The stricken district where the most severe shock was felt from the earthquake on the first day of September is shown in Fig. 1.
In Tokio and Yokohama, not only the houses were crumbled to the ground by the tremendous shock but were literally wiped out by the conflagration that spread immediately after the quake over two-thirds of Tokio and practically all of Yokohama. The appalling catastrophe which we had encountered could seldom be found in our long history, and, as a result thereof more than 300, 000 houses were burnt in Tokio and more than 70, 000 houses in Yokohama, more over about 100, 000 of human lives were lost.
The electric rower systems that supply the two cities are numerous as shown in Fig. 1; but these were all damaged more or less and it resulted in a complete interruption of service for two days in Tokio. However. after utmost efforts, electricity was first supplied to the reserve pumping plant of Tokio Municipal Water Works and to the wireless stations, then to the street lights. From the fifth day house lighting and small motor circuits were gradually put into service again, until the tenth day when the power supply in the district unaffected by the fire was almost restored. In Yokohama, from the eighth day power was sent into some of the unaffected districts: on the eighteenth the supply to these districts was nearly recovered.-Later, barracks were built rapidly in the devastated area and to-day, three months after the disaster, the supply of electrical power came up to about 70% of that consumed before the quake.
The system that suffered most damage is that of the hydro-electric plants of Hakone district (No. 1 and No. 2) where the banks of the reservoirs burst open, the water channel was demolished, the walls of the structures were cracked or tumbled down. In this district, even to-day, three months later, but few of the plants have been repaired. In the Katsuragawa system, (No. 4 in Fig. 1) open channels, reservoirs and brick structures that were located on a layer of loose earth were cracked, but those channels and reservoirs constructed on solid earth and buildings reinforced with steel frames were unaffected. In these plants, although the machines were all shut down at the time, 70% of the capacity is now being generated. All the other systems escaped from damage.
The transmission lines of Hakone system (No. 1 and No. 2) suffered heavy damage; the poles and towers were either leaning over or demolished. The 150, 000 volt transinission line of Keihin Denryoku, (No. 4) in spite of passing partly through the region affected by the severe earthquake, suffered no damage of consequence except that only two towers were toppled down, and consequently the line was restored on the thirteenth of September. In Katsuragawa, Gumma, Kinugawa, Inawashiro and Shin-etsu systems, (Nos. 3, 6, 7, 8 & 9 respectively in Fig. 1.) the transmission lines were safe and were able to transmit the usual power at once; the substations built of brick reinforced with steel frames or of reinforced concrete were safe, while those built of brick only were ruined.
As the transformers are commonly provided with castors for transportation, a number of them tore loose from their settings and broke the oil and water pipes in consequence. From this we have learned that such apparatus should have been fixed so as to prevent moving by earthshaking. Of lightning arresters both the aluminum cell and oxide film types were knocked over. As most of the storage batteries installed in the stations were smashed, the operation of oil circuit breakers had to depent upon the motor-generator at all. Of underground cables, where the method of direct laying in the ground was used, they were found to be without injury; however, owing to the burning down of bridges many of the cables were interrupted at those portions. Of those layd in ducts in loose earth, the ducts and manholes suffered some open cleavage.

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The free potential of the grid and plate of the triode valve was measured by means of a quadrant electrometer. The free potential of the grid was found to be negative in most cases even if the plate voltage is kept high by external source of E. M. F. The effect of grid leak on the free potential of the grid was studied in detail and from this result the apparent distribution of the initial velocity of electrons was calculated.
The capacity of the quadrant electrometer was measured by beat method using a triode valve audio-frequency oscillator. From this value of capacity, the leakage of the quadrant electrometer and the triode valve was determined by time constant method. The time constant of the discharge of the quadrant electrometer was increased when the grid is connected to the electrometer and the valve was filled with electrons by heating the filament previously. This is due to the space charge which gradually accumulate to the grid and discharge through the leak. By this conception the equivalent electrostatic capacity of the vacuum space of the valve was determined. (April, 1923).

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It is very important to determine directly the sense of rotation of various diagrams such as dynamic characteristics, Lissajous' figures, etc. appearing on the fluorescent screen of the Braun tube oscillograph. But so far there seemed to have been no such direct method as far as the writer is aware, and the sense of rotation has usually been infered from the properties of observed phenomena. The writer has recently tried a stroboscopic method which would render some service in the study of this line.
The necessary additional implement is a thin metallic disc revolved with a suitable motor which was, in the writer's exoeritnent, an induction motor connected to the same source as that of the diagram. The disc has some small holes equidistant along the circumference of a concentric circle.
If the diagram on the fluorescent screen is looked at along an imaginary line fixed in space through the holes of the revolving disc, the fluorescent spot may be seen to move in the same sense or opposite to the rotation of the diagram, according to the frequency of the diagram, the speed of the disc and the number of holes. If the number of holes be made equal to that of pairs of poles of the induction motor, the spot always seems to rotate in the same sense as the diagram.
The writer has made several experiments to verify this method. By aid of the results of the experiments, he confirmed that the method is applicable to the diagram of low and moderate frequencies.

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1. In the former paper (This Journal p. 535 1919; Researches of Electrotechnical Lab., No. 73, 1918.) the writer treated on the solenoid with rectangular section and derived a formula for the calculation of the self inductance of such solenoid. In the present paper the writer discusses the range of application in which the formula can be used with fair accuracy.
2. Dr. Esau's criterion on the applicability of the writer's formula (Jahrb. f. drahtl. Telegraphie, Dec. 1921) is reviewed and it is shown that Esau's conclusion must be modified owing to his erroneous calculation of the correction factor.
3. From experiments as well as calculation, it is shown that the writer's formula may be applied with accuracy for all the coils however flat may be with the ratio of pitch to the diameter of the wire g/2ρ less than 6 or 7 and even for coil with this ratio so far 20 or 30 the formula may be applied with several percents of error for moderate values of the ratio of the side of section to the length of coil (δ) such as 40 or 50. It is also shown that the range of δ applicable with certain percentages of error, becomes limited as the ratio of g/2ρ increases.
4. Formula for the self inductance of solenoid with similar concentrated windings at equal intervals is given.

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An apparatus was designed for the purpose of the direct comparison of the telephone receiver output, and a few study regarding to the telephone receiver output was done. The receiver whose resonance frequency is variable in a definite range of frequency is introduced in the appendix.

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