By the method described in our previous report the magnetic variations on the western and northwestern Pacific ocean were observed, 57 points in total, by the Umitaka Maru (The Tokyo University of Fisheries) at the intervals of about 150 miles along the meridian. The values of the variation observed are not far from the data recorded in the Admiralty chart, the chart of H.O. of U.S.A. and H.D. of Japan Maritime Safety Agency. The observed variations are also not so much different on a significant level of 5% by the chisquare test, from the variations used as reference.

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Characters of celestial line of position plotted on chart of Lambert conformal conic projection, e.g. ICAO WAC one millionth, are investigated. Error of length of the intercept caused by neglect of change in the magnification along meridian, error of the position of intercept terminal caused by the difference between straight line intercept and great circle intercept, and error of the direction of position line due to the convergency of meridians give final effect of third order infinitesimal or less to the position of ship or aircraft, and is practically neglegible even at high latitude or for high speed air navigation, at lower latitude in which cases the ordinary position line on Mercator chart gives serious error. The full text of the treatise shall be shown on the Contributions from the Marine Research Laboratory, Hydrographic Office of Japan, 1, 1, 20 (1959).

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The time required to sail between any two points is dependent on the distance, speed of the ship and the effects of external forces owing to the weather, sea conditions, etc. Accordingly, to select the most economic and efficient course, the navigator has to form his judgement on the basis of synthetical data founded on the efficiency and the condition of the ship, safety of the course, positions of the two terminals of the course, and season. In this paper, the writer, relying on assumptions, offered some considerations on the difference of distance between great-circle and rnumb-line, which is an element to be considered in the selection of the most economic course.

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The writers thought of various type of radar reflectors, and made some of them. They report the result of meaasured radar cross sectinos of these reflectors. Types of measured reflectors are as follows. a. Fixed type b. Constructive type i Reflectors of metal plates ii Reflectors of metalic Nets iii Reflectors of wooden plates, and wooden plates painted by conducting paint C. Folding type d. Balloon type

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Radar can give the navigator the information around the ship quickly and accurately in any sort of visibility. The picture on PPI scope, however, will not be so comprehensive as that obtained by the eye in clear weather. Since the radar assisted pilotage, the navigator has had the need for frequent and rapid references to the chart in order to check the identity of echoes on PPI. In this paper we introduce the process of the References aids to pilotage by radar in Naikai, which have been tried to produce from this point of view.

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The research of sea noise in the ocean or the detection of fish shoal by their swimming sound were usually made by research vessels, or, in case of set net fishing, by the line transmission of under water sound to coastal receiving stations by means of electric cable. For the purpose of listening to the sea noises of several locations simultaneously or surveying the fish location by the sound originated from fish shoal, it has been demonstrated that the "sonobuoy's disposition offers an easier and more economic survey. The observation is made by setting several sonobuoys at sea and receiving the under water sound transmitted through the radio system of a coastal station. The sonobuoy device consists of hydrophone, audio-amplifier, radio transmitter and receiver, speaker, pen-recorder and two channel magnetic tape-recorder. The sonobuoy adopts frequency modulation system at V.H.F. of 42.M.C. band and its effective communication range is up to 10km. The under water signal caught by speaker is recorded on pen-recorder or on magnetic tape-recorder. The observation by this device of the swimming sound of yellowtail in set-net fishing grounds has demonstrated that the sonobuoy can clearly distinguish the sound of yellowtail from the sea noise, and that the frequency of sound generation at the entrance of set-net has a certain relation with probable catch of fish. It is expected in future that we can tell the possibility of catch by listening to the sound of fish by means of this device. We can conclude that in feature, the forecast of fish catch may be possible by listening the sound of fish.

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We published that the echo-trace of the sea-bottom obtained by the 200kc echosounder with sharp beam is much more similar to the true shape than that by the lower frequency echo-sounder. We made a 200kc echo-sounder, the sounding range, the recording paper speed and the width of paper of which were the same as those of 14kc echosounder and made an experiment by these two echo-sounders on the sea off Kurihama, Kanagawa Prefecture, on 24th April 1959. We installed the 14kc and 200kc transducers on one side of the ship in order to avoid the change which the echo-traces underwent by the installation. There is no appreciable difference for the even bottom but differences come out as the shape of bottom becomes complicated. In case of 14kc it is often that one cannot measure the depth of the sea-bottom because many false bottoms are recorded on account of the dull beam, but in case of 200kc it is easy to measure the depth of the sea-bottom because nothing but the bottom is recorded and the accuracy of sounding is high on account of the sharp beam. In case of 14kc, the accuracy of sounding might be high if its beam is made as sharp as that of 200kc, but it is not practical because a very large transducer is necessary. A sharp beam is much more easily obtained by the high frequency than by the low one.

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Authors reported that Kapok was much affected on buoyancy by several kinds of mineral oil, as a conclusion of "On the efficacy of buoyant materials" last year. In this paper we will, furthermore, make clear the character of Kapok being affected on buoyancy by animal or vegetable oil, and etc. That is, we measured the Surface Tension of several kinds of oil and infiltrative velocity of them into Kapok. Then we tried some model tests of Kapok, and we followed tests of Kapok Life-jackets. And, the conclusions to which have come to authors as the result of above experiments are as follows: …a) Kapok is affected not only by mineral oil but also by animal or vegetable oil, e.g., Whale Oil or Rape-seed Oil. b) Kapok tends to be more affected by oil which has low Surface Tension. c) Anti-oil coating by painting on canvas cover is scarecely effective to protect Kapok from oil, etc. And, in point of fact, many people have been rescued by Kapok at the sea casualties. Kapok, however, has abovementioned defects in its character as the buoyant material of life-saving appliances. Accordingly, a counterplan, such as using P.V.C. or Polyethylene cover, must be considered against oil for the progress in saving life at sea.

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Following formulae for calculating the Transfer D_T and Advance D_A, in no dimensional form, were obtained by discussing the results of turning trials of many fishing boats and some cargo vessels. [numerical formula] In above equations the coefficients m', k, n' are shown by functions of practical turning factors as follows. i) Angular velocity in turning [numerical formula] ii) Ratio of final speed and initial speed [numerical formula] iii) Speed decreasing coeff. of exp. function [numerical formula] where W: Displacement in Kt. L: Ship's length between p.p. in m. B: Ship's breadth in m. d: mean draft in m. t : trim in m. C_b: Block coeff. or [numerical formula] A: Rudder area under W.L. in m^2. α: Actual rudder angle at rudder head in degree. t_0': t_0/√<L> t_0: Putting time of the helm angle in sec.

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The record of any properties of a ship's motion looks very much like the record of wave surface, and for analyzin of them, the same method has been used as in wave analysis. In this paper, the author sought to find the properties of ship's oscillation by TAKAHASHI and FUSHIMI's method, which has been used in the analysis for geophysical problem, as follows ; (1) By means of a periodgram of ship's oscillation, to find the irregularity of it (2) Calculating the properties of ship's oscillation by TAKAHASHI and FUSHIMI's method (3) Analyzing by means of harmonic analysis, to calculate the true period of ship's oscillation (4) On the motion record in Fig.1, the writer got the following results ; 1) True period T_0=6.3 seconds 2) Δφ= λφ^n n=1.67 Δφ: The decrement per swing φ: The mean angle of swing corresponding to the decrement 3) Bertin's coefficient N=0.017

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Through the investigations of electric power demand for about forty cargo vessels in every state, we have found that the rated capacity of Eelectric generator and primemover are too large for actual loads. We discussed that the discrepancies between the desigined capacity by N.K methods or the calculated capacity by the Kansai Zosen Kyokai methods and the measured actual loads on the three representativse liner ships. From those results, we have reached to the conclusion that N.K methods and Kansai Zosen Kyokai methods reguest too much greater capacity for the intermitent auxiliary load.

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The authors investigated the thresholds of the dark adaptation extending over 146 students of the Marine Technical School and studied the elements to be examined and the testing methods concerning the aptitudes of the night visual function which is required for navigators.

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