378 MR. P. O. PEDERSEN ON THE SURFACE-TENSION OF LIQUIDS 



The influence of the viscosity is, according to equation [(4), 1], determined by the 

 coefficient 



' - . '- - (3), 



where 8 is the logarithmic decrement oi the vibration. The determination of 8 is 

 made by measuring on the image (m-n, fig. 14) of the jet, making the supposition 

 that the amplitudes of the image are proportionate to those of -the jet. The results 

 are 



For water : 8 = 0'074 ; g = 1 '00014 ; 



98-04 per cent, alcohol + 1'96 per cent, water : 8 = 0'173 ; g = 1 "00076 ; 

 46'34 per cent, alcohol + 53'66 per cent, water : 8 = 0'210 ; g = I'OOllO ; 

 aniline: 8 = 0'265 ; g - 1'OOIS. 



The numbers given are only approximate, but they show that g, in all cases 

 considered here, is almost equal to 1, and as the determination of 8 is uncertain, no 

 correction is introduced. An exact investigation of the influence of the viscosity on 

 the form of the jet image cannot be made until the theory of this image is further 

 developed. 



Remarks on the Jet Photographs. 



13. On Plates 3 and 4 are shown fifteen jet photographs. In each photograph 

 the number of the orifice and the nature of the liquid are denoted. 



The photographs are arranged according to the orifices, in the same order as in 

 Table VII., and the remarks concerning them are given in the same order. 



Plate 3, figs. 6, 7 and 8, shows clearly the influence of viscosity on the damping of the 

 vibration. Fig. 6 is a water jet : this has only a very small damping. Fig. 8 is an 

 alcohol jet : with this the damping is a little larger. Fig. 7 is a jet of a mixture of 

 water and alcohol (46'34 per cent, alcohol + 53'66 per cent, water): with this the 

 damping is much greater than for the other two. The viscosity has about the follow- 

 ing values in these three cases (Tn. GRAY, ' Physical Tables,' Table 151, 1897) : 



, 0'012 by 15 C. : , 0'036 by 15C. ; , 0'014 by 15C. 



As the logarithmic decrement is the same for all vibrations, the fundamental 

 vibration will be purer at some distance from the orifice than immediately after 

 the jet has been formed, as is also shown on several of the photographs. 



It appears from these photographs that the jet image is very well adapted to 

 investigation of the jet vibrations. Similarly, they show that it is possible to make 

 orifices which for all practical purposes are correct. In further investigations by this 

 method it will be possible to go still farther in this direction. 



All the jet photographs commence about 1 '5 cm. from the orifice. 



