Manchester Memoirs, Vo/. x/v/. (\goi), No. fi. ii 



it might be intense enough to tear it close to the beam, 



the velocity V, which would produce rupture indifferently 



either at the top or bottom, would in the first experiment 



be 



54,400. 17,000 ^ 



1^=^^ = 30-8 feet per second, 



30,000,000 ^ ^ 



corresponding to a height of fall of 148 feet. 



In the second and third experiments we have 



F=45*3 feet, height = 32 feet. 



Dr. Hopkinson gives the observed heights, and he also 

 corrects these heights on the assumption that the blows of 

 the falling weights on the clamp were plastic ones (see 

 column 3); it is, however, more reasonable to suppose that 

 the blows were elastic, or, more correctly, that during con- 

 tact of the weight and clamp the velocity would be V, but 

 as soon as the two objects had separated again, the velocity 

 of the clamp would be almost twice as great as that of 

 the ball, and the theoretical height of fall could be 

 diminished to nearly one quarter. The pressure-wave in 

 the wire would therefore consist of a short length cor- 

 responding to V, followed by a longer one corresponding to 



2 V. 



J/+; 



The corresponding height is given in column 4 (" calculated 

 height for elastic blow.") 



Strange to say. Dr. Hopkinson's first experiments 

 agree fairly well with this view, but the second and third 

 sets are not satisfied either by this or the previous supposi- 

 tion. The discrepancy must be accounted for by the 

 plasticity of the material, energy being absorbed by the 

 plastic stretch. 



