Two problems are described in this paper. The first is concerned with the theory of the inclination error, i.e. both pitching and heeling error, in which the equations are led to separate principal parts from the coefficients of inclination error. The second is the new method of adjusting inclination error. When inclination error was corrected by vertical magnets well known at present time, continual readjustments are required by reason of its variation due to the variation of induced magnetism with change of magnetic latitude. But correctors proposed in Fig.1 and 2, when once adjusted, would no readjustment on change of locality.

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Mr. Y. Namikawa and I had studied the contours of constant probability density of Loran fixes gotten through the triplet; the stations of two pairs with the common master station. And then, I studied Loran quadrilateral and the special cases of two separate pairs of Loran stations, and drew the figures of contours of constant probability density in each of them. (Fig 1〜Fig 8) By those figures, it was evidently shown that the most advantageous arrangement of two pairs was the Loran quadrilateral, and that secondary was the triplet, and that two separate pairs were of no use to obtain the precise fix generally.

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One of the most important cause of the errors at the Loran system is the sky wave propagation error. This error is unavoidable by any careful observation. We investigated the significance of the mean values of several Loran readings and find that the sky wave propagation errors are considerably reduced by taking the mean values instead of the observed values. For example, when the probable error of observed values is 2.18μ.s., that of the mean value of twice observations is 1.77μ.s. (corresponding to 81% of that of the observed) and that of the mean values of five times is 1.48μ.s. (corresponding to 68%). In the other hand the errors by the navigation of own ship are increased, because the more the number of observations are, the longer the time required is. These errors, however, can be avoided by suitable correction.

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As well known, the direction finder has various kinds of error, that is to say, they are instrument's error, quadrantal error and errors which are influenced by natural features or astronomical phenomenon. The instrument's and quadrantal error mean stable error. Instrument's error can be artificially removed and quadrantal error can be corrected by applying the correction curve. The another errors are unstable, because they show the variety with the variation of geographical and astronomical conditions, accordingly, We are very suffered in the case of dealing with these errors. When Shinyo-Maru, training boat in our university, has sailed in the adjacent sea region of Japan during from october to november in 1955 and 1956, We observed the direction finder's errors in various conditions, and clarified these errors into parts caused by distance, daytime, night, twilight, and natural features. From these treatments, We calculated the standard and probable errors in each parts.

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Authers have planned and completed an automatic alarm device which will be additionaly fitted to the ordinary marine radar equipment. The idea is to set warning range ring zone of 1-2 miles, 2-3 miles or 3-4 miles (one mile's wide each) changeable mechanically as desired on the radar scope. And gives the sound and light alarm of the object when any target comes in this warning zone. After the shore and sea test it was proved to detect the objects-ship, buoy, rock or land-sharply and work in good conditions. The navigator on watch will be released from watching the scope continually, and be instantly informed when any object comes in the zone. So he is free from sight and mental fatigue resulting from his continuous lookout on the scope until he alarmed. This will greatly raise the reliability of marine radar equipment as navigational aid.

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The writers have measured the reflected-power from various vessels. They could decide the values of two constants from these data. These two constants are the effective area σ and the effective height H_e, which are closely related with the reflective characteristic of the target and important for the design of the reflector to improve the reflected-power and to extend the maximum search-distance. They explained moreover about the test to measure the reflected-power from simple target on the ground.

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A circulariser of special type is manufactured for producing the circularly polarized waves of marine Radar. The axial ratio of the circularly polarized waves is about 1.08 and the average intensity of the rain echo at a given range is reduced approximately 2/100, while the usual targets (ships and buildings) are being observed at the same time suffered a reduction of comparatively small amount. There are also listed many data as for various targets using the circularly polarized waves and the linearly polarized waves. The echoing signals of corner reflector are usualy very small when the circularly polarized waves are used but the echoing signal will be increased as much as that of lineary polarized waves if special devices are exercised at the side of the corner reflector.

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I had a bitter experience that my sailing pinnace was obliged to run ashore voluntarily at Surugawan coast on stormy weather at 19. March 1957. In this case I studied how to handle small sailing boat on heavy seas and found its navigable limit considering from wind force and condition of sea waves. On this paper, I described the development of this affair and some precepts, and added the data concerning performance for various Small sailers.

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In former paper author defined the critical ranges of ship's motions on the relation between ship and waves underway. In this paper, by means of analysis of the records of ships rolling and pitching underway, author examined and disscussed above theory.

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Formerly, authors had dealt with the fact the steering qualities of an actual ship may be described in brif by System parameter T and K in the transient response. Such treatment, in making analitical study, give a convenient guide to the problem of shiphandling at sea as well as to problem of design work refering to steering and course keeping. The above title considered here is one of their most striking applications, and is adequate as a method of maneuvering board when deducing at what distance from the intersection of the original course and desired course we ought to put helm over. To begin with, for want of the basic consideration of the Thumb rule for altering course, the author has taken up the analitical idea that Distance of New Co. are built up of straight running part V(T+t_1/2) and circulr running part [numerical formula] over the original course by using the System paramer, and, in the following part, has treated a practical method of deduction by making us of the Turning test diagram in consideration of the influence of ship's condition and steering, i.e. draft, angle and time when helm over, slip over the original course due to turning lag after easing helm amidship.

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In the case of joining ropes together on board, we often introduce the various knots or bends as occassion calls when we have not enough time for splicing or there is no necessity for doing so. It needs for the safety of work that we know the slipping and the breaking strain of the joining part of ropes. Therefore we have been to examine their strength on various methods in joining fibre or wire ropes. This time we examined about knots and bends on manila or wire ropes in the same way of the last time, in the case of the various splicings. Moreover we investigated a variety of ways of putting a rope stopper.

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From the measurement of rush current, hook speed, efficiency and the like of the Mitsubishi cargo winch of the pole changing squirrel cage motor type, voltage regulation and loading efficiency are discussed. The essential points are as follows ; (1) The rush currents at starting and changing notch are about 2 times of the rated current, but when the notch is changed to lower 2 notch from lower 3 notch the rush current is almost 3 times of the rated current is observed, but the duration of those rush currents are the order of 0.5 second in general. (2) The effect of voltage variation on the moter characteristics is small ; the slight increase of current and the decrease of hook speed are observed on the hoist 3 notch. (3) The loading efficiency of the Pole change winch is nearly equal to that of the Ward-Leonard winch.

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It is extremely difficult to estimate exact safty margin of tween deck strength. But, recently, sometimes we cannot avoid to take over weight cargos on tween deck, because nowaday our liner service is not perfect that is semi tramper. Then we consider to examine the various opinions on safty used stress of tween deck.

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In the case of fixing noon position by observing heavenly bodies, the combination of ante-meridian (1st) and noon (2nd) Sights by the sun is most generally preferred. It is well-known that in this case, the best opportunity to take 1st sight varies with the combination of latitude and declination. However, we must bear in mind that the ship's position fixed by such a method is generally low in accuracy ; accordingly it is desirable to add past-meridian (3rd) sight to them, i.e. both of ante-meridian and noon sights to increase the accuracy of the day's standard noon position. In this paper, the writer studied about the most suitable opportunities to take 1st and 3rd sights according to various combinations of latitude and declination, and the accuracy of ship's positions by this method. Herewith, he tried to analyze them provided that these 1st and 3rd sights are preferred without restraint.

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In the preceding paper, the writer studied about the method to fix the best noon position according to the combination of 1st, 2nd and 3rd sights provided that 1st and 3rd sights are preferred without restraint. Furthermore. since the day's noon position is paid much attention on the sea, he studied about the method to keep material increase in the accuracy of ship's position by adding 3rd suitable sight provided that the best combination of 1st and 2nd sights are preferred. In this case, he analyzed this problem taking 1st sight a constant dependent on latitude and declination and 3rd sight as a variable.

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I adovocate here a new spheric triangle on the celestial observation which is denoted by Opposite Meridian Zenith Distance (S), Zenith Distance (z) and Diagonal of a Square consisted of double Declinations and Hour Angle (H) on the Equator. Basing on this idea, the following cosine rule is produced : [numerical formula] By the formula, the author has gained a logarithmic nautical table with which nomogram is also drawn. I believe precisely that Zenith Distance at the moment is in proportion to Hour Angle corresponding to Meridian Zenith Distance (D) which is constant multiple, and that resolution into factors on the rule is very useful for the calculations on the sea, yet theoretical investigation is needed hereafter.

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[in Japanese]

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We report about the magnetic variation measured by ship's compass on the steel ship near the Japanese Showa base in the Antarctia. As the coefficient A of deviation was zero, the mean of the deviations should give magnetic variation at the ship's compass course of eight principal points. By this method, we measured the variation at 16 stations in the Antarctic Ocean. Observed variation curves were similar to the one reported by English admiralty chart.

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