1882.] 



On Liquid Jets. 



133 



resolution on the upward path may be effected. As the vibration 

 gradually dies down, the place of resolution moves upwards, but it 

 cannot pass a certain point. When the point is reached, resolution 

 into actual drops ceases, the upper part of the jet exhibiting simple 

 undulations, when viewed intermittently. The phenomenon is in 

 perfect harmony with theory. As it leaves the nozzle, the jet is un- 

 stable for the kind of disturbance imposed upon it by the vibrator. 

 The subsequent loss of velocity, however, shortens the wave-lengths 

 of disturbance, until at length they are less than the circumference 

 of the jet, after which the disturbance changes its character from 

 unstable to stable. The vibrator must evidently produce its effect 

 quickly, or not at all. 



Influence of Regular Vibrations of Low Pitch. 



§ 2. Towards the close of my former paper on the capillary 

 phenomena of jets, I hazarded the suggestion that the double stream 

 obtained when an obliquely ascending jet is subjected to the influence 

 of a vibration, an octave graver than the natural note, is due to the 

 compound character of the vibration. At the time of Plateau's 

 researches the fact that most musical notes are physically composite 

 was much less appreciated than at present, and it is not surprising 

 that this point escaped attention. I have lately repeated Plateau's 

 experiments under improved conditions, with results confirmatory of 

 the view that no adequate explanation of the phenomena can be given 

 which does not have regard to the possible presence of overtones ; 

 and I have added some observations on the effects of the simultaneous 

 action of two notes forming a consonant chord. 



In order to make a satisfactory examination of it, it is necessary 

 to employ some apparatus capable of affording an intermittent view 

 of the jet in its various stages of transformation. In the experiments 

 formerly described I used sparks from an induction coil, governed by 

 the same tuning-fork which determined the resolution of the jet. 

 This has latterly been replaced by a perforated disk of black card- 

 board, driven at a uniform speed by a small water-motor. The 

 diameter of the holes is one-fifth of an inch — about that of the 

 pupil of the eye, and the interval between the holes is about four 

 inches. Examined under these conditions the jet and resultant drops 

 are sufficiently well defined, and there is abundant illumination if the 

 apparatus is so arranged that the jet is seen projected against the 

 sky. The speed of the motor is regulated so that there is one 

 view through the holes in about one complete period of the phe- 

 nomenon to be observed. If the power is a little in excess, the 

 application of a slight friction to the axle carrying the disk renders 

 the image steady, or, what is better, allows it to go forwards through 

 its phases with moderate slowness. 



