184 L. M. Cheesman—Etf< ,-t of M, <■},,,,< leal Hardening 

 Set ITT. Ikon. Length 100mm* Diameter l-6Tmm. 



These wires were hardened by subjecting them to the action 

 of a stretching force in the apparatus made by Perreaux for 

 determining the "breaking weight" of wires. 



Wire No. 1, of Set III, being subsequently hardened by 

 ring," the increase in length due to the same being cut 

 off, had after magnetization a specific magnetism of 195. 



Wire No. 2, of Set III, having been bent several times and 

 remagnetized, had a specific magnetism of 189. 



Comparing I, II and III, we find in each set the smallest 

 value of the specific magnetism in the case of the softest wire 

 and a gradual increase of the same with the hardening, in set 

 III the increase amounting to 70 per cent. The increase of the 

 specific magnetism seems at times somewhat irregular; this 

 however is easily explainable by the remarks.made under the 

 head of "Hardening." 



Experiments made with a magnet of cast iron (length 102mm. 

 diameter 7mm.) also gave an increase of the specific magnetism 

 with the hardness, the hardening being brought about by gentle 

 hammering. 



9. Experiments with Steel. — In the experiments with steel a 

 difficulty presented itself, which though also present with iron 

 was far less annoying there, namely the fact that the different 

 wires Aire not homogeneous. r l lis >vas not enable not only 



from the fact that wires, in as far as possible the same physical 

 condition, coald be magnetized to very different extents, but 

 also in that their "breaking weights'" difVeivd widely. On the 

 other hand, however, pieces cut trom the satin' wire gave results 

 comparable with each other. 



In the follow in- experiments a piece of each wire used was- 

 left soft for the sake of comparison. 



