In the electrical prospecting, there are many problems to solve Laplace's equation by given boundaryconditions. These problems such as gravitation, electrostatics and magnetic, are investigated approximately by the resistance network analyzer.
In the present paper, the authors discuss the resistivity method, one of the electrical prospecting methods, by the analyzer which has been applied to the investigation of the electrical prospecting by the authors and their assistants since 1954.
It is shown that the resistivity curves obtained by this analyzer agree with the curves calculated theoretically and then the authors are sure that the method of determining the resistances of boundaries is settled satisfactorily, and this analyzer is a useful tool for the investigation of the resistivity method that can not be solved theoretically.

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In this paper the authors presented the results of the experiments in which the dynamic stresses within a rock caused by an explosion were measured. The dynamic stresses, γγ, θθ and ΦΦ, were calculated using the following relations derived from the theory of elasticity, _??_where U (γ, τ) =radial displacement, υ(γ, τ) =rate of change in radial displacement with time, γ=distance from the shot point, cL=propagation velocity of the longitudinal wave, λ, μ, =Lame's constants.
The experiments were carried out in a tuffacious rocks bearing copper ores and a 45g-cartridge of No.3 Take dynamite or Tokugiri dynamite was used as an explosive in each measurement. The results obtained are briefly shown below.
As to the characteristics of the dynamic stresses, it was found that the radial stress near the shot point (γ<about 1.5m) acted as the nonoscillatory compressive stress and this wave shape was almost similar to that of the radial displacement, but at about 2 meters distant from the shot poins, the wave length decreased rapidly and this stress became oscillatory, and the shape of the radial stress approached gradually to the wave shape of the rate of change in the.radial displacement with time with the increase of the distance from the shot point. On the other hand, the tangential stress started generally as the compressive stress, but it changed to the tensile stress at once, and its maximum value acted as the tensile stress. It was recognized that these characteristics agreed with those obtained from the theoretical calculation using Sharpe's theory. The values of about 600kg/cm² and 100kg/cm² were presumed respectively as the radial and tangential peak stresses at the point 0.5m distant from the shot point, and by comparing theses values with the results of the crater tests, which was carried out at the neighbouring place where the stress wave had measured, it was found that magnitudes of the stresses estimated by these experiments were reasonable.

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In designing the underground air conditioning, it is desirable to estimate the underground temperature and humidity that will be obtained after the air conditioning is operated, but the strict calculation of them is very difficult and too troublesome for practical purpose. The authors have studied on this problem for several years, The present paper describes the method of estimation, proposed by authors, which is obtained by summarizing the results of analysis recently carried out as well as already published and the results of measurement of underground temperature and humidity carried out over a long period of time.

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We have studied on the attempt to apply the electrostatic charge of dust particles to their suppression and collection.
In order to find out the dust suppressing properties of electrical neutralization, experiments were carried out with many powdered coal and rock materials and two-component mixtures of airborne dusts.
The results are summarized as follows:
1) The electrification of dust is affected by not only only its chemical composition, but also particle size, water content and velocity in a moment of injection or air pressure for thet action, e.t.c., .
2) Many silicates which caused silicosis are negatively charged, on the other hand, harmless dusts are generally electrified with positive charge.
3) The floatability of airborne dusts is suppressed by mixing with them the charged-dusts which have polarities opposite.

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Crack noises of rock specimens which are subjected to tensile or compressive stresses wers studied.
As the rock specimens, amphibole schist, slate, granite, liparite, porphyrite and tuff were used
A crystal cartridge and a D. C. pre-amplifier (Fig. 1) were used for recording the noises on a taperecorder. The figures and frequencies of noise waves were investigated on an oscilloscope. To count the noise frequencies, two types of recording appliances were developed; a D. C. motor type counter and an electromagnetic counter (Fig. 3).
Dimensions of the specimens, load applying method, induced crack noise frequencies, etc are summarized on the attached table. Fig. 5-12 are the crack noise count vs.' applied load. The crack noises of slate and granite were remarkable. The noise of tuff was poor.

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The floatability of the various non-sulphide minerals using dodecyl ammonium acetate, sodium dodecylbenzene sulphonate and sodium oleate as collector was measured, and the effects of the collector concentration and the hydrogen ion concentration on the floatability of them were considered.
The results of this study are summarized as follows;-
(1) The effects of the hydrogen ion concentration on the floatability of quartz, hematite, barite, calcite, scheelite, and wolframite were clarified in the solution of various concentration of the collector.
(2) The floatability of each non-sulphide mineral, as a rule, is governed by the ratio of [R⁺]/[H⁺] for cationic collector ro [R^-]/[OH^-] for anionic collector in the pH range in which each collector ion concentration is kept nearly constant.
(3) The critical contact curves for above minerals using dodecyl ammonium acetate, sodium dodecyl benzene sulphonate and sodium oleate were determined. The results are summarized in Fig. 15, Fig. 16 and Fig. 17, respectivelly.
(4) The relation between the collector concentration and the critical pH value was determined for above minerals; the following relationship comes into exsistence under the critical condition, [R⁺]/[H+] ^α=K for can ion i c collector or [R^-]/[OH^-] ^α=K for anionic collector, where both a and K are constant for each mineral

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Recent, developments in the field of measuring and controlling techniques are playing an important role especially in mineral dressing operations, where it is greatly expected to solve many complex and dynamic factors involved.
At Taishu mine, located on the TSUSHIMA Island (130km from Fukuoka), Nagasaki Prefecture, 14, 000 metric tons of a lead-zinc-iron sulphide are is being treated monthly by means of a straight differential flotation process accompanied with a dense medium pre-concentration.
Some experiments have been made with several new techniques in order to overcome operating difficulties, e. g. fluctuation in quality and quantity of run-of-mine ore, and poor separation of marmatite from pyrrhotite, etc., but many problems are still being left unsolved. A brief description is given on important matters in relation to the rationalization of milling operation in the mine.

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Effect of Impurities such as arsenic, antimony, bismuth and tin on the copper anode potential has been studied.
By the presence of β-Cu₃As in anode copper the anode potential is extremely raised, but a large portion of arsenic dissolves in electrolyte to form arsenic or arsenious acid. The raise in potential of antimony containing anode is caused by formation of Sb₂O₃ (ortho) slime. Bismuth does not dissolve in copper but presents at grain boundaries. Effect of bismuth on anode potential is quite different depending on Cl^-ion. The absence of Cl^-ion leads to raise in potential according to copper slime formed by the reducing reaction of bismuth. On the contrary, the presence of it brings about the fall in anode potential by means of a formation of bismuth oxychloride slime. Tin forms SnO₂ slime, but has no effect on anode potential. When the temperature of electrolyte is low, arsenic, antimony and tin lower anode potentials during the first stage of electrolysis. These phenomena can be explaind as the results of the decrease of activation polarization.

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The physical and chemical properties of the calcined dolomite are very variable by the calcining conditions.
The calcining conditions of dolomite, that is, temperature and time at the heating, are discussed.
The thermal decomposition temperature of dolomite is about 900°C.If the dolomite has been heated for a long time at the higher than this temperature, the density of the calcine increases, but the reactivity grows worse.
The measurement of reactivity using the hydration of the calcine is described, and it is found that this method is very effective to control the conditions of the calcination.

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