The results of fundamental experiments revealed that the coal filled in a pipe was moved by low water pressure, and it flowed in a pipeline with little delay when velocity of stream exceeded 3.5m/s. According to these results a multi-pipe type coal feeder was invented. It consists of several parallel long lock chambers which are branched from a delivery pipe of a high pressure pump. And they have approximately the same diameter of the conveying pipe. One of these is fed coal and water mixture by means of a low pressure sand pump. After this, the mixture is pushed into the conveying pipe by the high pressure water. This process is repeated one after another, and coal is transported continuously.
The auther produced a hand-operated model of this coal feeder for laboratory tests, then made its valves act automatically. The practical tests of this feeder was carried out at Yoshima colliery. 20.000t of coal was transported by 7 in. pipeline with it. The test results revealed that it had the transporting capacity of 100t/h, registering the volume concentration 20% Now the test is continued on commercial basis at Sunagawa colliery. The transportation height is 490m and the length of pipeline 2, 046m. There automatic control of concentration of coal in the pipeline is attemped to economize the transportation cost.

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Domengine sandstone, Boise sandstone have been. subjected to triaxial Compression in which strain, porosity and permeability are measured simultaneously. The experimental apparatus are assembled with testing machine, triaxial vessel, high pressure pump and two measuring appliances which are strain meter and mercury burette to measure the permeability and pore volume. Domengine sandstone is porous and brittle material. When confining pressure has been varied between 50 to 250 (psig), the elastic moduli are increased depend upon the raising of pressure.
On the Boise sandstone, the porosity does not so much change that the permeability does under triaxial tests. Porosities changed between 26.8% and 25.7%, but otherwise permeabilities varied from 1, 080 to 536 millidarcy.

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Chemical inter-diffusion coefficients of sulfur, selenium and tellurium in liquid _silver have been measured with the modified capillary reservoir method in the temperature range from 1, 000°C to 1, 300°C.
Several liquid Ag-S, Ag-Se and Ag-Te alloys ranging in composition from 0.2 to 0.8wt% S, from 0.5 to 3.0wt% Se and 5wt% Te were used as the liquid alloys for reservoir. Results obtained in the present investigation are summerized as follows:
1. The diffusion data fit the following Arrhenius type equations in the temperature range from 1, 000°to 1, 300°C
for sulfur Dc=6.0×10^-3exp (-11500/RT) cm²/sec Q=11.5±1.0kcal/mole for selenium Dc=1.9×10-3exp (-10300/RT) cm²/sec Q=10.3±1.2kcal/mole for tellurium Dc=9.9×10-4exp (-9200/RT) cm²/sec Q=9.2±1.8kcal/mole
2. The diffusivity increases (Ds>Dse>DTe) with the decreasing radius of diffusing particle (rS<rSe<rTe). it is indicating that the size of diffusing particle is of the important factor for inter-diffusion.
3: From the results obtained in this study and the previous one, it has been found that the rate of transportation of void or the re-distribution rate of free volume should be considered for the derivation of theoretical equation for inter-diffusion, as well as the size factor of solute.
4. Apparent activation energy for inter-diffusion may be expressed as the sum of the activation energy of self-diffusion of solvent and the interaction energy between solute and solvent. Values calculated from the following equation agreed very well with the experimental values.

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“Kuroko” so called Black ore is a kind of complex polymetallic sulphide ore, the texture of which is very intimately associated with sulphide minerals such as copper, lead, zinc, iron etc. Numeraous deposits of the ore, which are widely distributed in the north-eastern district of Japan, are actually being mined and their output are concentrated by differential flotation processes. But, because of complexities in the nature of the ores, namely the variety of mineral content and mineral composition, fineness of mineralogical texture and tendency to oxidize easily, it is considerably difficult to obtain satisfactory separation of the costituent minerals.
This article describes a general survey and some technical problems on the mill operations of the ores. The problems which were pointed out and reviewed by the author are as follows;
(1) ore characteristics and processes of separation.
(2) liberation of individual minerals.
(3) processes for treatment of slime.
(4) oxidation of ores.
(5) flotation reagents used and elimination of their residual effects.
(6) variation in grades and properties of feed ores and overall control of mill operation.

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