The common process of echo sounding is that a pen attached to an echo sounder slides over the recording paper at a uniform speed, marking the times of the transmission of a pulse and the reception of its echo, and the depth of the sea is read off the paper. This method has some disadvantages, the greatest of them being that it requires constant attention during operation and is apt to cause much inconvenience to the ship, especially when she is entering or leaving port. Fishing boats, most of which are insufficiently manned, are always feeling this disadvantage keenly. With a view to remedying this shortcoming, the authors have made an apparatus for tests which will ring a buzzer and light a lamp when the ship comes to a spot of a particular depth.

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Hokusin-Mechanical-Trackrecorder has especially been used by whale catcher boats in Japan. The instrument contains no vacuum tubes or other electronic components. Most of components are made of simple mechanical parts such as gears, coupling and motors. But the instrument only traces the track of ship's movement by mechanical Sine-Cosine roller-disc system, By using of this system, we could trace the ship's movement, at the same time, indicate the ship's Dead Reckoning Position by Latitude-Longitude counter, which is consists of four gears. The counter was used for reading the degrees and minutes. The equation of longitude at the precent latitude is d.Sin Co./Cos Lat. We made the data of cos Lat. which is continiously introduced from Lat. gears, insert into the mechanics of Long. gears. This instrument was installed in the new fishing training ship "Kagoshima Maru" built in 1960. We obtained a good operative record in maiden vayage.

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The author has investigated how the nearest approach changes when own vessel alters her course and speed. When the target vessel is comming down afor the beam, the ratio of the initial nearest approach to that after the alteration of own vessel is given by following formula.[numerical formula] Where m=the ratio of the nearest approach. ΔC=the amount of course alteration. r_1=the ratio of the initial nearest approach to the distance between the two ships. k=the coefficient due to the speed ratio. The value of m is shown in the table 2. The relation between factors to double or treble the nearest approach is shown in the table 3, 4, fig.3, fig.4 and fig.5. When own vessel changes her speed, m is less than the value which is shown in the table 2, so we must change the speed with a large margin, and its rough estimate is shown in the table 6 and 7.

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The Writers have made a transisterized radar-pulse receiver and tested a method of identification. They report the result of the test at Tsugaru Cannel on board the Ferry of Hakodate to Aomori.

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Numerous theories have been advanced to explain the corrosion of the cooling surface on cylinder liners. But if a few causes are eliminated, the tendency of the corrosion will be reduced because the various causes acceralate each other. This paper presents an advanced result of some anticorrosive methods treated on our Umitaka-Maru from a standpoint of operating engineer.

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The intensity of radio wave at one point over the sea surface is determined by the interference between the direct wave from the antenna and the indirect wave reflected from the sea surface. When the surface is very smooth and the grazing angle is very small, the intensity of the reflected wave is nearly equal to that of direct wave. Under these conditions, the intensity distribution of the radio wave has already been described. The authors calculated the intensity distribution when the reflected wave is not equal to that of the direct. From these results, one can see that, for very low objects, the less the reflected wave intensity is, the larger the detecting range of the radar is.

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When the distance between two transmitting stations, master and slave, is too long, or there is the ground between them, in some region it is impossible for us to receive both ground waves from the two station and yet two effective sky waves cannot be received because the distance from one station is less than 250 nautcal miles. For these special regions, it is required to determine the Loran fix by the time difference between the ground wave from one station and the sky wave from the other. In this case special correction must be applied. These special corrections are shown in the Loran Table. The accuracy of these special corrections has not been considered. The authors calculated the probable error of these special corrections and also the probable error of Loran fix determined using these special corrections. Then the accuracy of Loran fix determined by ground wave and sky wave is compared to that determined by usual sky waves.

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Foreign charts and publications are important navigational aids for oceangoing vessels. It is desirable that the navigator has a knowledge of what is available in this field, that is, how he can obtain various items, how he can be sure they are accurate and up-to-date, and what information he can expect to get from each. Instructions for the use of a number of these items are given in this text.

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The writer has planed and designed some new type of complemental tables and diagrams for astronomical navigation. Referring to similar study, he tried to make them for practical use because he himself is a navigation officer. 1. The Table of Time Lag and Max. Alt. Correction at Meri.-pass. 2. The Table of Time Lag and X-Meri. Reduction. 3. The Table of Time Lag and Star Identification. 4. The Diagram of Dep.-Δ・Long. 5. The Table of Time Lag and X-Meri. Reduction. These may help navigator's practice at sea.

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To analyze the effect of winds and waves upon a ship's speed is a very important problem which is concerned with the selection of the course, estimate of spare fuel and estimate of a ship's position. But each ship being different from any other in type, size, condition, ability, etc., it is not possible to formular any univrsal rules. In this paper, the authors has attempted, for an example, to analyze navigational records of the fishing training ship "Oshoro-maru" of Hokkaido University. As shown in Fig.1, all data are separated into 7 sections by the directions of the winds. The data are 520 in all ; 74 on the average in a section. The calculation of speed reduction is by the difference between the standard speed 9.45 Kt and the speed shown by the P. log under each condition ; the standard speed is that shown by the P. log when the standard rotation is 255 RPM and the influences of wind, wave and swell are nil. In order to know the relation between the force and direction of wind and speed reduction, as in Fig.2, the speed reduction is plotted on the ordinate ; wind scale on the abscissa. As the speed reduction (Δ)=aB+bB^2, if a smooth curve is drawn along the points plotted by data, the speed reduction due to wind force is shown by forms (1)〜(7) in each section, as shown in Fig.3. The mean direction angle of wind (class mark in each section) is plotted on the abscissa ; the speed reduction on the ordinate. The calculated values by forms (1)〜(7) are plotted and if the smooth curve is drawn along the plotted points, that curve approaches closely to the curve of 5th degree shown in (8)〜(14). In order to get the relation between wave height and speed reduction, the authors took the following method for deducing wave height from wind scale, that is, they got the average value of the grades of wind waves against each wind grade in 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 defference. When the relation between wind scale and wave height in this observation is plotted, it is as shown in Fig.5. The curve of which the points plotted in this connection are made smooth by the curve of a quadratic equation, is expressed by equations (15). As shown in Table 1, the relation between wind scale and wind velocity is epressed approximately by equation (16), and the relation between wave height and wind velocity is expressed by equation (17). Using the relation among equations (15), (16) and (17), and relation in Fig.3, as shown in Fig.6, the relationship between wave height and the speed reduction is expressed by a simple equation.

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船舶設備規程第163条並に英国Merchant Shipping Act Section 61によれば木材を甲板積する場合は水分の吸収による木材の重量の増加が復原性に及ぼす影響を考慮しなければならないと規定している。木材に吸収された水分は木材の重量をいちぢるしく増加させ、ある木材では木材自身よりも水分の方が重いことがある。このような木材を積載する場合は多量の水を運送することになり、これは復原性と共に運賃収入に大きな影響を及ぼすこととなるであろう。従来この水分吸収による重量がどの程度変化するか究明されていなかつたので下記のような実験を試みた。乾燥材を水に浸すと初めは急速に吸水するがその後吸水速度は次第にゆるやかになつてゆく。然しながらこの吸水速度は樹の種類によつて異なり、又同じ樹でも材の心材と辺材によつて差があり、又は材の組織の異なること例えば節が存在する等によつても相違があると考えられる。その上製材と樹皮付丸太との差があり、単に吸水性についてのみ考えても複雑であり、その上航海中水分の蒸発等の問題をも考慮しなければならない。そこで先づ第一段階としてある特定の木材を水に浸し最悪の状態に於ける重量変化を究明することとした。

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JIS-Stockless Anchor used most often, as described in the preceding paper, was not so much effectual anchor. However, it was expected that the anchor could be got a more efficient holding characteristics provided that the fluke is larger and the tripping palm is more expansive than JIS type. Then we decided to test four model anchors having partly changed forms with above expectation and a few superior anchor, i.e., Danforth patent anchor and Baldt stockless anchor, etc. for comparative study. From the results of these tests, we detected that the holding characteristics can be improved by welding the given plate or palm on the ordinary form, and that the raked tripping palm has effective operation for tripping into bottom when dropping anchor.

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