Chapter 87

For this long voyage, Hong Tao left Bozhu at home, taking only Karl and Bojiao with him, as the small boat couldn't carry too many people's supplies. △If anything went wrong, both he and Karl were outsiders, and their deaths wouldn't matter much. Bojiao was forced onto the boat by Bo Xiaoer, who said he had two sons; if Bojiao died, there was still Boyu, so he wasn't worried. Since they all had such a spirit of adventure, Hong Tao also agreed with an encouraging attitude. Exploring the sea, after all, where could you go without risking your life? If the Tanka people who lived on the sea didn't have this much courage, they might as well not live on the sea at all.

Before setting out, Hong Tao did two things. One was to boil all the fresh water on the boat in earthen jars, then pour it into small-mouthed jars used for whale oil, seal the jar mouths, and use whale skin and burned shell powder to seal them. If the jar mouth was concave, it meant the seal was successful and could be taken on the boat. If the jar mouth was flat, it meant it was leaking and needed to be refilled with hot water and resealed.

Food on the sea was easy to solve; they could bring raw rice, salted fish, and dried seaweed, which the Tanka people had plenty of, so there was no worry about food, but there was a worry about drinking. Fresh water, if stored in the same container for too long, especially in high temperatures, would start to spoil after two days. If it was left longer, it would start to taste bad. Although drinking it wouldn't immediately kill you, it wouldn't be good for your health. If you got dysentery at sea, there would be no good way to deal with it, and you might die from dehydration. Although Hong Tao's method couldn't preserve the water for too long, it was better than not treating it at all. He estimated that it should last about a week without problems.

The second thing he did was to go to the only jewelry store in Zhenzhou city and have the goldsmith make two small silver mirrors for him using the best silver. The frames had claws around the edges, and two pieces of natural crystal, which had been ground very thin and round, were fixed on top. These mirrors had a good reflective effect and didn't distort much. Hong Tao knew he couldn't make glass in the short term, let alone mercury mirrors, so he decided to use natural crystal and polished silver mirrors instead. As long as the flatness was sufficient, a little distortion wouldn't matter.

In addition to the small mirrors, the goldsmith also made a small cylinder and two small copper boxes for him using a copper-silver alloy. The cylinder, according to his requirements, was divided into two sections that could be screwed together, with the threads being a gift from Hong Tao to this era. The goldsmith was extremely grateful for this patent gift and refused to charge for the work. If Hong Tao weren't so young, he might have even knelt down to thank him. The function of the threads didn't need much explanation; with his years of experience in handling gold and silver jewelry, he knew it was a very useful technology. Getting a skill that could support his family for free, a bow was not too much to ask.

In each of the two sections of the cylinder, a piece of crystal of different thickness was fixed, and after several adjustments, the final design was set. This was a very simple telescope that could only be adjusted slightly, with a magnification of about four to six times, though Hong Tao couldn't measure it precisely.

In the small copper boxes, Hong Tao used a magnet and a sewing needle to make a magnetic needle, which the goldsmith fixed to the bottom of the box, allowing it to rotate freely. This was a simple compass. Additionally, the goldsmith, under Hong Tao's guidance, made a compass and a set square using leftover materials. Hong Tao didn't tell the goldsmith what these were for, and the goldsmith, understanding the rules, didn't ask a single question and even helped hide them from others until he handed them to Hong Tao.

With these items, Hong Tao could make his navigation tool, the sextant. The overall structure of the sextant is a fan shape, specifically one-sixth of a circle, with a movable arm at the center, called the index arm. The arc of the fan has graduations, and the index arm has teeth that mesh with the teeth on the fan, which Hong Tao carved from whale baleen and whale bone. On the sides of the fan, a small mirror and a telescope are fixed, and near the center, another mirror is fixed, connected to the index arm, forming a complete sextant.

The mirror at the center is a regular mirror, called the index mirror; the other mirror has only half a silver plate behind it, making it half a mirror and half transparent, called the horizon mirror. Together with the telescope, they form a triangle, creating a very good sextant.

How do you use this thing? First, you need a good foundation in geometry and the ability to use trigonometric formulas. Then, align your eye with the telescope and use the half-transparent, half-reflective mirror to make the horizon line up with the transparent half. Rotate the index arm slightly to find the target, which is the position of the sun or the star you are observing.

When you see the sun or star reflected in the index mirror and it lines up with the horizon, note the exact graduation indicated by the center of the index arm on the fan. This is the angle between the sun and the horizontal plane at your location. With this angle, you can calculate your latitude based on the sun's declination.

However, there is a small flaw in this method: on a ship, there is always some movement, making it difficult to keep the sextant level. What do you do? It's simple: you just need to gently shake the sextant, making the image of the sun swing back and forth. When the sun is at its lowest point in the mirror, the sextant is level.

But this still doesn't guarantee an accurate reading. No problem, just take multiple measurements, reading the scale every minute and averaging the results. This should give you a fairly accurate latitude. This method can only determine a rough latitude; you can't expect it to be precise to the minute. For long-distance navigation, a few minutes of error isn't a big deal. The purpose of using the sextant is to ensure the correct course, not to hit a specific target. Small errors can be ignored. On a ship, whether the captain or the navigator, they need to take at least two measurements a day, and if they find an error, they correct the course. Through continuous observation and correction, they can reach their destination.

Some movies show the navigator or captain making a mistake with the coordinates, causing the ship to go off course or even get lost. That's nonsense. Unless they make mistakes for several days in a row, they would realize the error within a few hours. For a sailboat, how far can it go in a few hours? What is a sea chart for? Every few hours, the captain or navigator marks the ship's position and relevant measurements on the chart. Even if a strong wind blows you off course, with the previous measurement data, you can easily return to the original course. If you say the navigator and captain didn't record the chart, that's a different issue. What issue? You followed the wrong navigator and captain, and they were just going to commit suicide.

So, with a sextant, a compass, a compass, a set square, a chart of the route, and a reliable timekeeping tool, and the correct way to use these tools, you will never get lost at sea. However, not getting lost doesn't mean you can navigate the sea freely.

No, first, you need to ensure your ship can withstand the raging waves, giving you the chance to continue sailing. Second, you need an accurate sea chart to know where the land is and how far away it is. Finally, you need good luck. In an era without weather forecasts, any storm could end your journey. Even the best ship can't withstand a typhoon; even a nuclear-powered aircraft carrier has to avoid a tropical storm, or it will face the same fate as a small sailboat.

Now, Hong Tao has some of these things, such as the correct usage method, a compass, a fairly accurate sextant, and a fairly reliable sailboat. What he lacks is an accurate sea chart and good luck. These two things he needs to explore on his own. The chart needs to be measured and drawn as he goes. He isn't a professional surveyor and hasn't studied projection methods, so he can only measure one point at a time and mark it on the chart, ensuring that the places he has been are accurately recorded. If he keeps this up for decades, traveling around the world, he might eventually create an accurate sea chart.

Don't underestimate this chart; with it, humans have the foundation to conquer the sea. Hong Tao can't guarantee that he will complete it, but he can ensure that it will be completed soon, as he will teach this method to children like Boyu, Bosha, and Bojiao and write it down in detail in a book to pass it on. As long as there are enough children like Bojiao, Boyu, and Bosha, even if he dies at sea, the sea chart will still be corrected and perfected by generations of sailors.

"Raise the sails! Your parents and siblings have endless things to say. If we keep chatting, we won't leave! Bozhu, you lead the way, get off the boat first." At the end of January, this small sailboat, named the Explorer by Hong Tao, was loaded with fresh water, rice, salted fish, dried seaweed, and coal, and the sails were raised, ready to set sail. He didn't care about life and death, but the others did. They kept giving instructions, endlessly. Hong Tao understood their feelings but couldn't bear the atmosphere, so he kissed Bozhu on the cheek and unceremoniously sent everyone who came to see them off.

"Don't stare! Come in, I need to explain the rules for this voyage. Each person will take a two-hour shift. During these two hours, you need to pay attention to the wind, the current, and the ship's speed, and use this tool to measure the position. I will teach you how to use it gradually. After the measurement, write the numbers on the whale skin, and each of us will have one. I will check them at any time, and I will teach you how to write them. The daily cleaning will be done by both of you, finished before lunch. Food and fresh water will be rationed, managed by Karl, and the usage will be recorded daily. These are valuable data for the future." As soon as the boat left the dock, Hong Tao called Karl and Bojiao into the cabin, giving each of them a bamboo tube containing a rolled-up piece of whale skin, a few pens made from whale baleen, and a black dye used by the Li people for dyeing cotton.

ps: Click, collect, and recommend! Throw them all to Hong Tao...

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