Mr Vincent, Experiments on Impact. 



351 



Direct determination of e for Steel Ball and Lead Block. 



The ball used weighed 67 grammes, was 2"54 cms. in diameter 

 and the pendulum was 109 cms. long. The block weighed about" 

 80 kilos, and was slowly a cooled one, exhibiting large crystals on 

 planing up the surface. 



After obtaining the values shown in Fig. 12 by points sur- 

 rounded by circles the block was hammered with a small hammer 

 till it was quite smooth, then a block of steel was put on the 

 surface, having a planed surface in contact with the lead. Repeated 

 blows with a sledge-hammer were then given to the steel block 



3 I'd. of Approach in cms. a sec. 

 Fig. 12. 



and the lead surface, this rendered quite flat was used again in 

 determining those points in the figure indicated by crosses. It 

 was at once noticed that hammering the lead made the results 

 more uniform. Hammering also raises the value of the coefficient 

 of restitution for any given velocity. 



On comparison with Fig. 7 it will be seen that these results are 

 in general agreement with those obtained by the measurement of 

 successive dents. 



In Fig. 13 some determinations are given for two lead blocks, 

 one chilled, the other slowly cooled. These results are set out 

 below : — 



Slowly cooled lead block. 



