As the first step of the researches in bottom Paint, the author has executed the various experiments on organisms which attach themselves to the bottoms of the ships in the naval ports in Japan. The items of the experiments are as follows.
(1) The methods of the inspection.
(2) The species of organisms which attached themselves to the panels.
(3) The habits of organisms.
(4) The species of organisms in each naval port.
(5) The growth of organisms in each naval port.
(6) The breeding-seasons of fouling organisms.
(7) The weight of organisms which attached themselves to the panels.
(8) The relation of the temperature of sea-water to the growth of organisms.
(9) The suitable season for docking.
(10) The species and the growth of organisms which vary in proportion to the depth.
(11) The effects of colours on organisms.
(12) The species of marine boring animals, and the extent of their wood destruction during a year.

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The paper deals with the result obtained by measuring the change of temperature of various parts in the combustion chamber of a cylinder in a single-acting two-stroke cycle diesel engine which was designed and manufactured by our navy as a test. The object of the test was : -
(a) To measure the change of temperature of the various parts exposed to heat when the engine is started or stopped and the engine load is increased or decreased, and to obtain the data for the aid to the engine driving.
(b) To measure the distribution of heat and the change of temperature under different loads, and to obtain useful informations for the design of high speed engines of large type.
The result gives us available informations.

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Several experiments were carried out at the Yokosuka Naval Dockyard to investigate the water and oil-tightness of the widely spaced riveted joint. Four model tanks, each capable of testing the pitches up to 13 diameters, were tested by the water pressure and afterwards by the oil pressure.
The chief conclusions drawn from this experiment are :
(1) The pitch of rivets is better specified by the thickness of caulking edges than by the diameter of rivets.
(2) The rivets spacing 13 thickness apart can easily withstand a water pressure of 10 lb./sq. in., and it corresponds to a pitch of 7.5 diameters of 19mm. rivet on 11 mm. caulking edge.
(3) Almost entire bulkhead liners or compensations due to the close pitch of rivets may be dispensed with and consequently, a great saving of weight and labour can be attained.

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The buckling of a long elastic plate which is clamped or supported at the edges and subjected to the boundary thrusts is studied in a similar manner as that which one of the authors employed in a paper read in 1925. The solution of the problem of the critical stability is deduced from the differential equation of a plane plate and the existence of the solution is critically examined. The relation between P₁b²/4D and k² for different values of P₂/P₁ is shown in diagrams, where P₁ and P₂ are the thrusts in x- and y-directions respectively, 2b is the breadth of the plate, and D=2Eh³/3 (1-σ²) in which 2h is the thickness of the plate and E and σ give Young's modulus and Poisson's ratio respectively. The distribution of the corrugated deflection of the plate is also illustrated. To compare the result of the mathematical calculation with some experimental data of a cylindrical shell, a modified differential equation and its solution in which the effect of the curvature is involved are devised.
From the results of the mathematical calculation it is confirmed that the critical thrust acting in one direction takes different values by adjusting the magnitude of the thrust acting transversely. The corrugation of the buckled plate has a uniform pitch depending upon the ratio of the thrust P₂/P₁ and edge conditions of that plate. The contour curves of any bulge of the corrugation take different forms in accordance with the conditions at the edges. The authors find a good agreement between the result of calculation and that of Viscount Tokugawa's experiment and they conclude from the comparison of these results that the criterion of stability applicable to the experiments is too complex to be defined in any simple manner.

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It is a well known fact that oil tankers in loaded conditions sustain severe sagging stress on top-side member in rough weather. The motor tanker “San Diego Maru” encountered extremely rough seas in Pacific Ocean during a winter voyage, resulting severe bucklings and some cracks on the upper deck plating and also upper strakes of longitudinal bulkheads in midship portion. The author analyses the causes of the damage referred to, describing her general longitudinal strength among waves, the effect of impinging water on decks, together with some investigation on the theoretical buckling stress on deck plating stiffened with beams of comparatively light scantling.

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The proposed apparatus is a track table modified by the author from that of Anschütz to determine the time of turning, the advance, and the tactical diameter in the turning trial of a ship. In this track table, the distance travelled by a ship and the change of the direction are simultaneously transmitted to the recording pen from the S. A. L. log and the Sperry-type or the Anschütz-type gyro-compass respectively. Thus the recording pen accurately traces the turning circle. The chief improvements made by the author are the increase of the accuracy and of the magnification of the record.
For the purpose of ascertaining the reliability of this apparatus, the author carried out systematic turning trials of two actual ships and compared the records of the one ship with those of the experiments of the model-ship obtained by the “camera” method. It was found that both records agreed fairly well with each other and the “buoy and sight” method hitherto used, could be replaced by the author's method. The discussion of the errors of the apparatus is also appended.

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It has been found that the corrosion, by sea-water, of steel plates and rivets for hull construction is very serious recently. A research committee has been established in the Naval Experimental and Research Institute with a view to finding the causes and the methods of preventing the corrosion.
The present paper is a report of the committee and its object is to detect the situation of the bottom paint against the corrosion of steel plates.
The followings are the subjects described in the present paper : -
(1) Measurement of the amount of sea-water absorbed by the bottom paint film.
(2) Measurement of the amount of sea-water penetrated through the film.
(3) Measurement of the electric insulation resistance of the film.
(4) Measurement of the galvanic action between the plate and the film
(5) Relation between the exfoliation of the film and the stress given to the plate.
(6) Chemical analysis of sea-water taken from different ports in Japan.
From the above experiments, it has been concluded that the function of the bottom paint now generally used in our Navy is not sufficient to prevent the corrosion.
Besides, the investigation on this line is not yet finished and many other experiments are now being carried out.

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