Rock specimens curred at various curring circumstances were prepared for this experiment. Dilatational wave velocity measured by ultrasonic pulse method, longitudinal vibration velocity measured by resonance frequency method and uniaxial compressive strength of the rock specimens were investigated and described to water content of them.
Results obtained in this paper are summarized as follows:
(1) The uniazial compressive strength varies in the form of following exponential relation as a function of the water content of rocks
σ_c=αe-^bω+c
Where, σ_c; uniaxial compressive strength (kg/cm²), w; water content (%) and a, b and c; constants.
(2) It was found that the rocks have a specific water content value which dilatational wave velocity becomes minimum. In the range of specific water content from this point to saturated state the dilatational wave velocity increases as the water content increases, and it increases again as the water content decreases in the range from the point to dry state.
(3) The longitudinal vibration velocity does not increase just as the dilatational wave velocity does. The velocity does not vary or tends to decrease slightly, as the water content approaches to saturation.
(4) At a certain specific water content, there is a point of inflection on this experimental curve relating of compressive strength, dilatational wave and longitudinal vibration velocity to water content of rocks. At the point of a certain specific water content, the action of the pore water is considered to divide into two stages, the one acts chiefly in free water the other acts chiefly in capillary water.

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Despite the large amount of investigation on the coal oxidation phenomena, there are many unknown parts about the behaviours of gaseous products, except for CO₂ and CO, in the early stage of the oxid tion process.
The authors have investigated the gases, especially the trace of hydrocarboneous gases, which were produced when the coal sample was heated in air or nitrogen atmosphere from room temperature up to 500°C and were analyzed by means of a gaschromatograph.
The present paper deals with the relation between the gaseous products and the temperature of the coal sample, and the strict classification of the primary gases (occluded gases) and the secondary gases (produced gas es). From the experimental investigation it is cleared up that olefin hydrocarbons such as C₂H₄ and C₃H₆ can be used as the most effective indicators for the early detection of the spontaneous combusotin of coal in mines.

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