ELEMENTS OF ELECTRIC TRACTION FOR MOTORMEN AND OTHERS. BY L. W. Gant. New York: D. Van Nostrand Company. 8vo.; cloth; 217 pages, illustrated. Price, $2.50. Electric traction is a branch of electrical engineering of the greatest importance, and an intelligent understanding of its principles by motormen and men of similar connection with its practice makes for greater public good. The "Elements of Electric Traction" is based upon a short series of lectures and practical demonstrations given during the last two years to a class of motormen and others at the Leeds Institute Technical School. It is designed as an introduction to the more advanced works on the subject, and as a supplement to the various handbooks that have from time to time appeared. The elementary principles of electricity, magnetism, and the related phenomena are explained in the first chapters of the treatise, before going on to the headings more germane to the title. The style of the work is very clear and lucid, and although the treatment is simple, nothing is lost in needless repetition. THE MARINE STEAM TURBINE. Second Edition. By J. W. Sothern, M.I.E.S. New York: D. Van Nostrand Company, 1906. Cloth; 158 pages; 8% by 54 inches; numerous figures and illustrations. Price, $2.50. The marine steam turbine is receiving more respectful treatment from marine engineers, since it has proved itself to be the successful rival of the reciprocating engine. In fact it almost seems that the turbine will some day entirely supersede the older form, for it is the ideal type of power producer for the modern high-speed steamship. The author, who has had exceptional chances of studying marine turbines from every point of view, has added in this, his second edition, more details relating to the practical construction and running of this type of engine than were contained in his excellent first edition. The work contains numerous drawings and sketches explanatory of the text ; in fact, the drawings alone would make the book one of great value. The text is arranged so as to most forcibly impress the mind without fatiguing the eye. THE MOON IN MODERN ASTRONOMY. A Summary of Twenty Years' Seleno-graphic Work, and a Study of Recent Problems. By Philip Fauth. Translated by Joseph McCabe. With an introduction by J. Ellard Gore. London: A. Owen & Co. 8vo.; cloth, illustrated. Price, $4. When telescopes were first invented, they were naturally turned upon the nearest celes-tial object, our satellite the moon. After its more apparent features had been noted, the enthusiasm of the early investigators was di- rected to other bodies, and the deeper prob lems of our neighbor planet were left more or less untouched, owing to the very desultory manner in which they were attacked. Mr. Philip Fauth has devoted a lifetime to the study of selenography, and has shown himself admirably fitted to distinguish the minute differences that the selenographer must be able to detect. His work is written in an agreeable style, and commands both the interest and the confidence of the reader. In spite of this there is in the last chapter a statement that seems to exceed "scientific probability." After saying that the moon is at a temperature of 273 deg. C, the theoretical "absolute zero," at which all molecular motion ceases, and that its surface is covered with ice, under which are seas of water, Mr. Fauth goes on to state that the waters have at times broken through the mantle of ice, and, by their ebb and flow, have melted depressions in it, making the so-called "walled plains." This seems highly improbable, for even if water could exist as a liquid at temperatures in the neighborhood of the "absolute zero," it is most unlikely that such an ebb and flow could take place, since in a liquid cooled below its freezing point, solidification is almost instantaneous when the solid phase of the compound is in contact with the liquid phase. At a temperature of 273 deg. C. a body of water, however large, would be cooled below its freezing point in a very short time interval, and freezing would be almost immediate. This would be more apt to result in the formation of mounds than of depressions.
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