THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



FEBRUAR Y 1896. 



X. The Filar Anemometer. By Carl Barus, Hazard Pro- 

 fessor of Physics, Brown University, Providence, U.S.A.* 



1. T N a remarkable paper, published some sixteen years 

 JL ago, Prof. Y. Strouhalf investigated certain laws 

 subject to which a sound is produced when the wind passes 

 transversely across a slender solid body. Placing his chief 

 reliance on the results obtained with metallic wires, Strouhal 

 found for thicknesses ranging from 0*018 cm. to 0*325 cm., 

 and for speeds from 2*1 met./sec. to nearly 12 met./sec, that 

 the whole group of phenomena could be expressed by an 

 equation of striking simplicity, 



n = Cv/d ; 



where n is the frequency of vibration, v the speed of the 

 wind, d the diameter of the wire, and where is constant 

 except as to temperature. When all data are expressed 

 relatively to metres and seconds, this constant has at atmo- 

 spheric temperatures a mean value ■ 



C = 0*200; 



and it is thus at once possible to compute the speed of the air 



* Communicated by the Author. 



It gives me pleasure to acknowledge my indebtedness to the Secretary 

 of the Smithsonian Institution, for materially promoting the present series 

 of researches. 



t Ueber eine besondere Art der Tonerregung, Wurzburg, Stahel, 1878. 

 The subject was suggested by Prof. F. Kohlrausch. 



Phil. Mag. S. 5. Vol. 41. No. 249. Feb. 1896. G 



