The Jobu Silk Road

The thread that pulled Japan into the modern world
Things we can learn from the silk industry

Continuous technological innovation and the cross-industry efforts that supported it.
Sericulture and silk reeling were at the forefront of Japan’s journey to modernization.
The industry transcends history, and is the progenitor of today’s cutting-edge industry.

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Technology exchange across provincial borders


There was an exchange of sericulture technology on the Jobu Silk Road.

The four assets comprising the World Heritage Site “Tomioka Silk Mill and Related Sites” are: silkworm egg production (Tajima Yahei Sericulture Farm), silkworm egg storage (Arafune Cold Storage), education in sericulture methods (Takayama-sha Sericulture School), and mechanized silk milling (Tomioka Silk Mill). These four assets functioned together as a model of operation for the silk industry, and together advanced innovation in sericulture and milling.
Evidence is recognized of technology exchange beyond Joshu and Bushu Provinces. At the end of the Meiji period, permission was obtained from the Meiji Government, and high-quality silkworm eggs imported directly from Italy and France for academic study were reared under contract by silkworm farmers who had graduated from sericulture schools such as Takayama-sha in Fujioka and Kyoshin-sha in Kodama. This region covered the local Tomioka area, the Tano and Sawa regions of Gunma Prefecture, the Kodama and Osato regions of Saitama Prefecture, and other areas.
In the early Taisho period, the government led development of high-quality silkworm strains to achieve standardization. The resulting “F1 hybrid” for practical use was initially popularized through efforts led by Tomioka Silk Mill (during the Hara GMK period). Silkworm farmers in Joshu and Bushu cooperated in test rearing, silkworm egg production, and providing guidance on rearing.

Steps in the improvement of silk-reeling machines


Tomioka Silk Mill introduced large-scale mechanized silk milling for the first time in Japan, and technological innovation was driven by improvement and upgrading of machinery.
During the era of Mitsui family ownership (1893–1902) the original silk-reeling machines were replaced with a new type, and raw silk for export to the United States was produced.
During the Hara GMK era (1902–1939), the mill adopted the Minorikawa multiple-spool silk-reeling machine, invented by Naosaburo Minorikawa toward the end of the Meiji period. This led to improved quality of raw silk and greater productivity. This was based on a completely new concept, namely that if silk is reeled from cocoons at a slow speed, in the same way as when a silkworm spins a filament, then the original quality of the silk thread can be preserved. Thus the speed was dropped to one-fifth the conventional speed, and the number of filaments (number of threads taken up) was increased by a factor of five to 20. Minorikawa Raw Silk produced using the Minorikawa multiple-spool silk-reeling machine was suitable for stockings and gained popularity in the United States.
In the early 1950s, during the Katakura era (1939–1987), the mill began phasing in automatic silk-reeling machines. These machines incorporated a system to detect the thickness of the filament during reeling and automatically replace with a new cocoon when the filament becomes thin. Automatic silk-reeling machines steadily improved and during the peak production period from the late 1960s to early 1980s the Nissan HR-type automatic silk-reeling machine was used. These can be seen today in the main silk-reeling hall of Tomioka Silk Mill. They show the most advanced form of the automatic silk-reeling machine. The same type of silk-reeling machine continues to be in use at the Usui Raw Silk Manufacturing Agricultural Cooperative Association in Annaka City, Gunma Prefecture.

Opening the distribution route to Yokohama

Raw silk and silkworm eggs produced in Joshu and Bushu Provinces were transported to the trading port of Yokohama as first-class export items. Before the opening of the railroad, they were transported by boat via the Tone-gawa River and other waterways. At one time, there were berths all along the banks of the Tone-gawa River and river transport flourished.

In 1872, a railroad connecting Tokyo and Yokohama was completed. To extend routes, the Takasaki Line provisionally started operation between Ueno and Kumagaya in 1883, as the first line segment of Japan’s first private railway company, Nippon Railway. The line opened fully the following year. The Takasaki Line was established for the purpose of transporting raw silk and silk fabric to Yokohama by rail.
In 1884, the Ryomo Line opened between Takasaki and Maebashi as an extension of the Takasaki Line, and this was a route for transporting silk fabric produced in Ashikaga, Kiryu, Isesaki, and other areas, as well as raw silk from the Ryomo region. As time went by, the Hachiko Line was opened in 1934 to transport raw silk and silk fabric from Takasaki to Hachioji. The Yokohama Railway (today the JR Yokohama Line) opened between Hachioji and Yokohama in 1908.
The Joshin Electric Railway running through the Seimo region (western Gunma Prefecture), where Tomioka Silk Mill is located, was established in 1895 as the Kozuke Railway, and two years later was fully opened between Takasaki and Shimonita. Tomioka Silk Mill was sold to the Mitsui family only two years prior to that in 1893. In addition to local capital, the Mitsui Zaibatsu business conglomerate also participated in the establishment of the Kozuke Railway. When first established, the railway was laid as a narrow gauge light railway (i.e., with a narrow width between rails) operating with small steam locomotives, but it was modified for electric operation on all lines in 1924.

Supporting raw silk through market formation and finance

In Jomo Karuta, a traditional Gunma Prefecture card game, the prefecture’s capital city of Maebashi is referred to as ito-no-machi, or “the city of silk.” From the time the Port of Yokohama opened in 1859, the city prospered as a collection and distribution point for large volumes of raw silk. Two years later, in 1861, the Raw Silk Export Inspection Office was established on Honmachi-dori Street to eliminate low-quality goods. The white building incorporating Western-style architectural features was built in 1878.
In 1874, Zenzaburo Hara (a raw silk export merchant from Kamikawa, Saitama Prefecture) and others established the Second National Bank in Yokohama. A branch was established in Takasaki the following year, and another branch in Maebashi the year after that. The Second National Bank eventually became the Bank of Yokohama, but these branches remain in operation today.

Much later, in 1944, the Bank of Japan opened a branch in Maebashi. This was the first Kanto branch of the Bank of Japan, and shows how important Maebashi was as a financial center. This was all down to Maebashi’s reputation as “the city of silk.” To this day, it remains one of only two Kanto branches of the Bank of Japan, the other being in Yokohama (established in 1974).

The continuing legacy of sericulture education


In its early years, Tomioka Silk Mill made efforts as a model training factory to technically train and educate its women workers, and the sericulture association Takayama-sha, founded by Chogoro Takayama, had a strong character as a research and education institution. Kikujiro Machida succeeded Chogoro, and in 1901 founded Takayama-sha Sericulture School to train instructors in sericulture. Enrollees included students from China, Taiwan, and the Korean Peninsula. Among the graduates was Senju Niwaya, builder of Arafune Cold Storage.

Takayama-sha Sericulture School closed its doors in 1927, due to the proliferation of sericulture-related schools established around the country. Students enrolled at the time transferred to Gunma Prefectural Silk High School, opened the same year. Gunma Prefectural Silk High School later became Annaka Vocational High School, and finally today’s Annaka General Academic High School in 2006. One of the current programs, the biological resources course, is perhaps a legacy of the Takayama-sha Sericulture School. The sericulture association Kyoshin-sha, established by Chogoro Takayama’s younger brother Kuzo Kimura, underwent a similar transformation. It became Kyoshin-sha Sericulture School, then Kodama Agricultural High School, and finally today’s Kodama Hakuyo High School. Its roots are carried on in the biological resources course.

As the roots of cutting-edge industry

There are some who say that “in the Meiji period, battleships were made by thread.” Immediately after emerging from isolation, the Meiji Government obtained foreign currency through the raw silk trade. This was used to build a foundation for encouraging new industry and for national wealth and military strength. Japan also experienced the Russo-Japanese War—a landmark event of the times. The delicate threads of raw silk were more powerful than anyone imagined.
Textiles are at the root of the industries that transformed Japan into a technological nation. This is true even for Toyota Motor Corporation, a dominant player in the automotive world. Toyota began when the founder Sakichi Toyoda invented an automatic weaving machine. Similarly, Sanden Corporation, located along the Jobu Silk Road, was originally in the textile business as well. In 1943, it started manufacturing products such as capacitors using mica as an insulator. This is similar to the transformation experienced by the Hara Silk Mill in Kamikawa, Saitama Prefecture, when it became a facility of Japan Mica Industrial, a manufacturer of mica, in 1940.

The Nissan HR-type automatic silk-reeling machines still extant at Tomioka Silk Mill were developed by the then-Prince Motor Company. Prince Motor Company descended in part from the Nakajima Aircraft Company of Gunma. In addition to automobiles, Prince developed weaving machines and designed and manufactured space-related equipment. IHI Aerospace, the manufacturer of the reentry capsule system for the Hayabusa asteroid explorer was previously Nissan Motor’s Aerospace and Defense Division, which was descended in turn from the Aerospace Division of Prince Motor Company. In addition, its rocket technology originated in rocket research conducted by Nakajima Aircraft. Incidentally, the production base for IHI Aerospace is located in Tomioka.
The Jobu Silk Road lies at the intersection of Japan’s transition from light industry to heavy and cutting-edge industry.

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