238 Mr. J. P. Joule on the Effects of Magnetism, Sfc. 



From the above experiments it will be seen that the same 

 remarks which were made with regard to the soft iron, apply 

 also to the soft steel. The superior retentive power of the 

 latter metal enables us however to trace the elongating effects 

 of the permanent magnetism, which, we see, diminish with the 

 increase of tension, until at last, as in experiment 24, they 

 cease altogether. 



Ea-perime?its "with Harde7icd Steel Wire. 



The following experiments were made with steel wire of the 

 same kind as that employed in the previous experiments. It 

 was however perfectly hardened, so as to resist the action of 

 the file in every part. 



Experiment 25. Hardened steel vrire, one foot long, a 

 quarter of an inch diameter. Tension 80 lbs. 



Experiment 26. Same hardened steel wire. Permanent 

 magnetism to begin with — 1"8 Tension 408 lbs. 



