Though the outline of the principle of a Bourdon tube is already well known, the mode of the displacement of its free end seems to have not yet been fully investigated, and an unsuitable mechanism having been adopted, the graduation of the dial plate of a pressure gauge using the tube is usually not uniform. Here, the writer of this paper considers that the displacement of the free end should be proportional to the pressure in the tube and be very nearly a straight line motion. This consideration is proved in this paper both mathematically and experimentally, and a simple formula is offered for the determination of the direction of the displacement. Using this formula, the writer has suitably improved the mechanism of a Bourdon tube pressure gauge and shows by an experiment that the indicating needle of the improved gauge moves propcrtionally to the pressure in the tube with a great accuracy. By the way, the strength of a Bourdon tube is treated in this paper.

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The theoretical amount of discharge of steam through orifices can be found by so called Saint Venant and Wantzel's equation, but owing to the various disturbances occuring in the orifices, the actual amount is not equal to the theoretical one. Bendemann found a very convenient empirical formula expressing the amount of discharge of steam through circular orifices with well rounded entrance, but for the orifices of other forms, it is unknown whether his equation can be applied or not. To confirm this point, the experiments were performed with eight orifices of different forms and dimensions as given in Fig. 2 and Table I, and the results may be summerized as follows : Under the same condition of steam, the same values of rate of discharge per unit area can be given for orifices A and B, for orifices C, D, E and F, and for orifices E′ and F′, the amount of discharge can be represented either by Bendemann's equation or by an equation introducting a coefficient of discharge expressed as a linear function of pressure ratio to the theoretical equation, the latter equation being accurately applied for orifices with sharp entrance than the former one.

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This report is an extension of the paper entitled "Effect of Smoothness of Bucket Surface on the Efficiency of a Pelton Wheel" read at the special joint meeting of the Society of Mechanical Engineers and the Society of Naval Architects of Japan, held at Fukuoka in March 1920. The wheel tested in the previous experiment was of a Pelton-Doble type, designed to develop 6 B. H. P. under 30 metre head at 400 r. p. m. previous results have shown that the efficiency of the wheel with polished bronze buckets, called "A" was 2.6% higher than that with rough bronze bukets "C" and 0.8% higher than that with painted rough bronze buckets "B", at a normal nozzle opening and a normal speed. In this experiment the same Pelton wheel was tested with rough cast iron and with enameled cast iron buckets ; and the result has shown that the enameled bucket was equal in its character to the polished bucket "A", the rough cast iron being almost to the rough bronze "C". The advantage of the enameled cast iron bucket with respect to the efficiency as well as the economy of material and construction was thus proved.

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