Mr Vincent, Experiments on Impact. 



353 



The results are given in Fig. 14, which shows that the square 

 of the diameter of the dent is approximately proportional to the 

 load. From this figure we find P the pressure which the lead can 



Steady load in pounds 

 Fig. 14. 



support to be 



pounds weight per sq. cm. or nearly 



7T x 0019 



3 x 10 8 dynes per sq. cm. Now from the impact experiments 

 already performed we find that p has a value always much greater 

 than this. But the dents produced by impact were measured for 

 this piece of lead and gave : — 



The mean value for p before hammering is thus 6*2 x 10 8 . 



This shows that the pressure the lead exerts on the ball during 

 impact is about twice as great as the pressure which the lead can 

 resist in the form of a steady load. 



The results in the above table show also that the increase in 

 the value of p due to hammering is accompanied by an increase in 

 the value of e. 



The value of P was also determined after hammering. A load 

 of 350 lbs. before hammering gave a dent '77 cms. in diameter, but 

 after hammering, the same load gave a dent - 7l cms. in diameter. 

 Thus P rises considerably, due to the hammering. 



The block of lead used in Fig. 11 gave a dent "69 diameter 

 with a load of 350 lbs. on a ball 2*54 cms. in diameter, so that 

 different specimens of lead even when chilled differ considerably 

 in the value of P measured under the same conditions. 



