548 SCIENCE PROGRESS 



Propagation of Sound in the Free Atmosphere and the Acoustic 

 Efficiency of Fog-Signal Machinery. An Account of Experi- 

 ments carried out at Father Point, Quebec, Sept. 191 3 " (Phil. 

 Trans. 1919, 218, A, 211-93). King discusses the theory 

 of plane and spherical waves of small amplitude, and the 

 propagation of aerial plane waves of finite amplitude. In the 

 experimental work use was made of Webster's phonometer, 

 described in the Proc. Nat. Acad. Sci. U.S.A., 1919. 



The scientific aspect of sound theory has enjoyed much 

 attention. The foremost prominence must be given to C. V. 

 Raman's memoir : " On the Mechanical Theory of the Vibra- 

 tions of Bowed Strings and of Musical Instruments of the Violin 

 Family, with Experimental Verification of the Results " (Pt. I, 

 Indian Ass. for the Cult, of Science, Bull. 15, 191 8). A judicious 

 combination of theory and experiment is used to elucidate 

 the nature of the vibrations of the violin. The equations of 

 motion are written down and solved for the strings and the 

 bridge respectively. The effect of the mute is investigated 

 by means of placing loads at various points, whilst the effect 

 is discussed of variations in the method of using the bow. 



Further papers on sound instruments and theory of vibrations are : 



Webster, A. G., Acoustical Impedance, and the Theory of Horns and of the 

 Phonograph, Proc. Nat. Acad. Sci. U.S.A. 1919, 5, 275-82, where the author 

 solves the equations of motion for the air in narrow channels of various shapes. 

 The results were used in designing horns for use in the war. 



Foch, A., Three papers on channels containing air pockets, Comptes Rendus, 

 1919, 169, 502-5, 569-71, 687-90. 



Banerji, S., On the Vibration of Elastic Shells Partly Filled with Liquid, Phys. 

 Rev. (2), 1919, xiii. 171-88. Three shapes of shell are discussed : hemi- 

 spherical cup, cylinder with flat base, conical cup. 



Barton, E. H., and Browning, H. M., Mechanical "Resonators" under Double 

 Forcing, Phil. Mag. (6), 1919, 37, 453-5, in which the authors discuss an 

 analogy of the resonance theory of audition. 



Dey, A., A New Method for the Absolute Determination of Frequency, with 

 Preface and Appendix by C. V. Raman, Proc. Roy. Soc. 1919, 95, A, 533-45, 

 based on the maintenance of sub-synchronous frequency in a pendulum by 

 means of a periodic field of force (see Phil. Mag., Jan. 191 5, August 1917). 



Rayleigh, Lord, Two papers on random vibrations, and unit vibrations with 

 random phases, ibid. (6), 1919, 37, 321-47, 498-515. 



Meteorology has been receiving increased attention from experimentalists as 

 well as from applied mathematicians. The following papers should be noted : 



Hildebrandsson. H. H., Reflexions preliminaires sur les mouvements gdne"raux 



de Patmosphere, Comptes Rendus, 1919, 168, 593 8. 

 Brazier, C. E., Influence de la distribution verticale de temperature sur les 



vitesses du vent mesurees au voisinage du sol, ibid., 1919, 168, 1160-1. It is 



shown that the ratio wind velocity/gradient of pressure is affected by the 



vertical temperature distribution. 



