, with the help of nautical charts, you can reach the Persian Gulf in about a month to a month and a half by walking a straight line distance directly in some sea areas!

According to the theory that Li Ke said before, if you can control the land within a month from the imperial capital, with the ocean, the land area that Datang can control is not small.

Li Ke raised his head again and looked at the map hanging on the wall, Li Shimin and Li Chengqian were a little confused, they were all looking at the map like Li Ke, they didn't know what he was looking at, if they were just looking at the ocean, this road was indeed far enough.

"Dad, I need your authority to give me." After a long time, Li Ke suddenly spoke.

"Authorize what?" Li Shimin was a little strange.

"The three of us only need to know about this matter, and we can't let the courtiers know, or we can't let them know the real purpose." Li Ke spoke in a serious tone.

Chang Lin: "......"

Roomman: "......"

Fortunately, Chang Lin had already driven away the little eunuchs with a clear ride.

"You say." Li Shimin didn't care.

"Trade with Sassanid Persia can be done privately in the name of commerce. This matter is not known to the outside world. Li Ke said very simply, "Moreover, I, Datang, want to vigorously develop the marine industry, and all Datang shipbuilding technology is strictly forbidden to be passed on, and violators will be punished by the nine clans." ”

For the first time, Li Ke's mouth spit out very harsh words.

Li Shimin and Li Chengqian's expressions became serious, Chang Lin and Qi Lang were already numb, you must know that Li Ke had never said anything about the Nine Clans when he said that Li Shimin would give up his rights, but now Li Ke said it.

"Your Majesty, Your Highness...... Why don't we leave first? The sitting roomman hesitated, but then spoke.

"No, you need to write these down, and they will be useful later." Li Ke directly stopped the movement of the living room.

Roomman: "......"

What else could he say, he could only sit here honestly.

"Why do you say that?" Li Shimin asked.

"Dad, you know, the main transportation of materials between my Xizhou and Chang'an currently comes from the Yellow River Valley, and the boats in the river are very important, so I spent a lot of money to get my people to improve the boats."

"At present, the inland waterway transport ships have improved two very good boats, as well as more advanced sails, so that the ships from Chang'an and Xizhou can travel faster! From this aspect, it can be seen that the importance of river transportation to Datang. ”

Li Ke marked the Grand Canal of the Sui and Tang Dynasties on the map, Li Ke cheaply dug the Grand Canal is not the Beijing-Hangzhou Grand Canal of later generations, the Beijing-Hangzhou Grand Canal of later generations was built by several later dynasties, Li Ke's cheap grandfather Sui Yang Emperor dug the Grand Canal from Chang'an together with the Wei River to the Yellow River, and then down the Yellow River to the lower reaches of Luoyang, in the lower reaches of Luoyang divided into two, one to the north, until Youzhou Zhuo County, Fanyang County (later Beijing).

The other is to use the chasm and Hanhan ditch to extend to Hangzhou in later generations, and now Qiantang County in the Tang Dynasty.

What is the chasm? The chasm is the famous Chu River Han Realm! The word chasm has later become an adjective, and in fact the chasm is an artificial canal dug in the Spring and Autumn Period and the Warring States Period.

In fact, it was only after coming to this era that Li Ke could understand how wise the ancient Chinese were, the kind of shock that comes from culture, the more he understood it, the more he felt that his scalp was numb.

Many things are traceable in history.

For example, Xingyang Zheng's! Why Xingyang? And not Namyang, Binh Duong, Anyang, etc.?

Because of the gap between the Spring and Autumn Period and the Warring States Period, Jishui, Rushui, Huaishui, and Surabaya figured out, and the Yellow River converged in Xingyang! And Xingyang from the Spring and Autumn Period and the Warring States Period is an important river traffic artery in the north and south of the artificial canal!

That's why it's Xingyang Zheng!

Although the chasm of later generations has long been vicissitudes, only part of the river has been retained for future generations to admire! But in this era, it has an extremely important role, the chasm according to the actual exploration of the Tang Dynasty and the information that Li Ke learned, the chasm is calculated according to the data of later generations, the flat-bottomed ship can carry at least a thousand tons of tonnage ships!

How many materials can be pulled by a thousand-ton wooden boat, there is no need for Li Ke to go into too much detail, of course, Datang can't build such a big wooden sailing ship.

"And by sea! Equally important! Li Ke took a deep breath and directly clicked two places on the map.

One is the Southeast Asian Peninsula in later generations, that is, Vietnam and other places.

"The land in this place is fertile, the climate is pleasant, and the rice can be harvested three times a year.

"And this grain is extremely cheap locally, and we can rely on convenient sea boats to transport it directly from this place, and then transport it to all parts of Datang through the Yangtze River or the Yellow River, and then through the canal." Li Ke kept making comparisons on the water system of the entire map.

And the living room next to him was quickly recording Li Ke's words.

Li Shimin and Li Chengqian were a little excited to see it, and they naturally knew how valuable it was.

"The point is that these places have great admiration for my Datang, such as my Datang's silk, cloth, porcelain, and tea can be sold here at least four to five times more expensive than Datang, and at this price, if you buy grain at only one-third or even one-fifth of Datang's price and transport it back to Datang, my Datang can completely solve the problem of grain." Li Ke first took an example.

Other things in addition to it immediately didn't say anything, there are a lot of good things in Southeast Asia, and the rubber and lacquer trees that are ready to be loaded in the back are relatively expensive things in Datang, in addition, there are also a number of dense Chinese medicinal materials in these places.

And in places like the Philippines...... And gold! A gold mine that can appear with doghead gold!

"The river." Li Ke drew on the map, this is the Mekong River in later generations, called the Lancang River in China, "I named it the Lancang River." ”

Li Ke rowed out the entire river domineeringly, "If we solve the problems of Tubo, Nanzhao and other places in the Tang Dynasty, this river, we will drive the improved Wan Hu hU boat (Hu, Tang volume unit) into this river, with the area of the river's basin, we can control all the land on both sides of the river." ”

Wan Hu ship converted, about a modern 600-ton displacement of ships, this displacement was very perverted in ancient times.