Kazuo Nimura
The Historical Development of Working Conditions at Ashio

II   Technological Changes in Ore Dressing at Ashio

1)   The Mechanization of Ore Dressing

Mechanical Ore Crushers

The first industrial process to be mechanized at Ashio was ore dressing, with the installation of a western-style ore dressing station in 1884.1) Previously, ore had been broken up with hammers and selected using bamboo baskets, an extremely slow and laborious process, described in the '1883 Ashio Mine Report' as follows:2)

"The raw ore is first placed on a flat slab and broken up into tiny fragments with hammers. The fragments are put into bamboo baskets and the ore is separated from waste in separator boxes (the square wooden boxes, measuring 90.9 by 90.9 cm and 75.75 cm deep, are placed in the ground. Water runs through them, and the ore dust which drops from the bamboo baskets collects in bowls at the bottom of the boxes)."

This process, in use at the time of Furukawa's takeover of the Ashio mine, was in fact inferior to the methods that had been employed in the gold and silver mines of the Edo Period, when water wheels were used to power ore-crushing stone mills, and ore was separated from rock with itadori and nekonagashi.3) According to the '1884 Ashio Mine Report', however, ore dressing was being conducted using three mechanical crushers, one crushing roll, and fifteen jiggers.4) The machines were driven by a 10 horse-power steam engine built by the Yokohama Steel Company.5) The new western-style dressing station was first used to process top-grade (around 12%) ore which had already been selected underground. Ore-bearing rocks were first put through sieves with a 30mm wire net mesh, and the lumps of ore which remained in the sieves were then crushed by the mechanical crushers and put into the sieves once again. Smaller lumps which passed through the sieves were further reduced by crushing rollers and fed into trommelles fitted with six types of net mesh of varying size from 1mm to 8mm which successively reduced them to the point where they were put on jigger belt machines to separate the ore from the remaining lumps of rock. The jiggers' wooden box-shaped sieves containing the pulverized ore were plunged into water about 60 times a minute; the heavier ore sank to the bottom, while the lighter rock fragments stayed on the surface. The six types of net mesh in the trommelles were needed to cope with the different weights of ore and rock. It was also necessary to remove the tailings which formed an intermediate layer between the ore and debris. This was processed by the traditional bamboo basket method.

In May 1885 the No. 2 ore dressing station was built at Honzan. It was first used to reprocess the tailings produced by the jiggers and sieves of No. 1 dressing station. These tailings were again sorted by jigger to retain any remaining scraps of ore- bearing rock which were then further pulverized by the steel pounders of four stamp machines. The pulverized remains were then sorted into either ore or residue by eight percussion tables and jiggers. Tailings produced by this process were sorted using traditional tools known as 'ôgibune'. These were fan-shaped boatlike wooden containers 2.73 meters long, the upper part being 15.15 centimeters wide and the lower part 1.51 meters wide. The pulverized tailings were washed into these containers with water, and the ore which settled to the bottom was repeatedly raked up with hoe-like implements. In this way the heavier pure ore remained in the upper part of the ôgibune while sand and pebbles collected at the bottom and even lighter material was washed away over the dividing boards together with waste water. Motive power for the No. 2 dressing station was provided by two steam engines of 14 and 15 h.p.6)

2) Addendum -- The Major Causes of Copper Pollution

The First Appearance of Mine Pollution

The subject of mine pollution does not strictly belong to the theme of this book, but as an important consequence of the development of ore dressing technology, it ought not to be passed over completely; it was after all, the main cause of the pollution of the Watarase River area. Most studies of pollution at Ashio have been content to indicate in general terms a link between the escalating incidents of pollution and the rapid increases in production achieved after the takeover of the mine by Furukawa; one has yet to see a clear and specific explanation of the direct causes of the pollution. Various reasons have been given to account for the pollution: the disposal of debris and waste from the ore dressing and smelting processes, the drainage of water from the pits and ore dressing stations, and also the waste water from the production of copper sulphates. These, together with the smoke produced by roasting ore and smelting, can of course constitute the causes of pollution, but as causative agents, they are not of equal significance. Smoke, for example, could well have been the main cause of damage to the pine trees, hamlets, and mountain forests surrounding the Ashio mine, but it certainly did not play a major role in the pollution of agricultural land along the Watarase River, and it is this latter case that will now be considered, since it became a social problem of no small consequence.

The first point to establish is the precise outbreak of pollution along the Watarase River. Shôji Kichirô has shown that the conventional dating of the first appearance of copper mine pollution (1880) is in fact erroneous, and that the first signs developed with the deaths of large numbers of trout on 6th and 7th August 1885.7)

The Ore Stamping Machine and Mine Pollution

This period was precisely the time when a stamping machine was being put through its paces at Ashio for the first time. Harada Shinji's 'Report from Ashio Copper Mine' was published in the March 1887 issue of the Bulletin of the Japanese Mining Industry Association, but its contents relate to the period from early to mid-August 1885 which the author spent at Ashio. Harada mentions that as I was walking around the mine (I noticed that) the installation of the stamp machine had been completed and it was being tested. The stamp was fitted with 20 steel pounders weighing a total of 240 kg and was used to crush ore fragments and debris left over from the No. 1 dressing station in order to recover any remaining ore. The waste water produced in the process was released as liquid mud into the Watarase River. Certainly, the waste products of the No. 1 dressing station had for some time already included pollutants such as water containing copper sulphates and iron sulphates, as well as minute particles of ore, but the new stamp produced far greater amounts of such ore dust than did the crushers and crushing rolls of the No. 1 dressing station, and consequently, richer concentrations of copper and iron sulphates. These may well have been the cause of the deaths of so many river trout in the first week of August 1885.

The No. 2 station began fulltime operation from the autumn of that year. The farming communities living along the Watarase River first became conscious of the pollution some two years later, but it was not until after the great river floods of 23rd August 1890 that it became a major social issue when seven counties, 28 villages, and more than 1,650 hectares in the two prefectures of Tochigi and Gumma were suddenly and drastically affected. The damage was so disastrously wide-ranging, because the flood waters bearing the pollutants in tiny particles of earth and sand overwhelmed the waters of irrigation channels. Those pollutants may well have been the ore dust produced by the No. 2 dressing station. This is not to assert that the drainage water from the pits or run-off water from debris piles was not free of pollutants. However, the absolute quantity of pollutant found in the irrigation water was minimal compared to the amount of ore dust particles produced by the stamp machine.
   The massive quantity of polluted liquid mud released from the No. 2 dressing station and the large amounts of copper residues left in it were attested to by Furukawa himself in his "Explanatory Notes to the Exhibits at the International Exposition" of 1892 in the United States:8)

"As the waste from the No. 2 dressing station was found still to contain some residues of copper ore, in order to recover even the smallest amounts of ore, we are currently building a new dressing station in which will be installed several machines capable of processing 3,600 kiloliters of waste sludge per working day. From this we shall be able to recover two tons of refined ore".

The dressing station referred to here is the No. 3 dressing station, which was completed at Honzan in 1893 in response to vociferous complaints from the rural population which had suffered from the pollution. The '3,600 kiloliters of sludge per working day' and the '2 tons of refined ore' mentioned by Furukawa confirms that prior to the construction of the No. 3 dressing station, 18,000 drumloads of waste sludge, which included some two tons of untreated copper ore, were being released directly into the Watarase River every day. As will be described more fully later, despite the introduction of the No. 3 dressing station, it was not possible to recoup 100% of the waste ore; in fact, only about 30% was retrieved at most, and six tons a day continued to be discharged as waste. Furthermore, this was the situation at Honzan only. New dressing stations were built at Kodaki in 1886 and at Tsudô in 1888. The waste sediment from these three stations settled at the bottom of the Watarase River over a period of five years, and in the great floods of 1890 inundated the rice paddies and fields on both sides of the river. It was hardly surprising that considerable pollution damage was sustained.

Needless to say, I am not the first to have suspected that the main cause of the pollution was ore dust. Experts who investigated the problem, as well as Ashio technical staff, also came to the same conclusion. In 1891 Prof. Tanba Keizô of Imperial University's Faculty of Medicine was asked to inspect the area on behalf of the pollution victims. He later wrote:

"Anti-pollution measures need to be taken in two places - at the source of the pollution and in the areas affected by it. At the mine, collecting devices should be installed capable of retaining 99% of the copper currently being discharged, in which case, only 1%, an insignificant amount, will reach agricultural land."9)

Associate Prof. Nagaoka Muneyoshi of the Imperial University's Faculty of Agriculture, who served on the first committee of inquiry into the pollution incident called for a halt to the practice of using water for ore dressing, and another committee member, Prof. Watanabe Wataru, of the same university's Faculty of Engineering, stated that the problem at the Ashio mine was one of excessive washing and excessive ore dust. It is unnecessary to pulverize high grade ore into dust...Ashio must take steps to reduce the amount of ore being discharged along with waste water.10)

Realizing that ore dust was the main cause of the pollution, the Ashio management claimed that the problem could be dealt with by installing dust collecting devices, and in 1893 a sand classifier, a sludge sorting box, a Herz-type fine sand jigger, a double revolving paddle, an Evans-type slime table, and a cesspool to collect runoff water were all duly installed at the No. 3 dressing station at Honzan. In the following year the dressing station at Kodaki was enlarged and a slime table installed. Most studies of pollution problems at Ashio have judged these various devices to have been largely ineffective, a reasonable conclusion in view of the continuing outbreaks of pollution after the company's insistence, when it concluded an out-of-court settlement with the pollution victims, that the devices were certain to remedy the problem. According to data gathered in 1897 after all the various anti-pollution measures had been taken, the efficiency of the sand collectors at Honzan was reckoned to be a maximum 80%, a minimum 14.1% and an average 37.3%. At Kodaki, the figures were 34.5% maximum, 6% minimum, and 11.1% average.11) At Tsudô's ore dressing station, however, no such sand collecting devices were installed, and waste water was simply discharged untreated into a cesspool. Clearly, the company's anti-pollution measures left something to be desired.

Nevertheless, taken as a whole, and including the cesspools and filterbeds, the measures can be seen as having suppressed discharges of ore dust to a considerable extent. This was shown by the floods of 8th August 1902, the effects of which were very different from the floods of 1890 and 1896. Researchers into the pollution incidents have pointed out that the flooding in 1902 dumped large amounts of new earth onto the land that had been ravaged by the pollution, and as a result, the productivity of the area revived to a certain extent,12) and that the flooding led to a good harvest in 1903.13) This must surely mean that after 1896 less ore dust was being discharged and settling at the bottom and along the banks of the Watarase River. The preventive measures of 1897 must therefore have had some effect. On the other hand, this further substantiates the supposition that the main cause of the pollution prior to 1897 was indeed the discharge of massive amounts of ore dust.

3) The Effects of the Mechanization of the Ore Dressing Process

Numbers of ore dressing workers

Returning to the situation inside the ore dressing stations, what effect did the mechanization of the ore dressing process have on the workers themselves?   Table 18 should help to make this clear.

Immediately noticeable is the sharp rise in efficiency in 1885. When Furukawa took over in 1877, the workforce numbered 265, including 50 convicts and 51 female ore refiners. At that time output of refined ore was about 937.5 kg per day, each female refiner processing on average a mere 18.75 kg. Originally, these female 'refiners' were miners' wives and daughters doing part-time work. As they did not work in the refinery all the time, but also carried ore from underground to the surface, their efficiency rates in the refinery were low. Even if they had worked fulltime in the refinery, however, their efficiency would still have been low, as they were only using hammers to smash the ore and bamboo baskets to sort it. Compared to this, just 116 workers in the western-style mechanized dressing station in a single day even in 1885 were able to process over 37,500 kg of ore, that is, over 375 kilograms per worker per day or more than 20 times the efficiency rates prior to mechanization. The increase was above all due to the mechanization of ore crushing. In one working day one crusher was able to reduce 11,250 kg. of ore-bearing rock to particles smaller than 30 millimeters, and the crushing roll further reduced 48,750 kg. of such particles to particles less than eight millimeters in size. To operate four crushers and one crushing roll required two workers per crusher - 16 workers working alternate shifts a day -and four workers at the crushing roll - eight workers a day. The jigger was worked manually, but one ore dresser was able to process 1,875 kg. a day, four times more efficient than the skilled female ore dresser, who with her bamboo basket, had been able to get through only some 450 kg.14)

In addition to mechanization, another major change was the replacement of female ore dressing workers by male workers. The job of sorting and selecting the ore by eye had been exclusively done by female workers, but male workers were employed in operating, and maintaining the machines and in hauling and loading the ore.
   However, there is one aspect of the improved efficiency of 1885 which is not explained by the factors discussed so far, namely, the seemingly incredible fact that 17,167,500 kg. of refined ore were obtained from 14,062,500 kg. of raw ore. Actually, this figure includes raw ore processed and refined in the previous year. Rather than there having been any dramatic increase in refining abilities, figures for ore processed toward the end of 1884 were carried forward into the following year. The quality of the ore processed in this period was good, and the method of dressing somewhat rough and ready, factors which also underlay the high efficiency of ore dressing in 1885 and 1886.

The lack of data for the late 1880s and the first half of the 1890s makes it difficult to get a clear picture of what the situation was in those years. However, it is known that despite the increasing mechanization of the ore dressing process, the number of workers involved in ore dressing continued to rise throughout this period. There was a tenfold increase over the 11 years from 1885 to 1896, from 116 workers in 1885 and 275 the following year to 753 in 1895 and 1,015 in 1896. More finished copper was produced, but this was not due to the increasing numbers of ore dressers; in fact, the amount of finished copper produced per man actually fell. The efficiency of the ore dressing process in itself did not improve so much, and again, there was a drop in the amount of refined ore produced per man. And yet, mechanization certainly continued apace. Jiggers switched from manual to mechanical power, and the loading of ore onto the crushers was partially automated. It is clear from the additional motive power employed - 10 h.p. in 1884, 39 h.p. in 1885, and 200 h.p. - that there was no let-up in mechanization during the period.

The expansion of Ashio's ore dressing stations

Why then did the number of ore dressers outpace the production of finished copper and why was there was no improvement in the efficiency of the ore dressing process?  A number of reasons can be offered, but foremost among them must be the expansion of the ore dressing stations.16)
    1885 Construction of Honzan's No.2 dressing station
    1886 Construction of the Kodaki dressing station
    1888 Construction of the Tsudô dressing station
    1889 Enlargement of the Tsudô dressing station
    1890 Construction of the Sunokobashi dressing station
    1891 No.1, No. 2 dressing stations built at Kodaki
    1893 Construction of Honzan's No. 3 dressing station

Dressing stations were built at Kodaki, Tsudô, and Sunokobashi as the exploitation of the Ashio area proceeded beyond Honzan. It made better sense to process raw ore in dressing stations close to the various pitheads rather then transport it all the way to Honzan. The new stations were not built simply to expand extraction sites and pits, but also out of the need to make the fullest use of lower grade ore which previously had just been left in the pits; the aim was also to extract all possible copper residues from debris. This was certainly the intention when Honzan's No. 2 station was built, and also in 1891 when a second station went up at Kodaki. It was an obvious policy for any mining company management planning a long-term strategy of exploitation.

There was another reason for the enlargement of the ore dressing facilities, namely, the fallout from the pollution scandal. The management felt the need to try to remove the cause of the pollution by extracting copper residues from class 2 raw ore sediment. Beginning with the new No. 3 dressing station at Honzan in 1893 and the installations of ore dust collectors at Tsudô and Kodaki, the expansion of Ashio's ore dressing facilities had become a vital necessity.

   However, after reaching a peak of 1,015 workers in 1896, the number employed as ore dressers then began to decline, a strange phenomenon given that it happened just when, owing to the switch from 'racoon dog digging' to the overhand stoping method of extraction, ever larger amounts of lower grade ore were arriving at the dressing stations. Several reasons account for this. First was the continuing pace of mechanization which had been extended from crushing and sieving to sorting raw ore lumps, ore-bearing shards and fragments, and debris, and also to such operations as transporting ore to the dressing stations and loading it onto the crushing and sorting machines. Also, the efficiency of the machines themselves was continuously upgraded; the 200 h.p. used to drive the dressing stations' machines in 1892 had been raised to 602 h.p. by 1906.17)
   Secondly, improvements in refining technology meant that it was now possible to refine and smelt lower grades of ore. At the same time, the new western refining techniques necessitated a reduction in the amount of ore dust and a higher proportion of lumps of ore. It was also realized that the main cause of pollution was excessive pulverization of ore, and as a result, it was decided that class 1 raw ore should be simply dressed by hand and sent directly to the refinery. This meant less work for the crushing machines and consequently, a slight reduction in the work of the dressing stations as a whole.  From around 1905, class 1 raw ore was no longer dressed at all; it was simply sent on to the refinery.

The human factor

Finally, whatever the material improvements in ore dressing efficiency, there remains the major question of the impact on the workforce. Despite the rapid introduction of western-style dressing stations, they were not immediately put to the best possible use, as it took some time to familiarize the workers with their operation. The job of ore dressing in itself did not call for a very high level of skill and training. The men's work was primarily to keep the crushers, trommelles, and jiggers fed with ore and essentially involved no more than hauling. The women workers engaged in sorting and selecting the ore by hand also did not require extensive training, even after the introduction of machines.

However, the arrival of the new machines did mean that a premium was placed on the knowledge, experience, and abilities both of the technicians who were responsible for the overall supervision of the dressing stations, and of the workers who had to operate and maintain the machines on a regular basis. For example, the crushers and crushing rolls which had to carry tremendous loads often broke down, thus interrupting the work of the entire station and lowering its efficiency. To reduce such stoppages and ensure the machines were working at maximum efficiency, one needed to know how to take all the necessary precautions, to know the size and amount of the lumps of ore being loaded onto the machine, to be able to recognize abnormal sounds and noises which were the signs of impending breakdowns, and to take the necessary preventive action. When breakdowns did occur, the problem had to be isolated quickly and appropriate measures taken to ensure a rapid resumption of work. All these factors greatly affected the station's efficiency.

And yet, while the new stations were being built and the latest machines installed, almost the entire workforce was either inadequately skilled or else completely unskilled in their operation and maintenance. Very different from the situation in state-owned mines, at Ashio there was not one foreign technician or worker.18) Everything had to be learned by Ashio men themselves through a process of trial-and-error. In such a situation, however consistently the process of mechanization may have been going ahead, a sudden take-off in efficiency was not possible until a certain stage had been reached, and that was not until the 1900s.

What must not be overlooked in this connection is the appearance at Ashio of skilled engineers in the areas of ore dressing, mechanics, and electrics. Before the riot there were three generations of such skilled technicians at Ashio. The first generation were mostly mining engineers who had learned through practical experience of mining conditions and who pioneered the first phases of the development of the mine under Furukawa. Among them was Nakae Tanezô who had worked under the French mining engineer François Coignet at Ikuno and who, as one of Furukawa's first chief engineers, played a major role in the early years of the Furukawa company. He was responsible for boring the main tunnels at the Kusakura copper mine and at Ashio he introduced hand and foot pumps and hand-held crushers as well as western-style bellows.19)

The second generation joined Furukawa when the company bought the Ani and Innai mines from the government; most of them were the first group of graduates from the mining department of the Imperial College of Engineering. Men like Kondô Rikusaburô and Odagawa Zenshi, who were members of the management cadre at the time of the riot, were of this generation. However, these second generation men were graduates of very young universities, and the level of their technical mining skills could certainly not be described as being very high. They too must have learned much of their profession from practical work in the mines. The big difference between them and the previous generation was that they had either studied abroad or else from foreign technical textbooks, and they had the ability to introduce what they had learned into Japan.

The third generation joined the Furukawa company immediately on graduation from the Engineering Faculty of The Imperial University in the late 1890s by which time university education in engineering had gradually improved, and the graduates already possessed a certain level of competence. Whereas second generation men tended to be all-rounders, able to apply themselves to all aspects of mining from pitface operations to refinery work, the men of the next generation were mostly specialists: mining engineers, ore dressing specialists, refinery engineers, electrical engineers, and mechanical engineers.20) In ore dressing, an important member of this third generation was Kojima Jintarô, who came to Ashio in 1898 straight after graduating from the Mining and Metallurgy Department of an engineering college. In 1897 he had visited Ashio to do practical work for his graduation and had spent most time in the ore dressing stations. In addition to writing a report of his observations, he also produced a plan for a new dressing station, which was later realized in 1904 in the form of the No. 2 dressing station at Tsudô. Years later, Kojima's design was still being highly praised: In addition to the excellent choice of equipment and its most thoughtful placement, great attention was paid to the location of drains and to the structure of the floor; it was a design that was to have a considerable influence. 21) It is noteworthy that attention was indeed already being paid not only to the choice of machine but also to the general layout of the workplace. The dressing station was seen as one whole facility which, no matter how advanced the machinery, required a smooth flow of materials - ore and rock - between the various machines in order to maintain a high level of efficiency. That this was recognized and put into practice was, despite the increasing amounts of ore processed, another reason for the declining numbers of personnel.

Notes

1) According to Watanabe Toshio 'The History of Ore Dressing Technology in Japan' ("The Bulletin of the Japanese Mining Industry Association" No. 319, Sept. 1911), Ashio's western-style dressing station was built in 1883. But it may well have started operating in 1884.

2) Itsukakai "The Life of Furukawa Junkichi" p. 34.

3) Yamaguchi Keiji 'Gold and Silver Mining Technology and Society' (a lecture in A Social History of Japanese Technology 5 "Mining and Metallurgy" Nihon Hyôronsha, 1983).

4) Itsukakai "The Life of Furukawa Junkichi" p. 41.

5) Itsukakai "The Life of Furukawa Ichibei" p. 145.

7) Shôji Kichirô 'The History of the Watarase River and Its Worsening Pollution Problems' (Iida Ken'ichi ed. "A Social History of Technology" 4, Yûhikaku, 1982).

8) "History of Tochigi Prefecture" Historical Documents - Modern 9, p. 45.

9) Iida Ken'ichi "A Social History of Technology" 4, p.112

10) 'Third Interim Report of the Committee of Inquiry into the Ashio Copper Mine Pollution Incident' ("History of Tochigi Prefecture" Historical Documents - Modern 9, pp. 702-704, p. 712).

11) Kojima Jintarô, "Report on Dressing Work at Ashio Copper Mine" 1898, Tôkyô University Faculty of Engineering, Department of Metallurgy Library Archive, pp. 159-160.

12) Sugai Masurô 'The Ashio Pollution Incident - Pollution Problems in the Early Period of Japanese Capitalism (II)' ("Pollution Studies" Vol. 3, No. 4, April 1974) p. 64.

13) Nunokawa Ryô 'Mining Pollution and Rural Populations' (Iida Ken'ichi ed. "A Social History of Technology" 4, p. 135.

14) Harada Shinji 'Report on the Ashio Copper Mine' ("Bulletin of the Japanese Mining Industry Association" No. 25, "History of Tochigi Prefecture" Historical Documents - Modern 9, p. 27).

15) "Explanatory Notes to the Exhibits at the Industrial Exhibition" of 1892 ("History of Tochigi Prefecture" Historical Documents - Modern 9, pp. 44, 49).

16) This discussion of the construction and enlargement of the ore dressing stations draws mostly on Watanabe Toshio 'The History of Ore Dressing Technology in Japan' ("Bulletin of the Japanese Mining Industry Association" No. 319, Sept. 1911, "History of Tochigi Prefecture" Historical Documents - Modern 9, pp. 98-108), but also partly on "The Life of Furukawa Ichibei".

17) Ministry of Agriculture and Commerce Department of Mines ed. "The Japanese Mining Industry in 1906" p. 193.

18) Ashio did, however, draw on foreign skills in other areas; the Frenchman, Denis LaRue was engaged to lay the Decauville rail track; two Germans, Hermann Kessler and his assistant, Blutgen, employees of the Siemens Electric Company, helped build the electric power station, and an American, Hay, was involved in the construction of the cableway. ("The Autobiography of Kimura Chôshichi", pp.174, 226, 232-234). The American, L.C. Trent, was engaged to assist with underground prospecting operations ("History of Tochigi Prefecture" Historical Documents - Modern 9, p.87). Normal day-to-day operations were conducted by Japanese staff only.

19) See Itsukakai "The Life of Furukawa Ichibei" p.83 and Watanabe Wataru 'The Ashio Copper Mine and Mine Pollution' ("The Life of Furukawa Ichibei" appendices pp. 14-16).

20) The difference between the two generations is seen clearly in their choice of university dissertations. While Watanabe Wataru, who graduated in 1879, chose to base his on observations he had made of Ikuno silver mine, Ôta silver mine, the Ôsaka mint, Besshi copper mine, Ichinokawa silver mine, and Takashima coal mine, and the theme of Kondo Rikusaburô's dissertation (1880) was the "The Progress of the Japanese Mining Industry", Kojima Jintarô in 1898 chose to write "A Report on Ore Dressing at the Ashio Copper Mine" and "A Proposal for an Ore Dressing Station at Ashio Copper Mine" and in the same year, Sakikawa Motarô wrote "A Metallurgical Report on Ashio Copper Mine" and "Metallurgical Proposals for the Ashio Copper Mine".

21) Watanabe Toshio 'A History of Ore Dressing Technology in Japan' ("History of Tochigi Prefecture" Historical Documents - Modern 9, p. 100).