48 Messrs. C. V. Raman and S. Appaswamaiyar on 



not impracticable and would be of considerable interest, as 

 affording a direct demonstration of the discontinuous distri- 

 bution of velocity indicated by the analysis. The present 

 paper deals briefly with the method adopted and the 

 results. 



The mode of vibration of the string is evidently determined 

 by its configuration and its velocities at either of the two 

 epochs referred to above. If, therefore, it is possible directly 

 to impose at every point of a finite string in its position of 

 equilibrium the initial distribution of velocities with a dis- 

 continuity at one end indicated by the analysis, the resulting 

 free oscillations should have the same characteristic vibration- 

 curves as a bowed string. We have found it possible 

 successfully to realize these conditions in experiment by 

 arranging that a stretched string has initially a uniform 

 angular velocity about one end, and that in the course of 

 this motion one point on it impinges upon and is suddenly 

 brought to rest by a fixed stop or bridge provided for the 

 purpose. The length of the string between the fixed extremity 

 and the bridge is thus isolated, and photographs of the 

 vibration-curves of the resulting motion are secured by the 

 following device. By setting a narrow slit across and 

 immediately behind the string in any desired position, and 

 illuminating the slit with the light from an electric arc, any 

 given point on the string can be caused to record its motion 

 photographically on sensitive paper contained in a dark slide 

 which is caused to move in a direction parallel to the string, 

 i. e. vertically downwards, with uniform velocity behind the 

 illuminated slit. The necessary movement of the string 

 itself is secured by drawing it to one side together with the 

 weight attached to its free end, and allowing it to swing 

 down in the manner of a pendulum before one point on it 

 comes up against a fixed stop, which is placed about three- 

 fourths of the way down between the upper fixed extremity 

 and the free end. The shadow of the string across the slit 

 records itself on the photographic paper as a white curve on 

 a dark ground. Six records obtained in this manner are 

 reproduced in Plate I. One of the points of observation 

 chosen was the centre of the string and the others were on 

 either side of it. 



It will be noticed that the records show the motion at 

 each of the points of observation, both before and after the 

 first impulse set up by the impact reaches it. The velocity 

 at every point in the initial motion is exactly the same as 

 the velocity of the upward motion in the vibration-curves. 

 The form of the vibration as shown by the records evidently 



