There seems to be very few quantitative informations about mining damages to the structures on the surface. The ponds which exist in the Kyushu coal fields and have been damaged due to mining subsidence were investigated concerning with the time, the point and magnitude of damage, the length of dam, the geological conditions and the mining map and were compared with the results of the theoretical calculation of the surface strains. The followings became clear after the comparison.
1) The position of dam within tension zones in both the directions of dam axis and flow axis affects the amount of mining damage to the pond.
2) Increasing the magnitude of tensile strain on the dam by more than 2mm/m a year causes leakage or exhaustion of pond water.
3) The effect of local geology on mining damage is of importance.

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As a means which concentrates iron sands to the appointed parts in pipe of hydraulic transportation of sea floor placers, many magnetic poles are arranged in a row along the pipe.
Leaving out of consideration a matter of flow, the subject of discussion will reduce to the relationship between magnetic forces acting on ferromagnetic particles and geometrical measures of the arranged magnetic poles.
From the experimental data, the following two empirical formulas were obtained._??_
where x is limited in the range of l/2≤x≤2l. Explanation of symbols are as follows
b: width of the magnetic poles [cm]
l: interval of magnetic poles in Fig.2 [cm]
x: distance from surface of magnetic poles to magnetic particles (Fig.3)[cm] B_x: magnetic flux density at the point of distance x (Fig.3)[G]
Bl/₂: values of B_x at x=l/2 [G]
F_x: magnetic force acting on a ferromagnetic particle [dyne]
V_p: volume of a ferromagnetic particle [cm³]
J: intensity of magnetization of a ferromagnetic purtile [G]

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The mass balance equation which simulates the comminution process is composed of the selection function and the breakage function. Usually it is assumed that these two functions are independent of grinding time. This means that these two functions are not affected by a change in the size distribution in the mill. These assumptions are studied in this report, especially the influence of the mill charge and that of the powder in a mill upon these functions are investigated.
The selection function and the breakage function are obtained from unit grinding data of a series of single size fractions, the single sizes being changed under various feed conditions.
The results and discussions are summarized as follows:
1) The selection function decreases as the mill charge increases. This suggests that there may be something like sheltering effect among particles.
2) The breakage function has a tendency to shift to smaller particle size as the mill charge decreases, and then the value of the selection function increases. From these results, it has been shown that with every change of the mill feed, there are intimate relations between these two functions, which will be applicable to the control of mill products.
3) The “cushioning effect” is also confirmed experimentally by using these two functions. An excess of powder in a mill keeps particles from being ground, therefore it affects both the selection function and the breakage function.

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By the electrochemical method, the effect of chromate ions on the galena flotation systems were investigated under several conditions. The following results were obtained:
(1) In the solutions including precipitants of lead ions, the curves of poralization on galena electrodes were similar to that of the metals at a passivation state.
(2) When the electrodes were set at 0.5 and 0.8 volts versus satulated calomel electrode in 1/30M K2CrO4 aqueous solutions, lead chromate and lead dioxide films were identified by means of electron diffraction methods respectively.
(3) When the galena electrode surfaces were completely covered with lead chromate films, its thickness were accumulated to the order of 55-110Å.
(4) The anodic films were suggested to be ionic conductive. The electric conductivity of the lead chromate films changed with current densities.
(5) By the contact angle measurements of bubbles, it was suggested that the formation of lead chromate films and the oxidation of galena were required to depress the dotabilities of galena in mild alkaline solutions.

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Following two systems of slag were prepared, (1) In the slag of SiO₂-Al₂O₃-FeO system, SiO₂ was replaced by Al₂O₃ (2) In the slag of SiO₂-Na₂O-FeO system SiO₂ was replaced by Na₂O. These slags were fused with the commercial matte under desired condition.
Then, the suspended matte and the dissolved matte in those slags was separated respectively by brommethanol leaching and analysed for copper photoelectric-colorimetrically, and also, viscosity of those slags
were measured by rotating boll method and obtained following results:
1) The higher content ofAl₂O₃ incresed the viscosity of slags slightly and the amount of suspended matte in slags, but decreased the dissolved matte in slags. The total Cu losses in slags were eliminated by Al₂O₃.
2) Na₂0 in slags decreased theviscosity, both suspended and dissolved matte in slags.
3) The higher temperature and the increased the dissolved matte and decreased the suspended matte, so tho total amount of copper losses in slags were a little.

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A study was conduced to the recovery of beryllium from beryl by the nitrofluor process. A complete disintegration of the beryl was achieved within ten hours in a nonaqueous solvent consisting of 80 mole % HF-20 mole % NO₂ at 80°C. During the decomposition, complex metallic fluorides were produced, and all of beryllium dissolved in the solvent while aluminum precipitated leaving a few percent in the solution.
For further isolation of the complex fluorides, the beryllium bearing compound was heated up to 400°C, redissolved in the solvent and then dried again. Subsequently, most of aluminum and silicon were eliminated from the beryllium fluoride due to a poor solubility of AlF, formed during the heating and a sublimation of (NO) ₂SiF₆ respectively.

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