ON April 14, 1917, the American Philosophical Society held at Philadelphia a “Symposium on Aeronautics,” of which the papers are now published in the society's Proceedings (vol. lvi., No. 3). The titles of some of the papers contributed to the conference—namely, “Dynamical Aspects,” by Prof. A. G. Webster; “Physical Aspects,” by George O. Squier; “Mechanical Aspects,” by Dr. W. F. Durand; “Aerology,” by William B. Blair; and “Engineering Aspects,” by Dr. Jerome C. Hunsaker—show that every attempt was made to ensure a thoroughly representative discussion. But in reviewing the proceedings one cannot help being struck with the opinion that modern aeronautics is too straggling a subject or collection of subjects to be dealt with efficiently in a meeting of this character. Thus, Dr. Webster, the author of a standard treatise on “Rigid Dynamics,” reproduces certain familiar diagrams of lines of flow and explains the meaning of lift and drag; Mr. Squier tells us that in the past few years several elements, helium, argon, neon, krypton, and xenon, have been found in the air; Dr. Durand enumerates the problems which have to be solved in the development of the aeroplane—problems more often enumerated than solved; while in Mr. Blair's paper a large amount of space is taken up with twelve diagrams, although he fails to explain what connection these figures have with the mean of wind observations in “Highs” and “Lows,” or what the different parts of the diagrams represent. The three pages which Dr. Louis A. Bauer devotes to his subject refer to difficulties attending the use of the compass in aeroplanes arising from deviations of the apparent vertical due to normal and other accelerations.