The paper deals with the minimal time ship routes using the sea condition prognostic charts which have been facsimile-broabcast. The results of the calculation with the aids of an electronic computer are presented. And it is suggested that the climatological data should be used when the data broadcast are invalid.

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Position fixing by cross bearing and its error adjustment are explained here. When a measured bearing contains an angle-error, it causes a distance-error of the position line proportional to the distance from the land mark. The author studied this aspect and formulated position fixing expressions. The formulas cover (1) cross bearing by two land marks, (2) cross bearing by three land marks in consideration of either a constant error only or accidental errors only. (3) cross bearing by four or more land marks in consideration of both a constant error and accidental errors or accidental errors only, (4) error ellipses in the above cases. The calculation method explained here is more roundabout than the usual drawing method, but it will be an easy and correct one, if digital computers are used in future. The angle-errors found in cross bearing at sea are to be surveyed and reported in his later papers.

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Concerning the probable circle, which is a method of expressing the error boundaries of a ship's position, the writer has investigated the terms in which the probability is 95%, when the accuracies of two position lines are alike ; and moreover he has described the method for applying it to the error boundaries of a ship's position fixed by three position lines, in an earlier paper. [1] However as the coefficient of the probable circle system is determined by the function of the intersecting angle of position lines and the ratio of accuracies of positon lines, he submits the 95% probable circle of the unequal accuracies of position lines, in this paper. The method: As shown in Fig.1, the probability of ship's position within the circle with an arbitrary radius is calculated according to the sum total of probability within the very thin parallelogram. And then the radius of the circle which includes the ship's position with 95% probability is found by repeating the above-mentioned method. However as massive calculation is required to do it, the writer calculated the radius of the 95% probable circle by integrating the probabilities when the ratios of standard deviation (σ_1, σ_2) of two position lines are 1, 2, 3, 5, 7.5, 10, and the other case they were estimated from Fig.3 & 4. The result : The radius of 95% probable circle are shown in Fig.5 & 4 and the coefficient(K) of the circle are shown in Fig.2 & 3.

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To analyze the effect of winds and waves upon a ship's speed is a very important problem concerned with the selection of an economical sailing course, the estimate of spare fuel and an estimate of the ship's position. But each ship being different from an other in type, size, condition, ability, etc., it is not possible to formulate universal rules. In this paper, the author has attempted, as an example, to analyze the navigational records of the fishing-training ship "Oshoro-maru III" of Hokkaido University. As shown in Fig.1, all data has been separated into 7 sections according to directions of the winds. The calculation of speed reduction has been made according to the difference between the standard speed of 12.03kt and the log speed converted to the speed when the revolution of the main engine and the angle of blade are standardized, under each condition ; the standard speed is that shown by the log when the rotation is 210 RPM and the angle of the blade is 21 degrees, and the influences of wind, wave and swell are nil. In Table 1, t---shows the weights of data (sailing time: minutes), Δ---shows the mean speed reduction. If the relation between the wind force (B) and speed reduction (Δ) are expressed by the equation Δ=aB+bB^2, they have been calculated by the data in Table 1 by means of the least square as forms (1)〜(7) in each section, as shown in Fig.2. In order to get the relation between wave height and speed reduction, he took the following method for deducing wave height from wind scale, namely he got the average value of the grades of wind waves against each wind grade in the navigational records, and replaced the wind grade by the average value of grades of wind wave scale. The intermediate value between the grades of the scale is shown by the proportional difference. When the relation between wind scale and wave height in this observation was plotted, it has been shown in Fig.5, and is expressed by the equation (8). The relation between wind scale and wind velocity is expressed approximately by the equation (9), and the relation between wave height and wind velocity is expressed by equation (10). Using the relation of equation (8) and the relation in Fig.2, the relationship between wave height and the speed reduction has been expressed dy a simple equation as shown in Fig.6, cxcept in the case of favorable winds.

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In general, it has been observed that the ships motion under towing a trawl-net which supported by "the towing block" on the her stern at starboard side is different from the motion without the net: In this report, the auther has analysed the ships motion, especially about the effect of towing tension on the ships motion in steered condition under a state as mentioned above. And the following tendencies werefoundout: (1) By the effect of towing tension on the ships motion, it is possible to make even dynamically unstable ships directionally stable without steered. (2) Under towing a trawl-net as mentioned above, the ships drift angle when steered the rudder angle is given a meeting rudder with a combination of angular deviation and velocity control, no return to zero. And in the case of that meeting rudder is a proper quantity, the ships track slightly come back to her initial course. (3) The ships drift angle under a state as mentioned above, increase proportionally to the towing tension of the net which supported by the towing block on the same position with uniform towing velocity.

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In these days the practical first order approximation is more familiar to us than the second order equation which expresses the motion of ships. That is the reason because the former is often used for few changes of the steering as z maneuvering test or manual steering. This paper investigates by the analogue computer if the first order approximation may be applied to the automatic steering with changes of higher frequency. And besides the author want to analyze the linear adjustment in autopilot and its optimal adjustment.

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This paper treats the analysis of nonlinear elements in autopilot by the analogue computer, and the comparison with the results by describing function method; as the result of which the author obtained some interesting responses, such as the amplitude of yawing by sine wave and the self excited vibration by nonlinear adjustments. And it was confirmed that the phase lag by weather adjustment gave bad influences for the automatic steering.

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Some quantities of Mn in sea water were measured by neutron activation analysis of chemical separation method in order to estimated the erosion of condenser tube of steam engine. The Samples, _ soaked sea water added MnCl_2 into a piece of filter paper were bombarded in thermal neutron flux of 4×10^<12>n/cm^2・sec for 20minutes at the Research Reactor Institute Kyoto University. After the bombardments, the samples were chemically separated Mn from ^<24>Na and ^<38>Cl to make microanalysis, the activities of ^<56>Mn were measured with RCL-256 channel pulse height analyzer. Mn in sea water could be determined up to 0.00005mg in 1cc of sea water with chemical separation method. The results of this experiments show the posibility of erosion in condenser tube by neutron activation analysis.

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Recently, in the westsrn coasts of Japan, the structure of purse seiners was changed into steel from wood-hull. Some of fishermen say, noise of the steel boat become loud and it may be disturbed fish-gathering effects. There are many reports on the ship-borne noise by Hashimoto, Maniwa, Nishimura, E.J. Skudrzyk, J.H. Janssen, and Yoshino and others reported on the orditory sense of fish. On June 18, 1965, authors carried out a preliminary study on the ship-borne noise by purse seiners at the northern waters off Hirado Island (Table 1). The instrument principally used such as a Hydrophone (OKI 57TA), Pre-Amp (57TA-2), Tape-Recorders (SONY TC-802 and FT-2) and Sound-Spectrograph (RION, so called as Sonagraph), and those resonance characters are shown in Fig.1. The acoustic pattern and section by means of the Sonagraph are shown in Figs.2-11. By those figures, we supposed that in the case of the purse seiner, there are some correlation between the ship-borne noise and the fishing effect. And we are intending continuousely to pursuit this problem hereafter.

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When a vessel is navigating with the aid of radar in restricted visibility, it is recommended that the alteration of course angle be substantially increased in order to prevent collisions. The substantial action is recommended not only because this would probably have the greatest effect, but also because it would be more likely to be noticed on the radar screen of the other vessel. As regards alteration in course angle, it is recommeded that a minimum alteration of 60 degrees be the standard navigational practice. However, the purpose of this recommended angle is not generally known to and understood by many navigators. In the study of the problem in question, the authors have made some studies and conducted some experiments with the use of the Marine Radar Simulator. As the result of these actions, one of the most important experimental studies was the study to determine the observer's notice of target's motion change which arises from the different angle of course alteration. We, therefore, advocate the results of experimental studies in substantial action which can make effective pictures on the radar screen to the navigators who are continuously watching it.

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Speeds, lengths and positions of ships were measured by "Pass Time Recording Method" on the Keihin Canal where ship lengths were observed to be mostly in between 10 and 50m and speeds ranging from 5 to 10 knots. The effective area, necessary for the deduction of the naval traffic capacity was obtained from the distribution of the relative positions of the following ships and it is about 200m in the course direction and about 120m in the direction perpendicular to the course. The effective area of ships which following ships mostly avoid to enter is also obtained from relative positions of ships observed on the Uraga Strait by "Ship Locating Recorder" and it is about 700m in the course direction and about 350m in the direction perpendicular to it for such ships whose lengths are in between 50 and 250m and speeds from 6 to 20 knots.

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In order to explain the confusion of ships passing through a fairway, author statistically analyzed the results of the investigation into actual traffic of some part of Akashi Strait as an example. And author got the following results ; (1) The number of ships passing through the fairway in short time Δt will follow to the Poisson distribution (2) The time interval between a proceeding ship and following one will follow to the Exponential distribution (3) By the following formula, ship's navigater can forecast the probability that proceeding ships exsist "k" within ΔL km in front of his ship. [numerical formula] where k=1, 2, 3…R=number of ships/km (4) "R" is one of indexes of the confusion of ships in a fairway.

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The ships' cargoes have increased recently owing to our country's economic growth and constructing of coast industry regions so ships of big and small or of various types have been made in high efficiency and up-to-date. Consequently, the sea traffics are drastically congested, especially in the harbours and along the coast. Accordingly, safety navigation and enhancement of maneuvering efficiency have been greatly thought of but every year there are quite amount of sea accidents. Exceeding speed forms a high percentage of the cause of sea mishaps under fog. Taking this into consideration, Harbour Maneuvering Technic Study Group of the Kobe University of Mercantile Marine has made a research of ships passing the Akashi Strait and have taken photographs of rader images for one year from March 1963 to February 1964. By using these photographs of radar images, this reports on the actual movements of ships under fog appeared at the above strait.

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The table of meridional parts is a typical formula of the integral navigation, but it is leaded one variable function. The auther, formerly, has been reported that the astronomical navigation table was consisted of several variables, therefore, if it was possible of partial differentiation to the original function, was constituted by integration. The principle was the same, the Newton's interpolation rule, on the process of integration, we found some partial derived functions and these compound functions. On the result of investigation, these functions were very useful for nautical calculation as follows ; (1) Calculated altitudes on the continuous observation became speedy and simply, therefore, navigators are applied to the differential calculation not only the sun but also the stars this method. (2) Partial derived function may also be used for Johnson's method obtaining the ship's location at very easy works. (3) In this table, the calculated altitude or hour angle is given in any factors using assumed or estimated latitude. (4) With two position lines, one crossed point is calculated, and it is possible to obtain the accurate ship's location at Ex-meridian altitude.

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Up to this time, the tention and configuration of the towing rope was calculated as a catenary curve. In practical towing condition, the configuration of rope will differ from the catenary curve by the effect of hydrodynamic force. This paper present the results comparison between the calculated value obtained by the basic assuption in analyzing the configuration of towing rope and observed experimental value. Both value are nearly the same without the condition where both the length of rope is very long and the depth of rope is very small.

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Drinking water in freshwater tank of ship is, in general, high in pH. This may be due to alkaline substances derived from the coating material-wash cement. To find the coating material suitable for preservation of drinking water, the authors examined the alteration of the quality of water stored in the experimental tanks coated with some synthetic resin paints. The experiments showed the following facts : The phenol resin varnish paint and the polyester paint could hold the quality of water good for drink. But they have the following demerits-expensive and dangerous exhaling poisoneous and inflamable gas during coating work. The water stored in the tank coated with wash cement was good for drink with respect to all the items except pH value. These suggest that it is necessary to develop inexpensive coating material with satisfactory quality or to find some effective methods of preventing the dissolution of alkaline substance from the cement coating.

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The previous experiment showed the following possibility: the wash cement may be applicable to the coating material of freshwater tank, if we have some practical methods of preventing the alkalization of water. Calcium hydroxide dissolved from cement coating is thought to be the main ingradient of alkalization of water in tank. This suggests that it may be one of the inexpensive and practical methods to apply dry ice to the present purpose. A series of experiment was, therefore, conducted in an attempt to find the relation of pH value of water stored in tank coated with wash cement to either the lapse of time from coating to dry ice supply, the amount of dry ice supplied, or the lapse of time tightly-closed. The results obtained are summarized as follows: 1. The pH value of water in dry ice treated tank rose gradually with lapse of time after filling of water. 2. Water in tank treated 12 hours after coating showed always lower value of pH (not higher than 9.0) than any other case (after 3, 6, 9, and 24 hours). 3. The amount of carbon dioxide needed to congeal 1kg of wash cement is estimated to be about 240g. But attention should be paid to the following result: This expected value was too small to get good result and the lowest value of pH was observed in the tank treated by dry ice three times as much as the expected value. 4. The pH value of water stored in tank differed with the lapse of time tightly-closed before filling of water: as early as 12 hours after filling, the water filled in tank six hours after dry ice supply exceeded the permissible range of pH for drinking, but the water filled 48 hours after dry ice supply was kept in the permissible range of pH as long as 24 hours.5. Water stored in dry ice treated tank was good for drink with respect to all the items except pH value. 6. It may be said that application of 750g of dry ice per 1kg of wash cement could counteract, in some extent, the alkalization of water (water filled…pH 6.7, stored one day in treated tank…pH 8.9, control…pH 10.6), although this was still insufficient (permissible range…pH 5.8 to 8.6).

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High alkalinity of drinking water in tank of ship is thought to be due to calcium hydroxide from cement coating. It is probable that presence of carbonate radical in water accelerates the dissolution of calcium hydroxide from cement coating by converting it into insoluble calcium carbonate, and also this calcium carbonate film covering cement wall forms obstruction of dissolution of calcium hydroxide from cement. Application of dry ice to tank water may make it possible to keep the pH value of water filled after treatment within the permissible range of drinking. To confirm this possibility, a series of experiment was conducted. And the results obtained are summarized as follows: 1. For the water filled in 200l tank coated with 1kg of wash cement, a single supply of 240g of dry ice (=estimated, amount needed to remove calcium hydroxide in 1kg of cement) could keep the water within the permissible range of pH. But this treatment could not keep the water filled after treatment within this range of pH. 2. A single supply of 120g of dry ice to 200l of water in tank coated with 1kg of wash cement could keep the water within the permissible range of pH. This treatment could keep the water filled after treatment within the permissible range of pH. 3. A single supply of 60g or 24g of dry ice to 200l of water in tank coated with 1kg of wash coment was not enough to keep the pH value of water within the permissible range of drinking. The former case needed 3×30g additional supply and the latter 5×24g. These treatment yielded the same results with respect to the prevention of alkalization of water filled after the treatment. 4. It may be said that the repeated supply of dry ice in small doses to the water filled in tank coated with wash cement can keep the water filled after treatment within the permissible range of pH for drinking. Here, it is important to pay full attention to the fact that an excess of dry ice supply to water ended in rather harmful result.

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According to the statistics of the total loss distress of the steel ships presented by the Lloyd's Register of Shipping, the probability of maritime distress shows different value in each country, which deeply affected by many factors as natural circumstances, social conditions, historical process and characteristics of nations. Japan shows the least value among the important ship owning countries in the statistics mentioned above. This fact might be the result of best endeavor of the whole Japanese people and organization, to minimize the maritime distress.

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The images of PPI radar echoes are different from the coastlines on the chart because the radar beam cannot arrive at the regions behind the hills or islands. In Naikai, many islands, hills and mountains are distributed near the recommended route and there are many narrow channels having strong tidal currents. If we meet the dens fog in such a channel, we must navigate by the informations of radar and lead our ship to the safety region. Therefor the navigator must determine the position by obsrving the radar scope at once. So we must have full knowledge about the characteristics of radar echoes in Naikai. We provided the radar pilot charts in Naikai along the recommended route, giving the important characteristics of radar echoes. Several of them are shown in this paper. It is said that if you train yourself by these radar pilot charts, you will easily be able to identify the echoes corresponding to any one point on the charts.

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Position lines of a satellite Doppler navigation are the lines that the cones and the earth sphere cut each other. They resemble hyperbolic lines. Differentiating the equation of position lines, we get the formula which gives the accuracy of the position lines. When the observations are repeated the fix position is obtained. Its accuracies are investigated along track and cross track. If height error exists the position lines are displaced. Then, we showed the family of position lines.

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