186 L. M. Cheesmcm— Effect of Mechanical Hardening 



It -will be observed, however, that the dimensions of the 

 magnets used in these later experiments were very different 

 from those of the magnets used earlier, when the magnetism 

 was found to decrease with the hardening; in the former case 

 the ratio of the length to the thickness being 14"3, in the latter 

 case in the neighorhood of 65. 



To ascertain whether this caused the apparently contradictory 

 results obtained, a magnet was made of " English Silver Steel," 

 the length being so chosen as to obtain a magnet with about 

 the same value of — as in the case of those magnets, which had 

 shown an increase of the specific magnetism with the harden- 

 ing. 



The constants of the magnet were : length = 21 'Omm., diam- 

 eter = l-54mm., — = 13 -6. The magnet showed a 30 per cent 

 larger specific magnetism in the hard than in the soft condi- 



Thus the apparently contradictory results with steel seemed 

 to be due to the different values of the ratio ™. 



The following sets of experiments, VI, VII and VIII. were 

 made to test this conclusion more fully. 



Set VI. " English Silver Steel." 

 The wires designated by (b) were hardened by a stretching 



Set VII. From one wire of " English Silve 

 lb, 2b, 3b were hammered to obtain la, 2a, 



