The demand of electric power increases and decreases in winter and summer season respectively. On the contrally, we have shortage and surplus of water utilized for hydro-electric power in respective season. To suit the demand by hydro-electric power, we have its enormous excess in summer season. Unfailing remedy to the objection is to utilize the power for the electrification of farming, that is, 1. Cultivation 2. Hulling and drying ec. 3. Subsidiary works, -poultry, sericulture ec. 4. Draining 5. Irrigation About 350, 000 HP will be wanted for draining and irrigation in the main parts of Japan. The writer investigated specially the load curve of manual power for farming, and the objection of unequal demand and supplly can be solved by the investigation about the farming load curve and hydrograph of the rivers in Japan.
By Campbell's frequency bridge, we measure the frequency of the alternating current by known mutual inductance. and capacity. The same circuit can be utilized to determine the natural frequency of a coil used as the primary of the mutual inductance, knowing the frequency of the current and the capacity, which gives the balance. In the experiment described in this paper, the frequency is determined by standard tuning forks. A theory by which the natural frequency and the self-capacity of the primary coil can be obtained by taking the balance at two known frequencies is worked out the actual method of experiment and the experimental check of the theory are described. When the sharpness of the balance is greatly affected by the effect of the selfcapacity, it can be improved by a simple modification of the circuit as shown in Fig. 6. (Jan, 1924, Sendai, Japan)