At the Kamioka Mine, Mitsui Mining & Smelting Company, now daily outputting 3600 metric tons of zinc and lead ores, two underground chambers of 8000 cubic meters capacity for compressed air and water have been constructed mainly for the following purposes.
1. To cut the electric peak load by 1100kW-1500kW by means of midnight driving of air compressors and shorter driving in the daytime.
2. To save another new 600HP compressor which would be required for the increasing production plan.
Before the construction work the writer had carefully investigated and determined the econamical size, type, details of the air receiver and leakage characteristics of the surround rocks, which are mostly granitic gneiss.
Contrary to expectation the constructed chamber showed conspicuous leakage of air through cracks and fissures, for which the conventional grouting work was proved useless. The writer had been able to solve this difficulty of the air tightening by using the water saturated with lime, from which CaCO₃ precipitates and fills the fissure, being combined with the natural CO₂ contained in the compressed air.
The writer thus proved that even in such strongly faulted rocks in this country, it is possible to make the air receiver of such a large capacity.

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In the wire rope stretch there are two kinds involved; one is stretch on service and the other is stretch which occurs during breaking test. The stretch under breaking test is distinguished constructional stretch, elastic stretch and plastic stretch. In this study the stretch under breaking test of 6×7 lang lay rope will be discussed. Namely ropes, which have been respectively abraded, made broken wires, corroded and made deformation experimentally, are put to breaking test, then relations between percentage loss of breaknig strength and stretch are induced and shown in curves. more than two hundred of ropes which have been used on mines are inspected, and from breaking test, relations between percentage loss of breaking strength and stretch are got. Classify these by Their cause of deterioration, namely (A) abrasion, (B) broken wire, (C) corrosion, (D) deformation, these relations are shown in curves respectively.
From above, standard curves for 6×7 rope are induced.
These curves vary by type of deterioration within a definite range.
It will be seen that there are a close connection among the type of deterioration, percentage loss of breaking strength and elongation under breaking test.

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In this study the author obtained theoretically the head H (m) to be given in the delivery of pump and the water horse power N (FP) from the equation of “Equilobrium of Energy” in the transportation of coal by the vertical pipe H₀ (m).
Then by considering the efficiency ofp ump the shaft horse power N'(FP) and so the theoretical and actual efficiency of transporting coal were obtained.
Consequently in the case of changing the diameter of pipe, the effects upon the characteristics and efficiency were discussed by the numerical calculations.

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This paper reports a modified electrophoresis apparatus by the microscopic method in the surface electrochemical study of flotation.
After examining the apparatus with platinum electrodes in all its aspects, an acrylite new apparatus with non-polarizable calomel electrodes as the working electrodes so as to avoid polarization was designed and was proved satisfactory for use. Cell dimension was 2.108mm in depth, 19.87mm in width and 200mm in length, and electrophoresis was measured at the stationary level so that electroosmotic flow was zero. Field strength was measured by the vacuum tube voltmeter by putting the small calomel electrodes in the cell.
By considering the theoretical equation on the electroosmotic flow in the cell, derived by Komagata, it was found that ratio of width to depth of the cell must be more than 5, and the deviation in the focusing point is discussed. Effects of the settling of particles during the mobility measurement and of particle size were also considered, and it was concluded that the former is negligible small when measured under the condition in which particles are observed within the focusing depth, and that the most suitable particle size is less than about 2μ in diameter.
A mobility of -1.07μ/sec/V/cm in distilled water at 25°C was observed on the sphalerite sample and the calculated electrokinetic zeta potential was -14mV.

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The small particles of copper matte were settled in the liquid silica saturated FeO-Fe₃0₄-SiO₂ slag at 1300°C. Appreciable amount of sulfur dioxide is produced by the reaction between magnetite and matte only when the content of magnetite in the slag is about 10-13% and over. But the presence of magnetite in the slag, even less than 10-13%, prevents the settlement of matte particles, especially that of the lower grade matte, and raises the grade of the settled matte. The slag loss of copper is mainly due to the suspension of matte particles for the lower grade matte, and to the dissolution of copper for the higher grade matte.

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The decomposition voltage of molten lead silicate was measured using Pt anode and molten Pb as cathode at 800°C, 850°C, and 900°C. On the curves showing the relationship between decomposition voltage and compositions of silicate, small discontinuities were observed at th compositions corresponding to 2PbO·SiO₂ and PbO·SiO₂. The electromotive force of the cell (-) Pb/PbO (in silicate)/O₂C (+) was also stndied. There was general decrease of E. M. F. with increasing temperature and concentration of PbO. The activity of PbO in the PbO-SiO₂ melts obtained from decomposition voltage and E.M.F. measurments was compared with values from Richardson's experiments. Furthermore, the X-ray analysis of PbO-SiO₂ glass as well as crystal, which was considered to be better approach to understand the constitution of molten lead silicate, has been carried out. The results indicate that there are three sets of similarity on the patterns changing at the neighborhood of each composition.

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