352 



Mr Vincent, Experiments on Impact. 



Chilled lead block. 



The values of e are given to three figures because they are the 

 mean of a number of observations. 



From this experiment e is less for chilled lead than for slowly 

 cooled lead, while the effect of hammering is to raise e (for any 

 velocity) by approximately the same amount for both blocks. 



\ Vel. of Approach in cm.s a sec. 

 Fm. 13. 



• Cooled slowly and hammered. 



O ,, ,, (before hammering). 



* ,, quickly and hammered. 



x ,, ,, (before hammering). 



Before hammering the chilled block, dents for various steady 

 loads were measured. The dents were made with a steel ball 

 similar to that used in the pendulum experiments. This was 

 constrained to move in a vertical direction by contact with a 

 conical hollow tool placed in the jaws of a drilling machine. The 

 load was applied slowly by a screw, which when turned sufficiently, 

 lifted a scale-pan containing the weights. The pressure was thus 

 transmitted by the vertical rod of the drilling machine to the 

 ball. This rod moved quite freely in well lubricated bearings in a 

 vertical direction, and thus the ball had only one degree of 

 freedom. Some experiments in which the ball was not thus con- 

 strained were useless owing to the dents being ill-shaped. The 

 above arrangement worked quite satisfactorily. 



