24 Dr. Topler on the Application of the Principle of Stroboscope 



(3) As a matter of course, the beautiful experiments of Mag- 

 nus on the dispersion of the emergent jet can be readily repeated 

 with the above apparatus, using a small velocity of the disk, and 

 a small number of holes*. 



(4) Vibrating strings are observed in front of an illuminated 

 surface, or, if they are lustrous metallic wires, with a good light 

 over a blackened surface. If the entire wire is to be conveniently 

 seen, the vibroscope is so placed^ approximately in the direction 

 of the string, that this appears shortened. When strings are made 

 to sound by striking, besides the vibration established which cor- 

 responds to the fundamental note, there are always bendings which 

 run backwards and forwards on the curved string. This is best 

 seen with long thin metal strings. I have often been surprised at 

 observing in these that the acceleration at the moment at which 

 the string passes the position of equilibrium is by no means of 

 the form to be expected from theory. 



(5) The phases of vibration of the singing harmonicon-flame 

 are well seen if observed in a darkened room. The object bears 

 indeed some magnifying. In a separate paper I shall describe 

 the principal forms of vibration of the singing flame. It may be 

 anticipated that the experiments of Dr. Kundt on the double 

 refraction of sounding glass rods might easily be repeated with 

 the rotating disk, whereby the gradual change of the figure of 

 polarization, as regards time and position, would doubtless be 

 better seen than by the rotating mirror. 



(6) Experiments with Wheatstone's kaleidophone (Lissajou's 

 luminous figures) assume a very instructive form with the vibro- 

 scope, inasmuch as some conclusions may be drawn not without 

 interest as regards the theory of the apparatus. Suppose, for sim- 

 plicity's sake, a horizontal bar clamped at one end, whose free end 

 executes an elliptic vibration when struck excentrically; this, as we 

 know, is made visible by having a bright polished steel sphere 

 at the vibrating end brightly illuminated. The vibroscope must 

 of course resolve the luminous curve into a single point of light, 

 which, according to the direction of the apparatus, appears slowly 

 to complete the vibration in a positive or negative direction, or 



* I may mention here that Dr. Kersting of Riga exhibits on a large scale 

 the shape of the emergent jet by a very simple experiment. From a tube 

 half an inch in width, making an angle of 80° with the horizon, a dense 

 jet ascends to a height of about 8 feet. The long and wide vulcanized sup- 

 ply-tube is provided with a large tap which can be very rapidly closed. 

 The ascending jet from a certain height appears turbid. If now the tap 

 be rapidly turned, the mass of water suspended in the air falls down late- 

 rally, and the upper part is seen to consist of clear water-bulbs 1 to 1| inch 

 in diamater, while the lower part still hangs together, but has regular con- 

 tractions and expansions, increasing upwards ; these are not turbid, but clear 

 as glass. The elasticity of the supply-tube is essential in these experiments. 



