Physiological and psychological aptitude tests for cadets who are going to be engaged in sail handling on high place, as masts and yards, were performed, and neccessary countermeasures were adopted for cadets of lower limit value,

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The objects of the work summerized in this paper were to investigate on the relation of the anchor holding power to pulling speed and on the dragging force of an anchor at short scope. Experiments on model JIS-anchors were held in new tank with sea sand bottom. As model experimental results we found that the increase of pulling speed made the holding power strong, and we can explanate such results as the effect of dilatancy in Soil Mechanics. Therefore, ship maneuverer should avoid the snubbing by the bower with too much headway on when come to, and also should consider that the dragging force of at short scope with little way on will be 1.5 to 2.0 times the anchor weight if the length to be veered cable is 1.5 to 2.0 times the height of hawsepipe on sea bottom, and that the probability of imparting to the anchor trip will be much more provided that the length is over 3 times its height.

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As the catch of tuna long line fishing decrease near Japan, the clippers must go out deep sea fishing for the sake of compensating the loss of ecoonomy. Consequently they have a tendency to become larger and larger, and to have a large power engine. But large ships are not always effective since there is no difference in fishing method between the large and the small boat except the numder of basket of long line. Essentially, there should be an opposite properties between the fishing ability and navigational requirements in fishing boat, and so, we have limitted allowance to satisfy both requirements. The author collected the data of tuna long line fishing boats more than 50 in number and tried to solve in this problem on the view point of both economical and fishing ability.

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In traverse sailing, when the ship alters her course from time to time along rhumb lines, the departure for the course and distance made good from her initial position to her final is generally unequal to the total of the departures on every course between them. So, it causes an error to her final position. We studied the nature of the error and considered the counterplan about it.

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It is very difficult to determine the position of a ship at a point near the coast or others when it can clearly receive the waves transmitted from a pair of station but cannot receive well those from another pair, or when the hyperbolic line of position (LOP) is widely spread out. In regard to such cases, we made an experimental test on a practicability of obtaining the position by using the Loran receiver as the Lodar to determine the bearing line of the master or slave station and finding its intersecting point with the hyperbolic LOP of the pair of station. As a result, we found the following facts. 1. Lodar method is successfully applicable when visibility is limited, namely at a cloudy or rainy weather or when the land is covered with gas or mist and surveying is impossible, or at a point near the coast where it is difficult to determine the position of the ship by hyperbolic LOP. 2. In such cases at night, measurement by Lodar method seems to be of higher accuracy than by sky waves transmitted from a pair of station. 3. As the Lodar is highly sensitive, relative bearing is easily obtained, but on account of rolling of the ship it was difficult to determine it at one time of measurement. We measured six or eight times and took the mean value. 4. It seems that the error becomes larger as the angle between the hyperbolic LOP and the Loran bearing line gets sharper (namely, as it enters into, what is called, back side of the Loran station).

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Recently, the Loran Navigation Method which is one of the Radio Navigation Methods used by the ships, has shown rapid prevalence, and ships which are epuipped with the Loran Receiver have indicated a tendency of doubling in number, year by year. Consequently, the Loran Receiver began to exhibit a tendency of becoming automatic, of course. In order to meet with this new trend, the writers have made research on the automatic type Loran Receiver for the past few years, and have finally succeeded in completing an Auto-Tracking System for Loran pulse. The outstanding characteristics of this Auto-Tracking System Loran Receiver compared with the conventional Loran Receiverr used hitherto, is the fact that it has the functional circuits shown below: (1) Automatic Synchronized Circuit for the signal. (ASC) (2) Automatic Gain Control Circuit which controls the signal amplitude of the Master Station and the Slave Station. (AGC) (3) Circuit for synchronizing the radiowaves of the Master Station at a fixed position, at all times. (AFC) (4) Circuit for tracking the radiowaves of the Slave Station at a fixed position, automatically. (ATC) Since the above circuits are used, the Loran signals are selected at the left end of the pedestal, automatically, and the wave forms are superimposed immediately. It also gives a digital indication of the Loran time difference, automatically. In addition to the above, if the station selection of the Loran pulse is made, the change in the Loran time difference caused by the movement of the measuring point will be continuously and automatically traced, and indicated.

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This supersonic observing apparatus has a long-distance cable connected with the transducer and is to catch underwater information by transmitting and receiving supersonic waves from the transducer submerged in the water. The experiment as to this apparatus was done and the methods of it are as follows : (1) The method in midwater trawling By the operation of an indicator equipped in the ship, fitting the transducer to the head of a midwater trawling net through a long-distance cabtyre cable and transmitting and receiving the supersonic waves by the transducer, thus it measures the depth of the net, the height of net opening, the entering status of fish group into the net, etc. remotely from the ship. (2) The method in set net This method is to catch the status of fish group in the set net remotely from the land office by fitting the transducer to the buoy in the set net and then operating an indicator at the land office being connected with a long-distance cable. (3) The method of dropping down transducer This method is to observe the status of fish group, fry group, planktons, other living things, etc. by transmitting and receiving the supersonic waves in vertical or horizontal direction, positioning the transducer at each optional depth after dropping down it being connected with cable into the water. Further, it has been confirmed by the above experiment that a "Pre-Osc. Amp." is required in order to compensate the attenuation, which is increased by the cable for the supersonic observing apparatus when such cable used in especially long length and which influences clearly and interferes with their signal transmission.

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Marine Radar can receive frequencies for instance Radar Beacon and others than its own. Providing the frequency signal to the operating Radar and with the Electronic Tuner of the Radar Reflex Klystron Oscillator (2A25) was able to result the receiving frequency band of 51Mc.

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The antenna horn of the marine radar is sealed by the thin plastic sheet for water and dust-proofing. The surface of the seal is exposed to the precipitation of the vapour of the sea water, the soot and the dust in the air. The salt and others deposited on the surface of the seal will cause the extra attenuation of the radar power. Here is reported the transmission loss resulted from the salinity of the surface of the horn seal. Followings are concluded: (1) The amount of the transmission loss will increase exponentially with the relative humidity. (2) The loss will not exceed 6db in the extreme case. (3) The loss is fairly small (approx. 2db) in the ordinary case.

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