This paper presents a general description of solar furnaces and a survey of high-temperature physics conducted by using a large furnace in Tohoku University. A general description involves the solar energy available on the earth, the optics of a solar furnace and some large furnaces in the world. A solar furnace in Tohoku University is that of the heliostat type, provided with a paraboloidal concentrator, 10m in aperture and 3.1 in aperture ratio. Mirror segments of the concentrator have been ground and polished into portions of a paraboloid and aluminized to have the highest optical quality. Using the furnace, crystals of various oxides including MgO, CaO, Y₂O₃, ZrO₂, ThO₂and UO₂were grown, and some of their optical properties were investigated. In order to measure the surface temperature of a target, a pyrometric method has been developed using infrared radiations which are abscent in solar radiation on the earth. A high-temperature X-ray diffractometer has been designed and constructed in which the specimin is heated by a solar furnace. By this apparatus, the thermal expansion of CaO and SnO₂were measured at high-temperatures. Using micro-wave technics, a novel method of measuring electrical properties of oxides at elevated temperatures has been developed also, by which the electrical conductivity of MgO is being investigated.

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The dynamic stresses in a material caused by a blasting in close proximity to the pre-split have been analysed with the aid of a numerical technique which involves the finite-difference approximation to the momen -tum equations. And then, the effects of the pre-splits produced by the pre-splitting on both the vibration and the breakage caused by the blasting in close proximity to it, so called a main blasting, have been discussed quantitatively. The main results obtained are as follows;
1) Both the amplitude of the vibration and the growth of the cracks caused by the main blasting are reduced considerably due to the existence of the pre-splits.(See Fig. 4, Fig. 5, Fig. 9 and Fig. 12)
2) Existence of many discontinuities makes the greater change in the wave form of the stress waves which propagate across the discontinuities.
3) The pre-split has a greater effect on the control of the cracks caused by the main blasting even if it has a smaller effect on the reduction of the vibrations.

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The forced vibration of an off-shore boring rod caused by wave was analysed under the assumptions of a linear damping of the surrounding water and of a deep water wave with finite amplitude for a disturbing force.
The results obtained by this analysis were as follows:
1) The maximum amplitude of lateral vibration of rod caused by the wave occurred in different positions according to the vibration modes.However, the maximum bending stress produced on rod always occurred either on the surface of the sea or at the bottom of the sea.
2) The condition of resonance appeared when the quantity, kcu/ω_n, approached to the value little less than 0.5, wherek, cωandω_nwere wave number, wave velocity and circular natural frequency at nth order respectively.In the narrow range of this quantity including the resonance point, both the amplitude and bending stress of rod abruptly increased their magnitude.
3) Within the range in question, the amplitude of vibration of rod in resonance decreased and the corresponding bending stress increased in higher modes of vibrations.In addition, the amplitude as well as the bending stress in resonance was exponentially decreased as the increase of damping effect of the surrounding water.
4) The amplitude and the stress in resonance increased with the increase of value of the weight parameterW, and decreased with the increases of the'weight ratioKandl/L, these quantities of which were defined by the author.

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In this paper causes of an outbreak of gas-outburst have been discussed that occurrence of gas-outburst is due to blasting. Under the condition that, geologically, gas-outburst is apt to occur, but actually does not happen only by such reason, the effect of blasting forces to the surrounding causes gas-outburst to be necessary.
Consequently, the state and the result of its occurrence sometimes is similar to that of the case which might be caused by geological reason.
As concerns these, this paper give an example and concludes the cause of gas-outburst statistically, and also at the last parts refers to the reason why occurrences of gas-outburst are very few in the long-wall mining system.
Many researchers regard that the cause of gas-outburst is gas pressure or earth pressure, and some others consider that blasting is the initiator of gas-outburst. But here is a significant value in this paper to put forward that in almost all cases the main cause of gas-outburst, is due to the effect of blasting forces.

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Outbursts of coal and gas occurred at the longwall faces in two collieries recently. From investigation into these outbursts, it became evident that the burst coals were from “Ganbai” (soot-like coal) of the upper band in the working seams and from “Hiki” (drag coal) along the faults. Samples of gas and coal taken from the burst coal seams were analyzed, and it has been found that the burst coals protruded into the faces and the solid coals left around the burst cavities indicated low atomic ratios of hydrogen-carbon and oxygen-carbon, and the compositions of gas were mostly methane and nitrogen. Such facts lead us to the consideration that some outbursts occurring at coal faces as well as at coal headings are possibly related to gases and vapour which had risen through faults from magma reservoir.

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In the present paper microscopic studies of fissures in coals picked from coal seams are described. The results obtained are as follows:
1) The fissures in coals thrown out by outbursts which occurred recently in 3 or 4 coal mines including Simizusawa Coal Mine, show the same appearance as shown in the previous paper.
2) In the samples of coals taken from the vicinity of folds, foults and volcanic dikes underground, the fissures are not found, but in the samples crushed by air hammer, the fissures are found. These fissures are similar to the fissures in coals thrown out by outbursts. From this fact, it is presumed that these coals have been kept under the tectonic stress.
3) When a normal volume of cuttings is produced by boring in the working face, the fissures are not found in the cuttings, but when the several times of cuttings are produced, the fissures are found. Therefore, the measurement of the volume cuttings of by boring in a coal seam may be used, as a method of the practical prediction of outbursts.
4) In the coal fractured by adding an external force such as compression, tension, bending or shearing stress, the fissures are not found. But after the above fractured coal is crushed by air hammer, the fissures similar to those in coal thrown out by outbursts are found in coal crushed by air hammer.

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The potential and pH measurements of the SO₂-H₂O system were carried out at 90°Cby decreasing the pH of sulfate solutions (about 1g-ion/l) containing dissolved sodium sulfite (1, 0.1, and 0.01mol/l) or absorbed SO2 by the aid of a rotating Pt electrode, a glass electrode, and two reference electrodes (S. C. E.).
The results obtained were summarized in the potential-pH diagrams (Fig. 3 and 4). A large discrepancy between measured and calculated potentials, suggested that the potential of the system was not directly determined by the sulfate/sulfite redox reactions and that a certain oxidized or reduced intermediate species hould be taken into account. Redox reactions containing dithionate ion as such the species were discussed.

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The zinc reduced ash of Annaka Refinery, Gunma Prefecture, is treated at Fujioka Refinery, where pig iron, electrolytic iron and other valuable matters are recovered successfully.
The object of this investigation is to clarify properties of the zinc reduced ash as raw material. The results obtained are summarized as follows:
1) The most frequent size of the reduced ash lies between 5 and 10mm, and the 80 per cent size based on Gaudin-Schumann graph corresponds to 15mm.
2) As a result ofX-ray diffraction concerning the reduced ash, diffraction lines ofα-Fe, FeO, ZnO, C, α-Mn, Pb, ZnO·Fe₂O₃, Zn₂SiO₄, CaO·Al₂O₃·2SiO₂and 4CaO·Al₂O₃·Fe₂O₃were recognized.
3) Chemical analysis, visual inspection, microscopic observation and observation byX-ray microanalyser were performed for the purposes of confirming the result mentioned above and investigating textures of the reduced ash.

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