The present paper is concerned with the problem of the self-exciting process in magneto-hydrodynamics studied in a previous paper (referred to as Paper I). In §2 and §3, by solving a differential equation numerically, the results in Paper I are checked in a conclusive way. The existence of a self-exciting dynamo having thus been shown, the detailed structure of this dynamo is studied in §4 and §5. In §6, a new approximate method of solving the problem is proposed and applied to the problem in Paper I. This method of approximation is found to be fairly useful. By using this method, it is shown in §7 that the self-exciting dynamo is possible by the fluid motions of considerable varieties. The orders of magnitudes of the fluid velocities required are found to be the same as that in Paper I.

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1. The question, "Is the earth's core gas or liquid ?" has been discussed from the standpoint of statistical mechanics. It has been found that for each element there is a critical temperature, below which the liquid state is stable in the core and above which the gaseous state is stable and this temperature depends on the atomic number of the element. This temperature is named the critical temperature for that element. 2. The molecular viscosity coefficient of the core has been computed. In case the liquid core is stable, the coefficient is 10-2-10-1 poise, while it is 10-3 poise in case the gaseous core is stable. Moreover, it has been shown that we can estimate the temperature of the liquid core, if its composition is known, or, conversely, we can estimate the composition, if its temperature is known. 3. Using the theory of visco-elasticity, the attenuation coefficient of the core for seismic waves has been obtained. The result agrees with observations of seismic waves. 4. The electric and thermal conductivities have been obtained, using formulas of statistical mechanics. Following values have been obtained: electric conductivity: 2-4×103 ohm-1 cm.-1, thermal conductivity: 0.05-0.5 cal. cm.-1 sec.-1 deg.-1.

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At one of the tiltmeter stations operated by us, an unusually large tilt of the ground was observed during 3 months preceding the occurrence of the strong earthquake of March 7, 1952, of which the epicentre happened to be not very far from the station.
After careful investigations of the reliability of the observations, it has been concluded that the ground tilt was really in an intimate connection with the earthquake occurrence. It is emphatically stated that the observations of the ground tilt are one of the promising methods useful for predicting the occurrences of destructive earthquakes.

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Concerning the relations between geomorphological ground conditions and earthquake damages throughout the Prefecture of Kochi, Shikoku, Japan, due to the Great Nankaido Earthquake of December 21st, 1946, we have noticed several interesting facts:
i) On the sandy ground of beach ridges, damages were found only in those parts, where the basement bed rock lies deep, or where some kind of soft mud layers lies beneath sand, or where the ground consists of very soft sand, which has been deposited in very recent years or accumulated by wind blow. On the contrary, there was scarcely any damage, where the bed rock lies near the surface, or where hard materials such as pebbles or stones lie under the sandy ground, or where the surface sand are consolidated. Practically, of course, some of the above mentioned conditions coexist complicatedly combined in the same place.
ii) There were severe damages on swampy low lands behind the beach ridge.
iii) Even on alluvial plains, we found patches of rather slight damages among otherwise severe damages. Under those patches of slight damages stony layers were usually found as is the case on beach ridges.
We have examined the hardness of the surface ground by a simple hand-boring stick of about 1m. length.
Existence of the stony layers under the ground was conjectured by the distribution of Cl' contents in underground water. Where there are stony layers under the ground, underground water flows constantly and the Cl' contents must be small. On the contrary, underground water cannot flow easily in clay, mud or fine sand layers, and the Cl' contents must become great there. A typical example of the above two cases was encountered in the town of Nakamura, where the geographical distribution of earthquake damages clearly agrees with the Cl' contents distributions. (Fig. 10)

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A method has been shown to calculate the distribution of ∂g/∂z from that of, g. The second derivative method has been critically reviewed.

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The gravity anomaly is necessarily associated with the anomaly of the vertical gradient of gravity. The relation between the two kinds of anomaly has been invest gated. The anomaly of the vertical gradient is sometimes too large to be neglected in the free air reduction of gravity.

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