The problem of critical speeds of aeroengines is solved in the following four steps. 1) Reducing the masses of the pistons, of the connecting rods and of the crank to a single equivalent mass concentrated on the centre of the crankpin. 2) Solving the equations of oscillation modified for a crank, putting these values of equivalent masses into them. 3) When the critical speed is considered as variable with the crankangles, obtaining the equivalent masses and solving the equations of oscillation at every moderate interval of the crankangles, and plotting the critical speeds with respect to the crankangles, 4) When the periodic external forces are taken into account, obtanining the equivalent masses and solving the equations of forced oscillation. The above calculation for torsional vibrations of a crankshaft of an aeroengine is verified with experiments on an Hispano 〓 aeroengine, whose critcial speed is expected to be about _26∞ R.P.M.

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The anthor has investigated the corrosion and the deterioration of some tool steels heated in various salt baths, and developed an empirical formula concerning the relation between the amount of corrosion and the time of heating. The amount of corrosion and the raggedness of surface on steels heated in salt baths are very small compared with those of steels heated in air. Among his experiments, the least amount of metals is corroded in the salt bath consisting of 7BaCl_2+3KCl when steels are heated at about 800℃, and BaCl_2 is very suitable for heating steels at about 1250℃.

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When a tool is hardened by quenching its volume increases, but the change of its dimensions is not the same on different directions and local distortions are also accompanied. The author has investigated these quenching deformations on prisms and cylinders of various lengths or sections made of one carbon steel, two special tool steels and one high speed steel, and studied these causes comparing the deformations of specimens made of Armco Iron. The warpings of steels due to quenching are also demonstrated in this paper. These deformations and warpings are produced by the differences of structure change and of thermal expansion at different spots ; especially the permanent set occured in steels by thermal stresses seriously affects on these phenomena.

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The petroleum refining has made remarkable progress these few years. Among others the development of the cracking process and the vacuum distillation are great, technically and commercially. Cracking-The demand for gasoline for automobile and chemical uses are increasing yearly; but the quantity of the gasoline from crude oil by ordinary refining way can not satisfy the demands. There are many ways to change heavier oils to gasoline; among others heat and pressure cracking method are now in success. There are many thousands of patent, but only six systems are now in success commercially. The cause of their success are the taking off the produced carbon out of beating zone and the ingeneous constructions of every parts to stand for heat, pressure and chemical actions. Vacuum Distillation-The developement of exquisite machineries demands good lubricating oils to fit for. It is well known that the lesser the pressure the better lubricating oil distillate is gained in petroleum distillation. It was qiute difficult to make high vacuum in still. Recently Schultze system and Steinschneider system succeeded in high vacuum distillstion, even under 5 milimeters of mercury of absolute pressure. The cause of their success are : making good vacuum pump, the enlargement of piping to prevent the friction of gas and oil, the complete sealing of the joints by electro-welding and others, and the ingeneous constructions and arrangements of every parts.

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