A theoretical method of calculation of the lattice parameter of titanomagnetites, based on the concept of invariance of the distance “anion-cation” is presented. For the system Fe₃O₄-Fe₂TiO₄, experimental results obtained for synthetic titanomagnetites agree well with the theoretical curve if it is calculated by using the Akimoto model of cation distribution. Lines of equal lattice parameter between the joints Fe₃O₄-Ti Fe₂O₄ and Fe₂O₃-Fe TiO₃ have been drawn by assuming that only the Fe³⁺ located in the octaedral sites is oxidized. It is shown that our method of calculation of the lattice parameter can be used, reciprocaly, to determine the degree of oxydation of any natural titanomagnetites, even when they contain an important percentage of “minor” elements such as Al, Mg or Cr.

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From a palaeomagnetic study and radiometric investigation of Cretaceous intrusive rocks it was recently suggested that the Palaeozoic basin formed in the northeastern Japan was severely deformed at the end of Mesozoic era. This resulted in a narrowing and shortening of the entire length of the Japanese islands. The northeastern block moved southwestward by approximately 200km and southwestern northeastward by 150km, whereas the middle block remained relatively unmoved but was compressed between the two blocks. As the compressional forces increased, first the Palaeozoic sediments of the central block were uplifted, and subsequently the “median line” was formed. Along the latter line, the northern half of the southern block moved eastward relative to the southern half. A strong uniaxial stress superimposed upon a hydrostatic one occurred associated with the relative movement. The sediments as the results recrystallized to form the three major metamorphic belts.
During and after these movements, the compressed zone in the middle of the island was pushed to the east to form a great warp in the island. Such a simple model of a bend accompanied by a tension crack as predicted by Kawai, Ito and Kume several years ago was reconsidered. The contraction of the basin was finally related to the eastward drift of Asian continent upon the Cretaceous Pacific sea floor. The drift of the continents around the Pacific resulted in the narrowing of the ocean as well as the shortening of the coastal line. That of the Japanese islands is a part of the shortening that occurred around the Pacific zone.
We suggest that the heat of friction was accumulated at the deep-seismic plane (Benioff zone) at which the down and west going ocean floor and the up-thrusting mantle have been conflicting. The mantle nearby the deep-seismic plane was, therefore, warmed up until it partially melted. An acidic and migmatitic magma initiated at the friction interface was intruded into the pre-existing fracture zone occupying the front. Production of frictional heat was, we believe, succeeded even in the Tertiary period when effective drift was no longer evident but the retardation of the motion of the continent was much stronger. Heat required to cause the Tertiary volcanic activity might be due to this friction.

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Simultaneous measurements of the total geomagnetic field intensity by the same type of the proton precession magnetometers at two stations in NW Turkey have been taken cooperatively by a research group since December 1970. Up to the end of July 1971 mainly three probable local magnetic changes were observed. It was seen that after a decrease in the local field at a magnetic station (Erdek) a few earthquakes occured at either nearly N or S of that station, and after an increase in the local field an earthquake took place nearly W of the same station. In this paper the data and some results of the first part of observations are given.

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Simultaneous observations of the three components of geomagnetic variations were made with five flux-gate magnetometers and two Askania magnetometers on Miyake-jima Island during a period from November, 1969 to July, 1970. Observed records are analyzed mainly by making use of the techniques of power spectral analysis and transfer function. The island effect on geomagnetic variations is approximately separated from the effect of the central Japan anomaly by comparing transfer functions determined at each observation point. As a result of the analysis, it is found out that the central Japan anomaly gives rise to peculiar frequency characteristics at stations on Miyake-jima Island.
As for the island effect, a model calculation is made on the basis of a non-uniform thin sheet model. According to the comparison between the observed and calculated transfer functions, it turns out that the observed values amount to only about fifty percent of calculated ones as regards the transfer function Au. But in the case of Bu, the observed values seem to agree with the halves of calculated value as in the case of Au provided a constant, 0.1 say, is subtracted from the observed values. The constant thus introduced may be attributed to the effect of an east-west undulation of the conductor in the upper mantle near the Izu-Mariana island arc. The fact that the observed values amount to only about fifty percent of the calculated values seems to reflect the coupling between the sea water and the subterranean conductive layer which weakens the current induced in the sea.

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A field station for atmospheric electricity observations at Lanehead in the north Pennines is described, and results from July 1967 to July 1969 are presented. The diurnal variations for potential gradient, averaged over that time, show the universal 24-hr cycle with maximum at 19 GMT associated with ocean measurements, and the course of the other parameters is discussed. The station promises to be of value for studying both global and local effects.

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A simultaneous recording of electrostatic (e.s.) field, low frequency (l.f.) field change, optical, 1MHz and 14MHz radiations from ground flashes in a tropical area was made on a multichannel magnetic tape recorder. The pre-predischarge radiation was identified at high frequencies without corresponding optical, e.s, or l.f. changes. No sudden field change was observed at the beginning of the B process and, in general, the e.s. field change during the leader process could not be divided into the B, I and L stages; but the 1MHz and 14MHz radiation components could be divided in this way in many cases. The charges brought down by tropical ground flashes were found to be of the same order of magnitude as in other areas. The charge height of the cell leading to the first stroke was estimated at 6km.

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Lightning discharges which do not reach the ground have been divided into three types: (1) from the negative charge centre to air, (2) from the negative charge centre to the lower positive charge, (3) from the negative charge centre in a horizontal direction inside the cloud. No evidence of a vertical discharge to the upper part of the cloud was observed. (1) and (3) are similar in many respects electrostatic field change, optical radiation, low frequency variations) but the 14MHz radiation is different, (3) being quite different from others. Complex electrostatic field changes were recorded for the three types.

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An index for the quantitative expression of short-period geomagnetic activity is being proposed. The index is based on the peak-to-peak range in 2 (or 2.5) min intervals, and is derived from amplitude-linear (fluxgate) instrumentation. It is easily derived, objective, and has high resolution in both time-scale and amplitude; however, it does not distinguish between different frequencies. Such a simple “general-purpose” index is meant to supplement, rather than to replace, the more specialized indices which are currently used for specific applications. Specifications and criteria are outlined, and examples of applications to specific studies (diurnal and stormtime variabilities) are shown.

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The correlation analysis among A₁-absorption data measured over Calcutta with solar 10.7cm radio wave flux and X-ray energy flux between 0-8 and 8-20Å bands has been made. The absorption data are found to correlate with 10.7cm flux values more strongly than with the X-ray energy fluxes, thereby clearly suggesting the importance of UV fluxes, having very good correlation with 10.7cm flux values, in D-region ionization.
The response (denoted by b in the equation B=a(1+b⋅R_z) (db); see the text in detail) of A₁-absorption data for frequencies in the range from 2.2 to 5.5MHz towards sunspot number has been found to vary from 2.3×10^-3 to 8.0×10^-3. The increase in response can be attributed to an increase in the collision frequency in the deviative region with increasing solar activity.

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