The British called the island Argonaut. Previously, the French had also mapped Ulleungdo at its correct position and called it Dagelet. This resulted in Western maps showing two Ulleungdo's, one real and the other non-existent, as can clearly be seen from the maps of that period. The new Meiji government referred to these inaccurate western maps when making their own maps and often mislabeled the non-existent island of Argonaut as "Takeshima," and Ulleungdo as "Matsushima," which was the name the Japanese had been using for Liancourt Rocks.
In 1876, a Japanese businessman named Mutoh Heigaku (武藤平学) proposed to the Japanese Ministry of Foreign Affairs that the government allow him to develop "Matsushima," which he knew to be Japanese territory; however, the island he assumed was Japan's Matsushima was actually Ulleungdo, which the Tokugawa shogunate had previously given to Korea. Mutoh apparently believed that the non-existent island of Argonaut was Korea's Ulleungdo and the real Ulleungdo was Japan's Matsushima.
Mutoh's 1876 proposal to the Meiji government was entitled "Argument for the Development of Matsushima" (松島開拓之議). The document, which is translated below, started a Japanese government investigation to determine exactly where Mutoh's Matsushima was. The investigation continued until 1880, when Japan finally sent a ship to survey the area. The Japanese ship finally determined that Mutoh's Matsushima was actually Ulleungdo.
Here is a translation of Mutoh Heigaku's letter to Japan's Ministry of Foreign Affairs:
Argument for the Development of Matsushima
I humbly say this. I am from the countryside and of humble birth. I am not talented, so I am not a man who considers national affairs or national policy, which makes me unsure of whether I should talk about something I do not know well. I have hesitated to write about this, but since it may help to strengthen our nation, I cannot refrain from talking about it. It involves an island called Matsushima, which is located northwest of our country. I have traveled to Vladivostok three or four times in the past three years, and I have seen the island from a distance whenever I go there. Although it looks to be just a small island, it could be profitable for the Japanese Empire since it is more significant than Ogasawara island in the south. Nevertheless, the island has no residents or arable land. Naturally, foreigners take profits from the island, but I cannot stand this. Foreigners are already freely cutting down trees, and I have heard that they sometimes carry the logs away by ship, so here I submit a petition with a summary.
Matsushima, which is located north of Onshu (Oki island), is an isolated island about five or six ri (20 to 24 km) long from north to south and two to three ri (8 to 12 kilmeters) wide from east to west. [The map to the right shows Ulleungdo labeled as "Matsushima" and the non-existent island of Argonaut labeled as "Takeshima, 大日本四神全図 - 1870年、橋本玉蘭著] No houses can be seen from the sea. Matsushima and Takeshima exist between Japan and Joseon. Takeshima is closer to Joseon, while Matsushima is closer to Japan. On the northwest coast of Matsushima stands a wall of rock stands and there is a precipitous cliff several hundred jo (1 jo equals 3.03 meters) high. No one can get close except flying birds. On the southern coast, the mountains gradually decrease in height sea level. There is a cascade of flat land about 30 to 40 percent of the way down from the mountains, where it would be possible to cultivate fields. There are small inlets at various places along the shoreline, which should be convenient for mooring boats. The island is full of pine trees which make the island look dark green.
People also say there could be a mine on the island. I have already heard from an American named Cobel, who is staying in Vladivostok. He said, “There is an island that belongs to Japan called Matsushima, which Japan has not started developing yet.” If Japan allows some other country to possess an island under the jurisdiction of Japan, it means Japan is giving away Japanese treasure to another country. The island has a mine, huge trees, and there should be large amounts of fish.
If you could lend me the island, I would make a big profit from it each year. I think the fishing would be profitable, but there would be more profit than just from fishery. This man, Mr. Cobel, is living in a huge residence in Vladivostok. He is a famous merchant, and few of the merchants could surpass him, but he is not only engaged in trade; he also gives his undivided attention to mining. He operates a mine that uses many Manchurians. He asserts that there should be a metal mine on Matsushima.
I have seen Matsushima three times or four while traveling back and forth by ship over the past two or three years. Although it is not apparent from the appearance, there could be a mine. The island is full of huge pine woods with some barren hills, which mining specialists say should hold a mine. However, since I haven’t heard of a judgment about a mine, I will not argue more about it. I would like to cut down large trees on the island for export to Vladivostok, where a new harbor has just been opened, or I could sell them in Shimonoseki for profit. If there is a mine, I would start a mining project while also developing fishery and agriculture, which will benefit our empire.
Since Japan has already concluded a treaty with Joseon, we could trade with each other if a harbor is opened somewhere in Hamgyeong Province. Matsushima is an important island located in the main sea route. When our ships or their ships are in trouble in a storm or needed firewood or water, it would be convenient for them to anchor at the island. As the harbor at Vladivostok becomes prosperous, ships from other countries will travel to and from Vladivostok to trade. They will also have to take shelter at the port of this island if they met a storm or need firewood or water. Therefore, we have to open a harbor and build a lighthouse to show that the island is ours. The sailors of other nations would feel relieved and respect the thoughtful policy of our empire. This would be like killing two birds with one stone; that is, treating outsiders with humanity and making profit for ourselves. More show of love and humanity between Japan and Korea would not only benefit the two countries but will also firmly build the respect and friendship for our empire from the people of other countries.
I hope you will open this island, bring in fishermen and farmers, and try to harvest its products. I have taken three or four voyages past the island over the past two or three years, and whenever I look at the island, I always think that a port of the island should be opened. Especially, when I visited Vladivostok in November 1875 (the 8th year of Meiji), we had a storm off the southern coast of the island. We feared we would run aground at Matsushima, and all the passengers on the ship had a hard time. At night, the storm changed to a snowstorm, and we could not see the island. All the passengers worried silently, so I would like to request that a lighthouse be built there as soon as possible.
(the 9th year of Meiji)
Mutoh Heigaku (武藤平学)
Mutoh Heigaku (武藤平学) also wrote the following, which showed his concern that Korea might try to claim Matsushima:
Some say that if Japan touches Matsushima, Joseon will claim it, but Matsushima is nearer to Japan, and it has belonged to Japan since ancient times. It has also been shown as Japanese territory on Japanese maps. It is Japan’s land. As for Takeshima, a dispute arose in the medieval period of Tokugawa, and it was given to Joseon, but there was no argument about Matsushima, so it clearly belongs to Japan. If Joseon tries to claim it, we should admonish them and use various evidence to prove that it is a Japanese island. It is not only in a critical location for traffic between Japan and Joseon, but it is also in a critical location for travel to countries to the north. Also, it is urgent that a lighthouse be built at good harbors in Japan and Joseon, which will benefit all countries.
The text was found in the third volume of a 3-volume set of documents entitled, "A Study of Historical Evidence on Takeshima" (竹島考証), which was published by Ministry of Foreign Affairs Secretary Kitazawa after the investigation of the islands around Ulleungdo by the warship Amagi in 1880. Here are pictures of the original Japanese documents: