One of the important problems in tunnelling technique is drilling, specially, drilling on hard rocks. It is said that brittle materials are easily fractured by impact. Therefore, supersonic vibration has been used for cutting of hard, brittle materials.
Application of vibration cutting on the rocks are stated in this paper using the ordinary rotary drilling apparatus on which supersonic vibration is added.
Although complete data on vibration drilling are not obtained in this series of experiments, some intermediate conclusions are obtained as follows ;
1. Penentration rate is increased with low thrust, on the contrary, cutting torque is decreased by adding vibration on the rotary drilling.
2. On the supersonic drilling bits.
a) Shape of bits: Rotary type of bits is effective compared with rotary-percussive type of bits when vibration (about 15μ) is added on the rotary drilling.
b) Abrasion of cutting edge: Abrasion of cutting edge is small when vibration is added on the rotary drilling, and abrasion rate is decreased in accordance with the increasing amplitude of vibration. Also, better penetration data are obtaied when high thrust is added on slow rotation.
3. Effects of amplitude.
It is found that some appropriate combinations are necessary between thrust and amplitude to get good results on vibration drilling. Therefore, to increase the penetration rate, optimum thrust and amplitude should be given in accordance with hardness of sample rocks.

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The authors describe a series of laborotory experiments to investigate the influence of surfactants on spontaneous heating of coal. The experiments have shown that suitable surfactants are able to protect from spontaneous heating. To decide whether surfactants be effective or hot, by the Wheele's method, have measured the differences of spontaneous ignition temperatures between coals treated by dilute aquaous solutions of surfactants and not. Even though adhesive moisture has evaporated from the coal treated by dilute solution of surfactants, the coal has shown higher temperature of spontaneous ignition than not treated. We have immersed coal into dilute solution of surfactants under high pressure. But the ignition temperature was almost as equal as the samples which were immersed at atmospheric pressure.
The prospective actions of surfactant as anti-oxidant is not chemical but physical. As thin film of surfactant covers coal surface, oxygen in air can't react with coal surface. The period of spontaneous heating f rom room temperature to ignition temperature of the treated coal is three times longer than untreated one.

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At Chikubetsu Coal Mine, we have begun excavation of prospecting mine road about 1, 700 meters long, using Russian PK-3 heading machine since February, 1966.
There are some difficulties in working, e. g. maintenance of PK-3's loop-feeder and transporting debris cars, we could perform heading of mine road in coal seam 20 meters per day.

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To study the correlation between the characteristics of fracture surface and the electrochemical properties of aluminum-silicate minerals, cleavage planes of kyanite, andalusite and sillimanite have been predicted from crystal structures of these minerals, and then the arrangement of atoms exposed to the surfaces along these ckavage planes have been assumed.
The electrochemical phenomena of these minerals in the solid-solution interface are discussed with respect to the weighted average charge per metallic atom on the assumed cleavage planes. The weighted average charge has been calculated as a function of oxidation number of the metals and number of oxygen atoms coordinated to these metallic atoms.
It is found that the pH of the isoelectric point of kyanite, andalusite and sillimanite decreases as the weighted average charge increases. Together with the above three minerals, corundum and quartz are found to be in good linear relation between the pH of the isoelectric point and the weighted average charge, indicating that the arrangement of metallic atoms on the fracture surface of minerals plays an important role upon their surface properties.
The effect of surface oxygen atoms on the pH of the isoelectric point of minerals is also discussed briefly.

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Iron sulfate was aimed to be utilized as a reaction reagent for sulfating roasting of pyrite cinder, intending to extract the containing copper by leaching. Optimum condition was obtained experimentally, and a mechanically raked multiple furnace was concluded as the most suitable type from chemical engineering standpoint. A 100t/day furnace was constructed and the good results were obtained. FeSO₄·7H₂O addition was observed a tendency to stick are at the drying hearth, and so FeSO₄·H₂O addition was prefered.
In the case of chloridizing roasting with rock salt, fine are is avoided because of sticking tendenig in the furnace. This ferrous sulfateaddition roasting can treat easily even all fine are charge.
Mixing with rock salt was effective in charge blending with copper smelting slag, in this roasting method.

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It is said that the coal crisis of today is in no way related to business cycles but arises from the growing structural change in the field of energy consumption. In our country, the coal mining industry has received various forms of protections from our government. If the coal mining industry in the future must reach a state of efficency whereby he is able to do his business without any government protection at all, what is to be done in the present days?
The most important demand for coal has been in the energy market. In this market the coal is challenged by the petroleum and will be challenged by the atomic energy. The situation of this competition is not in favour for coal. Coal as a chemical raw material also has received a challenge of the petroleum, and the situation is difficult for coal.
However in the author's opinion, this difficulty comes from the present technical level of coal chemical industry because our industry has lagged in a research to develope potentialities of coal. And the author believes that there are some new fields of chemical industry to utilize some particular properties of coal, such as high molecular weight, large numbers of condenced aromatic rings, etc., Then the author would propose to begin some research programes to develope a new chemical industry of coal.
Another field in which the coal has a special advantage is the metal refining industry, especially iron and steel making. As a reducing agent of metals, coal has many advantages, but the coking coal which is used for the present blast furnace is in poor production and inferior in quality in Japan. This is one of many reasons of particular difficulties in our coal mining industry.
This is the reason that we must attempt to develope some new iron making process without present high shaft furnace. Then the author would emphasize new developments of an iron making process with low shaft furnace which needs not the coking coal of high quality or some new processes with direct charge of coal.

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