The auther studied a non-contact method of measuring a small displacement from about 10^-4 to 10^-2cm. The diaphragm of a special condenser type electroacoustical transducer is closely fixed near the measured object so that there exists between the diaphragm and the surface of object a thin air layer, the damping effect of which on the diaphragm changes with the thickness of layer, being accompanied by a change in amplitude of the diaphragm. The relation between the thickness of layer and the amplitude has theoretically been studied, and the calculation of an example and its characteristics are given.

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The first interest in the modern rolling mill is to achieve the maximum production yet retaining the metallurgical requirements on product by means of the "quality heating." Therefore, the heating of steels in the furnace is of utmost importance. Complicated operation of the furnace, especially that of triple fired furnace, necessitates the automatic control. Although, the various automatic control has been recently adopted in our country, the measuring of steel temperature in such furnaces has presented a more difficult problem than the case of open hearth furnaces. Since January, 1953, we have adopted a automatic control to our triple fired furnace and met various difficulties. Followings are the short discription of our outomatic control and the results of our experiments performed on the temperature measurement. (1) The radiation pyrometer is employed for measuring temperature. Direct measuring of ingot temperature by the open end sighting tube was unsuccessful and now the good results are obtained by the closed end sighting tube. (2) Locations of measurement were determined after various discussions at the time of designing furnace. However, actual operation forced to change them later and the best location was chosen by comparing the readings of the optical pyrometer and those of the radiation pyrometer. Many problems are still left on the analysis of these controlling technology.

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The naval architects, are interested in the modern developments of the automatic control or servomechanisms. This brief argument relates to their applications to the experimental techniques at towing tanks, where many important tests of ship forms and propellers are under way. Servomechanisms are seemed to find two kinds of application there; the one is the motion control of towing carriage, model ship, and etc., and the other is the measurement of auto-balancing type. The former has come from Constant Speed Control of Towing Carriage during a test F. 2 showes two actual examples of this control with a feed back by a tacho-generator. This type of control keeps not only a constant speed during a test, but makes the towing carriage system much quick response and shortens the travel of the carriage for the acceleration and the retardation. Now, the motion control is utilized to more varions purposes. For example, two systems showned on F. 4 & 5 are following-servo to eliminate the relative mean speed between the carriage and the model ship during a test, The begining of auto-balancing measurement at towing tank is Gebers' resistance-dynamometer (F. 1), which have been used since about 1920. Substituting a two-phase servomotor for the DC-reversible motor, and a continuous displacement detector and a vacuum tube amplifier for the pair of electric contact, the dynamometers of this kind attain the much better performances. F. 6 shows a thrust meter of this type for self-propelled tests. It should be noted that the auto-balancing dynamometer has superior quick response ability in spite of its high sensitivity, therefore, it is specially disirable to tank tests with severe limitation of measuring time. The applications of the autobalancing measurement are not only the dynamometer, but miscellaneous. The hot wire currentmeter of auto-balancing type (F. 7) is a exampl of them.

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In this paper writer will discuss about the performance of mashroom valve from the results of model experiment and will also shows the improved valve characteristics. The mashroom valve are usually used for air inlet valve in natural draft type furnace such as old open hearth furnace and soaking pits. In naturaldraft it is very difficult to measure the flows of combustion air, and that the combustion regulation was performed by the waste gas analysis. The improvement of mashroom valve is very important for better combustion in such furnace.

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