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XII. Determination of the Surface-Tension of Water by the Method of 



Jet Vibration.* 



By N. BOHR, Copenhagen. 



Communicated by Sir WILLIAM RAMSAY, K.C.B., F.R.8. 

 Received January 12, Read January 21, 1909. 



Introduction. 



IT has been shown that one of the most important and difficult questions in regard to 

 the determination of the surface-tension of water is to produce a sufficiently pure 

 surface, and in later investigations great importance has therefore been attached to 

 this point. 



In 1879 Lord RAYLEIGH, t however, indicated a method which solves the above- 

 mentioned difficulty in a far more perfect manner than any other method used 

 hitherto ; this method makes it possible to determine the surface-tension of an almost 

 perfectly fresh and constantly newly formed surface. 



In the paper cited above, Lord RAYLEIGH has developed the theory of the vibrations 

 of a jet of liquid under the influence of surface-tension, and as appears from this 

 theory, it is possible to determine the surface-tension of a liquid when the velocity 

 and cross-section of a jet of liquid, and the length of the waves formed on the jet, 

 are known. 



Lord RAYLEIGH has attached a series of experiments to the theoretical development. 

 By these experiments, however, it was more especially intended to give illustrations 

 of the theory rather than to give an exact determination of the surface-tension. 



If, however, this is the problem, it is necessary to consider more closely some 

 questions which are not discussed in Lord RAYLEIGH'S investigation, for it is necessary 



* Based on a response to Det Kongl. Danske Videnskabernes Selskabs (The Royal Danish Scientific 

 Society's) Problem in Physics for 1905; delivered October 30, 1906; awarded the Society's Gold Medal. 

 (The investigation has since been completed with a number of experiments.) 



t Lord RAYLEIGH, 'Roy. Soc. Proc.,' vol. XXIX., p. 71, 1879. 



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