SUKF ACE-TENSION OF WATEK BY THE METHOD OF JET VIBRATION. 317 



considerable irregularities near the generator, the wave-length here being dependent 

 on the distance from the plate and first becoming constant at a greater distance from 

 this. The authors mentioned, being aware of this fact, used for calculating the 

 surface-tension only the length of waves which were at a certain distance from 

 the glass-plate (DORSEY 4 cm., and KOLOWRAT-TSCHERWINSKI 8 cm.). As the 

 wave-length near to the glass-plate was larger than further out, this may explain the 

 fact that DORSEY and especially KOLOWRAT-TSCHERWINSKI have found lower values 

 than other investigators who have used the same method, but as it seems have not 

 taken precautions in this direction. 



The other method, using the standing waves, suffers, as also KOLOWRAT- 

 TSCHERWINSKI remarks, from certain defects, because the measuring of the wave- 

 length taking place on the straight line which connects the above-mentioned pins, 

 those waves only can be examined which are at so short a distance from the pins that 

 there is no security of the phenomenon being sufficiently regular. On account of 

 this the results found by this* method do not seem to be very reliable, especially the 

 very high values of the surface-tension, and the great deviations between the result 

 of the single experiments found by GRUNMACH, BRUMMER, and LOEWENFELD may 

 probably be explained by the very small distance (1'8 cm.) between the pins used by 

 these investigators. KALAHNE, who employs the same method, but has a distance of 

 7 cm. between the pins, also finds a value considerably lower and with a much better 

 mutual conformity than the above-named investigators. 



In consequence of these considerations it does not seem necessary for the author to 

 conclude that the method of capillary ripples in reality gives a value essentially higher 

 than the one found by the method described in this paper. 



Conclusions. 



In the present determination of the surface-tension of water the method of jet- 

 vibration proposed by Lord RAYLEIGH is used ; this method has the fundamental 

 advantage that a perfectly fresh new-formed surface can be examined. 



In the first part of this investigation it is shown how Lord RAYLEIGH'S theory of 

 infinitely small vibrations of a jet of non-viscid liquid can be supplemented by 

 corrections for the influence of the finite amplitudes as well as for the viscosity. 



In the experimental part of this investigation an attempt has been made to show 

 how in a simple manner it seems to be possible to secure that the jet-piece used for 

 the measurement satisfies the assumptions on which the theoretical development 

 rests. 



As the final result of his experiments the author finds the surface-tension of water 

 at 12 C. to be 7 3 '23 dyne/cm. 



