138 THE ROYAL SOCIETY OF CANADA 



74 '56. Hence the mean value of the surface tension of water at 12° 

 is found to be 74-6 dynes. 



The stream in which the waves have the largest amplitude is 

 shown in Fig. 11. In the first wave r and D/2 have values -09535 and 

 •1002 respectively. This makes r^ equal to -00909 and a\ -000023. 

 Hence ^ a^ in formula (5) may be neglected and v calculated by means 

 of formula (6). 



The results obtained for water are somewhat higher than those 

 found by Bohr, who, using the vibrations of a horizontal jet, deter- 

 mined the value of the surface tension of water at 12° to be 73 - 23. The 

 value 73-22 (obtained at 20°) agrees within 1% with the most recent 

 static determination^ of the surface tension of water at 20°. 



The method of using the vertical jet is very simple and requires 

 little apparatus. It may be employed for solutions and liquids other 

 than water. The greatest error occurs in the determination of the 

 velocity, i.e., in the measurement of the radius of the jet. The pre- 

 cision with which this measurement can be made depends on the ac- 

 curacy of the micrometer screw of the microscope. 



In conclusion, I wish to acknowledge my indebtedness to Mr. 

 Werner for his aid in the photographic part of the work. 



Department of Chemistry, 



McGill University, Montreal. 



'T. W. Richards, Journ. Amer. Chem. Soc, p. 1656, 1915. 



