102 



Mr. Sudhansukumar Banerji on Aerial 



towards the origin 



distances, and it is only when we come 

 that the curve shows a tendency to assume a parabolic shape. 

 Further, measurement of the deflexions for different velocities 

 of impact shows that within the range of the experiment the 

 deflexions vary directly as the squares of the velocities. The 

 results are shown in Table I. When the squares of the 



Table I. 



Nos. 



Velocity of Impact. 



Mean Deflexions. 



1 



23-06 

 21-32 

 19-50 

 17-75 



10-80 



8-63 

 7-53 

 6-82 

 5-20 

 1-43 



2 



3 



4 



5 



velocities are plotted against the deflexions they give prac- 

 tically a straight line passing through the origin. Expe- 

 riments have also been made with pairs of balls of the same 

 material but of different diameters. In this case it is found 

 that the deflexions vary practically as the fourth power of the 

 diameters of the balls. The results for the case of three pairs 

 of wooden balls are given in Table IT. All these results 

 show, as we shall presently see, that the apparatus practically 

 measures the intensity of the sound produced by impact. 





Table II. 





Nos. 



Diameters of the 

 Balls. 



Mean Deflexions. 



1 



2 



3 inches. 

 2\ inches. 

 1£ inches. 



21-92 

 7-02 

 1-35 



3 



3. Nature of the Wave-Motion. 



A complete theoretical investigation of the nature of the 

 wave-motion started by impact, assuming that no vibrations 

 are excited in the balls, is beset with considerable mathe- 

 matical difficulties. We shall confine ourselves to the case of 

 two equal balls. As a result of the impact, the balls suffer 



