Author studied about the primary problem of the damping curve of the magnetic compass card in the liquid when vessels are yawing or steering at sea, and provided it with second order's differential equations after a systematic experiment. The damping coefficients of the equation are followed. [numerical formula] We can estimate the damping property by them to design the compass cards.

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In order to preserve the security of navigation, the numerals of the depths shown on chart should represent that at which the handling of vessel is just affected by the resistance of the bottom of sea. But when the bottom is composed of very soft mud, the ordinary soundings do not always give this adequate values.

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Es ist gewohnlich, dass die Gezeitenstrombeobachtung im allgemeinen nur auf 25 Stunden Dauer erhalten ist, weil die kontinuierliche, lang dauernde Strombeobachtung nicht leicht ausgefuhrt werden kann. Von diesen Materialien konnen wir mit der Fourierschen Analyse die Ellipse jeder Tiden (ein-, halb-. und vierteltagige Tiden) leicht berechnen. Aber die Grosse, Gestalt and Richtung dieser Ellipse verandert sich wegen der Veranderung des Mondalters und der Mondesdeklination. Der Verfasser versuchte von den 25 Stunden dauernden Strombeobachtungen aus die Grenzwerte an der Springzeit d. h. Geschwindigkeit und Verspatung zu berechnen, und es gelingte ihm, durch die verhaltnismassig einfache Methode diese Werte zu bestimmen, solange die Verhaltnisse von Geschwindigkeit und Verspatungsunterschied zwischen M_2, S_2 und K_1, O_1 aus einem gewissen Grunde angenommen werden kann. Bei eintagigeim Gezeitenstrom ist dies kurz nach dem Eintritt der grossten nordlichen oder sudlichen. Deklination des Mondes der Fall. Zum Schluss erzahit er die Methode, diese Verhaltnisse von den Gezeiten an den Kusten aus annahernd zu bestimmen.

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The line of position of heavenly body plotted on Mercator's chart deviates from the true circle of position as follows: (i) the length of intercept is not exactly correct because of the scale of meridional parts, (ii) the position of the terminal of intercept plotted as a loxodrome deviates from that of intercept plotted as a great circle, (iii) the azimuth of the line of position is not equal to that at the estimated (or assumed) position owing to the convergency of the meridians, and (iv) the line of position is plotted as a loxodrome whereas the true line of position is a kind of a plane curve of transcendental equation on the chart. Moreover, if the correction for run is reckoned: (v) the tangent to the locus of the probable transferred position does not coincide with the transferred line of position obtained by the parallel displacement. Investigating these esrors in turn, we get the correction formulae and their nomograms for high latitndes. For their effects to the line of position, the component for latitude and longitude due to (ii) cancels each other, and it is sufficient to account only for (i) and (iii). (The effect of (iv) is, as is well known, neglegible unless the altitude of the heavenly body is greater than 60°, and its corrections are found in many nautical tables.) Adopting the probable maximum values, the ultmate errors of the ship's position obtained at the chart can sufficiently be negligible for the latitude of 70°, and we may use the ordinary method of Sumner's line in the coming antarctic operations of SOYA to the Prince Harald Coast (lat. 70°S) without any anxiety on Mercator's position plotting sheets.

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It is well known that radial error system, probable ellipse system, error parallelogram system are considered concerning how to express the error boundaries of ship's positions; the crux of the problem is how to measure accuracy and how to combine theory and practice. The writer made careful examination of these methods from the point of view of studying the error boundaries of ship's positions in the following four cases. (1) error boundaries of ship's positions fixed by astronomical position lines. (2) error boundaries of ship's positions by position lines gotten by land objects (objects are fixed). (3) error boundaries of ship's positions by bearings gotten by land objects (observed point is fixed). (4) error boundaries of ship's positions by Loran position lines.

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Astronomical refraction at low altitude varies with temperature, pressure, humidity, temperature gradient, azimuth, colour of light, wind velocity, irradiation, etc., and on the approximate values and nature of them, reached at on some observations and assumptions, I reported at the ninth meeting of the Japan Nautical Society. Now it is impossible either in theory or in practice to correct the refractions for all these factors. So, this time, we have determined to examine the reliability of the Radau's Refraction Table (that is used in our nautical table) and its effect on the observational position line at low altitude. According to our observations, the values of the Radau's Refraction Table (1882) are greater than ours by 1.08% in arithmetical mean, and its variations in probable error are as shown in fig.2. It has been our custom to avoid low altitude observations at less than 10 degrees on account of their low accuracy, but the fall in accuracy is mainly due to great variations of refraction, and we think the graph shows clearly that low altitude observations, as observations at less than 10 degrees are here called according to the custom, are fairly reliable and it is not necessary, in altitudes of more than 3 degrees at least, to expect errors twice as large as those in ordinary observations. Moreover, the variations are greater, though by a small amount, during 40 or 50 minutes after sunrise than they are during the corresponding time before sunset.

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We drew the contouis of constant probability density of loran fixes, and tried to draw up the "Loran Navigation Charts" of several parts in the loran service areas. By these charts, the navigator can select the best two pairs of the stations at once, because the sea areas are divided by several colours representing two pairs by which loran fix has the best accuracy.

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The characteristics of Loran sky wave propagation errors is very important in order to determine the probable errors of Loran fix using the sky wave. These errors near the Japan area are evaluated by measuring the Loran sky wave time differences from each Loran station to the fixed receiving position and compared with the Pierce's equation. Observed results are shown in the figures representing the relation between the relative number of observation and the sky wave reading. By Pierce's equation, the probable errors of sky wave delay are depend on the distance between the Loran station and the receiving position. So the errors of sky wave reading depend upon the both distances from the master and slave station to the receiving position. We propose the equivalent distance by which the errors are decided. The errors, however, are also the function of the base line length. We can decide these errors by the equivalent distance and the base line length. The probable errors of Loran sky wave propagation calculated from the observed results are shown in the figures as the functions of the equivalent distance and the base line length, and one can see that these results are considerably agree with the Pierce's equation.

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Self-floating corner reflectors of which mechanical strength and accuracy are maintained by use of polystyrene foam, light in weight and transparent to microwaves, as medium among reflecting surfaces of metallic foil are trially manufactured and tested. The results are reported here. The weight is only 440g and able to float on the sea surface without any devices. The main characters are equal to ordinary corner reflectors without any perceptible losses due to polystyrene foam medium.

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New designed draft meter is coustructed with three bellows and two vacume chambers. Four years ago, I designed high accurate marine barometer with crank gear and toothed wheel instead of hair spring and chain. In this draft metar, I adapted same method with above mentioned barometer. We can read the index of draft rightly at wheel house or mess room without change by the difference of tempereture and atomospheric pressure.

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It has been mentioned in some texts on seamanship that the Relieving tackle should be used in rough sea for emergency and it has a buffering effect. But the analysis of its action has not been performed. In this paper, the auther finds out the changes of tensions of ropes involved in the Relieving tackle and the resisting pull of it when the tiller is moved, and then considers on the effect of buffer. In the result, the general conclusions are as follows: -(1) It is recommended, if the Relieving tackle is intended to use, the securing positions of the tackle, the kinds of ropes, blocks and tackle in use have to be designed in previously. (2) The buffering effect is not so much and can be expected only for a Hand steering gear with steering chain. (3) So, in general, the Relieving tackle has to be used only for the emergency gear.

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As well known, Sea Anchors are effective not only to keep ships to the wind and sea but to lessen leeway. So the use of them are advocated by many writers on Seamanship, especially with small ships. However, there are some considerable problems for the practical use, that is, Sea Anchors must be large enough and strong enough to be effective and easy to handle. We know various kinds of Sea Anchors, e.g., Sea-Kite, Conical, Parachute, Multiplane, Fishing Nets, Spar and etc. On the size of Sea Anchor, it is said the diagonal length of Sea-Kite type requires about I/2B, and only Conical type for Life Boat is stipulated in Japan. In this paper, authors researched on some types of Canvas Sea Anchors and described some characteristics of them.

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Some shipping companies have thier 'sen-soku' (ship's regulation or standing order book for company's vessels). This is an administrative tool for the personnels on board ship in the shipping company. Of course the necessity to have it as well as its substance should follow the situation of each company. In our country, I believe, it is very significant that most officers and engineers are recruited by graduates from marine academies and high-schools, for this is one of the important factors which need such a written regulation. I could gather six regulations and analyzed them as a company's (formal) document of its partial organization, say as a ship's 'management guide'. I wish to expect for our shipping managers to distribute their endeavors on these organization problems too.

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It is extremely difficult to estimate and figure up exact amount of bunker fuel to be consumed at sea. The writer got anquetes to this problem from ships through shipping companies by their courtesy choosing following two routes i.e. a. North Pacific, Japan to U.S. West coast including B.C. Canada and vice versa. b. Muroran to Keihin and vice versa, including some prolonged routes. As the first step to find out reasonable amount of spare bunker fuel, he investigated on comparison between ships' estimated amount of consumption on sail and actual consumed amount on arrival, hope and expect future investigation getting much more anquetes.

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When the fuel oil adheres on the commutator of the D.C. machines, it happens sometimes that the fuel gas take fire, if the number of revolution and the brush current densety of the D.C. machine have some values. For such a case, the danger range to the ignition of the fuel oil, were obtained by experiments. The results of our experiments showed that the D.C. machine is the most dangerous to the fuel ignition when it has low speed and large brush current density. Further more by the theoretical investigation auther ascertained that the course of the fire at the engine room of a certaine ship was by the D.C. machine in such a danger range.

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The present auther studied the relations between a power driven vessel fitted with Radar and the Rule of the Road at Sea, and reached the following conclusions. (1) There is a great difference between visual sighting and radar detection. (2) The speed of a radar-fitted vessel in fog, should be "moderate", and reasonable speed may be lower then this when ships sail in fog toward one another, diminihshing the time and space available for detecting. (3) Rule 16, (b) of the International Regulations for Preventing Collisions at Sea, which is concerned with the position of a vessel, may not safely be applied to positions determined by radar detecting.

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