SURFACE-TENSION OF WATEE BY THE METHOD OF JET VIBRATION. 309 



We see that the mean radii a, determined in the two ways, are very nearly the 

 same (mutual deviation less than O'l per cent.). This conformity having been stated, 

 the velocity-determination was omitted at the later experiments and a was 

 determined by help of the photographs only, whereby the experiments became very 

 much simplified. 



The Results, of the Experiments. 



In the above we have described the methods used in the different measurements ; 

 it is further mentioned how it was possible, by the arrangement described on p. 301, 

 to keep the pressure-height and temperature of the water constant during the 

 comparatively long space of time taken to determine the discharges, the velocity, the 

 mean radius, and the wave-length. 



Before giving the results of the experiments we must, however, call attention to 

 some special circumstances occurring in the determination of the wave-lengths sought, 

 due to the fact that the wave-lengths found were not equal at different distances 

 from the orifice. In order to show plainly what is meant by this, we shall commence 

 with mentioning four experiments (one executed with each of the four tubes) carried 

 out at a pressure-height of about 100 cm., in which the single wave-lengths were 

 determined immediately outside the orifice and as far out on the, jet as its stability 

 permitted. 



The results can be seen in the table overleaf. 



As it will be seen, the differences between the readings are not constant, but 

 increase until they reach a maximum, whereupon they slowly decrease again. The 

 same can be seen from the table on p. 311, where the numbers in the column 

 designated by "mean values" are calculated from the table overleaf by a simple 

 adjustment. 



The variation of the differences read off is, however, the result of many causes, 

 among which are some the influence of which can be directly calculated. The first 

 cause is the curvature of the jet, the effect of which is partly that the differences 

 found are not equal to the real wave-lengths (see p. 306), partly that velocity and cross- 

 section are not the same at different places of the jet-piece examined. The second 

 cause is the decreasing of the wave-amplitudes, the influence of which appears from 

 the equation (37) on p. 296. The column of the table on p. 311 designated by "corrected 

 values " therefore contains wave-lengths, at different distances from the orifice, 

 belonging to a horizontal jet which has the same velocity and cross-section as the jet 

 examined on the horizontal place and which executes vibrations with infinitely small 

 wave-amplitudes. 



We see that the numbers in the last-mentioned column increase until they reach a 

 maximum, whereupon they keep very nearly constant. This seems to show that all 

 the causes of the variation of the wave-length, the influence of which is not cor- 

 rected for, must originate in irregularities ot the phenomenon which arise in the 



