chemically analysed specimens of homogeneous titanomagnetites separated from various volcanic rocks were examined magnetically and crystallographically. Care was taken not to use the titanomagnetite carrying exsolved ilmenite-hematite series minerals. About 80 percent of the present specimens possesses the chemical composition situated in a magnetite-ulvöspinel-ilmenite compositional field in a FeO-Fe₂O₃-TiO₂ ternary system. Natural occurrence of the homogeneous titanomagnetite of which chemical composition enters into a magnetite-ilmenite-hematite compositional field was also found in some volcanic rocks. The concept of the generalized titanomagnetite, i.e. the spinel phase in the FeO-Fe₂O₃-TiO₂ system with varying vacancy in the metal ion site of the crystal structure, was applied for the magneto-chemical study of these natural titanomagnetites. The magnetic and crystallographic properties of the present specimens are interpreted successfully by making use of the equal lattice parameter diagram and equal Curie temperature diagram on the FeO-Fe₂O₃-TiO₂ system both of which have been determined from the synthetic experiments. A remarkable character that the titanomagnetite in some volcanic rocks is separable to an ensemble of the single phase grains of which chemical composition varies grain by grain nearly along the reduction-oxidation line was also found.

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For the daytime E-layer ionospheric scatter propagation, the controlling solar influences cannot be neglected. To account for the experimental results obtained by D. K. Bailey et al., showing solar influences, a new theory is proposed which introduces the effects of ion production and recombination to villars-Weisskopf's pressure theory. The electrons are assumed to be compressed or dilated at the same rate as the air itself, the latter being subject to adiabatic change of pressure, while the electrons and ions moving with the air molecules are produced by solar radiation and then recombined. The results obtained are quite satisfactory to account for the dependence of received scattered signal intensity on both frequency and scattering angle, at least concerning the daytime solar controlled scatter propagation in the E-region.

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Experimental studies have been carried out on the remanent magnetization generated by chemical reactions (which may properly be called chemical remanent magnetization or C. R. M. in abbreviation) for both natural and synthetic specimens. Remanent magnetization generated during two kinds of reaction processes, that is, reduction of α-Fe₂O₃ to Fe₃O₄ and oxidation of Fe₃O₄ to maghemite is firstly examined (Part I). It may be safely concluded that the remanent magnetization thus generated has an intensity which is intermediate between isothermal remanent magnetization and thermo-remanent magnetization, and that its magnetic and thermal stability is similar to that of thermo-remanent magnetization, much higher than that of isothermal remanent magnetization.
In Part II, magnetic properties of several natural rocks and ore deposits containing maghemite are systematically examined. These natural specimens can be classified into two groups with respect to the magnitude of Qn-ratio; the one has large magnitude of remanence and large Qn-value amounting to 100, while Qn of the other is quite small. Greatest parts of natural remanent magnetization of the specimens having large Qn-value are attributable to the chemical remanent magnetization of maghemite, which is considered to result from oxidation of magnetite probably by weathering at nearly atmospheric temperature. On the other hand, the natural remanent magnetization of the specimens belonging to the second group with low Qn are found to be merely isothermal remanent magnetization. These two groups are also compared with each other from the petrological point of view.
The results of these investigations suggest that various magnitude of remanence can be generated by chemical processes possibly according to the mode of precipitation of ferromagnetic minerals.

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In this paper an attempt is made to determine the atmospheric temperature and wind velocity at high altitude from sound propagation.
The space to be measured is divided into several layers, in each of which the temperature and wind distributions are assumed to take the form of second order equation with height. In this assumption the formulae to deduce the temperature and the wind are given by use of Snell's law for sound propagation under the existence of wind.
As the results involve hyperelliptic integrals, it is difficult to get explicitly the quantities giving the distributions of temperature and wind velocity. But it will be possible to find the numerical values of the required quantities by numerical calculus of integral.
It is shown that the results are determined uniquely, in general, and that in the simple case, too, for explaning this theory and using practically.

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