There are many limonite deposits genetically related to the mineral springs at the vicinity of the Azuma Volcano, Fukushima Prefecture. Near the Nuruyu Spa three limonite deposits are found, and the mineral water shows highly acidity owing to the presence of sulphuric acid.
This paper is concerned with studies on the chemical compositions of both mineral waters and limonites, and the relation between the pH of mineral water and limonite depositions. It seems probable, on the basis of the experimental evidence, that the optimum pH range for the iron depositions is 3.5-6.0 and that in this pH range iron precipitation is increased with higher pH. Differential thermal analysis curves and X-ray powder diffraction patterns show that the limonites deposited from the mineral springs essentially _consist of amorphous iron hydroxide containing a small quantities of goethite. Odo or yellow limonite from Akanuma and Fukuo shows the clear X-ray powder diffraction patterns of goethite.
And as the result of experiments, it is shown that various minerals such as goethite, lepidocrocite, magnetite, and siderite are formed in accordance with the change of pH from 5.0 to 12.0 when NaOH or (NH₄) ₃CO₃ solution is added to ferrous sulphate solution containing sulphuric acid or oxalic acid.

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The Efficiency Reserch Group of Yanahara Mine, founded in 1953, have engaged in the studies analysing mine works and setting up measures to determine those performance standards available for universal, conditions at workings.
The purpose of these studies is to get the bases of plans, operations and determination of incentive. wages necessary for engineers or supervisors.
Among those studies, this paper is related on Diamond Drilling, and is composed of following items;
(1) General equation of performance standards
(2) Ready Charts to determine the performance standards
(3) Work analysis on the operatinal conditions, i, e. rate of drilling, time for bit exchange and core recovery, accessory time accompanied with driling work, etc.
(4) Case study utilizing above Ready Charts, regarding (a) the relation between the efficiency and representative conditions such as depth of bore holes, rate of drilling, frequency of core recovery, ete.(b) optimun height of boring tower, (c) comparison between wire line type and conventional one.

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Since this new mining method was introduced to Japan, many experimental works have been carried out in laboratories and at collieries. Many good results were reported already and some coal mines have achieved very high productivity.
But development of this technique requires theoretical analysis as well as experimental works on parameters of high-pressure jet directed against the face, and stress distribution in coal seams in hydraulic crushing.
The auther analyzed these problems theoretically and mathematically. Results acquired show relations between parameters of jet and stress distribution in coal seams related to distance between face and nozzle.

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For the purpose of determining the performance of nozzle of the hydraulic mining device, the authors investigated the flow characteristics of water jet which had ever studied theoretically and r, experimentally under changing the discharge pressure between 3kg/cm² and 10kg/cm² at nozzle mouth with diameter 6 mm.
The flow characteristics of water jet were given as follows;
a) Divergence coefficient of jet;_??_
b) Profile of jet;_??_
c) Dynamic pressure distribution along center line of jet;_??_
d) Transition length of jet;_??_
e) Dynamic pressure distribution along radial axis of jet;
_??_
Where l=distance of the jet from the nozzle, l_T=transition length of jet, D₀=diameter of the nozzle, R₀=radius of the nozzle, R=arbitrary radius of the l jet at the distance l, D_l=diameter of the jet at the point of distance l, _??_(called Jet number, γ, γa=specfic weight of the water and air, H₀=discharge pressure head and Ci =surface tension), P₀=discharge pressure, P_m=dynamic pressure along center line of jet and P_m=dynamic pressure at the point of arbitrary radius R.

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The extraction of nickel from the New Caledonian garnierite are with sulfuric acid solution was studied:
1) 10g of the are was pre-treated with sodium hydroxide solution of the concentration of 33-150g/l at about 200°C in a autoclave before leaching with sulfuric acid solution. The pre-treated are was leached with 200 ml of 5% sulfuric acid first and then leached again with 10% of sulfuric acid for an hour. The nickel which was leached out with the above mentioned treatment was 89% of the total nickel in the ore, but it was about 79% in the case of one which was not pre-treated with sodium hydroxide solution.
2) The pressure leaching of nickel with sulfuric acid was applied to the are which was not pre-treated. 20g of this was laachd with 300ml of sulfuric acid solution under the compressed air at different temperatures. 90% of the nickel in the are was leached out under the following condition; the concentration of sulfuric acid was 10%, the temperature 180°C, total pressure being 10kg/cm², the time 2 hours, and the agitation speed 200 r.p.m.

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