The effect of temperature upon the time limit of an induction type relay is very remarkable beyond expectation, especially so for small Ampere setting.
The angular displacement of the relay disc by over load is more accurately recorded than in Mr. Kamiya's experiment and the effect of holes in the aluminum disc of the relay is clearly demons strated.
When intermittent over-currents are sent through the relay, the disc makes to and fromovements and comes at last to the final contact. The angular displacement is recorded by means of a specal recorder.
A rotating commutator makes a sip all current and an over current to flow alternately through the relay. The ratio of duration can be varied at will, and the period of alternation can also be freely varied between 0.03 sec. and 15.0 sec.
If the over-current flows for a time somewha shorter than the time-limit and ceases, then the disc will begin to return to its normal positios. But, owing to its slow backward movement, if the second over current would come after a sho t interval, the disc would come to its final contact much faster than its prescribed time-limit.
The motion of the relay disc under intermittent over loads are fully studied and it is shown that the time-limit may often become quite uncertain due to its flcating effect.

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This article deals with the civil crgineering works of The Oi Development which has recently been completed by the Daido Denryoku Co. on the Kiso River. Oi Power Station one of the so called "Dam system power house" and has a high masonry dam as its special feature. This covers cheafly the design and method of construction of the Oi dam.

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The present issue offers a supplementary extension of the previous paper on the same subject in our Journal, No. 434, p. p. 803-847, Sept. 1924. At first it is intended to explain physically how earth coils suck in the charging current on a grounding accident of a transmias on line and how the line-current distribution would be affected accordingly.
Then a practical line-length capable to be compensated through earth coils is suggested, after having compared with some other usual ground systems of the neutral points. When the line-lesgth l=π/2βr km on compensation at either one end of the line or when l=π/βs km on compensation at both ends, where βs √b11[x11+(n-1)x12]approximately, the earthing current Ix comes into resonance and when "l" grows up still longer there seems no favorable compensation possible. Although on the case of both ends compensation the line-length in question may be regarded as twice times great as on one end compensation, the neutral points are apt to be subjected to a fairly high voltage stress at l=π/2βs km on a grounding accident. Consequently the practical line-length may be safely regarded up to about l=π/4βs km as one section, the value amounting to about 500km or 300 miles for a 100-KV single- or three-phase line.
In conclusion the effect of third harmonics component in the working e. m. f. on the earth current is considered on the earth coils compensation, being compared with those on the other usual grounding methods of the neutral points. Although the earth current through neutral at normal operating condition of a three-phase circuit as well as the earthing current due to the third harmonics at a grounding accident of a transmission line in general may come into resonance at certain particular line-lengths, it is not owing to installation of the earth coils themselves but due to the line constants proper.

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The magnitude of the tooth pulsations is calculated for rotary machines where both members are slotted.
(1) To calculate the permeance for fringing at the position of minimum air-gap reluctance, compare slot pitch of both members, and dran a symmetrical figure as a part of slots lying between the center line of slot of shorter slot piteh and the tooth of which the flux pulsation is to be calculated. Next, for these modified slots, apply the Carter's fringing constants, which are applicable only for the slots situated opposite to each other, and expressed graphically in this report.
By these methods, the maximum permeance is calculated accurately, for the cases which are likely to occur in practise for induction motors.
(2) Even if the tooth width is shorter than the slot opening in opposing surface, the minimum permeance is easily calculated by using the writer's experimental formula proposed in the previous report.
(3) The pulsation amplitudes calculated by these experimental formulae are checked with the test results, and compared with the approximate formula proposed by T. Spooner.
(4) In the above-mentioned methods, the saturation effects, and the effects of shortcircuited windings are not considered.

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It is already well known that the frequency of oscillation of an audiofrequency triode oscillator is different from the natural frequency of the oscillation circuit, as calculated by the formula ω0²=1/CL•.
The discrepancy which amounts to several % in certain cases depends upon the circuital constants as well as the valve conditions such as the filament temperature etc.
Explanation is here given from the point of view that the grid current the principal cause of the variation.
For the sake of simplicity the author considers the case in which the instantaneous value of the plate potential is throughout its pulsating cycle always higher than the grid potential, so that the grid current may be considered as a function of the grid voltage only.
The actual frequency ω is related to the simple theoretical frequency ω0 by the equation:
ω2=ω0 ²[1-kx0 ²MLg/(rp+Rp)(rg+Rg)]……(13)
The effect of the grid current upon the amplitude of the oscillation is φ considered for the case of small amplitude, and the following equation is given for the amplitude of the plate current pulsation:
a²=a0 ²[1-1/aG(kM/L-1)(M/CR)⁴]……(23)
where a0 denotes the value when the grid current is negligible.
In the next place, the oscillation characteristics are observed dynamically by means of the Braun tube oscillograph. It is ascertained that the hysteresis loops, which become apparent when either the frequency or the intesity of the oscillation is increased, are due to coming into existence of the grid current.
This paper includes the following topics.
I. Introduction.
II. Effect of grid current upon the frequency.
III. Experiments as regards the frequency variation.
IV. Dynamic oscillation characteristics.
V. Effect of the grid current upon the amplitude.
VI. Conclusions.

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This report of long distince communieation test on short wave incudes the following items.
1. On the relation between wave length and range of communication.
2. The sending set used for this experiment.
3. The receiving set used for this experiment.
4. Roult of the experiment, and the conclusion.
(i) Almost no absorption in the air for short wave under one hundred meters during the night range of both stations.
(ii) Extrimely little statics and easy to receive signals on such short wave.
(The experiment is still going on, and the result will be published later.)

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Three winding transformers afford many advantages on large power systems and their use has become widely extended in recent years. Originally designed to eliminate insulation strains when operating on the star-star connection the third winding is now frequently used to supply power in the interchange of energy between two transmission lines, and for power factor correction of long high voltage lines by means of synchronous condensers. A number of concrete examples are given.
A brief discussion follows of the inherent charact, rristics of three winding transformers with regard to short circuit stresses and voltage regulation; some of the limitations are indicated. In conclusion the superiority of the three winding shell type over the core type is pointed out.

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(1) The creeping phenomena in paraffine oil and benzol purified by H₂SO₄ is similar with that in transformer oil.
(2) In paraffine wax solidified in atomosphere, the creeping phenomena with the electrodes placed on opposite sides of the glass plate is similar with that in air.

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