The forgeability and acid resistivity of Cu-Ni and Cu-Sb-Ni alloys (Sb less than 20%) against 10% aquous solutions of H₂SO₄, HCl and HNO₃ have been studied, and it is found that (1) the acid resistivity of Cu-Ni alloys against H₂SO₄ and HCl is comparatively large, except alloys with Cu content more than 40%, (2) the resistivity of Cu-Ni alloys against HNO₃ is very small as compared with that by H₂SO₄ and HCl, and the addition of Cu from 15 to 40% to Ni greatly increases the resistivity, but the larger addition of Cu decreases the same property, (3) the addition of Sb to Cu-Ni alloys is beneficial with regard to H₂SO₄ and HCl solutions, (4) with regard to HNO₃ solution only a small addition of Sb to alloys is markedly beneficial, and Sb content more than 2% is no effect, (5) the effect of Sb on the corrodibility of the monel metal is beneficial, (6) the forgeability of Cu-Sb-Ni alloys with Sb less than 2% is comparatively good, but more than that amount causes to increase the brittleness, (7) the effect-of Cu on the forgeability of the ternary alloys at high temperature is very great, the property being the remarkable the larger the Cu content, (8) the most effective Sb concentration for the acid resistivity and forgeability of this series of alloys is less than 2%.

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Various types of optical methods for determining the crystal orientation are systematically described, and a full explanation of the method of light figures which has been developed by the author is given for its principle, apparatus, appropriate etching techniques, procedure for the determination, and accuracy. The metlod of light figures is excellent in simplicity and rapidness and has a sufficient accuracy within 1° This method has given satisfactory results in its application to single crystals of nickel, copper, iron and aluminium, and has a possibility of being further extanded to single crystals of any other metals and alloys.

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The Electro-static Method of Discriminating the Liquid Phase of Alloys. It has long been known from the experimental results obtained by former investigators that the water drops falling down from an orifice undergo a periodic deformation, together with the fact that the amalgamation or the separation of these dropswould take place by their electrification. Especially, with, regard to the aforesaid deformation of the drops, the functional relation of its frequency v to the surface tension T and to the volume V (=⁴/₃πα₀³) of each drop, was theoretically deduced by Lord Rayleigh and others.
By way of collating and expatiating the results of these previous investigations, the present writer performed a calculation to find the influence of a definite amount of the electric charge E carried by each drop of a given liquid) upon the periodic deformation, As the consequence of this calculation, it became clear, in thefirst place, that the frequency of the periodic deformation excuted by each drop, decreases, at the rate of ^Δ_v/_v=^E2/_32πa³0T due to the. electrification, when the amount of the electric charg E is comparatively small. In such a stage of the electrification, the drops were inferred to have the more remarkable tendency to amalgamate with each other by the collision, the more they are electrified. But, it was also found, in the second place, that these drops usually tend to separate again more minutely than before, through the electrification increasing so large without giving rise to any electric discharge, as to be expressed by E²_??_17.7a₀³T. Moreover, the equilibrium of continuing the periodic deformation is confirmed to be completely violated, when the electric charge E increases to an amount satisfying the condition E²_??_50.3a₀³T. Consequently, the permanent deformation or the separation of each drop should be inevitable, in the extreme case lastly mentioned.
The considerations above given, enables us to examine the surface' tensions of various liquids, least of all, of the melts of metals, by electrifying their drops. Accordingly, we may construct an arrangement following to these considerations, which will be available to the discrimination of the liquid phase of several alloys.

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The author discusses the mechanism of the fracture of metal under a cyclic stress. He paid a special attention to the relation between the repeated stress vs. slip-phenomenan, slip-phenomenan vs start of fracture, growth of fracture vs. crystalline boundary, etc. The specimens used were a sheet of Super-Duralumin for the preliminary test and α-Brass for the final test. The surface of these specimens were polished and etched before setting them on Sehenck's Vibratory Endurance Testing Machine. Thus, the author observed the structural change of the specimen by microscope at the various stages of stress and the stress due to number of repetitions of testing.

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The growing demand of die-casting in industry and for household articles is very great, and hence the author studied die-cast aluminium alloys and compared the mechanical properties with the gravity cast specimens of the same alloys. For the as-cast state, die-casting has superior qualities to gravity casting, and no beneficial eftect is noticed by heat treatments, but annealing, if neccessary, should be made at 100-200°.

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