1. The Volcano Yakedake (Prefectures Nagano-Gifu), in Central Japan has been almost dormant since 1932, only with weak fumarole activity in and around its summit dome. 2. Temperature of the fumarole gases, steam vapour with or without a little amount of H₂S and SO₂, is not higher than 100℃. 3. The water in these five craterlets on the summit faintly contains some chemical components and in the two of them, some influences of volcanic emanation are found in the composition of the water. 4. In the peripheries of the active fumaroles, some alteration minerals such as halotrichite, alunogen, and natron-alunite, were identified. The former two are mixed with each other in various proportion. The chemical transformation of the volcanic rocks in its alteration processes is here discussed.

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Nature and origin of volcanic micro-seisms (micro-tremor or harmonic tremor) are to be attached great importance for the prediction of eruption of volcanoes, especially of Strombolian and Hawaiian type. Ten years ago, OMER. G.C. advocated the origin of volcanic micro-seisms observed at various volcanoes as the natural period of longitudinal vibrations of horizontal elastic layer composing the outer superficial layer of the volcanoes. However, his adopted materials, being the base of the calculation, jumbled the observed data obtained by the seismographs of various characteristics and at various distance from the origin. Therefore, we gathered the seismograms observed by the seismographs of the same frequency characteristics and registered very near the source (not more than 600m). The frequency distribution of micro-seisms were constructed for the volcanoes Kilauea, Nyiragongo, Mihara. Aso and Sakura-zima. The results show that the predominating period of the micro-seisms becomes shorter as the volcano becomes acidic. The author concluded that the volcanic micro-seisms are generated by the free logitudinal vibration of the viscous lava column having the effective length of 500m. The natural period for each volcanoes as calculated by verifing the viscosity of the column agreed satisfactorily with the observed predominating period of volcanic micro-seisms.

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At the bottom of the crater and the slope of the central cone Myokogatake of Mt. Iwate many fumaroles are found, from which an enormous amount of volcanic gases containing H₂O, H₂S, SO₂, CO₂, HCl, HF, HBr etc. flow out. The authors examined those fumarole gases on July 27 and September 29～30, 1960. We found sublimates of alunogen, halotrichite, sulfur etc. at such fumaroles that show the temperature near to 100℃ and ammonium chloride at the fumaroles showing 144～205℃. As to the chemical compositions of ammonium chloride, condensed waters and fumarole gases, the following results were obtained : 1) Ammonium chloride No.1. Temp. 205℃, NH₄ 33.5, Cl 65.9, SO₄ 0.0, Br 0.15, B 0.000 (wt. %) (Theoretical value: NH₄ 33.7, Cl 66.3) No.2. Temp. 183℃, NH₄ 33.4, Cl 66.1, SO₄ 0.0, Br 0.21, I 0.0003, B 0.000 (wt. %) No.3. Temp. 144℃, NH₄ 33.6, Cl 66.3, SO₄ 0.0, Br 0.14, I 0.0003, B 0.000 (wt. %) 2) Condensed water . No.2. Temp. 183℃, pH 1.4, H₂S 104, SO₂ 143, SO₄ 5.4, Cl 2876, Br 1.0, I 1.8, B 0.0, Na 2.38, K 0.16, NH_4 16.2, Fe 0.10 (mg/l.) No.3. Temp. 144℃, pH 1.8, H₂S 241. SO₂ 297, SO₄ 1.0. Cl 784, Br 0.2, I 0.3, B 0.0, Na 6.21, K 0.43, NH₄ 18.4 (mg/l.) 3) Fumarole gas No.2. Temp. 183℃, H₂O 98.3, CO₂ 1.46, H₂S 0.109, SO₂ 0.0817, HCl 0.0376, NH₄Cl 0.00181 (vol. %) No.3 Temp 144℃ H₂O 98.2, CO₂ 1.84, H₂S 0.117, SO₂ 0.152, HCl 0.0185, NH₄Cl 0.00167 (vol. %) The temperature above mentioned was measured at the orifice of fumaroles.

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